contents
contents
volume 76 . number 12 . december 2023
8
THE BUILDING ENVELOPE TRANSITION
Air Barrier to Fenestration
Designing the transition between an effective air barrier and fenestration, such as curtain wall and storefront, can present challenges for the designer and specifier. Too often, the interface between the air and water barrier and fenestration are overlooked.
Kevin Haynes

Sound and Wellness
STUDYIING NOISE IN OFFICE DESIGN
To tap into the built environment’s full potential to improve wellbeing, it is important to better understand how noise affects occupants’ physical and mental health.
Niklas Moeller and Viken Koukounian, PhD, P.Eng.

COVERING IT ALL
EXPLORING LIGHTWEIGHT CLADDING
Lightweight cladding is gaining traction in the construction industry. Aesthetics aside, it offers sustainability and energy efficiency, and installation is safer and easier for crews on site.
Karine Galla

BALANCING PRACTICALITY
WITH FENESTRATION
Balancing Practicality with Fenestration Systems
Fenestration is often designed as a key architectural feature and tends to be one of the first design elements to be value engineered. The construction of a building is when the designer’s vision comes to reality.
Bradford J. Antes, PE, and Erin E. Regan, PE
8
16
16
30
42
30
42
On the Cover
For this industrial-style, high-rise building in Washington, D.C., New York-based Morris Adjmi Architects teamed with local architect Eric Colbert and Associates. The design team specified thermally broken, aluminum-framed, unitized curtain wall and window wall, plus windows and terrace doors. Signage, bricks, and steel salvaged from the former Atlantic Plumbing Supply Co. building that once occupied the site have been incorporated into Atlantic Plumbing’s lobby.
See the article on page 8.
Photo courtesy The JBG Companies and Wausau Window and Wall Systems
Departments
NEWS/NOTES
6 – The Impact of Artificial Intelligence (AI):
From Adoption to Education and Economics
FAILURES
50 – Kick-out Flashings: Diversion Ahead
Kenneth Itle, AIA

CSI
123 North Pitt Street, Suite 450
Alexandria, VA 22314
Tel:	
(800) 689-2900 
(703) 684-0300
Fax:	(703) 236-4600
csi@csinet.org    www.csiresources.org
volume 76 . number 12 . december 2023
www.constructionspecifier.com
The Official Magazine of CSI
Editorial
Editorial Director
Blair Adams
Executive Editor
Jason Cramp
Associate Editor
Farheen Sikandar
Online Editor 
Arslan Ahmed 

Audience Development
Mei Hong
Blanca Arteaga
Camille Garcia
Catherine Ho
CheukWai Chan
Frances Li
Irene Yu
Sonam Bhardwaj (maternity leave) 

constructionspecifier.com
Andrei Kurpatov
Hon Mun Mak
Lillian Hu
Sanjeev Deshar
Boyang Qian
Krina Li

Design
Senior Graphic Designer 
Catherine Howlett
Graphic Designers
Alfi Ichwanditio
Lisa Greco
Steve Maver
Elaina Adams
Production
Director of Production and Projects
Matthew Buckstein 
Senior Production Co-ordinator
Melissa Vukicevic
Production Co-ordinators
Falon Folkes  |  Heather Donnelly
Digital and Marketing Specialist 
Alvan Au
Administrative Assistant
Bess Cheung
Advertising Sales
(866) 572-5633 toll free
sales@constructionspeciﬁer.com
Vice-president of Sales
Joseph Galea 
Group Publisher, Construction 
and Metal Groups
Melanie Kowal
Sales
Dianne Mahoney
Nikki Stefaniuk
Sales Operations Manager
Tim Broderick
Sales Co-ordinator
Ines Abbey
kenilworth Media inc.
CEO
Erik Tolles
Chief Financial Officer
Philip Hartung
Senior Director of Operations
Krista Taylor
Director of Business Development 
John MacPherson
Accounting Manager
Bochao Shi
Accounting Assistant
Audrey Tang
Administrative Assistant
Helen McAuley 
Chief Executive Officer
Mark Dorsey, FASAE, CAE
mdorsey@csinet.org

Business Development
Brian Knotts
bknotts@csinet.org

Member Services
Memberservices@csinet.org
1-800-689-2900
(M-F 8 am - 8 pm ET)

EDITORIAL ADVISORY BOARD

Kathie Petrella, BPSArch., 
BArch. Sc. CSI, CSC

Lane Beougher, FCSI, Lifetime Member, CCS, CCCA, CDT, CSC, DBIA, FAIA, LEED AP, NCARB
Ohio Facilities Construction Commission

Michael Chambers, FCSI, CCS, CDT, FAIA
MCA Specifications

Carolyn Charles, CSI, CDT, AIA, LEED GA
MHTN Architects

Lynn Javoroski, FCSI, Member Emeritus, CCS, CDT, LEED AP, SCIP

Margaretha Eckhardt, CSI, Member Emeritus, CCS, AIA

Brian Joos, PE, BS, CSI, CCS, CDT, EIT
J3 Group

Barbara Matejka, CSI, CCS, LEED AP
HHSDR Architects/Engineers

Mark Ogg, CSI, CCCA, CDT, PMP
JLL

Katherine Thomas
Baskervill

Kathryn D’Andrea, CSI, CCS, CCCA
Little
Board Chair
Cam Featherstonhaugh IV, CSI, CDT

Chair-elect
William Sundquist, FCSI

Secretary
Jori Smith, CSI, CDT

Treasurer
Michael Young, FCSI, CCS, CCCA, CDT

Director-at-large
Kevin Wang, CSI, CCS, CDT

Director-at-large
Jarrod Mann, PE, CSI, CDT

Director, North Central Region
Andrea Zawodny, CSI, CCS, CDT

Director, Northeast Region
Thomas Lanzelotti, CSI, CDT

Director, Gulf States Region
Betina Latiker, CSI, CCS, CDT

Director, Northwest Region
Georgia Spenser, CSI, CDT

Director, Great Lakes Region
Ivette Ramirez Bruns, CSI, CCS, CDT

Director, Southwest Region
Morayma Bittle, CSI, CCS, CDT

Director, South Central Region
Lynsey Hankins, CSI

Director, Southeast Region
Amy Hockett, CSI, CDT

Director, West Region
Patrick Comerford, CSI, CCPR, CDT

Director, Middle Atlantic Region
Robert Vaughn, CSI
How to Reach Us
266 Elmwood Ave. #289, Buffalo, NY 14222, (866) 572-5633
Production Offices 
15 Wertheim Court, Suite 710, Richmond Hill, ON, Canada L4B 3H7, (905) 771-7333
Speak to the Editor
We want to hear from you! Please email editorial inquiries, 
story pitches, press releases, and letters to the editor to:
jcramp@constructionspecifier.com
Subscription
To subscribe to The Construction Specifier, call: (866) 572-5633; 
email: circulation@constructionspecifier.com
Rates	1 Year (12 issues):	2 Years (24 issues):	3 Years (36 issues):
U.S.	$59.00	$99.00	$139.00 
Canada	$69.00	$109.00	$149.00
Foreign	$199.00	
For members of CSI, $16.50 of annual dues are allocated to the publication 
of The Construction Speciﬁer.
Postmaster: Return undeliverables to: CSI 
123 North Pitt Street, Suite 450 Alexandria, VA 22314 
Tel: (800) 689-2900 (703) 684-0300, Fax: (703) 684-0465 (703) 236-4600
The Construction Specifier (ISSN 0010-6925) is published monthly by Kenilworth Media Inc. for CSI, 123 North Pitt Street, Suite 450 Alexandria, VA 22314. Periodical postage paid at Alexandria, Virginia, and at additional mailing offices. Printed in the USA.
Reprints
To order a customized reprint, contact Mossberg & Co.’s Jill Kaletha 
Tel: (800) 428-3340, ext. 149; email: jkaletha@mossbergco.com
Editorial Policy: The mission of CSI is to advance building information management and 
education of project teams to improve facility performance.
The magazine acts as a moderator without approving, disapproving, or guaranteeing the validity 
or accuracy of any data, claim, or opinion appearing under a byline or obtained or quoted from an acknowledged source. The opinions expressed by authors do not necessarily reflect the official views of CSI or Kenilworth Media Inc. Also, appearance of advertisements and new product or service information does not constitute an endorsement of products or services featured by the Institute or Publisher. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is provided and disseminated with the understanding that the Publisher and the Institute are not engaged in rendering legal or other professional services. If legal advice and other expert assistance are required, the services of a competent professional should be sought.
The electronic addresses contained in this magazine are for inquiring about a company’s products and or services or to contact an author, and not to be used for sending unsolicited marketing or promotional messages.
Copyright 2023. CSI. All Rights Reserved, including World Rights and Electronic Rights. No part of this publication may be reproduced without permission from the Publisher, nor may any part of this publication be reproduced, stored in a retrieval system, or copied by mechanical photocopying, recording, or other means, known or hereafter invented, without permission of the Publisher.
www.constructionspecifier.com
The Impact of Artificial Intelligence (AI):
From Adoption to Education and Economics
Artificial intelligence (AI) is dominating the headlines, 
but what does this technology mean for the architects and specifiers of today and tomorrow?
CEO of construction tech firm Part3, Jack Sadler, will be at the Winter Master Specifier’s Retreat (MSR), happening February 7-9, 2024, at the Royal Sonesta in San Juan, Puerto Rico, to share practical examples of AI, tips for getting started, and the wide-ranging impacts this technology has on our profession.
The mission of Part3 is to enable architects and engineers to take back control over their projects and manage construction administration with speed, automation, and intelligence. Sadler has held strategic roles and helped launch multiple tech companies prior to taking on the challenge of connecting construction teams and starting Part3.
You can learn more about MSR at csiresources.org/MSR.
CSI’s new Construction Contract Administration Workbook is here
The new CSI Construction Contract Administration Workbook is not only a great overview of the practice of contract administration, but also an excellent study tool to prep 
for the CCCA certification exam.
It is full of interactive exercises, case studies, and examples that address construction contract administration and the roles and responsibilities of all parties.
The CSI Construction Contract Administration Workbook is now readily available in the CSI bookstore at csiresources.org/bookstore.
CSI National Conference Awards The Construction Specifier’s Article of the Year
The Construction Specifier’s feature, “Building for Better Resilience in WUI Zones,” was awarded article of the year in October at the Construction Specifications Institute (CSI) National Conference in Minneapolis, Minnesota.
Written by Rick Roos, the article delves into the ongoing growth of Wildland-Urban Interface (WUI) zones, a phenomenon driven by the constant increase in population and urban sprawl. Leveraging his expertise in fire safety, hygrothermal building performance, and acoustic control, Roos provides a comprehensive perspective on the development of codes and standards. Within this piece, he elaborates on how this expansion leads to significant housing development encroaching upon areas where fires can easily spread from forests and grasslands to residential neighborhoods. Building codes often feature relatively rudimentary fire protection regulations, focusing on essential prerequisites homes must meet, including permissible materials, acceptable construction methods, and the minimum ASTM material criteria. Consequently, it becomes crucial for the project team to adopt a holistic approach to planning and design, with a specific emphasis on reducing fire risks and bolstering fire resilience.
This award is presented to the author or authors of an original article published in The Construction Specifier during the 2023 fiscal year. Individual articles are nominated by the magazine’s editorial staff and judged by its editorial advisory board.
From left to right: Lynsey Hankins, FCSI, director from the South Central Region of the Construction Specifications Institute (CSI); Rick Roos; Cam Featherstonhaugh IV, CSI, CDT, CSI’s board chair; and Jason Cramp, executive editor of The Construction Specifier.
Photo courtesy Construction Specifications Institute (CSI)
Save the Date for the 2024 
CSI National Conference
Thank you to everyone who supported and participated at the 2023 CSI National Conference – our third sold-out event!
Mark your calendar to join us next year, October 16-18, in Houston, Texas, as we overcome, adapt, and succeed.
You can sign up to get updates and early registration access at csiresources.org.
The Building Envelope Transition
Air Barrier to Fenestration
By Kevin Haynes
Photo ©Joshua Jay Elliot/courtesy Works Progress Architecture 
and Wausau Window and Wall Systems
Designing the transition between an effective air barrier and fenestration, such as curtain wall and storefront, can present challenges for the designer and specifier. During the design phase, the process of selecting and specifying a curtain wall and/or storefront, in some cases is limited to aesthetics, structural considerations, thermal performance, and cost. Too often, the interface between the air and water barrier and fenestration are overlooked. The goal is to maintain continuity of the air and water barrier (AWB) assembly and its connections with the building components to ensure the building’s performance and long-term durability.

Specifying an air barrier system in commercial buildings can improve indoor air quality (IAQ), provide energy savings by reducing heating and cooling cost, help control air leakage, and support sustainable design. Uncontrolled air leakage and moisture within the building envelope can affect building occupants and may cause premature deterioration of materials, leading to costly damages. An effective AWB controls both air leakage and vapor diffusion through the building envelope, helping prevent materials’ deterioration. A greater amount of moisture is due to air leakage moving through a wall or roof compared to the amount of moisture attributed to vapor diffusion.

Air barrier assemblies
Air barriers consist of various materials and assemblies, and all are intended to manage air flow between unconditioned and conditioned space. It is also important that the air barrier assembly controls air leakage, bulk water intrusion, vapor diffusion, and thermal performance. The selection and specification process should consider the building type, the project location (climate zone), and the performance requirements.
There are at least six types of manufactured air barrier systems available:
• 
Self-adhered membranes
• 
Liquid-applied membranes
• 
Mechanically attached – building wraps
• 
Insulating board stock – rigid insulation
• 
Spray polyurethane foam (SPF)
• 
Factory bonded – membranes to sheathing

Determining what types of manufactured air barrier systems work best with curtainwall/storefront system, it really comes down to the design of the interface between the wall and the glazing system. The key is that the continuity of building envelope barrier is maintained and compatibility between materials is assured.
Compatibility between the air barrier materials and the glazing assemblies, such as curtain wall and storefront, is critical to maintain a weather-tight barrier. Depending on which air barrier is specified, chemical and adhesion compatibility needs to be addressed in the design phase to ensure proper interface between materials.
Storefront, curtain wall, sealants, backer rods, and transition membranes are components of the air barrier assembly. It is important for the designer and specifier to understand the difference between curtain wall and storefront systems, especially regarding air and water tightness. This will help determine the interface with the AWB and the critical seal location (wet/dry line) 
of the curtain wall verses storefront systems.
Thermal performance must also be considered to maintain optimal energy efficiency in the building. Overall thermal performance in the wall assembly can best be achieved by aligning the wall insulation with the thermal break/isolator in the storefront and curtain wall system. Avoid thermal “short circuits” where conductivity occurs in flashing, masonry sills, and lintels that extend into the interior.
When the building envelope’s thermal break is compromised, heat loss and heat gain can result. In addition to consuming resources and increasing operational costs, a building’s poor thermal performance can affect interior temperature management and may promote condensation. When moisture is present, it can lead to mold, mildew, and other potentially harmful microorganisms. Unhealthy, unsightly, and uncomfortable interiors can have a negative impact on people’s wellness and absenteeism, concentration, productivity, and job satisfaction. Building owners also can experience a negative impact in lower lease rates, more vacancies, and reduced property value.

Code compliance
Model building energy codes and standards, including the International Building Code (IBC), and the International Energy Conservation Code (IECC), and ASHRAE Standard 90.1, Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings, require controlling air leakage through the design and construction of a continuous air barrier in the building envelope.
The 2018 IECC notes a continuous air barrier is required in all U.S. climate zones except Zone 2B. Zone 2B comprises a handful of locations with warm, dry climates, such as Arizona’s Yuma County, California’s Imperial County, and Texas’ Real County.
IECC section 402.5.1 says air barriers may be located inside the building envelope, outside the building envelope, within the assemblies’ composing envelope, or any combination thereof. Air barrier compliance methods follow in sections:
• 
C402.5.1.2.1 Materials, which states, “Materials with an air permeability not greater than 0.004 cfm/ft² (0.02 L/s•m2) under a pressure differential of 0.3 inch of water gauge (75 Pa) when tested in accordance with ASTM E2178 (Standard Test Method for Determining Air Leakage Rate and Calculation of Air Permeance of Building Materials) shall company with this section. Materials… shall be deemed to comply with this section, provided that joints are sealed and materials are installed as air barriers in accordance with the manufacturer’s instructions.”
• 
C402.5.1.2.2 Assemblies, which states, “Assemblies 
of materials and components with average air leakage not greater than 0.004 cfm/ft² (0.02 L/s•m2) under a pressure differential of 0.3 inch of water gauge 
(75 Pa) when tested in accordance with ASTM E2357 (Standard Test Method for Determining Air Leakage Rate of Air Barrier Assemblies), ASTM E1677 (Standard Specification for Air Barrier (AB) Material or Assemblies for Low-Rise Frame Buildings Walls) or ASTM E283 (Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Skylights, Curtain Walls, and Doors Under Specified Pressure Difference Across the Specimen) shall company with this section. Assemblies… shall be deemed to comply with this section, provided that joints are sealed are the requirements of Section C402.5.1.1 are met.”

The air leakage of fenestration assemblies is determined in accordance with AAMA/WDMA/CSA 101/I.S.2/A440, 
North American Fenestration Standard/Specification for windows, doors, and skylights (NAFS), ANSI/NFRC 400, Procedure for Determining Fenestration Product Air Leakage, or ASTM E283. Along with storefront and curtain wall, fenestration in architecture refers to openings in the building envelope that include windows, doors, skylights, vents, and more.
A sampling of maximum air leakage rates for fenestration assemblies per the 2018 IECC C402.5.2 Table include:
Fenestration assembly	Maximum rate L/s•m2 (cfm/ft²)	Test procedure	
Curtain walls	0.0283 (0.06)	NFRC 400 
or ASTM E283
at 75 Pa 
(1.57 psf)	
Storefront glazing	0.0283 (0.06)		
Commercial glazed swinging entrance doors	0.4719 (1.00)		

Key considerations: Curtain wall
Storefront and curtain wall systems share similar functions and appearance. Both can protect the building and its occupants from weather, while providing daylight to the interior and views to the outside. Beyond these commonalities, these fenestration systems have numerous differences in how each best suits its intended application.
Curtain wall is a non-load-bearing exterior wall cladding that is hung to the exterior of the building, usually spanning multiple floors. It also can be used in large spans and punched openings on mid-rise to high-
rise buildings. Glazing in-fills, such as glass, can be installed as captured or structural silicone glazed (SSG) method. Captured uses a pressure plate or pressure bar that is fastened to the back member mullion. Gaskets form the seal to limit air and water intrusion. Face caps provide an aesthetic appearance and conceal the pressure plate fasteners. The SSG method eliminates pressure plates and gaskets, and relies on sealant to create an adhesive bond on the interior side of the glass and back member. This can occur at the verticals or horizontals, or both to create all-glass appearance.
There are two main classifications of glazed curtain wall: stick-built and unitized. In stick-built curtain wall systems, the frames, glass, and/or in-fill panels are furnished as individual components and installed on site, piece by piece or in pre-assembled sections. Unitized curtain wall are modular systems composed of large units, usually spanning floor-to-floor that are assembled and glazed in the factory, shipped to the job site, and erected in sequence on the building.
Curtain wall systems perform at a high level, especially when considering air and water management. Rather than attempting to drain the entire frame, curtain wall systems isolate water within each individual lite of glass. This occurs in the glass pocket that captures the insulated glass units (IGUs).
Weep holes installed in the pressure plate and face caps allow water to drain to the exterior, as well as create pressure equalization. After assembling the vertical and horizontal back member mullions together, water dams are installed using sealant (Figure 1).
Prior to setting the IGUs, interior gaskets are sealed in each corner (Figure 2), creating the critical seal on the interior side of glass pocket and insulated glass. This is the location of the wet/dry line as illustrated in (Figure 3, page 14).
Of equal importance is recognizing the location of the primary line of the perimeter sealant, which is crucial in maintaining the continuity of the AWB. In stick-built curtain wall, the primary line of sealant is installed behind the glass in the same plain as the wet/dry line. In this case, the perimeter sealant and backer rod provide the transition from the curtain wall wet/dry line and the air water barrier (Figure 3). The transition between the curtain wall and the opaque wall must allow for both thermal and differential movement. The sealant joint installed at exterior face of the curtain wall is a weather seal and is not the primary line of sealant.
When it is not possible to install the primary perimeter sealant joint, a transition membrane is often detailed. This is normally achieved by using pre-formed silicone sheets that attach to the glass pocket of the curtain wall prior to installing the pressure plate and face cap (Figure 4, page 14). Curtain wall manufacturers have developed specialized extruded adapters that connect the silicone sheet membrane directly to the curtain wall at the perimeter of the frame (Figure 5, page 14). Designers and specifiers have numerous other options in detailing the transition between the AWB and the curtain wall assemblies. To ensure the best possible solution, consulting the curtain wall manufacturer in the design phase is recommended.
Since curtain wall assemblies are considered non-load bearing walls, they must be supported by the building structure. In stick-built systems, curtain wall typically relies on “T” and “F” anchors installed in the top and bottom of the vertical mullions and jamb members. The anchors are designed to withstand the imposed structural loads and to accommodate movement between the building structure and curtain wall assemblies.
Additional anchor methods include perimeter “F” clips and, for curtain wall assemblies spanning multiple floors, steel angles are used to connect vertical mullions at each floor slab. The transition of the AWB to the curtain wall must be completely sealed at the anchors, and accommodate shims, adjustments, and building movement. It is crucial that transition membranes are installed in a manner that does not interfere with or block installed weep holes, preventing proper drainage of the curtain wall.
Installation must work in sequence involving coordination between trades to ensure a continuous, completely sealed AWB is achieved in the building envelope. However, the sequence may vary depending on the type of AWB specified and the fenestration selected. For practical purposes, the interface between the installed curtain wall and the AWB assembly should be completely sealed prior to installing the surrounding cladding. In this manner, all seals and connections within the AWB, transition assembly, and curtain wall can be inspected and tested to address any issues, if necessary.

Key considerations: Storefront systems
Storefront systems are the most economical commercial glazing assembly available due their simplicity. However, they are limited in size, performance, and where they should be used on a building. Today’s storefront systems are typically stick-built and pre-assembled in small sections, making it easier to transport to the job site, and they can be installed in sequence within the building openings. In this process, sealant is applied between
 the connection in the horizontal and vertical members prior 
to assembling the frame sections. The critical seal is located on the interior side of the glass pocket behind the glass.
In storefront, the entire elevation is drained at the bottom of the frames with internal drainage occurring in the glass pocket area, whereby water is directed from the horizontal, down the vertical mullions using water deflectors. Sub-sill flashing installed underneath the frame is an integral part of the drainage process. The flashing includes a vertical leg at the interior side and end dams installed on each side forming a panning condition. Bulk water is contained in the sub-sill flashing and drained to the exterior through weep holes.
Since storefront consist of open back frame members at the perimeter and sub-sill flashing, the actual air and water seal is located at the interior side of the frame. Therefore, the wet/dry line is not a continuous plane; it is offset to the interior side of the storefront frame (Figure 6). This is important when designing the interface or transition from the storefront to the AWB.
To conclude, designers and specifiers should consider the following design criteria when considering the building envelope AWB and fenestration:
• 
Transition of the AWB assemblies and fenestration needs to align as close as possible.
• 
Connections must accommodate anchors, shims, adjustments, and building movement maintaining continuity of the building envelope AWB.
• 
Avoid thermal “short circuits” and align thermal breaks 
in fenestration with surrounding wall insulation to optimize energy performance.
• 
Coordination between trades is recommended, allowing for installation to work in sequence. Curtain wall and storefront frames need to be installed and sealed prior to the cladding being installed.	CS
  the construction specifier  |  december 2023
DC Group’s “expand in place,” 4,088 m2 (44,000 sf), two-story office industrial project in North Minneapolis features a contemporary design by UrbanWorks Architecture. The new and the 1,301 m2 (14,000 sf) existing structure were blended using a combination of aluminum-framed curtain wall, storefront, and entrances. The framing was finished in a Class I clear anodize including the curtain wall’s mullions which were incorporated as extended exterior fins.
Photo ©Paul Crosby Architectural Photography/courtesy Tubelite
The North American headquarters for Vaisala, in Louisville, Colorado, blends Scandinavian style and sustainable, net-zero-ready functionality. OZ Architecture specified high-performance curtain wall and window wall systems, contributing to the two-story, 3,252 m2 (35,000 sf) design. Thermally broken aluminum framing, low-e insulated glass, and thermal pressure plate further support the building envelope’s sustainability and energy-efficiency goals.
Photo ©Matt Puckett/courtesy Tubelite and Deceuninck
Figure 1
After assembling the curtain wall’s vertical and horizontal back member mullions together, water dams are installed using sealant.
Illustrations courtesy Tubelite
Figure 2
Prior to setting the insulating glass units (IGUs) in the curtain wall, interior gaskets are sealed in each corner creating the critical seal on the interior side of glass pocket and insulated glass.
Figure 3
This shows the curtain wall’s wet/dry line in context with the air and water barrier (AWB), and the primary line of sealant.
Figure 4
Figure 5
An alternate attachment method using specialized extruded adapters that connect the silicone sheet air and water barrier (AWB) membrane directly to the curtain wall at the perimeter of the frame.
The curtain wall’s wet/dry line in context with the air and water barrier (AWB) membrane attachment to the curtain wall.
Figure 6
The air and water seal for storefront is located at the interior side 
of the frame. This means the wet/dry line is offset to the interior side, following the interior frame and interior glass plane.
Additional Information
Author
Kevin Haynes is the architectural representative at Tubelite. He draws from more than 35 years of architectural consulting, technical sales, and engineering within the fenestration, glass, and glazing industry. He works closely with commercial and institutional building teams to design, evaluate, and specify aluminum-framed curtain wall, storefront, entrances, and daylight control systems. He can be reached at khaynes@apog.com.

Key Takeaways
Designing the transition between an effective air barrier and fenestration, such as curtain wall and storefront, can present challenges for the designer and specifier. During the design phase, the process of selecting and specifying a curtain wall 
and/or storefront, in some cases is limited to aesthetics, structural considerations, thermal performance, and cost. Too often, the interface between the air and water barrier and fenestration are overlooked. The goal is to maintain continuity of the air and water barrier assembly (AWB) and its connections with the building components to ensure the building’s performance and long-term durability. Supporting this goal, this article describes air barrier assemblies, code compliance, and key considerations for curtain wall and storefront systems.

MasterFormat No.
07 27 00—Air Barriers
08 40 00−Entrances, Storefronts

UniFormat No.
B2010–Exterior Walls

Keywords
Division 07, Divison 08,
Air barriers,
Curtain wall,
Storefront,

Sound and Wellness 
Studying Noise in Office Design
By Niklas Moeller and Viken Koukounian, PhD, P.Eng.
Photos courtesy Fotoworks/Benny Chan
While sight is generally prioritized over other sensory modalities during building design, a completed structure’s aural qualities do not simply provide a neutral backdrop for activities—a fact apparent to those who managed to carve out “quieter” home offices during the pandemic, only to be called back to noisy, overstimulating commercial and public spaces.

During the intervening pandemic period, many employees also began paying greater attention to their personal well-being, intensifying expectations for healthy workspaces. Although the workplace category remains the slowest growing within a projected USD $7 million world wellness market by 2025, the Global Wellness Institute (GWI) attributes this lag to the shift organizations are finally making from compartmentalized wellness programs aimed at treating symptoms—such as stress, disengagement, and absenteeism—to more holistic and proactive approaches that tackle problems at their source by, for example, leveraging workplace design.
To tap into the built environment’s full potential to improve well-being, one needs to better understand not only how noise negatively affects occupants’ physical and mental health, but the ways in which “the sonic aspect of buildings can be intentionally articulated to achieve a richer, more satisfying built environment: one that responds to the ear as well as the eye.”1

Auditory health effects
Hearing is a historically undervalued and underserved sense, at least within Western societies. It was not until the mid-20th century—as public awareness of the need for stricter occupational health and safety guidelines grew—that the requirement to preserve it garnered widespread support. Numerous studies subsequently demonstrated strong correlations between sudden or sufficiently prolonged exposure to higher noise levels and temporary or permanent hearing loss, which is generally understood to mean damage to the hairs or nerve cells within the ears, affecting their ability to transmit information to the brain. Other potential consequences may involve tinnitus, characterized by ringing or other “phantom noises” in the ears, and hyperacusis, which refers to the increased sensitivity to ordinary sounds.
Today, most people are well-acquainted with the auditory health effects of high noise levels, as well 
as the associated “safe limits” established for workplaces. Basically, the risk of hearing loss is immediate when the noise level approaches or exceeds 120 decibels (dB) (e.g. from an explosion), while impairment due to lower levels (e.g. from machinery) usually requires longer exposure; for example, a 15 minute exposure to 100 dB or a two-hour-long exposure to 90 dB.2 In the U.S., the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit (REL) is 85 A-weighted decibels (dBA) averaged over an eight-hour work shift.3 As noise increases above that level, the allowed exposure time decreases.

Non-auditory health effects
Fewer people are aware of the potential non-auditory health risks of lower-level noises, below the established thresholds that one associates with hearing impairment. Over the past decades, researchers started exploring the impacts of various sources (e.g. road, rail, and airplane traffic), and the results are mixed. As a general, non-specific stressor, noise has been found to have non-auditory health effects—such as changes in hormones, sweat response, metabolism, heart rate, and blood pressure, as well as outcomes related to its disruptive effect on sleep and immune response—but not consistently. Further, it is difficult to conclusively link noise to, for instance, the development of heart disease, which can also be linked to other health-related factors.
This is not to say there are no such adverse impacts; in fact, some experts maintain the question is no longer whether noise causes cardiovascular disease, for example, but to what extent.

Noise sensitivity
Research consistently demonstrates noise level alone is not a sufficiently strong indicator of potential health consequences. One must also take into consideration additional characteristics such as frequency, predictability, complexity, duration, and the meaning of the noise in question, the listener’s acoustic environment (including ambient or background spectra and levels), and the listeners themselves—perhaps first and foremost, their sensitivity to noise.
A growing body of literature dealing with the non-auditory effects of lower-level noise differentiates between “noise exposure” and “noise sensitivity.” In a review, Brown et al. cites Schreckenberg et al., who found that noise affects different people differently, as well as Shepard et al., who “found noise level does not necessarily determine noise annoyance, but rather other factors play a role, in particular, noise sensitivity.”4 The findings, presented by Park et al. (2017) in a paper titled, “Noise sensitivity, rather than noise level, predicts the non-auditory effects of noise in community samples: a population-based survey,” show the effects—specifically those pertaining to mental well-being—on an individual’s health are more strongly correlated with their sensitivity to noise than other variables (e.g. sociodemographic factors, medical illness, duration of residence, and so on).
Although the focus of such research largely remains an assessment of the person (a comprehensive description of the acoustic conditions is seldom provided), distinguishing between noise exposure and noise sensitivity has advanced understanding of the non-auditory effects of noise and led more researchers to question whether different people react similarly—or the extent to which they do—when exposed to lower-level sources, and to focus on the psychological, as well as the physical, impacts.

Neurodiversity and noise
Researchers are also exploring how individual differences come into play within the workplace. For example, neurological differences—such as autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), dyslexia, and dyspraxia, as well as neurological challenges resulting from brain injury—can impact how individuals process sensory information (e.g. increase noise sensitivity), which in turn affects their social and occupational functioning. Employees can also suffer from misophonia, or other auditory hypersensitivities, whereby common sounds such as chewing, breathing, and repetitive tapping—or stimuli related to such sounds—elicit a strong emotional response ranging from mild irritation to anxiety, anger, disgust, and even significant distress.
While offering privacy pods and headsets might seem like relatively simple solutions, these tactics may not send the desired message of inclusivity 
or be the most sustainable given neurominorities already comprise 15 to 20 percent (some suggest as high as 40 percent) of the population, and that figure is expected to rise in the coming years.5, 6 More holistic approaches to acoustical design will not only better accommodate increasing numbers of neurodiverse individuals, they will also greatly benefit those considered neurotypical because no one is immune to environmental stressors and, particularly, to noise.

POEs highlight ‘poor acoustics’
Indeed, post-occupancy evaluations (POEs) such as those conducted by the Center for the Built Environment (CBE) show that “poor acoustics”—predominantly lack of speech privacy and noise from conversation—consistently ranks as the top source of workplace dissatisfaction. Parkinson et al.’s recent in-depth analysis of more than 600 office buildings with 62,000 occupants in the CBE’s database reveals that, of all sources of dissatisfaction, acoustics most strongly interferes with self-reported work performance—a conclusion supported by numerous studies demonstrating its negative impact on focus.7 Additional well-documented effects include: productivity losses due to increased errors and time spent on tasks, diminished capacity for creativity, innovation, and problem solving, reduced collaboration due to fear of being overheard and disrupting others, and increased use of electronic communication and headsets, as well as requests to work remotely.
“Poor acoustics” also takes a psychological and physical toll on employees, who report feeling uncomfortable, edgy, irritable, and unmotivated in noisy workspaces. By stimulating the sympathetic nervous system (i.e. the “fight-or-flight” response), noise can have cardiovascular-, gastric-, endocrine-, 
and immune-related impacts. The attempts to overcome this constant environmental stimulus causes cognitive strain and stress, contributing to mental health issues such as anxiety and burnout, which can, in turn, make people even more sensitive to acoustical disturbances. Since people are typically an organization’s largest cost, one must also consider the financial impact of workforce “unwellness”—including stress, disengagement, and illness—which GWI estimates may cost the global economy 10 to 15 percent of economic output annually.
Workplace design that respects rather than challenges the senses by, for example, mitigating disruptive noise, supports the health and well-being of all an organization’s members and allows everyone to achieve their full potential. In other words, it is not only “neurodiverse design,” but also considered “good design.”8

Acoustics and ‘good design’
People principally rely on sound level, reverberation time, absorption, sound insulation, and vibration isolation to quantify the acoustic properties of materials, assemblies, and spaces, but those metrics do not indicate or assess a person’s acoustical experience. Large POE datasets such as those the CBE has compiled, on the other hand, do empower building design professionals to make practical, data-driven decisions to help achieve occupant-centric goals, such as focus, comfort, privacy.
Parkinson et al. points out that bridging the gap between this data and actionable insights to improve workspaces “may require a shift in focus from the determinants of overall satisfaction to common sources of occupant dissatisfaction.” It also involves centering design on the main way employees use these facilities. According to Gensler’s U.S. Workplace Survey 2022, most employees primarily use the office as a dedicated space for focused work, and they spend most of their time working independently. Moreover, 69 percent of these tasks demand a significant level of concentration. The firm concludes that supporting this type of work provides “a crucial foundation of the workplace experience,” but, at the same time, their data indicates workplace effectiveness in this regard has declined to the lowest levels since 2008.9
Design trends have increasingly favored collaboration in workspaces over the last decade. Given that “poor acoustics” is the number one cause of dissatisfaction and focus work is the primary objective of those using offices, it is clearly time to prioritize occupants’ need for quiet and privacy. Fortunately, spaces designed to facilitate concentration have also proven to be more conducive to collaboration than those primarily designed for only collaboration.
Of course, offering adjunct spaces where employees can join their colleagues for face-to-face time is also important. Considering 72 percent of adults report feeling lonely—and hyposensitive neurodiverse individuals require more, rather than less, sensory stimulation to focus and feel safe in social engagement—communal areas that help build relationships and offer more “energetic” acoustics also support mental health and well-being.10 Organizations can also offer additional aural experiences such as relaxation rooms that employ natural sounds to stimulate the parasympathetic nervous system (i.e. a “rest and digest” state). Providing a variety of spaces with different auditory features from which to select has the added benefit of increasing occupants’ feelings of control over their work environment.10
That said, self-awareness is likely insufficient to achieve occupant-centric goals because there are aspects of the environment that occupants may not consciously recognize or fully appreciate as being either beneficial or detrimental to health and well-being. At the same time, these aspects are not adequately accounted for in current noise-rating systems or even in recently developed building standards geared toward well-being.
Indeed, most employees’ understanding of acoustics primarily stems from noise exposure theory and its focus on level or, more colloquially, “loudness.”11 Hence, the answer to the question “What constitutes ‘good acoustics’ within the workplace?” is often simply “an environment with little to no noise.” Given this viewpoint, the notion of intentionally increasing ambient sound levels to achieve a quieter environment—or, rather, one occupants will perceive as quiet—may seem counterintuitive, but, contrary to popular understanding, a person’s perceptions of sound have less to do with the lowest level of sound humans they can hear, and more to do with their ability to identify and discern sounds within their acoustic environment.

Sound versus noise
To move acoustic design forward, one must first address what is perhaps the most pervasive source 
of confusion in architectural acoustics: misuse of the terms “sound” and “noise.”12
Although these words are often used interchangeably—as are “ambient sound” and “ambient noise”—“sound” refers to acoustic waves (or, in the case of occupants, the transportation of physical vibrations in the air within the human ear’s frequency range of 20 to 20,000 Hz), while “noise” is essentially “unwanted and/or harmful sound” or, in Kryter’s words, “audible acoustic energy…that is unwanted because it has adverse auditory and nonauditory physiological or psychological effects on people.”13
The classification of some types of sounds as “unwanted” is key to achieving “good acoustics.” Many studies into non-auditory health effects consider noise emitted by industrial and environmental sources, as well as transportation (e.g. road, rail, and airplane traffic); however, in spaces with higher occupant densities such as offices, occupant-generated noise is the most significant cause of acoustical dissatisfaction. Traditional assessment methods seldom make provisions for this source (focusing on building-related systems, services, and utilities) and, because of its complex nature, building professionals are not easily able to account for it during design—that is, unless they put sound to work.
Sound is continuously produced and present in the built and natural environment—by individuals and those around them, office equipment, and essential building systems, services, and utilities that support other environmental parameters within the space—and it also enters from the outdoors. This understanding—that everyone is constantly surrounded by acoustic energy—helps in exploring more nuanced acoustical concepts, such as the “audibility” of sound and its beneficial uses (i.e. how it can be leveraged to support occupant needs), and not only the adverse effects of noise.

The Masking Effect
As an example, imagine a room that has sufficient insulation to prevent noise transmission, allowing one to solely focus on the interior ambient conditions. Occupancy is limited to one person. The resulting space is one in which the overall background sound level is exceptionally low. Now imagine what this space may or may not sound like. Most would describe it as “silent.” In practice, environments designed to meet this extreme criterion are highly specialized acoustical facilities, such as anechoic chambers, and occupants often describe their experience as uncomfortable, unsettling, or even intolerable for reasons that include being able to hear their own heartbeats and other bodily functions, given the lack of “interfering” sound. Similarly, ambient “silence” (in this case, low or intermittently low background sound levels) in an office makes surrounding conversations and acoustical disturbances easier to hear.
Other sounds present within a space, particularly its ambient acoustic conditions, such as background sound (or lack of it), affect the perception of sounds in that space. The physics behind this effect was documented as early as the 1950s and referred to as the Masking Effect. To be clear, it does not explain human acceptance or assessment of sounds, only the ability to hear, identify, and differentiate between them. It is an effect routinely experienced in everyday life due to things such as blowing wind, running water, a murmuring crowd, and HVAC, but rarely thought about in the context of the built environment. That said, the only time such ambient sound typically falls below the threshold of hearing is when special effort is made to reduce it, as in an anechoic chamber or recording studio. Since background sound is present in just about every inhabited environment, in addition to making people more vulnerable to acoustical disturbances, its absence can also feel “unnatural.”
As interest lies in conditions conducive to acoustical comfort rather than discomfort, the reader is now invited to add a level of background sound to the imaginary room, such as that produced by HVAC. Technically, this sound corresponds with the typical maximum limits (30 to 55 dBA) defined in the ASHRAE Handbook – HVAC Applications. Since frequency plays a role in determining comfort, with low, mid, or high frequencies potentially causing discomfort due 
to their rumbling, buzzing, or hissing content, the reader should also apply an appropriate spectrum—
a concept at the heart of most noise-rating systems, which depend on a reference contour to assess whether the ambient acoustic conditions are spectrally “neutral.”
However, because building-related systems, services, and utilities are designed to support other functional needs (e.g. thermal, air quality, water, lighting) and sound is simply a byproduct, it varies (temporally) according to the optimal performance and efficiency conditions of the various components. At the same time, the positioning and arrangement of these sources, which encompass elements such as ductwork and piping, exert a significant influence on how acoustic energy is distributed within a facility, particularly in terms of its spatial transmission. In other words, in practice, the background sound (or noise) produced by such equipment is not temporally or spatially consistent, or spectrally neutral.14 Building design professionals can only strive to ensure overall levels do not exceed acceptable maximum limits.
To dependably manage the overall level and spectral distribution of background sound within the built environment—thus ensuring the minimum limit needed for speech privacy, as well as the frequency range required to effectively mask speech and a wide range of noises, while maintaining occupant comfort—one must employ a sound-masking system: an acoustical solution intended to manage the ambient acoustic conditions in a space.15
Masking technology has come a long way since its inception in the 1960s; with the introduction of small control zones and precise computer tuning, appropriately trained technicians are now able to control its output with precision. When handled correctly, the sound achieved within the space not only minimizes the disruptive impact of noise and protects the privacy of conversation, but it also does it consistently and unobtrusively. In this case, sound has a “damping” effect, rather than acting as a stimulus, as it either entirely masks noise or diminishes its disruptive impact. This reduction in the dynamic range, which denotes the variation in sound levels over time or the difference between the loudest and quietest sounds measured over a period, plays a crucial role in mitigating distraction and discomfort. Consequently, it helps in averting the activation of the sympathetic nervous system responsible for the “fight or flight” response.

Implementation of masking sound
The importance of managing beneficial background sound within interiors is increasingly recognized in standards, guidelines, and codes worldwide, but obstacles remain in understanding how one should handle it. Despite its role as one of the three pillars of effective architectural acoustical design (i.e. the “C” in the “ABC Rule,” which stands for “cover” or, more accurately, “control”), sound masking remains the most poorly understood. In the absence of industry standards pertaining to design and performance, notably significant variations also exist among the available sound-masking systems and implementation methods.
While the concept is straightforward, one cannot achieve the benefits of the Masking Effect via a “plug and play” electronic system. As the generated sound is affected by the facility’s interior layout, furnishings, and finishings, effective application requires not only diligent design through small control zones, technical expertise in sound masking and general acoustics, and specialized equipment (ANSI Type 1 one-third octave analyzers and Class 1 calibrators), but also precise field tuning in line with ASTM E1573-22, Standard Test Method for Measurement and Reporting of Masking Sound Levels, Using A-Weighted and One-Third Octave-Band Sound Pressure Levels. Further, to be accountable to the construction specifications and, ultimately, to the client, the contractor must properly measure and report the tuning technician’s results.
It is worth noting sound masking’s current location (27 51 19 Sound Masking Systems) within MasterFormat, Division 27–Communications means it is often managed from a communications (A/V) perspective rather than an acoustical one. Although audio and masking systems use similar components (e.g. electronics, cable, loudspeakers), their purpose is fundamentally different: the former distributes communication, while the latter is intended to obscure it. Masking also fulfils other goals outside the scope of communication systems such as acoustical comfort. Given the lack of industry standards, project teams are heavily reliant on experts and contractors to provide guidance and masking delivery. Signaling in MasterFormat that masking is an acoustical technology rather than an audio system would afford building professionals the opportunity to carefully consider what parties are best suited to provide advice and handle masking implementation.
Indeed, managing perceived levels of sound by defining the background sound conditions (i.e. background noise criteria and masking sound) for a given space is only the first step; it then becomes possible to use the remaining acoustical strategies involved in the “ABC Rule” to manage the transmission of sound into (or out of) spaces to maintain those conditions as closely as possible: “A,” which stands for “absorb,” and “B,” which stands for “block.” For example, Figure 1 shows various sources of sound and its transmission toward a building/rooms. The use of outdoor barriers, the building envelope, internal walls, and furniture attenuate the level of sound from various sources that differ in their level, spectral properties, and location. The use of absorptive tools, such as panels, ceiling tiles, and carpet help remove acoustic energy that, if not successfully blocked, would continue to reverberate after entering these spaces.
In other words, application of masking also informs decisions regarding wall construction (e.g. sound transmission class [STC] ratings; full or partial height), ceiling selection (e.g. noise reduction coefficient [NRC] and ceiling attenuation class [CAC] ratings), and other acoustical materials such as absorptive panels, tying it thereby more closely with architectural and acoustical design.

In conclusion
Failure to incorporate appropriate acoustical solutions raises concerns for occupants’ physical and psychological safety, along with potential impacts on organizational diversity and productivity. While most building design professionals are familiar with the “ABC Rule”—and, indeed, that one must use a holistic approach to achieve the desired experiential outcome—the role of background sound (the “C”) remains widely misunderstood.
Fine-tuning the acoustical vernacular helps identify acoustic conditions that provoke adverse effects, and how sound can be used to mitigate them. At the same time, looking to recent research to further the understanding between “acoustics” and “human perception” (specifically within the realm of psychoacoustics, even prior to the complexities introduced by the architectural environment) provides a framework for achieving “optimal acoustic conditions”—one formerly obscured by reluctance to speak openly about mental health and neurological differences, as well as the ease with which noise complaints were dismissed as neurotic, weak, or self-centered.
While the vagaries of individual perception are worth exploring, the interest ultimately lies in the practice of acoustics within a communal workplace environment. Addressing the issues the POE data has brought forth—and transforming occupant-centric objectives into quantifiable acoustic criteria—requires a nuanced exploration of sound’s attributes. This encompasses not only its level, but also its spectral, spatial, and temporal qualities, within the context of common objectives such as achieving acoustic comfort and maintaining acoustical privacy.
Although acoustical comfort is a relatable concept, many consider it more subjective than objective. By quantifying the degree to which humans can perceive sound—and, in the case of masking technology, conforming to a preferred spectrum—the Masking Effect demonstrates why this belief is misinformed. Similarly, the argument for acoustical privacy is often perceived as niche and only relevant to occupants of certain spaces (e.g. in medical exam rooms), even though the conditions required to achieve it are the same as those needed for focus (e.g. in open plan offices).
In the end, sound is all around and the physics relating the Masking Effect are omnipresent conditions. Building design professionals can intentionally shape those conditions using the type of noninformational broadband sound that forms the backdrop of occupants’ daily lives, but optimized for productivity, health, well-being, and satisfaction.	CS

Notes
1 Refer to T. Sheridan and K. Van Lengen, “Hearing Architecture: Exploring and designing the aural environment,” Journal of Architectural Education, November 2003.
2 The decibel (dB) is typically used to express the “loudness” of sound. The scale is logarithmic, so although the numerical difference between two levels might appear small, the actual difference is exponential. For example, the energy of an 80 dB sound is 1,585 times greater than one of 48 dB. Expressed in terms of distance, if 80 dB is equivalent to 1.6 km (1 miles), 48 dB is only 1 m (3 ft).
3 The A-weighted level (dBA) provides better indication of occupants’ impression of sounds than the decibel (dB) because it applies a set of “corrections” to instrument-measured sound levels that account for our sensitivity to different frequencies. For example, if two tones (e.g. 200 Hz and 1,000 Hz) differ in non-weighted level (e.g. 60.85 dB and 50 dB, respectively), people may still perceive them as having equal “loudness” (e.g. 50 dBA) because humans are less sensitive to lower-frequency sounds than high ones.
4 Refer to B. Brown, P. Rutherford and P. Crawford, “The role of noise in clinical environments with particular reference to mental health care: A narrative review,” International Journal of Nursing Studies, vol. 52, no. 9, 2015.
5 See V. Drummer, A. Taylor and S. Basque, “Designing for Neurodiversity: Creating spaces that are inclusive of all,” www.stantec.com/en/ideas/topic/buildings/designing-for-neurodiversity-creating-spaces-inclusive-of-all, 2013.
6 To help prevent hearing loss related to use of a personal audio system (PAS) such as a mobile phone and headset, one should follow the recommendations outlined in ITU-T H.870 (03/2022), Guidelines for safe listening devices/systems. It is also important to note that noise-cancelling headphones block speech and background noise equally, meaning the relative difference between them remains the same; they do not reduce speech intelligibility.
7 Refer to T. Parkinson, S. Schiavon, J. Kim, and G. Betti, “Common sources of occupant dissatisfaction with workspace environments in 600 office buildings,” Buildings and Cities, 4(1), 2023.
8 See note 5.
9 Refer to the Gensler Research Institute, “Returning to the Office” briefing based on data captured by Gensler’s U.S. Workplace Survey 2022.
10 To avoid interruption from external sources, the intentional introduction of aural experiences in spaces requires careful control of their boundaries and the acoustic conditions within them.
11 Level is a single-value metric arrived via the sum 
of its frequency components, measured over time. 
Its simplicity—in terms of both measurement and as a concept—is one reason why it is commonly used by those in the building industry (e.g. owners, architects, designers, engineers), but there are nuances to this parameter that often cause confusion (e.g. as sound 
is measured over time, a constant sound and an intermittent sound measured over a certain sampling period may be equal in level) and the numeric value offers little insight into the characteristics of a noise, only its relative “loudness.” Sounds can also vary in spectrum (e.g. rumbly, buzzy, hissy), temporal characteristics (e.g. constant, fluctuating, surging, intermittent), as well as spatially (e.g. overhead, adjacent, throughout a space).
12 For more on this topic, see “Rethinking Acoustics: Understanding silence and quiet in the built environment” by V. Koukounian and N. Moeller in the August 2020 issue of The Construction Specifier.
13 Refer to D. Fink, “A New Definition of Noise: Noise 
is unwanted and/or harmful sound. Noise is the new ‘second hand smoke,” Acoustical Society of America’s Proceedings of Meetings on Acoustics, January 2019.
14 Similarly, music and nature sounds cannot be relied upon to mask noise and speech adequately or consistently. It is also important to note that they are also subject to personal preference, and occupants’ response to nature sounds (e.g. running water) can be further affected by lack of associated visual stimulus (e.g. a waterfall). Where appropriate (e.g. in lobbies and relaxation rooms), these sounds can be used in conjunction with masking; the latter establishes the foundation for speech privacy and noise control, while the former achieves other auditory goals.
15 For more on this topic, see “In Pursuit of Acoustical Equity: Controlling temporal, spectral, and spatial properties of sound” by V. Koukounian and N. Moeller in the May 2021 issue of The Construction Specifier.
Studies show neurological differences such as autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) can affect noise sensitivity and auditory processing.
Photo ©istockphoto.com/Ivanko Brnjakovic
The human ear basically consists of three parts: the external ear, middle ear, and inner ear. This cross section shows the hair cells that transform the sound vibrations in the fluids of the cochlea into electrical signals that are then relayed via the auditory nerve to the brain.
Illustration ©istockphoto.com/ttsz
Given neurominorities already comprise 15 to 20 percent of the population, providing headsets and privacy pods may not send the desired message of inclusivity or be the most sustainable, particularly given that figure is expected to rise in coming years.
Photo ©istockphoto.com/Bojan89
Many people assume a facility’s acoustic conditions are fairly uniform throughout; however, without the use of a properly designed and tuned sound-masking system, they actually vary considerably, as demonstrated 
by these ambient (i.e. background sound) measurements taken within 26 locations in an unmasked, mostly open-plan office space.
Illustrations courtesy PKR Moeller Associates Ltd.
 A facility’s unmasked ambient level (in green, left-hand side) is typically too low to cover noises (in red). When a sound-masking system is used to provide an effective, comfortable level (in green, right-hand side), it either completely covers noises or reduces their disruptive impact by minimizing the difference between the noise floor (i.e. the lowest level of sound in the space, which is now provided by the masking sound) 
and the loudest noises in the space.
Since the noise produced by HVAC equipment is simply a byproduct, it varies according to the optimal performance and efficiency conditions of various components, as well as their location and placement. It also cycles on (red line) and off (green line) throughout the day. While one can try to ensure overall levels do not exceed acceptable maximum limits, this equipment cannot be relied upon to provide the consistent minimum level needed to mask acoustical disturbances or the particular frequencies required for speech privacy and occupant comfort.
In high-density spaces such as offices, occupant-generated noise is the most significant source of disruption, and because of its complex nature, building professionals are not easily able to account for it during design, unless they implement a sound-masking system.
Photo ©istockphoto.com/Katleho Seisa
Figure 1
Once background sound conditions are defined using a sound-masking system (blue circles indicate loudspeakers), other acoustical strategies 
and materials can be added to the design to maintain those conditions as closely as possible by managing transmission of sound into or out of spaces. This type of ‘masking first’ approach typically reduces wall (e.g. sound transmission class [STC]  ratings; height) and ceiling (e.g. noise reduction coefficient [NRC] and ceiling attenuation class [CAC] ratings) requirements, as well as those of other acoustical materials (e.g. absorptive panels).
Illustration courtesy KR Moeller Associates Ltd.
In order to dependably manage a facility’s ambient acoustic conditions, 
the sound-masking system must be both properly designed and adjusted for the particular space. Here, a system design with small control zones has been tuned for volume and frequency to the National Research Council (NRC) masking spectrum using specialized software, providing uniform acoustic conditions throughout the office space.
Illustration courtesy KR Moeller Associates Ltd.
Additional Information
Authors
Niklas Moeller is the vice-president of K.R. Moeller Associates Ltd., manufacturer of the LogiSon Acoustic Network and MODIO Guestroom Acoustic Control. He has more than 25 years’ experience in the sound-masking industry. Moeller can be reached via email at nmoeller@logison.com.

Viken Koukounian, PhD, P.Eng., is director of engineering at Parklane. He is an active and participating member of many international standardization organizations, such as the Acoustical Society of America (ASA), ASHRAE, ASTM, the Green Building Initiative (GBI), and the International WELL Building Institute (IWBI), the Standards Council of Canada (SCC), and also represents Canada at International Organization of Standardization (ISO) meetings. He completed his doctorate at Queen’s University (Kingston, Ontario, Canada) with foci in experimental and computational acoustics and vibration. Koukounian can be reached via email at viken@parklanemechanical.com.
Key Takeaways
Failure to incorporate appropriate acoustical solutions raises concerns for occupants’ physical and psychological safety, as well as for organizational diversity and productivity. While most building professionals are familiar with the “ABC Rule”—and, indeed, a holistic approach is required to achieve the desired experiential outcome—the role of background sound (i.e. the “C”) remains widely misunderstood. Although acoustical comfort is a relatable concept, many consider it more subjective than objective. By quantifying the degree to which humans can perceive sound—and, in the case of masking technology, conforming to a preferred spectrum—the Masking Effect demonstrates why this belief is misinformed.

MasterFormat No.
09 80 00–Acoustic Treatment

UniFormat No.
C10−Interior Construction

Keywords
Division 09
Acoustics
Design
Noise
Sound
PRODUCT SPOTLIGHT
Covering it All: Exploring Lightweight Cladding
By Karine Galla
Photos courtesy Sto Corp.
Lightweight cladding is gaining traction in the construction industry. With advancements in material science, the benefits of such cladding are increasing, and it is no longer necessary to use heavy materials such as masonry, concrete, metal panels, precast, porcelain, or even fiber cement to achieve the look of brick, wood, concrete, or metal. With the latest industry innovations, all these looks for building exteriors can be achieved using lightweight claddings. Aesthetics aside, sustainability and energy efficiency are major advantages, and installation is safer and easier for crews on site.

Cutting down on carbon
Carbon emissions from the building sector are significant, and they have an impact on the environment. In fact, according to the New Buildings Institute (NBI), “Building operations and construction-related activities are responsible for approximately 39% of humanity‘s global greenhouse gas (GHG) emissions. More than a fourth of those are embodied carbon emissions, those associated with the production of building materials, construction activities, operations, and end of life.”1 Therefore, both embodied and operational carbon are crucial considerations in today’s construction sphere.
Operational carbon is the amount of GHG emissions that are released during the in-use phase of a building. This includes the use, management, and maintenance of a product or building. In short, it takes into account the variety of carbon emission sources that are active throughout the operating period of a building.
How do lightweight cladding materials positively affect the carbon footprint? Starting from the top, lightweight materials are thinner, lighter, and take up less space during transit. This translates to less trucks overall and less gas expended to transport materials to the job site. By nature, lightweight materials also simply make for a lighter load to haul, which impacts fuel efficiency. For every 453-kg (1,000-lb) increase of vehicle weight, fuel economy drops by approximately 0.5 percent.2 Reducing the weight of the materials shipped across multiple truckloads can result in significantly reduced environmental impacts and diminished carbon emissions.
There are also key differences when it comes to the preparation of lightweight cladding materials compared to their heavier counterparts. Consider masonry cladding that requires heating and drying for extended periods of time in an 800-degree kiln. This consumes a great deal of energy. With lightweight cladding alternatives such as resin-cast brick, construction stakeholders can achieve the look of masonry, but in a much lighter-weight solution that takes a fraction of the energy to fabricate.
From an operational carbon perspective, lightweight cladding options that are installed as part of a fully integrated system deliver even greater savings. Innovative systems that combine lightweight, high-performance cladding, superior air and weather barriers, and excellent thermal properties via continuous exterior insulation save on energy consumption, generating additional cost savings for owners. Therefore, specifiers can choose systems that meet the most stringent building code standards, as well as those that meet requirements for an NFPA 285 compliant assembly.

On-the-wall energy performance
One of the most important benefits of lightweight cladding is its on-the-wall energy performance. Take exterior insulation and finish systems (EIFS), a lightweight cladding system that provides a continuous insulated building envelope at about 0.5 kg/m2 (1.5 lb/sf). EIFS is applied in multiple layers over exterior sheathing to create an energy-efficient, fire-resistant, low-maintenance, and versatile exterior cladding.
A study by Oak Ridge National Laboratory (ORNL) showed that EIFS walls perform better than several other wall types for moisture and thermal performance. The 15-month ORNL study conducted in the southeastern region of the U.S. showed EIFS outperformed walls made of brick, stucco, concrete block, and cement board.3 
• 
EIFS are sustainable, durable, and resilient.
• 
EIFS are among the most water-resistant 
exterior surfaces.
• 
EIFS have passed the major fire resistance tests that are required by the building codes. This includes fire resistance, ignitability, intermediate multi-story, and full scale multi-story corner tests.

EIFS is just one example of a lightweight cladding system that delivers value across residential, multi-family, and commercial construction sectors. From a visual perspective, if a design team is looking for something other than EIFS, there are other lightweight cladding options that can provide the same benefits and still achieve the true look of what they are designed to mimic.

Authentic aesthetics
Innovations in cladding technology have allowed architects and specifiers to achieve a variety of cladding looks by employing a unified, tested, and higher-performing system compared to traditional materials. For example, architects can now specify lightweight, flexible, resin-cast wood grain planks for a building’s exterior or interior that look like real wood, but without the performance downsides. This provides a durable, realistic, and low-maintenance alternative to natural or engineered wood cladding. Plus, these new products can be integrated within fully engineered wall systems that include all the control layers (air/water/vapor, moisture, thermal, and durability) for modern building performance while providing a one source solution and warranty. This allows architects to meet project demands for building exteriors that require a number of colors, textures, or materials on the same structure with seamless integration of the control layers behind each aesthetic. In this instance, the only thing that changes is the building’s exterior finish.
Instead of real brick, facades today can feature flexible resin-cast brick shapes to achieve a variety of unique designs. These materials give designers freedom when it comes to color choice, and they consume significantly less energy to manufacture and transport, compared to traditional heavy bricks.
From a health perspective, there is no dust generated from resin-cast brick, and because it contains very little silica, it keeps production workers and installers safe. Further, these resin-based bricks and organic mortars are cement-free and significantly reduce the risk of efflorescence, which is the whitening of the material due to the migration of salt to the surface of porous materials, often occurring with real brick or concrete. From an installation perspective, these thin, pre-formed brick shapes are fast and easy to install, no special tools are needed to cut them, and there are no concerns about hauling a load of heavy bricks around the job site.
More visual options for lightweight claddings include those used to create facades resembling split face block concrete masonry units (CMU). Designers can circumvent having to specify heavy CMUs and instead choose lightweight cladding systems that offer products that achieve the look 
of a true cement block.
The construction community has access to ready-mixed, acrylic-based materials that are applied to a building’s substrate using simple tools such as a finishing trowel. Once completely dry, applicators sand down the surface to the desired texture, wash the finished facade, add formwork marks, and apply a clear coat sealer for the desired gloss. The end result is an exterior wall that looks like CMU, but is much lighter and can also be finished in a variety of colors or textures. In addition to a CMU appearance, this same method can be used to create the look of brick, stone, tile, wood, limestone, metal, and more. Plus, behind the facade finish, these aesthetic options can be part of an integrated wall system that combines insulation and weather barrier layers to ensure long-term building performance and thermal efficiency.

User-friendliness
It is clear that installing lightweight claddings is simpler and safer for construction crews. Consider the scenario of installing cladding on a multi-story commercial building. Installing heavy cladding panels requires specialized equipment and lifting substantial materials high above ground; and this brings inherent safety risks. Compare this to applying lightweight materials to the face of a building.

Made for the retrofit market
While lightweight materials make sense in any construction environment, they are particularly suited to the retrofit market.
The most sustainable way to build a structure is by renovating an existing one. This is the most eco-friendly option, but it still presents a host of challenges. The insulation typically needs to be installed if not upgraded, and the exterior walls often need to be revived. Instead of adding additional layers of heavy materials or doing a complete reclad, which increases the embodied and operational carbon of the building, construction stakeholders are selecting lightweight products that minimize carbon emissions, and also are less of a disturbance for the occupants of the buildings.
For the renovation of aging structures, lightweight EIFS assemblies are an ideal option. With EIFS, if the building has an existing brick or CMU exterior, contractors can overclad the structure by putting a liquid-applied weather barrier over the existing masonry, a layer of continuous insulation (ci), the application of a base coat and mesh, and then finally the finish that the customer desires. This is dubbed an overclad, and it can only be done with lightweight cladding.
The overclad method saves time and money for the owner funding the renovation and for the installation crews as well. It is also a much more sustainable option than demolishing a building, dealing with material waste, and expending considerable amounts of energy to construct a new one.
Another benefit is that if an existing exterior is already completed with EIFS, overcladding is still an option for the future because of how thin it is relatively to many other cladding options. For example, if a home or building has EIFS on it, but the owner decides they want to change the cladding to a wood alternative, they can simply install resin-cast wood over the EIFS. Both materials are lightweight, so the structural integrity of the building will not be compromised. This is an important consideration, because the thicker a wall gets, the more impact it has on other portions of the structure, such as the framing of the structure, windows, and doors. In sum, a wall can only be so thick. Therefore, thinner, lightweight claddings are advantageous for any potential building retrofits in the future.
Finally, repairs to an exterior are simpler with lightweight cladding systems such as EIFS. If there is a minor dent in an EIFS wall, an applicator can cut a section of the material out, fix it, and finish it without any visible inconsistency in the wall’s finish and without compromising the performance of the air, water, or thermal control layers. Compare this to having to replace a metal or fiber cement panel on a commercial building, where crews need to order a replacement panel, wait for it to ship, then uninstall the damaged panel and install the new one. This is more time consuming, and material production and transportation release more carbon into the atmosphere.

Keeping it light
The benefits of lightweight cladding stretch beyond the performance of the structure itself. Owners, installers, architects, and the living environment can all benefit from these types of materials. This includes lower energy bills, a more comfortable environment for occupants, near limitless design freedom for architects, and a lower carbon footprint for the planet.
Lightweight claddings deliver on the performance that today’s structures require and have proven to be an excellent fit for the retrofit market to rehabilitate buildings of the past for another lifetime of use. With sustainability at the forefront of the conversation, lightweight claddings help limit carbon emissions. With so many aesthetic options, they also meet any project’s design vision. For the many stakeholders involved in the construction process, lightweight claddings can lead to a holistic solution for the building envelope, one that impacts everyone on the project.	CS

Notes
1 Learn more about embodied carbon by visiting, newbuildings.org/code_policy/embodied-carbon/.
2 Examine the fuel economy weight at www.internationaltrucks.com/blog/fuel-economy-weight.
3 Read the report, “Energy – Wet, warm wall worries.” Oak Ridge National Laboratory, www.franklin.in.gov/
egov/documents/1501244146_07449.pdf.
4 Refer to the “Benefits of EIFS.” EIFS Industry Members Association, www.eima.com/eifs/benefits.
5 Learn more about Environmental Product Declarations at www.stocorp.com/epd/.
This brick is bonded instead of bricklaying. This opens up diverse range of design options, from recreating the appearance of brickwork to originating unique artistic designs.
Riverbend Food Pantry uses a resin cast wood plank for its overclad project on an existing concrete masonry units (CMU) walls.
Five planes of control are needed for protecting the building and creating buildings that are energy efficient, durable, safe, and sustainable while still providing aesthetic appeal.
Continuous insulation (ci) replicated a smooth finish of porcelain tile and mimicked the grout lines with expertly rendered trowel marks.
Additional Information
Author
Karine Galla is director, product management for Sto Corp. She has more than 20 years of experience in product marketing in exterior insulation and finish systems (EIFS), stucco, air and moisture barriers, and other materials. Galla has a master’s degree from the University of Lyon, France. She is multilingual and holds AWCI’s EIFS Doing it Right and Building Envelope Doing it Right certifications, as well as the ISO Internal Lead Auditor certification from Georgia Tech.

Key Takeaways
Lightweight claddings are gaining traction in the construction industry. As new technologies are emerging, benefits of such claddings are increasing. It is no longer needed to use traditionally heavy material such as masonry, concrete, metal panels, precast, porcelain, or even fiber cement to achieve the look of brick, wood, concrete, metal and more, as all these looks can be achieved using lightweight claddings. Besides the aesthetic aspect, sustainability is a major advantage of lightweight cladding as it greatly lowers the embodied carbon footprint of the material, and affects the operational carbon, especially when waste and repair/maintenance are considered. As the renovation market is rapidly growing, lightweight claddings are ideal for this type of use and can easily reclad an existing structure to either refresh the appearance of the building and/or improve the energy performance of the building.

MasterFormat No.
07 24 00—Exterior Insulation and Finish Systems

UniFormat No.
B2010–Exterior Walls

Keywords
Division 07
Continuous insulation
EIFs
Lightweight cladding
*Companies that appear in the Manufacturers’ Profiles section prepare and submit their own information. Kenilworth Media Inc. does not assume any responsibility for the content of the Profiles.
Construction Realities
Balancing Practicality with Fenestration
By Bradford J. Antes, PE, and Erin E. Regan, PE
Photo © Tampatra1| Dreamstime.com

Providing a comfortable and attractive interior space for the building’s inhabitants is a primary concern of the design team. A large component of this is preventing water leaks to the interior of the building. The recommendations and considerations in Part 1 of this article, published in the August issue of The Construction Specifier, will help prevent water leakage into new buildings and this article will discuss what can happen when some of those recommendations are not followed due to the nature 
of construction.
Sometimes these changes may be due to value-engineering decisions communicated between the owner and contractor to reduce the project budget which, unfortunately, the design team may not know about until construction is underway. Other times, changes may occur due to incomplete shop drawings, unknown or unforeseen site conditions, construction sequencing, or supply chain issues which can lead to the construction team figuring it out and making changes at the time of installation.

Submittals process
During construction, the first place the design team will review information for the project is during the submittal process. Some of the most important submittals for the fenestration system include product data, lab test reports, and shop drawings. 
The most important and often most complex part for the fenestration submittal process is the shop drawings. The shop drawings should show all relevant information for the product, flashing, waterproofing, anchorage, and tie-ins to the surrounding construction (for coordination, even if it is not in the fenestration contractor’s scope).
All too often, a set of shop drawings will be submitted several times and will not include the surrounding detailing, making it difficult to accurately depict the adjacent construction and intent for how to drain incidental water that travels through the fenestration system. This is when the language included in the specifications in the design phase, requiring project-specific shop drawings and fully coordinated drawings including adjacent trades, can be referenced.
Usually, a submittal will require reviews from multiple parties, resulting in a rushed review if one or more parties are not on schedule. This can lead to problems with reviews being incomplete or submittals being approved, despite missing critical information, just to keep the project on schedule. 
Approving the shop drawings during the submittal process, with the mentality of figuring it out in the field, can lead to owners requesting the design team to complete the review, in order to not hold up production or ordering materials, both of which could result in costly delays. However, an incomplete shop drawing package, which is rushed through the review process, may ultimately cause a longer delay, due to possible window leaks discovered during field testing due to the original design details not being followed. 
Coming up with a solution to address the leakage and implementing it may cost the project more time than if the shop drawings were complete and followed from the start. Further, a ‘figure it out on the fly’ mentality can result in inadequate field details that can put the project at risk for condensation or water leakage and no paper trail to hold the correct party accountable.
There is a balance between holding firm on the correct detailing in a set of shop drawings, versus accepting a manufacturer’s typical package without any project-specific detailing to keep the project moving. When it comes to reviewing project submittals and shop drawings, the goal is to provide helpful and actionable reviews without derailing the project budget and schedule with extreme requests. A designer who takes an uncompromising position may end up causing more problems (e.g. delays, costs, or an owner who overrides them) than one who can identify and accept reasonable compromises to the design.

Window testing 
The proof test of all the thorough detailing in the design and reflected in the shop drawings is the first window test. This is when the fenestration is put to the test for air and water leakage. However, if conducting a performance mock-up (PMU), additional tests may also include structural components, such as inter-story drift and load testing or condensation resistance modeling. 
Ideally, this first test happens during a PMU, but for simple configurations using off-the-shelf (i.e. pre-tested) windows, the first test may be completed in situ. For field testing, only air and water leakage are tested. Another window test that may be done at, or ideally sometime before, the start of the construction phase is a lab test at the manufacturer’s facility to confirm that its internal assembly procedures results in a sound system, or that a particular manufacturing line is producing windows with the same performance as an originally tested sample.
Prior to testing any units on the job, a field-testing protocol inclusive of all the fenestration systems should be documented and agreed upon by the project team. This ensures everyone is on the same page, and that the contractor is aware of all testing requirements early in the construction phase. More importantly, it helps avoid disputes over test results 
if the passing criteria and test procedures are clearly laid out and agreed to by the relevant parties.
Laboratory testing is a hybrid solution between a fully constructed, project-specific PMU and in situ field testing. A lab test on the window unit can be done for semi-custom systems that may have a unique size or atypical framing/glazing conditions, but are based on a previously tested assembly, where the budget cannot accommodate a PMU; typically, these tests are done at the manufacturer’s facility. This would include air, water, and structural testing of the window unit.
Lab tests can be performed on units pulled directly off the assembly line as quality control (QC) during fenestration production to ensure the manufacturing, assembly, gasket, and sealant installation are all done properly prior to the windows arriving on site. This provides additional confidence that the windows will pass the field testing, or at least not have systemic manufacturing issues within the system.

Testing without all parties present 
Whenever the window testing is performed, ideally 
at the start of the project, all parties must be present to observe the window test, including the installer and manufacturer’s representative. When one of 
the parties is not there to witness the test, there are several problems that may arise if a leak is discovered during testing. 
If it is the fenestration system, and the manufacturer’s representative is not present, the installer may not understand the system well enough to diagnose the issue. If the installer is not present and there is a leak at a perimeter condition, then no remedial action or investigation into the leak can take place. If neither party is there and a leak occurs, it is the responsibility of the general contractor (usually after receiving the testing report) to communicate with both parties. 
However, if both the installer and manufacturer’s representative witness the leak during the test, the diagnosis and remediation can start immediately. If the unit can be repaired on the spot, a retest may be done while all parties and equipment are already on site. If the manufacturer needs to come out to visit the site, make the repairs, and then reschedule another test, the testing schedule will be extended, which sometimes does not agree with the project timeline.

Testing when installation is (almost) complete
Postponing testing until the window installation is almost complete happens far too often. If something is discovered during testing, or a leak occurs, what does this mean for the project? The first field window test should always be done during the early stages of installation. Even if there are no resultant leaks, it confirms the installation and production methods are sound.
Conversely, if there is a product leak or an installation issue, it is better to know early on, before more units from that production run (which may also include a potential systemic issue) or too many units with the same installation defect are installed. Referencing explicit language in the project specifications can ensure windows are tested at appropriate project milestones and can be incorporated into the project schedule.
Without any specific milestones listed, the contractor may set up the testing when it is most convenient for the project schedule, which is usually when the installation is complete, as to not cause a delay for the installer. However, it is in the best interest of the project and all parties to perform a test early on, before installation gets too far along, so any design, manufacturing, or installation issues can be caught before more work is performed and the cost of remediation becomes significant.

Inswing windows
If a project has elected to use inswing operable windows, there is a higher chance the window may leak under negative pressure when tested to ASTM E1105, Standard Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, and Curtain Walls, by Uniform or Cyclic Static Air Pressure Difference. Leaks are often discovered at the operable sash when testing due to negative pressure, pulling the window slightly open and pulling water through any minor gaps in the operable sash gaskets. This is certainly a window type where it is important for the manufacturer and installer to witness testing and make any adjustments to the window operability, should a leak occur. If improvements to operability are made, the design team must ensure the same protocols are done to all windows on the project to reduce the risk of leakage.

Non-domestic windows
As discussed in Part 1, quality standards and testing requirements are different for domestically made windows when compared to non-domestic windows (e.g. European-made). Leaks resulting from field testing a foreign-made window to U.S. standards can cause confusion on a project due to the “passing” criteria being different.
A non-domestic window also means it is far more difficult to make repairs to the windows in the event of a systemic failure as the manufacturer is not local to the site. If the windows passed their respective European (EN) or similar window testing standards, there is not much recourse with the manufacturer to address the leaks observed during the field testing to U.S. standards.
In some instances, with smaller non-domestic manufacturers, addressing leaks can be limited to additional sealant to frame joints, which are not required per the manufacturer’s installation instructions. This makes it even more difficult for the owner to hold the contractor responsible for these repairs since it is not standard protocol. These repairs may also affect the warranty provided by that manufacturer. Larger-scale non-domestic manufacturers have better support and repair options and may have local representatives to figure out the issue.

Unexpected site conditions  
Some level of change during construction or unexpected site conditions that vary from the design are inevitable. These can be due to owner-directed or contractor-led changes, or because of unforeseen conditions as the building is constructed. Another potential scenario is where a detail is installed, but it is not similar to the drawings, and the owner is now seeking the design team to come up with solutions—working with what is installed without compromising performance. This results in the design team needing to document the changes and how the field conditions differ from the design in case the change leads to a lower performance of previously approved systems or details. In some cases, it is also on the shoulders of the design team to work with the changes that occur and offer constructive recommendations that will still benefit the project. It is imperative for the design and construction teams to work together to detail surprise conditions effectively and efficiently.

Sill flashing 
One detail which is constantly under the threat of being value-engineered out of the project is the fenestration sill flashing. Ideally, the design includes a membrane sill pan with an upturned leg and end dams and a metal sill pan with an upturned leg, end dams, and fully soldered corners. When it is time to price this and the value-engineering process is underway for the fenestration systems, the metal sill pan is often the first thing to go. Common reasoning includes the installer saying they have not used sill pans in the past and have not had problems or the manufacturer not requiring a sill pan. Both arguments can sound very convincing to an owner who needs to reduce their budget, although owners who have experienced window leaks on past projects will be much more hesitant to make this change. The following will describe alternative options in the field in lieu of the metal sill pan flashing.

Membrane sill pan  
If the metal sill pan flashing is removed from scope due to cost issues or coordination concerns, then the next best option is a standalone sheet membrane sill pan with an upturned leg and end dams. This will still capture any leaks through the window system and prevent them from migrating to the interior as long as the inside corners are properly sealed. This installation is more favorable as the window installer or waterproofing professional can install the membrane sill pan without having to potentially introduce another trade (roofer/sheet metal worker). This can also be installed in the field and is easier to cut and fit in the rough opening compared to a sheet metal sill pan.

Fluid applied membrane sill pan
Another sill pan configuration often used is a fluid-applied membrane. This is common in exterior insulation finish systems (EIFS) as they regularly use a fluid-applied weather barrier as part of their proprietary system. A caveat to using fluid-applied membrane sill pan flashing is that its installation is very sensitive to workmanship, especially at the inside and outside corners of the sill, and in maintaining the required membrane thickness. 
Some sort of reinforcement, (e.g. fiberglass scrim) is a good option to help with durability and consistent thickness, as the mesh needs to be fully embedded and covered by the fluid-applied membrane. The back dam for these can also be made of plywood or continuous blocking, depending on the window attachment, with the membrane turned up onto that surface. Fluid-applied sill pan flashing is also common below window wall systems within a slab depression as discussed in Part 1. Here, the membrane will extend up the backside of the depression, creating a bathtub effect below the window wall system. In either case, all fasteners and penetrations going through the fluid-applied sill pan need to be sealed to prevent leaks to the interior.

Membrane wrapping rough opening
One of the most common sill flashing details in construction does not even include a dedicated sill pan. It simply consists of the sheet membrane (i.e. sheet membrane flashing) wrapping the rough opening of a punched window and terminating horizontally on the rough opening surface.
Contractors often suggest this as it is shown in the manufacturer’s typical detailing, with the addition of interior and exterior sealant joints (note: the waterproofing surrounding the fenestration is not warranted by the window manufacturer and therefore, they do not own that trade or responsibility). This relies only on an interior sealant joint to act as a back dam and prevent any water or air that leaks through the window from getting to the interior. This setup will likely pass an initial window water and air test, but sealant joints will not be as durable as a flashing (metal or membrane) and are more workmanship sensitive. Over time, the sealant may debond or become damaged, eventually allowing leaks to the interior. This method does not have any backup measure compared to other methods which include a dedicated sill pan below the entire window unit.

Fastening through sill
If the project makes it through design and into construction and a metal sill pan is installed as part of the fenestration installation, considerations need to be made to not have the window anchors fastened down through it. If the metal sill pan is part of the installation, an alternate method of window anchorage needs to be reviewed, approved, and ultimately installed independent of the horizontal sill surface to maintain the integrity of the sill pan flashing. It is recommended the window be anchored through the vertical leg of the sill frame to avoid horizontal penetrations, with tapered shims for dead load support.
In a typical curtain wall system, anchors are installed in the dry zone, therefore not requiring a sill pan to extend the full depth of the system. Installing flashing inboard of the wet zone provides no benefit, both because of the lack of exposure to water and the multiple penetrations that occur at each vertical mullion anchor. The sill pan should be made an integral part of the drainage system and does not need to extend beyond the glazing pocket.
 
Storefront tie-in
As discussed in Part 1, one of the most challenging transitions is between a storefront system and foundation waterproofing. This transition is often difficult due to site conditions and damage that occurs during typical construction activities. If a curb is not installed, the eventual tie-in will be significantly more difficult, given foundation waterproofing will be covered up at the time the storefront is installed. 
If there is no curb, some removal of fill may be required to install a transition membrane between the storefront system and foundation waterproofing. Foundation waterproofing that is damaged during construction needs to be repaired prior to the storefront installation (whether at curb or at grade). In addition, if the transition is at grade, care needs to be taken to protect all repairs. To avoid damage to the foundation waterproofing, temporary protection should be installed to protect the waterproofing until the storefront tie-in can be done and the storefront system is installed, and then backfilling can take place.

Conclusion 
All the effort put into the design means nothing if it is not built properly. How unforeseen circumstances are handled during construction can make or break a project’s success—whether this is a part of the sill flashing details 
or the testing procedures. Fenestration systems and their associated installations remain a hotly contested item for new buildings and require a healthy mix of field experience, testing knowledge, and sometimes creative detailing to accommodate changes that occur that stray away from the original design, in order to still achieve the desired aesthetic and performance.	CS
Figure 1
Lab test of a window unit.
Photos courtesy Simpson, Gumpertz & Heger Inc. (SGH)
Figure 2
Window testing in progress.
Figure 3
Leakage at inswing window.
Figure 4
 Leakage at non-domestic window.
Figure 5
Fluid-applied membrane sill pan.
Figure 6
Membrane in 
rough opening.
Figure 7
Fastening through sill.
Additional Information
Authors
Bradford J. Antes, PE, is a consulting engineer within the building technology division in the Simpson, Gumpertz & Heger Inc. (SGH) New York office. He is experienced in the design and investigation of new and existing building enclosure systems. He regularly collaborates with owners, architects, and contractors during design and construction of the building enclosure systems. He can be reached at bjantes@sgh.com.

Erin E. Regan, PE, is a senior consulting engineer within the building technology division in the Simpson, Gumpertz & Heger Inc. (SGH) New York office. She focuses on building energy analysis, finite element analysis, roof design, window and curtain wall systems, and below-grade waterproofing. Regan has experience in design, investigation, rehabilitation, commissioning, and construction administration of historic and contemporary buildings. She can be reached at eeregan@sgh.com.

Key Takeaways
Just about every new commercial and residential building constructed includes some level of fenestration as part of the building enclosure. Fenestration is often designed as a key architectural feature and tends to be one of the first design elements to be value engineered. Acting as the weatherproofing, thermal and air barrier, and acoustics barrier, fenestration systems receive significant attention in both design and construction. It is highly scrutinized as windows, doors, and curtain walls are common sources of air/water leakage or related problems. The construction of a building is when the designer’s vision comes to reality. A large part of the design often revolves around the fenestration system of the building. As discussed in Part 1 of this article in the August issue of The Construction Specifier, these are often scrutinized during the design and construction phases. This second article discusses the impact of when the details change from the design phase into the construction phase. Oftentimes, these changes will compromise the performance of the building and/or fenestration system if not addressed properly.

MasterFormat No.
08 10 00–Doors and Frames
08 40 00−Entrances, Storefronts, and Curtain Walls
08 50 00–Windows

UniFormat No.
B20–Exterior Vertical Enclosures
B2010–Exterior Walls
B2050–Exterior Doors and Grilles

Keywords
Division 08
Curtain wall
Doors
Fenestration system
Glass
Glazing
Windows
Figure 8
Sill flashing at curtain wall extending beyond glazing pocket.
Figure 9
Damaged foundation waterproofing at grade.
Classifieds
failures
Kick-out Flashings: Diversion Ahead
Wood-framed residential buildings rely on the continuity of weather barrier and roofing assemblies to protect structural materials from decay. Three-dimensional, complex intersections can pose design and construction challenges. An important but often overlooked detail is where roof gutters meet rising walls, requiring a kick-out flashing to divert water traveling down the edge of the roof into the gutter, especially when using materials such as wood, stucco, cement board, or vinyl siding.
Many industry groups recommend kick-out flashings, and various prefabricated options for three-sided flashings are available; however, they are not consistently used where needed. Two recent projects show the severe consequences when this critical component is omitted, leading to significant structural deterioration only a few years after construction.
The first project was a stucco-clad residential building in the Midwest. At various gable-end locations, the walls rise above the roof as a low parapet wall, and the hanging gutter assembly terminates in line with the inside face of the parapet (Figure 1). No diverter flashing was installed, and water was able to penetrate the top edge of the stucco at this corner and migrate into the wood-framed wall. The owner remained unaware of the issue due to closed-cell spray foam insulation in the stud spaces. The deterioration of the oriented strand board (OSB) sheathing became widespread before it was discovered, necessitating extensive repairs and the replacement of large areas of stucco.
The second example was an apartment complex in the South. Various cement board cladding profiles were used, with each unit having a projecting bay that abuts an adjacent roof with a hanging gutter (Figure 2). At this key transition, the lack of a diverter flashing allowed water from the lower roof to bypass the gutter’s end and penetrate the cement board cladding and trim. Within a few years, severe damage had affected the wood-framed structure, leading to the replacement of all cladding at the perpendicular wall and structural repairs to the wood sheathing and framing (Figure 3).
In both cases, the addition of a kick-out flashing at the gutter termination would have mitigated most, if not all, of the water infiltration, avoiding extensive and disruptive structural repairs. Within less than 10 years after initial construction, both projects experienced considerable damage to 
the wood structure, demonstrating the critical importance of the kick-out flashing detail for the performance of the wall and roof assemblies.	CS
Figure 1
Kenneth Itle, AIA, is an architect and associate principal with Wiss, Janney, Elstner Associates (WJE) in Northbrook, Illinois, specializing in historic preservation. He can be reached at kitle@wje.com.
At the gable end parapet walls, the gutter terminated in line with the wall’s inside plane, lacking flashing to prevent water from flowing past the gutter. While exterior staining on the stucco was evident, more concerning was the structural damage to the underlying wood framing.
Photos courtesy Wiss, Janney, Elstner Associates (WJE)
Figure 2
Where hanging gutters met the perpendicular building wall, no flashing was provided, and the gutter’s end cap was butted against the cement board trim and siding.
Figure 3
Leakage at the gutter/wall interface caused oriented strand board (OSB) sheathing and wood 2x wall framing deterioration, necessitating structural repairs to restore the building’s frame.
The opinions expressed in Failures are based on the authors’ experiences and do not necessarily reflect that of The Construction Specifier or CSI.