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ASTM Standards for Correctional Facilities

There have been numerous standards sponsored by ASTM Committee F-33 on Detention and Correctional Facilities.

Familiarity and being able to adhere to these standards is a must. They

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not only cover testing procedures and degree of detention, but also assemblies and fastening methods that must be incorporated into the design and construction. These tests are also required in order for a certain detention system to provide the proper physical barriers, which are crucial for this building type.

The following is a list of the present active standards consistently used and identified in the project specifications:

  • ASTM A627-03 (2011), Standard Test Methods for Tool-resisting Steel Bars, Flats, and Shapes for Detention and Correctional Facilities;
  • ASTM F1450-12a, Standard Test Methods for Hollow Metal Swinging Door Assemblies for Detention and Correctional Facilities;
  • ASTM F1592-12, Standard Test Methods for Detention Hollow Metal Vision Systems;
  • ASTM F1915-05 (2012), Standard Test Methods for Glazing for Detention Facilities; and
  • ASTM F2322-12, Standard Test Methods for Physical Assault on Vertical Fixed Barriers for Detention and Correctional Facilities.

Additional standard testing methods are being proposed that will add essential overall detention requirements to these facilities. The following are under consideration:

  • ASTM WK9092, Standard Test Methods for Physical Assault on Overhead Horizontal Fixed Barriers for Detention and Correctional Facilities;
  • ASTM WK14507, Guide for Selection of Security Fasteners for Detention and Correctional Facilities; and
  • ASTM WK25858, New Test Method for Anchor Systems Used for Detention Hollow Metal Vision Systems and Door Assemblies.

Knowledge of these standards is essential for the proper design and construction of these facilities.

To read the full article, click here.

Specifying Successful Systems for Detention Facilities

Photo © Bo Parker

Photo © Bo Parker

by Ruben Caro, CSI

The construction of detention and correctional facilities, as well as holding cells in courthouses, is not the same as for other building types. Some of the more complex of these facilities, due to the magnitude of program space requirements, can be more than 55,740 m2 (600,000 sf) (Figure 1). In addition to standard construction materials and practice, these buildings are designed with a multitude of special materials and systems, known collectively as ‘detention equipment.’

The materials and systems—doors, frames, and windows—are specifically fabricated and produced to ensure public safety is not compromised. Additional security measures are provided by the inclusion of electronic security equipment systems. The coordination of the detention equipment installation with other building systems and components can be complex and arduous.

Integration of materials and building systems must be carefully constructed and coordinated to ensure not only the confinement of inmates to designated secure areas, but also to make certain officers, administrative staff, and visitors are safe. Knowledge of how these systems are installed, operate, and function is a must for both the design team and the contractors and subcontractors responsible for the actual construction. There are numerous detention equipment components and systems requiring contractors to be proactive during the submittal and construction phases to ensure the proper operational objectives and procedures determined by the design team and clients are met.

These buildings are constructed to varying degrees of detention and complexity requirements. They could range from a minimum security facility to a super-max—each having different operational objectives and security requirements. They are carefully reviewed and predetermined by the design team and the clients during the project’s design phase.

Types of detention perimeters, building construction, detention equipment, and electronic and communication systems must be extensively discussed and carefully specified. A specialist in this type of construction, is an invaluable member of the project team. Detention equipment contractors (DECs) can be made responsible for the control and accountability of providing and installing the detention equipment as delineated in the construction documents.

This large correctional facility is nearly 55,740 m2 (600,000 sf). Photo © Mark’s Photo Professional Photography and Services. Photo courtesy GRW Engineers

This large correctional facility is nearly 55,740 m2 (600,000 sf). Photo © Mark’s Photo Professional
Photography and Services. Photo courtesy GRW Engineers

Rebar placed through hollow metal frame anchor for additional strength. Photos courtesy Ricci Greene Associates

Rebar placed through hollow metal frame anchor for additional strength. Photos courtesy Ricci Greene Associates

 

 

 

 

 

 

 

 

Specifying the detention equipment
A contractor who has knowledge of how detention and correctional facilities are constructed and operate should be a prerequisite for any firm seeking to bid on these building types. A qualified DEC has the expertise to handle the high degree of coordination necessary for undertaking such facilities.

Due diligence in the preparation of specifications is a must for detention equipment contractors working on these projects. Qualifications must be carefully researched and stated in the project specifications. A DEC firm should have at least five years of proven experience in projects of the same size and magnitude as the project currently being constructed. Simply speaking, if a 1000-bed facility is being built, a firm with only a couple years of experience in building only police precincts with five to 10 cells should not qualify. Additionally, firms should have no less than five completed projects in operation for more than five years. A list of prequalified DECs should be added to the specifications. Any that are not prequalified but still wishing to bid on the project must submit evidence they meet the qualifications of specifications before bidding.

Undeniably, due to the building type complexity, the DEC plays an important role in the facility’s construction. Certain minimum construction tolerance and sequencing must be adhered to for the proper installation, completion, and successful operation of the detention systems and building. They must be in constant communication with the general contractor and other subcontractors, exchanging information concerning the scope of work for the construction package. Being proactive during the construction phase is a must.

Security grille within ductwork in a concrete masonry wall (CMU) wall.

Security grille within ductwork in a concrete masonry wall (CMU) wall.

A heavy gauge cover will have to be installed in order to enclose the conduit and junction box not installed within the CMU.

A heavy gauge cover will have to be installed in order to enclose the conduit and junction box not installed within the CMU.

Coordination, sequencing, and scheduling
Coordination, sequencing, and scheduling are an essential part of the construction phase. An integral part of the interior and exterior security walls, certain components must be installed in accordance to ASTM standards to ensure they meet the rigorous testing required for the proper performance of the product. (See “ASTM Standards for Correctional Facilities.”)

Some of the components require appurtenances be delivered to the field before installation. For instance, steel plates must be in place before the installation of spilt frames and/or security bar grilles for proper welding. To maintain the project’s critical path, these steel plates must be delivered to the field for installation and proper anchorage during the security wall’s construction, whether masonry or poured-in-place concrete. Other important coordination issues that must be in place before the security walls are items such as detention door and window frames, if they are not split-frame types. The proper installation and anchorage of these frames is paramount to the effectiveness of the security wall openings to ensure ASTM compliance (Figure 2).

One of the most critical coordination items is integration between the electrical systems, security electronic systems, detention hollow metal doors, door frames, and vision panels, as well as detention hardware. To ensure inmates do not have access to any of the electrical conduits, they must be placed within the concrete masonry unit (CMU) walls. Additionally, careful coordination between the DEC and the security electronic contractor must be maintained to ensure the proper installation of the wires to allow for the detention hardware connection such as locks and door monitoring devices. These items all require special attention.

Informational submittals should include coordination drawings that indicate all interrelated and interfacing of detention components, security electronics, and surrounding construction. Additionally, the scope of work items should be reviewed by the DEC before submitting to the design team for their review.

Yet another organizational task performed by the DEC is project administration. Information concerning the project development of the detention equipment delivery and installation must be maintained and related to the contractor and subcontractors. This is accomplished by means of schedules, meetings, and reports outlining all detention equipment construction activities.

An installed security hollow metal frame, with security mesh and stainless steel counter in non-contact visitation. [CREDIT] Photo courtesy Maximum Security Products

An installed security hollow metal frame, with security mesh and stainless steel counter in non-contact visitation. Photo courtesy Maximum Security Products

This dayroom has numerous detention equipment components and systems that must be installed and coordinated by the Detention Equipment Contractor (DEC). Photo courtesy Peter Krasnow

This dayroom has numerous detention equipment components and systems that must be installed and coordinated by the Detention Equipment Contractor (DEC). Photo courtesy Peter Krasnow

Installation of detention components and systems
There are many different building systems installed in a correctional facility necessitating the need for penetration prevention and vandalism by the inmates, which fall under the scope of work for the DEC.1 Some of the products are:

  • security access doors and frames;
  • detention doors and frames;
  • detention windows;
  • detention hardware;
  • detention and/or security glass;
  • security grilles;
  • security ceiling assemblies; and
  • detention furnishings.

Architectural components must be anchored in such a manner they meet the ASTM standard ‘tested assembly’ for the detention grades and impact requirements identified in the construction documents. Detention furnishings (e.g. cell bunks, decks, and shelves found in the cells), and dayroom furnishings must be installed in such a manner to prevent inmates from removing and destroying these items or using them for self-harm.2 Materials part of the detention barriers, such as the hollow metal, security grilles, and security ceilings must be properly anchored to the security walls and structure, to ensure the security perimeter is not compromised.

In addition to the installation of various architectural components, the necessity to coordinate with the security electronics subcontractor is an absolute necessity. The installation of each one of these components must be properly installed to ensure the central control station operates correctly. Some of the items requiring coordination are:

  • access control;
  • intrusion detection; and
  • detention monitoring and control systems.

To be certain all the detention equipment requirements operate as designed, a field quality control (QC) report should be prepared and included as part of the submittals process.

Material knowledge
Most of the architectural components employed for a correctional facility are constructed using materials that will form an effective detention barrier. Walls are constructed with reinforced masonry, for example. Doors and windows are fabricated using heavy-gauge metal and internally reinforced to ensure confinement and prevent escape.

Ceilings within inmate-occupied areas must be constructed of durable materials. Door hardware should be a special type with heavy internal components, some of which are electrically operated. All components must pass rigorous testing in order to maintain a secure environment.

This photo shows a conduit waiting to be enclosed within the CMU walls. Photo courtesy Ricci Greene Associates

This photo shows a conduit waiting to be enclosed within the CMU walls. Photo courtesy Ricci Greene Associates

This photo shows the inside of a control station. Photo courtesy HTK Architects and KMD Consulting Architects

This photo shows the inside of a control station. Photo courtesy HTK Architects and KMD Consulting Architects

Turnkey operation
The ultimate goal of having a detention equipment contractor is to produce a project with ‘turnkey operation.’ A DEC will assume a single-source responsibility for all the detention equipment’s scope of work concerning the coordination, installation, and operation. Therefore, if there are any problems during construction, items on the ‘punch list,’ or possible call backs for the detention equipment scope of work, it will be the DEC’s ultimate responsibility to determine what course of action must be taken to rectify any problems. This, within itself, could eliminate the possibility of countless hours during the construction process of determining the party responsible for any potential omissions or problems.

As part of the overall turnkey operation, the DEC could be required to provide demonstrations in their scope of work. This will allow the owner’s personnel to attend training sessions on how to adjust, operate, and maintain the equipment installed by the DEC. The number of personnel that will attend the demonstration should be discussed with the owner, and then included in the specification and location.

Specification requirements
The specification for the project’s detention equipment portion needs to be carefully prepared. The section identifying the requirements of the DEC must include the scope of work, minimum qualifications, and all responsibilities. The scope of work should summarize all the materials and products incorporated into the project. Each material should have an individual section indicating all the requirements and ASTM designations for the product and degree of security when applicable.

Conclusion
As detention and correctional facilities become more complex and state-of-the-art, the need for a qualified team of professionals, with the knowledge on how to design and construct one of these facilities, is a must. Delivering a building with such high expectations is by no means an easy task. The construction team is faced with constructing a building with numerous systems that must be totally integrated and perform without problems.

The DEC becomes responsible for making certain the key components essential to the successful operation of the facility are correctly installed in accordance with the construction documents and industry standards. Not using an experienced DEC may jeopardize the intended function and operation of the facility. The necessity to have an experienced DEC with knowledge and expertise cannot be understated.

Notes
1 For a deeper look at glazing, see this author’s article in the August 2009 issue of The Construction Specifier, “Transparent Security: Selecting Glazing for Detention and Correctional Facilities.” (back to top)
2 For more, see The Construction Specifier articles, “Specifying Windows for Behavioral Healthcare Projects,” by Lisa May (February 2013) and “Preventing Jail Suicide with Better Design” by Randall Atlas, PhD, AIA, CPP (March 2009). (back to top)

Ruben Caro, CSI, has an associate’s degree in construction technology and studied architecture at New York Institute of Technology. He has been involved with the preparation of the construction documents and construction administration for more than 30 correctional and detention facilities and holding cell areas for courthouses across the United Sates. As RC Consulting for Architects, he provides technical services to the architectural and engineering communities. He has been part of technical committees assisting in the preparation of standard details and specifications for correctional facilities and providing quality control/assurance (QA/QC) reviews for a variety of building types. Caro can be reached at rcaro@nyc.rr.com.

This photo shows the inside of a control station. Photo courtesy HTK Architects and KMD Consulting Architects

Stay in Control: Specifying building automation systems for cost savings

The Sheraton Phoenix Downtown Hotel uses a BACnet (data communication protocol for building automation and control networks) compatible building automation system (BAS) for energy savings and occupant comfort. All images courtesy Alerton

The Sheraton Phoenix Downtown Hotel uses a BACnet (data communication protocol for building automation and control networks) compatible building automation system (BAS) for energy savings and occupant comfort. All images courtesy Alerton

by Kevin Callahan

In the same way today’s mobile phones have capabilities far beyond traditional telephones, modern building automation systems (BAS) have added many benefits transcending their original roots in heating and cooling control.

Today’s BAS help facility professionals obtain greater efficiencies from numerous building systems, including:

  • lighting;
  • security/access control;
  • fire and life safety;
  • elevators and escalators;
  • irrigation; and
  • HVAC.

An appropriately equipped BAS can also meet specialized needs such as emergency and critical systems monitoring in hospitals, and tenant billing for leased spaces in office buildings.

With rising energy costs, an increasing number of building owners and operators are including BAS in new buildings, as well as in retrofits. More than half of U.S. buildings larger than 9290 m2 (100,000 sf) have a BAS installed.1 The market is forecast to grow between seven and nine percent from 2014 through 2017, for a net growth of more than 40 percent above the 2012 level, according to researchers at IHS Technology. A key driver of this “/>growth is a projected eight percent annual increase in retail electricity prices through 2020.2

Building automation systems software with an intuitive, graphical interface is simple to use and helps reduce or eliminate the need to train staff on operating the system.

Building automation systems software with an intuitive, graphical interface is simple to use and helps reduce or eliminate the need to train staff on operating the system.

Vendors now offer BAS wall units with the sophistication and elegance of smartphones.

Vendors now offer BAS wall units with the sophistication and elegance of smartphones.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BAS benefits
Automation can reduce a building’s total energy consumption between five and 15 percent annually because of more efficient control of various building systems. Savings can surpass 30 percent annually in older or poorly maintained buildings. Additionally, a BAS can help reduce building maintenance costs by alerting facility managers when equipment is operating outside of specifications and therefore might be at risk of failure.3

The facilities management and planning department at Boston University outlines these and other BAS benefits as follows:

  • control and diagnose what is going on in buildings;
  • create a graphic representation of building settings;
  • see and fix programmatic problems quickly;
  • generate reports usable by management for tracking energy consumption and the operational status;
  • schedule and control temperature settings for increased energy savings; and
  • collect and store data on energy consumption over long periods.4

Project examples
From commercial offices and government buildings, to schools and hospitals, energy saving benefits can be achieved in virtually every type of project.

Commercial offices
Seattle’s Columbia Center is the tallest building in the Pacific Northwest, with 76 stories and 142,900 m2 (1,538,000 sf) of total floor area. A BAS integrates all the building’s HVAC systems—including 2200 heat pumps, ventilation and exhaust fans, boilers, heat exchangers, cooling towers, and circulation pumps.

The building is one of the city’s largest electricity-consumers, using approximately 111,600,000 megajoules (31,000 megawatt hours) annually. However, with an energy-efficient BAS, it consumes only about 13 percent more electricity than the next highest building electricity consumer in the city, despite having 50 percent more floor area.

Government buildings
In 2009, the state of California opened a new central utility plant in Sacramento to heat and cool many office buildings throughout the city. The 7246-m2 (78,000-sf) facility supplies chilled water and steam to 23 buildings that total 510,967 m2 (5,500,000 sf) of space. One BAS monitors and controls the central utility plant, while another BAS serves the 23 buildings. The BAS for the chiller plant enables it to operate at about half the energy use of a traditional chiller plant.

K–12 schools
At Irvington High School in Fremont, California, the local school district installed a BAS as part of a set of energy-saving actions that reduced the school’s energy consumption by approximately one-third, which equates to annual savings of about $10,000. Much of the savings result from data provided by the BAS, which allows the district to shed energy loads under a peak pricing program offered by Pacific Gas and Electric (PG&E).

Universities
Eastern Connecticut State University in Willimantic installed a BAS in the Windham Street Apartments—a 30-year old, nine-story residence hall housing 224 students. The BAS reduced the building’s annual electricity consumption by 234,000 megajoules (65 megawatt hours), for a 12 percent energy cost savings. The university achieved these savings despite also adding cooling to the building, when previously it only had heating.

Hospitals
As part of a facility expansion and upgrade project, New York University Medical Center in Manhattan retrofitted outdated building controls in 13 buildings totaling 278,710 m2 (3,000,000 sf). The new BAS enables staff to manage the campus and outlying facilities through a single system, for better energy efficiency. Additionally, trend logs generated by the system illustrate how closely actual room temperatures match the set point, which allow staff to closely control the environment for patient comfort, health, and safety.

This wall unit includes subtle light-emitting diodes (LEDs) along its bottom so users can see at a glance when the HVAC system is in heating or cooling mode.

This wall unit includes subtle light-emitting diodes (LEDs) along its bottom so users can see at a glance when the HVAC system is in heating or cooling mode.

A properly equipped building automation system allows higher education facility managers to centrally monitor and control multiple buildings across campus, including at campuses in other cities.

A properly equipped building automation system allows higher education facility managers to centrally monitor and control multiple buildings across campus, including at campuses in other cities.

 

 

 

 

 

 

 

 

 

Maximizing BAS benefits
To receive the most benefits from implementing a BAS, it is important to focus on analytics and building commissioning.

Analytics for high-performance building operations
A BAS is a powerful tool for gathering data needed to make informed decisions on energy management. To maximize its cost-saving potential, one must pay attention to the data the system is generating and to use it to make strategic energy usage choices—this is the concept of building analytics. In short, a BAS is not a tool to install then simply turn the heating, cooling, and lights on and off according to a set schedule.

Analytics is about ensuring a building’s managers have enough of the right data being collected for analysis. It is important to use analytics to ensure any BAS programs created to reduce energy—or any other objective—are actually accomplishing what was intended. An appropriately equipped BAS allows the facility staff to collect and store data so there is history to compare it to.

For example, analytics can help the facility managers ensure they are not heating and cooling the same spaces at the same time, as well as confirm lights are on for a purpose, rather than solely for convenience. Analytics provide a way to determine whether energy is being wasted, and where.

A BAS delivery agent (i.e. manufacturer, dealer, or consultant) can be a valuable resource for determining what analytics are needed to meet the building owner or operator’s specific goals.

Building commissioning
A sometimes overlooked benefit of BAS is the system can be used to simplify the commissioning process, for both new construction and building retrofits. Some BAS include programs to verify HVAC and other building systems are performing according to the design intent. The wall sensors of an advanced BAS enable technicians to access the system throughout the building to conduct tests and verify environmental conditions, without carrying separate diagnostic tools—the result is faster and more accurate performance verification. Proper building commissioning is crucial to achieve efficient building operations.

“The operating costs of a commissioned building range from eight to 20 percent below that of a non-commissioned building,” reports the U.S. Environmental Protection Agency’s (EPA’s) Building Commissioning Guidelines. Additionally, it is noted commissioning costs typically range from only 0.5 to 1.5 percent of construction costs, and reduce operating costs throughout the building’s life.5

For initial commissioning, the building systems as a whole need to be commissioned at the time of construction to ensure they are operating as designed and their integration with the BAS is correct. This helps ensure the building is operated appropriately to satisfy its occupants’ needs. As a basic example, in an office building the HVAC and lighting would need to be commissioned for controlling the indoor environment while the building is in use during standard working hours, whereas in a warehouse the utility needs would be different because the building likely is not in use at all times.

An even more critical action than initial commissioning is the periodic re-commissioning of a building to ensure the systems are still serving the occupants’ requirements. Additionally, because systems can degrade over time, it is important to tune them up for optimal performance.

The Russellville School District in Arkansas uses its building automation system to monitor food and beverage freezers and coolers in its facilities.

The Russellville School District in Arkansas uses its building automation system to monitor food and beverage freezers and coolers in its facilities.

The BAS for this Sacramento central plant enables it to operate at about half the energy use of a traditional chiller plant.

The BAS for this Sacramento central plant
enables it to operate at about half the
energy use of a traditional chiller plant.

 

 

 

 

 

 

 

 

 

Specifying a BAS
Design professionals can select from numerous BAS. Several important features to consider when choosing the system include:

  • degree of interoperability of the control module;
  • software’s ease of use;
  • security measures; and
  • usability and design style of the wall sensors.

Control module
The control module is the central processing unit of a BAS. Until the mid-1990s, the communication protocols these units used to interface with building equipment were proprietary to each manufacturer. As a result, various components would not work together unless using a single manufacturer’s equipment.

In 1987, the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) began to actively develop a standard protocol to enable a wide range of controls and equipment to work together (i.e. interoperable). In 1995, it published that standard—known as BACnet (data communication protocol for building automation and control networks), which has since been widely adopted by BAS and building equipment manufacturers.6

“Capabilities vital to BA [building automation] applications were built into BACnet from the beginning in order to ensure the highest possible level of interoperability in an environment possibly involving multiple vendors and multiple types of building systems,” according to a report from the Institute of Electrical and Electronics Engineers (IEEE).7

Such interoperability helps ensure a BAS can adapt to emerging technologies and evolving building occupancy needs, without having to start over.

BACnet is unparalleled in providing integration of the disparate systems within a building, including HVAC, lighting, access, irrigation, utility monitoring, and metering. For example, instead of having separate systems and building occupancy schedules for a building’s lighting and HVAC systems, BACnet allows for clean integration of both systems so the scheduling is from one source.

By analogy, a BAS using BACnet is like a symphony orchestra, wherein the control module is the conductor providing direction to the numerous different building systems (i.e. individual musicians) using a common protocol (i.e. BACnet) they all understand (i.e. movements of the baton, hand gestures, and facial expressions). Although a violin is different from a trumpet, the conductor’s common direction enables them to work together to produce beautiful music.

Some BAS control modules incorporate multiple protocols (BACnet and Tridium’s Niagara Framework) for even greater interoperability than relying on a single protocol. Other protocols, like LonTalk, are also available.

Software—ease of use
Learning a new software program often involves hours of training, and/or trial and error, both of which can mean thousands of dollars in staff time. This is especially true for specialized programs such as those included with a BAS.

However, a key differentiator among BAS software is how intuitive and simple it is to learn. Although many programs now employ a graphical interface, rather than text entry alone, ease of use varies. The most sophisticated BAS software includes simple schematics clearly identifying the equipment throughout a building, and its operating status (e.g. heating, cooling). Such programs enable even novice users to readily interpret the environmental or other monitored conditions anywhere in the building, and to adjust the appropriate building system, as needed.

Another simplifying feature introduced with BAS software this year is use of HTML5. With the latest HTML format, facility professionals can access the BAS remotely from any Internet-connected device, without the time and compatibility hassles of downloading a third-party’s software plug-in. As a result of this wide system accessibility, a technician could troubleshoot a piece of equipment from the field, or a facility manager could make necessary system adjustments when traveling away from the office.

Security measures
As large online security breaches have come to light in recent years, building professionals are increasingly asking about how to secure their Internet-facing building BAS. For the building design team, three cyber security best practices will improve the security of a building automation system against unauthorized access:

  • ensure network isolation by deploying behind a firewall or on a virtual private network (VPN);
  • use the security features built into the BAS; and
  • configure the system securely by disabling guest user accounts and using strong password protection protocols.

Since BAS are networked throughout buildings (and often to the Internet) to enable remote access by facility managers, it is crucial to isolate the automation system from other internal networks, such as financial management or credit card processing. To accomplish this, the building design team should involve the client’s information technology (IT) experts early in the BAS selection process, as this is a specialized aspect of specification writing and usually requires acquisition and installation of additional hardware dedicated to protecting the building networks from both external and internal attacks. This hardware (e.g. firewalls, VPN routers) is extremely important and needs to be state-of-the art to combat the evolving means of attacking networks.

For the BAS itself, a control module with multiple Ethernet ports is an important security feature that helps to isolate the network. Such control modules physically separate the building systems from connections to outside networks. It is also important to specify a BAS that can be configured to use signed certificates for web connections to prevent ‘man-in-the-middle’ attacks when users log into the server. Beyond network connections, another security feature built into some BAS is a system that does not automatically execute code from USB thumb drives. This helps prevent a BAS user from inadvertently introducing a virus or other malware into the BAS.

Building automation systems are installed throughout the world, including in this Turkey skyscraper.

Building automation systems are installed throughout the world, including in this Turkey skyscraper.

Securely configuring the system once it is installed is important, so it is critical to ensure the BAS has a security manual that provides information on how to best accomplish this task, and then make sure the contractor follows those guidelines. Additionally, the BAS integrator should have documented the processes and procedures they followed for designing and implementing the system, which will be a crucial reference for the building owner.

Cyber-security threats change frequently, and need constant vigilance. Anyone who touches the system should be trained at a minimum in cyber-security awareness, and ideally should be certified to securely deploy vendor systems. It is also important they are aware of the building owner’s cyber security standards and practices. Building owners should also keep in mind the BAS will require maintenance, which might include patches to the operating system, and anti-virus software updates and management.

Strong cyber-security is a three-legged stool comprising:

  • manufacturers and software vendors, who continually evaluate and improve the security of products;
  • contractors and installers, who ensure their customers’ systems are properly and securely installed; and
  • end-users, who build and maintain a culture of security within their organizations through the use of cyber security best practices.

Wall sensors
As with BAS software, a key differentiator among wall sensors is how easy they are to use—important for both facility staff and building occupants. Vendors have become increasingly sophisticated with designing wall sensors. One unit introduced in 2014 was designed according to what users are accustomed to seeing with their smartphones. For example, the unit includes easy-to-interpret icons for temperature control, and clear navigation tools to see interior and exterior temperatures, relative humidity (RH), and carbon dioxide (CO2) levels. To enable building occupants to see the HVAC operating condition from across the room, the unit has color light-emitting diode (LED) lights along its bottom to indicate either heating (red) or cooling (blue).

In terms of design styling, in commercial buildings, thermostats have often been visually ‘boxy.’ Now, manufacturers are focusing on aesthetics of these units in addition to performance. Some units are designed to be sharp and crisp with a low profile to complement modern architectural styling. Building owners and occupants have even gone so far as to say such units are ‘sexy.’ At any rate, a thermostat does not necessarily need to be a clunky box hidden around a corner, but can be a sleek addition to a room or hallway.

Conclusion
A properly equipped and configured automation system can save building owners tens of thousands of dollars or more on annual energy costs. Additionally, some facility professionals use the systems to save costs in other ways. For example, in Russellville, Arkansas, the school district officials use their BAS to monitor food and beverage freezers and coolers in schools throughout the area. The system sets off an alarm if temperatures begin to go out of range, which enables the facility staff to take prompt action and thereby avoid costly and wasteful spoilage.

To maximize the cost savings, when specifying an automation system it is important to think about each component—control module, software, and wall sensors—and consider how easy they are to use, and how flexible they are to changing technologies and building user needs.

Notes
1 For more, see “Building Automation Systems” at fpl.bizenergyadvisor.com. (back to top)
2 Visit “U.S. Building Automation Market Primed for Growth,” at technology.ihs.com. (back to top)
3 See note 1. (back to top)
4 See www.bu.edu/facilities/what-we-do/buildings/building-automation/ for more. (back to top)
5 Visit “EPA Building Commissioning Guidelines” at www.epa.gov. (back to top)
6 See “BACnet overview” at www.bacnet.org. (back to top)
7 See “Communication Systems for Building Automation and Control,” by Kastner, Neugschwandtner, Soucek, and Newman, Institute of Electrical and Electronics Engineers (IEEE), at www.researchgate.net. (back to top)

Kevin Callahan is a product marketing manager for Alerton, a Honeywell business. He has 38 years of experience in the building control technologies field, including control systems design and commissioning, facilities management, and user training. Callahan can be reached at kevin.callahan@honeywell.com.

What Do You Mean By ‘Polyurethane?’

All photos courtesy Quest Construction Products

All photos courtesy Quest Construction Products

by Steven Heinje

‘Polyurethane’ is not a useful specification term on its own. It is akin to saying, “I want a form of transportation,” as opposed to something much more specific, like, “I want a four-cylinder sedan.” Getting to the point where a manufacturer or supplier will only offer products meeting a specific project’s needs will require more precise and non-proprietary terminology that makes performance the outcome.

The term ‘polyurethane’ simply means many repeated units of urethane, much in the same vernacular as ‘polypropylene’ or ‘polyester.’ Often, these coatings are referred to as ‘urethanes,’ similar to the way terms like epoxy or acrylic are employed. They are all polymers of the key reactive or function group. The urethane group confers many of the traits of a polyurethane—most notably, adhesion—in much the same way most acrylic paints share ultraviolet (UV) resistance.

Typically, a Technical Data Sheet (TDS) for a polyurethane coating will include a long list of tests, often with some impressive numbers. A few of these will find their way into various specifications. Perhaps they will include a benchmark product and later a few ‘equals’ will be added—such a specification is representative of the standard of care for using a polyurethane in today’s construction marketplace.

This article seeks to add some background and a few key details so specifiers understand what type of product is actually being offered, what are its intrinsic performance attributes, and whether it truly has adequate offsets. (The focus is on coatings; polyurethane foams for insulation are outside this article’s scope.) A little chemistry is required to fully grasp the concepts, but the desired outcome is for design professionals to know what questions to ask and ultimately to be able to write better specifications and avoid failures.

This 100 percent aliphatic polyurethane has exceptional ultraviolet (UV) resistance needed to hold this deep blue color on the very visible roof of Marin County Civic Center (San Rafael, California).

This 100 percent aliphatic polyurethane has exceptional ultraviolet (UV) resistance needed to hold this deep blue color on the very visible roof of Marin County Civic Center (San Rafael, California).

The fl exibility and hydrophobicity of a specifi c polyurethane was chosen over an epoxy alternative for this plant near Shanghai.

The flexibility and hydrophobicity of a specific polyurethane was chosen over an epoxy alternative for this plant near Shanghai.

 

 

 

 

 

 

 

 

 

 

Why use a polyurethane?
Polyurethanes have the broadest range of any product group: they can be soft as a baby’s skin or hard enough to be machined and tooled. Some may yellow and chalk severely, while others are among the most light-stable coatings available. Chemical resistance, including water resistance, is similarly variable.

Polyurethanes combine toughness and flexibility—a unifying trait that comes from the urethane linkage itself. Urethanes form a molecular spring based on the intense attraction of the urethane groups to each other, so they form hard domains within a softer and more flexible matrix. This link is flexible, and more importantly, it is recoverable; this leads to products that combine high tensile and high elongation, and even maintain high hardness and flexibility at low temperatures (down to −30C [−22 F]) and up into higher temperatures (75 C [167 F]). This feature allows them to be used as high-performance coatings, as well as durable foams.

In most cases, another key trait is adhesion. As a rule, urethanes bond to various substrates, often better than styrene-ethylene/butylene-styrene (SEBS), acrylic, silicone, and even butyl. Adhesion is important to consider because maintenance coatings are often used over unknown, older surfaces, or even multiple surfaces giving the contractor or specifier a good reason to specify a polyurethane above other more-restrictive options.

Beyond toughness and flexibility, all other traits—gloss retention and resistance against abrasion, water, UV, solvents, and acids/alkalines—depend on the ‘backbone,’ as defined later in this article. Application traits are another mixed bag, relying on the nature of the curing chemistry, which is referred to as the ‘curative.’ With the appropriate formulation, there is no other class of product that has a better balance of adhesion, UV resistance, abrasion resistance, and flexibility. By contrast, epoxies are too hard, acrylics exhibit poor abrasion performance, and silicones show relatively weak physical properties as a product class. There are few properties a urethane cannot be formulated to achieve.

However, high heat resistance is an overall weakness. Below 75 C is urethane territory: applications include roofing and most industrial and sealant applications. While some specialty urethane products can perform long-term above 100 C (212 F), these high temperature applications typically require silicone and epoxy products.

This polyurethane system has exceptional fi re retardancy for use on sloped roofs.

This polyurethane system has exceptional fire retardancy for use on sloped roofs.

A low-toxicity polyurethane coating was used on the structural concrete for this wastewater treatment plant.

A low-toxicity polyurethane coating was used on the structural concrete for this wastewater treatment plant.

Types of urethanes: Varnish to airplane components
ASTM D16, Standard Terminology for Paint, Related Coatings, Materials, and Applications, defines six types of polyurethanes.

Type I: One-package (1K) urethane alkyds1
Like all alkyds, or ‘oil-based paints,’ these cure by oxidation of a drying oil and solvent evaporation. They are used as varnishes, floor finishes, and abrasion-resistant paints. They do not cure by a urethane reaction. In this category, the oil-based paint becomes a platform for using an aromatic polyurethane to enhance the former’s performance. (This is also done with acrylics and epoxies, but in those cases they are not referred to as ‘acrylics’ or ‘epoxies’ in the way varnishes and paints are called ‘polyurethanes.’) Looking at toxicity, they have no free isocyanate, which means they are no more toxic than other alkyds.

Type II: 1K moisture-cured paints and industrial coatings
This important type is often employed in high-performance thin film (i.e. 25 to 75-µm [1 to 3-mil]) floor and industrial paints. This class also includes higher-build (i.e. 0.5 to 2-mm [0.02 to 0.08-in.]) elastomerics such as those described in ASTM D6947/D6947M, Standard Specification for Liquid-applied Moisture-cured Polyurethane Coating Used in Spray Polyurethane Foam Roofing System. This class uses atmospheric moisture to act as the curative, allowing them to be reactive 1K products. This can cause problems and limitations along with advantages.

Unreacted isocyanates, such as those found in Type II urethanes, react with many other chemical species found in wood, metal, epoxies, and acrylics—this gives these resins exceptional adhesion. Moisture cures are often high in solids, relatively low in viscosity, and have moderate volatile organic compound (VOC) content. When they cure, however, they release a lot of carbon dioxide (CO2) gas. Consequently, Type IIs used in flooring and corrosion protection need to be applied thinly, so not too much gas is evolved from curing. Elastomerics have a lower concentration of isocyanate, allowing them to tolerate thicker films before they exhibit the same foaming problems.

The moisture cures require experienced contractors because bubbles, foaming, and blisters present high risks. Most of these Type II products are aromatic, which means they will yellow. ASTM D6947 moisture-cured coatings used in roofing are typically blended with asphalt. These sealants and coatings are not UV-stable, but when used for roof details and crack-bridging or caulk applications at thicknesses approaching 2 mm, they can weather for more than a decade.

Type III: 1K heat/oven-cured elastomers and industrial coatings
These elastomerics are generally not used as maintenance coatings. Instead, they are reserved for industrial products, car bumpers, or technical fabrics for sportswear.

Type IV: Two-package (2K) products
These materials are similar to the Type IIs; in fact, some may simply be a Type II product offered with a liquid curative. This eliminates the need to rely on atmospheric moisture to cure the resin, and it avoids the release of CO2 gas. They generally have higher solids content and moderate pot-life in the range of an hour. They are still prone to problems with CO2 gas when used carelessly.

As an example of diversity within polyurethanes, there is a Type IV industrial that uses a pure aliphatic resin cut in solvent and is cured as a polyurea—it achieves 34,475 kPa (5000 psi) tensile and 400 percent elongation, is easily sprayed, and has a two-hour pot-life. Further, as a polyurea, it is not affected by moisture at all.

Another case is a sub-group used in roofing and flooring: moisture-triggered (oxazolidine) cured aliphatic urethanes. They are described in ASTM D7311/D7311M-10, Standard Specification for Liquid-applied, Single-pack, Moisture-triggered, Aliphatic Polyurethane Roofing Membrane. This is another example of a specific urethane chemistry not prone to gassing even in thick films due to the special chemistry of the oxazolidine curative.

Type V: 2K urethanes
Important commercial products used in industrial applications (and to a lesser extent in roofing), these urethanes are typically used in a 1:1 volume ratio with plural component equipment.2

Most are 100-percent-solids elastomers or coatings. A sub-group, called ridged polyurethanes, is specifically devised for tank, pipe, and petrochemical use. Some have enough pot-life to be rolled or squeegeed, but most require plural component equipment, in-line heat, and will cure within minutes. Also within this group are the so called polyureas, which represent another approach of avoiding the issue of atmospheric moisture and CO2 gassing by using curatives that produce an almost instantaneous reaction. These require the use of an impingement mixing plural component spray gun. The reality is most polyureas are hybrids of both polyurea and polyurethane reactions and should be treated as another flavor of the Type V polyurethanes.3

Type VI: One-package solvent-based urethane lacquers
VOC restrictions have largely eliminated this type of polyurethane from commerce, but they may still be found in adhesive applications. (Water-based urethanes, or ‘urethane latex,’ could also be included here.) Often blended with acrylic emulsified resins, these are finding use in floor coatings, primers, and other high-performance and specialty applications.

There are a few words of caution related to the use of the term ‘urethane,’ which can be a marketing selling point. There are examples where a urethane material has been used to thicken an acrylic latex product, which is then illegitimately branded as a urethane. In other cases, a low level of a legitimate urethane resin may be added for marketing purposes. A urethane’s key properties—being flexible and tough—does not ‘play well’ with the high levels of fillers typically included in vinyl, styrene-acrylic, and acrylic paints. If a product has a high density (i.e. > 1.4 g/L [11.7 lb/gal]), then it is functionally not a urethane.

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For this underground concrete storage tank, a polyurethane able to resist alkaline patching materials was required.

For this underground concrete storage tank, a  polyurethane able to resist alkaline patching materials was required.

Form follows function: A primer on the chemistry
With so many different types of polyurethanes, a specifier has many factors to consider in selecting the right product for the job. The three key components to understanding what a polyurethane provides in terms of performance are:

  • isocyanate used;
  • curing chemistry; and
  • backbone.

For most specifiers, the best understood difference between types is aliphatic (highly UV-stable) versus aromatic (less UV-stable) urethanes, which is based on the type of ‘iso’ they have. The curing chemistry is generally recognized and understood in terms of application by the experienced contractor.

Less obvious is how the curing chemistry also has an impact on the film or membrane’s long-term performance. Most specifiers understand urethane varnish acts and bonds like a varnish. They know 2Ks and moisture cures tend to have good adhesion (due to unreacted isocyanate) and they know ‘polyureas’ require specific equipment and are not very moisture-sensitive. However, less visible to specifiers, is the ‘backbone.’

The backbone is the softer portion that forms a matrix around the urethane groups. The backbone is itself a polymer, and so it bring its own set of strengths and weaknesses. For example, if the backbone is not UV-stable, even an aliphatic urethane may not exhibit good weathering. This level of detail gets lost in technical data and specifications; it is rarely adequately captured by the test reports—and this is where things can go wrong.

While the list of materials shown in Figure 1 covers most products, it is not comprehensive—there are more than 300 potential combinations, and each could perform quite differently. Further, this list does not take into account the fact coatings are compounded products that allow blending of these materials in various ratios. Fortunately, a much smaller subset sees use as coatings.

Figure 2 lists polymer backbones representing at least 95 percent of the commercial volume of coatings and their typical application. Drilling down a little deeper, the resistance properties in Figure 3 make product selection clearer and more specific. For example, an aliphatic acrylic is a step above most polyester-based urethanes, and so they find use in automotive applications. Castor is a bit weak physically, but its water-resistance and low viscosity mean it can be used to good effect in a 100 percent solids adhesive.

Castor backbones can be found blended with other agents to achieve a lower VOC. This is significant because increasingly restrictive VOC rules favor materials inherently lower in viscosity. One hears more about polyethers, castor, aspartic esters, and polyetheramines (as polyureas) being used to meet VOC restrictions. Often, the backbones that require the most solvent are the toughest. Materials including polytetrahydrofuran (PTHF) and acrylic polyols are seeing less use. The material polycaprolactone, which once might have found use in a high-end roofing product, will now be used as a substitute for an acrylic in a less cost-sensitive industrial paint application as it moves up the VOC and cost ladder. Products are changing in response to regulation, and achieving lower VOC content is linked to changes in the backbone and curative chemistry.

For this reason, one should always specify with reference to the backbone. When a certain product worked as a low-build industrial finish for metal, and was an aliphatic acrylic, then “aliphatic with acrylic backbone” should be accordingly specified. It is important not to overlook referencing the material safety data sheet (MSDS) as a possible source for this information.

At the same time, a specifier will be forced to accept compromises to meet VOC restrictions; he or she must be careful about these inevitable substitutions.

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Urethanes in systems
Another area where urethanes excel is to serve roles within coating systems to meet specific challenges. A common roofing practice is to use an aromatic primer or base coat with an aliphatic top coat. These pairings can also be done with other properties.

Today, a manufacturer might use a primer based on aromatic isocyanate and castor that will have lower costs, reduced VOC content, and excellent corrosion resistance, and then pair it with an impact-resistant, aliphatic polyester top coat that meets a lower VOC rule—together, they cover the needs.

A traditional combination is to use an epoxy primer and an aliphatic urethane surface coat. This works because the epoxy primer typically has unreacted amines available to the isocyanate for reaction—a single molecule between the primer and surface coat. The point is these products work as a system, and substitutions that are not specific cannot be expected to perform the same.

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Specifications, testing, and what data sheets do not reveal
In the paint industry, there is little standardization and few requirements for third-party testing. In roofing, there are more specific protocols, but not many for polyurethanes. When looking at a technical data sheet, the reality is the values shown—for example, “250% elongation per ASTM D412”—may state a method, but are not well-defined and often lack sufficient context for the public bid process and apples-to-apples comparisons.

Although an ASTM test is cited, the values reported could have been derived in many ways and under different conditions. For example, manufacturers could run the same test methods under two conditions to get optimal values for tensile and elongation. This is not to suggest TDSs are all useless or deceptive, but if one were to compare products between manufacturers based on independent testing and technical data, the information may be nebulous. Third-party testing organizations tend to maintain a more consistent practice and should be requested.

The more accurate way to compare data is to reference a specific protocol. In roofing, these would be:

  • ASTM D6497, Standard Guide for Mechanical Attachment of Geomembrane to Penetrations or Structures;
  • ASTM D7311; or
  • ASTM WK9048, Elastomeric Coatings Used in Spray Polyurethane Foam Systems (the current designation for the new classification due to be published next year).

These material standards include specific test methods: they define how the test is run, how the sample is cured, how thick it is, and other parameters allowing the data to be used for commercial comparisons.

Another hard truth about testing is it is often not demanding. In many cases, procedures are run without comparison to some type of control or to unfavorable conditions; consequently, they are unlikely to be run until failure. For example, it is not unlikely for a urethane to sport a D412 tensile of 13.8 MPa (2000 psi). That same product tested after immersion in water for 28 days might only have a tensile of 2758 kPa (400 psi), but this would not be reported on the TDS. Unfortunately, the post-immersion tension value is the more appropriate one for a deck coating. Another product may note a 6895 kPa (1000 psi), but may have a 8274 kPa (1200 psi) after 28 days of immersion. In short, traditional paint testing does not predict service life.

Most troubling is how this data gets used in commerce. A bid may be lost for $0.20 on a basis of $30 per gallon, which is less than one percent of the total. This process rests on the assumption testing values are the most relevant factor, and they allow for direct comparison between different products. The tests are not nearly as precise as the accounting, and worse, the tests typically are not run in the same manner. If the product is only described as a ‘polyurethane,’ the chances are good one will be picking a product based on only the tensile value under ASTM D412, Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers.

There are many other important product attributes that need to be considered beyond this limited view—for example, ASTM D471, Standard Test Method for Rubber Property: Effect of Liquids, which tests the effects of water, is singularly useful. It is important to bear in mind any number without context is not necessarily good information and a low test value is not reason enough to reject a product with a long track record of performance. “Or equal” substitutions in specifications involving polyurethanes are intrinsically risky.

Construction specification documentation needs to be better for this group of products. Using the ASTM D412 test for tensile/elongation as an example, instead of accepting:

ASTM D412 > 23.8 N/mm (2000 psi)

one should call for:

ASTM D412 Tensile initial and after 1000 hours of ASTM D4798 weathering at 0.35 watts/m2 @340 nm.

Part of a material standard can be called out even when it does not quite fit, such as ASTM D6497. When the application is critical, a ratio—rather than a minimum value—should be specified. This example adds specific parameters to the test method, along with a ratio:

less that 30% loss of the original value when run per ASTM D-6497.

Another approach is the addition of a basic chemical description, such as:

aliphatic polyurethane using polyurea curative, IPDI and polyether chemistry per ASTM D6497.

Conclusion
Polyurethanes are a useful and necessary part of coatings technology, but they are often misunderstood—the confusion can ultimately lead to failures. Specifying a polyurethane by its backbone chemistry is the most important and necessary step to ensure the right product is being chosen for the job.

Before selecting a product, specifiers must ask themselves what does it really need to do, where do these products go wrong or how do they fail, and are the properties that play into these failures really reported?

Knowing which tests and standardized test methods, or ratios, to use for a specific application can provide the same benefit: a specification that links the track record and expected service life with the specific parameters required for the application. The best approach, however, is not a long list of random test methods, but rather specific testing protocols such as those cited in this article that give the type of comparable data needed for use in open bids.

Notes
1 ‘One-package’ (also written as 1K for ‘Kompent,’ the traditional abbreviation) means the entire product is a single can that does not require mixing in or another catalyst, agent, or Part B. (back to top)
2 The SSPC: The Society for Protective Coatings has information on the various types of Type V urethanes. Molded parts can even be made with these products. Search www.sspc.org for more data. (back to top)
3 Design professionals can learn about these products from the Polyurea Development Association (PDA). Visit www.pda-online.org. (back to top)

Steven Heinje is the technical service manager for Quest Construction Products, headquartered in Phoenix, Arizona. He has degrees in biology and chemistry, along with an MBA. Heinje has 30 years of experience in roof coatings, specializing in acrylic elastomers and urethane coatings. He is a vice president and board member of the Roof Coatings Manufacturers Association (RCMA), and leads several task groups in ASTM D08 roofing, as well as maintaining active memberships with American Society for Quality (ASQ), RCI, Reflective Roof Coatings Institute (RRCI), and the American Chemical Society (ACS). Heinje can be reached at heinje@quest-cp.com.

Using Temperature to Control Condensation in Cold Climates

Photo © BigStockPhoto/Pavel Losevsky

Photo © BigStockPhoto/Pavel Losevsky

by Daniel Tempas

Designers have been concerned about condensation in walls for decades. Since the mid-1970s, the greater amounts of insulation specified in the building envelope has increased the likelihood for condensation somewhere in the assembly. Many articles have been written over the years describing the physics of the problem and, for the vast majority of the time, there has been a laser-like focus on one solution.

Initially, water vapor diffusion was seen as the likely culprit for condensation problems and designers and consultants spent hours running and analyzing wall assemblies using the ‘profile’ (or ‘dewpoint’) method (Figure 1). With such analyses came the concept the wall system should be tuned for maximum condensation resistance by altering or selecting the appropriate permeability of the wall components.

The rule of thumb became to place low-permeability materials/retarders on the wall’s warm side, and higher permeability materials on the cold side (Figure 2). In this fashion, the designer strove to make it difficult for water vapor to enter the wall (lessening water’s ability to condense in the wall) and easy for water vapor to leave the wall (drying out any water that still managed to get inside). Manufacturers began to introduce high-permeability air barriers, water barriers, and sheathings along with ‘smart’ vapor retarders for the warm side of the wall.

This low-perm/high-perm strategy reveals two goals in wall design: the efforts to decrease condensation potential and increase drying potential. Reducing condensation potential is fairly well-understood but increasing drying potential is a less commonly sought after goal. Both are important for robust wall design.

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Problems with permeability
While all this sounds good, it was not necessarily preventing condensation problems. There are some basic facts about permeability designers need to understand to get a better grasp on not only controlling condensation, but general wall design.

Fact 1: If a material’s temperature gets low enough, water vapor will condense on or in it, regardless of how high its permeability.
This is something to keep in mind in cold climates. This author has seen both fiberglass batts and high-perm air barriers with ice encrusted on their surfaces. When a material gets cold, its effective permeability dramatically drops. High permeability is useless at low temperatures. In other words, condensation is a temperature-related phenomenon.

Fact 2: Cold water dries slower than warm water, no matter how permeable the shell surrounding it.
Increasing a wall assembly’s drying potential is an important and valuable goal. However, water at lower temperatures will take a long time to dry because the related evaporation rate is slow. Simply put, robust drying potential cannot be achieved in the layers of a wall assembly that are at low temperatures.

For example, one can consider a puddle on a sidewalk (Figure 3). How long does it take that puddle to dry? If the ambient temperature is 32 C (90 F), it will not take long at all, perhaps only several minutes. However, when the ambient temperature is only 4 C (40 F), the puddle might take hours or even days to evaporate. This is an example of the profound effect temperature has on evaporation rate.

Fact 3: Air movement transports far more water vapor than diffusion.
This is something that has been understood by building scientists for quite some time, and has been filtering into the design community for decades. However, the subtle ramifications of this knowledge are just now finding their way into the world at large. The fact air movement is so dominant in water vapor transport (and subsequent condensation) means any vapor retarder must work either as, or in conjunction with, a near perfect air barrier.

Any installation flaw or penetration in the air/vapor barrier on the higher temperature side will result in an amount of air leakage that will overwhelm any planned benefit from that barrier’s diffusion characteristics. This will result in a much greater potential for condensation in or on any layer that is at a low enough temperature for condensation to occur. Additionally, this means diffusion-based analyses of the wall system are rendered moot.

Fact 4: Water vapor does not move from areas of higher temperature to lower temperature.
Thinking this is the only direction water vapor flows is incorrect. Water vapor moves from areas of high concentration to low concentration, regardless of the direction of heat flow. This is an important concept when it comes to understanding drying verses condensation.

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Temperature to the rescue
After considering these four facts regarding water physics, it would seem there is a great deal of confusion and trouble regarding wall design. The manipulation of material water vapor permeabilities in a wall design cannot achieve a truly robust assembly. What can be done?

‘Temperature’ is the common thread running through the facts regarding water vapor condensation in wall assemblies. A wall assembly’s temperature profile plays a critical role in the ability to resist condensation and promote drying. This is not an unknown concept, of course—a quick search of building science literature will yield the occasional article mentioning the importance of the temperature profile. The problem is temperature profile manipulation is far down the list of the wall designer’s methods for creating a more robust wall. It is seen as unimportant when in reality, it is the opposite.

As much of the wall insulation as possible should be placed on the outbound side of the assembly (Figure 3). This is easy to do whether the base wall is metal stud, concrete masonry unit (CMU), or poured concrete. In cold-weather conditions, this will warm the entire interior wall, changing the temperature profile with far-reaching consequences (Figure 4).

For example, designing a wall assembly so more of the components will be in the higher temperature portion of the wall profile significantly reduces the potential for condensation. Not every part of a wall is equally sensitive to exposure to moisture. A standard rainscreen veneer wall assembly (Figure 5) is not sensitive to water, as it must be exposed to the elements on a constant basis. The support elements for the veneer are also not sensitive to water—they are in the drainage space behind the veneer and quite a bit of water reaches that space. As for the insulation layer on which the supports rest, it too must be moisture-resistant for the same reason. If condensation can be forced to happen only around components immune to water, then the wall design is completely robust in its resistance.

Designing a wall assembly so more of the components will be in the higher temperature portion of the wall temperature profile also significantly increases the drying potential for any water that does find its way into the wall. Referring back to the puddle example, higher temperatures means much higher drying rates. Combine the greater drying temperature with the longer drying time and one has a wall with a drying potential increased by an order of magnitude or more.

The importance of temperature modification to improve walls systems can be better understood when considering that both condensation and drying are two-step processes (Figure 6):

  • movement of water vapor to or from the point of condensation or drying; and
  • actual phase change of water from the vapor phase to the liquid phase (condensation), or vice versa (drying).

No matter how rapidly water vapor is transported to a given location in a wall assembly, either by the slow process of diffusion or the rapid process of air infiltration, condensation will not take place if the temperature of that location is high enough. This is also true in the drying process. No matter how easy it is for water vapor to exit a given location in a wall assembly, either by the slow process of diffusion or the rapid process of air infiltration, drying will not take place when the temperature of that location is too low. Again, temperature plays a critical role in the condensation and drying processes in a wall assembly. Altering the temperature profile of a wall assembly through judicious placement of materials is an effective method to control these processes.

The aforementioned Fact 4 about the true nature of the movement of water vapor makes it clear even when the exterior sheathing/insulation is completely impermeable, the drying potential of this wall is much greater than the previous design and the condensation potential is much lower. Since it is at a temperature near to that of the interior, any water in the stud cavity will have a much higher evaporation rate, which means a much higher drying rate. Also, it will easily dry to the building interior.

Proper placement of the right insulation negates the need for a vapor retarder. Why worry about water vapor getting into the wall when most of it is at a temperature far too high for condensation to take place? If the insulation has been well-chosen, any condensation taking place toward the exterior of the building will be minute and meaningless. Besides, the stud cavity needs to dry to the interior, and an interior vapor retarder will only get in the way.

The overall robustness one gains from placing most wall components in the highest temperature part of the temperature profile overwhelms almost every other condensation/drying consideration in the wall design.

Using the temperature profile of a wall as part of the design process leads to a wall that is easier to build. Relying on permeability (to alter water vapor diffusion rates) in the design process for a wall assembly results in a dependency not only on material properties, but also on the quality of installation.

A critical part of any vapor retarder (or air barrier) is its continuity. Any flaw in the installation process of that air/vapor retarder that results in breaches of its continuity heavily compromises its ability to reduce condensation potential. This would include unrepaired construction damage or poorly sealed seams. Even normal penetrations in the wall assembly, like outlets and switches, present opportunities for discontinuity in the air barrier/vapor retarder.

On the other hand, manipulation of the temperature profile of a wall assembly is only about positioning the right amount of insulation in the right location in the wall. A board of insulation is far more robust that film of plastic, making insulation continuity far easier to achieve. Also, the outside of the wall typically has far fewer penetrations, making them far easier to handle.

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Conclusion
Designing wall assemblies by adding or altering the permeabilities of the wall components is an artifact of the limited analysis tools relying on investigation of water vapor movement via diffusion. Such walls gain only mild improvements in condensation resistance and, more importantly, drying potential. To create a truly robust wall system with the greatest condensation resistance and drying potential, designers must look at altering the temperature profile of the wall assembly by moving insulation as far as possible to the wall’s exterior.

This does not mean one should no longer think about, or design with, the permeability of materials in mind, of course. Rather, it means the water permeability analysis/profile part of design efforts should be relegated to the proper place in the design consideration hierarchy: behind the wall temperature profile design effort.

Daniel Tempas is a building envelope technical service representative for Dow Building Solutions; he has held technical and engineering positions at the Dow Chemical Company for almost 30 years. Tempas is a (HERS) rater, a Leadership in Energy and Environmental Design (LEED) Green Associate, and a member of the RESNET Training Committee. He has also been a member of ASTM, Exterior Insulation and Finishing Systems Industry Members Association (EIMA), and Building Thermal Envelope Coordinating Council (BTECC). Tempas can be reached atdtemp@dow.com.