Tag Archives: 07 24 00−Exterior Insulation and Finish Systems

Energy-efficient Building with EIFS

Photo courtesy Sto Corp.

Photos courtesy Sto Corp.

by Michael DeLaura, LEED AP BD + C

Among the efforts to create more energy-efficient and sustainable buildings, there has been a shift toward lightweight cladding options for the exterior. One such product is exterior insulation and finish systems (EIFS).

EIFS provide a number of features and benefits including an air barrier, continuous insulation (ci), and an aesthetic finish. The assemblies trace their roots back to early 1950s Germany. Originally designed for commercial use, EIFS made their way into the residential market in Europe a decade later. Introduced into the United States in 1969, the product has evolved over the last 45 years. It gained popularity in the 1970s as a result of higher utility costs and the need to improve energy efficiency.

This shows the application/spraying of a fluid-applied air and moisture barrier, providing superior protection against air and moisture intrusion in various applications.

This shows the application/spraying of a fluid-applied air and moisture barrier, providing superior protection against air and moisture intrusion in various applications.

The original product consisted of an adhesive applied with a notched trowel to form vertical ribbons that attach the expanded polystyrene (EPS) insulation board to the substrate. The EPS was then rasped or sanded before application of a base coat; which then had a fiberglass mesh embedded into it. The mesh is embedded into the basecoat over the entire surface of the EPS for reinforcement of the system The final layer consisted of a decorative acrylic finish coat. The finish was available in a sand, swirl, or freeform texture, and offered in various colors. EIFS became a popular cladding since features such as curves, quoins, arches, reveals, and accents were easy and economical to fabricate and install. It offered a new look and an energy-efficient way to wrap the outside of the building providing continuous insulation and lowering heating and cooling costs.

EPS insulation can be installed up to 304 mm (12 in.) thick to achieve significantly higher R-values than other claddings, provided proper fire tests have been done with 304-mm thick EPS. Placing the insulation outbound of the sheathing eliminates thermal bridging, which, in some cases, can reduce the effective R-value between the stud insulation by nearly 50 percent.

Recent code revisions to the 2012 International Building Code (IBC) require use of continuous insulation outbound of the sheathing, making EIFS suitable for a building’s exterior. These code changes, along with technology advancements and introduction of the Leadership in Energy and Environmental Design (LEED) program, have also contributed to the development of the assemblies.

A recent U.S. Department of Energy (DOE) and EIFS Industry Members Association (EIMA) study conducted by the Oak Ridge National Laboratory (ORNL) shows the system can perform better than stucco, concrete block, fiber cement siding, and brick in energy efficiency, moisture intrusion, and temperature control. EIFS with fluid-applied air barrier and continuous insulation increases flexibility, while a drainage plane controls moisture intrusion and temperature. This can make it a suitable choice for mixed, coastal, and hot and humid climates.1

EIFS can contribute to LEED Points in the following categories:

  • Energy & Atmosphere (EA), Credit 1, Optimize Energy Performance;
  • Materials & Resources (MR), Credit 1, Building Reuse;
  • MR Credit 2, Construction Waste Management;
  • MR Credit 4, Recycled Content;
  • MR Credit 5, Regional Materials; and
  • Indoor Environmental Quality (EQ), Credit 4.2, Low-emitting Materials.

EIFS evolve with air/moisture barriers
Over the last 15 years, one of the biggest changes in EIFS assemblies has been the introduction of a fluid-applied air/moisture barrier installed over the substrate. This offers the option to use one continuous barrier over the substrate regardless of the cladding. The fluid-applied air/moisture barrier is seamless, and provides protection against moisture intrusion, water leakage, mold, and mildew.

The Homewood Suites project in Nashville, Tennessee employed an exterior cladding combination of natural limestone on the first floor and an exterior insulation and finish systems (EIFS) on the upper floors featuring an air barrier, continuous insulation designed to replicate the look of traditional brick and natural limestone.

The Homewood Suites project in Nashville, Tennessee employed an exterior cladding combination of natural limestone on the first floor and an exterior insulation and finish systems (EIFS) on the upper floors featuring an air barrier, continuous insulation designed to replicate the look of traditional brick and natural limestone.

EIFS allow design flexibility, as the structure can be waterproofed with various claddings. The cladding itself was once thought to be the building’s weatherproof layer. One advantage of a fluid-applied air barrier is the building can be protected from inclement weather once the windows and doors are installed. All EIFS adhesives are compatible with fluid-applied air barriers.

The installation of the cladding can take place up to six months after the building has been dried in. This refers to the substrate and connections having a continuous seal. The exterior cladding, whether brick or EIFS, become a decorative feature.

However, with advancements in building science, cladding is now more of a decorative feature, and the air barrier and water-resistive barrier (WRB) the substrate protection and weatherproofing. Air barriers also lower heating and cooling cost and increase occupant comfort. Then help maintain constant temperature by controlling air leaks through the wall assembly, which can contribute to heating and cooling loss.

The National Institute of Standards and Technology (NIST) study, “Investigation of the impact of Commercial Building Envelope Airtightness on HVAC Energy Use,” confirmed air barriers promote energy savings from 30 to 40 percent for heating climates and 10 to 15 percent for cooling climates. An air barrier can be vapor-permeable or impermeable, depending on the climate and location. Impermeable air barriers are typically used in colder climates, and permeable air barriers are often used in warmer climates. The changes to the newest version of LEED will offer additional points in the Energy and Atmosphere (EA) category for air barrier and building envelope testing.

EIFS panelization
As more efficient building procedures developed, contractors started building with EIFS panels. Since panels are typically manufactured in an enclosed shop or warehouse, benefits include:

  • increased quality control;
  • highly engineered panels and connections;
  • no interruption during inclement weather;
  • improved productivity;
  • little or no scaffolding required; and
  • reduced safety risk in comparison to stick-built construction.

The panels consist of metal studs, sheathing, air barrier, adhesive, EPS insulation, basecoat, mesh, and finish. One of the major advantages of panelization is construction schedule compression since the panels can be manufactured offsite and installed as soon as the project site is ready. Panelization can significantly reduce the construction schedule as compared to stick-built buildings.

Two different EIFS finishes are displayed here. The small medallion in the left corner shows a smooth finish to replicate limestone. The finish in the rest of the sample is shown in gray and and a contrasting red color. This finish consists of a ceramic bead in a clear acrylic binder for abuse resistant interior and exterior applications. Photo courtesy Southern Stucco

Two different EIFS finishes are displayed here. The small medallion in the left corner shows a smooth finish to replicate limestone. The finish in the rest of the sample is shown in gray and a contrasting red color. This finish consists of a ceramic bead in a clear acrylic binder for abuse resistant interior and exterior applications. Photo courtesy Southern Stucco

Since the units are manufactured offsite, wall panels can be built while the floors are being poured. Once the floors are completed, panels can be installed using a tower crane onsite, reducing the entire construction schedule by 30 to 40 percent.

Panels can be either structural or non-structural. Depending on the type of construction and building height, both types may be installed on new or existing structures. The structural panel assembly consists of the following components:

  • metal stud frame;
  • exterior sheathing;
  • air barrier;
  • adhesive;
  • insulation;
  • basecoat;
  • mesh; and
  • finish.

The panels are taken to the site on a flatbed trailer; they tend to be sized to allow for economical transportation from the fabricator. They are attached to the substrate by being welded or bolted to a clip or anchor placed in the concrete when it is poured. Panels are usually installed using a tower crane already onsite. A double silicone sealant joint is typically placed between the panels to tie them together and provide a watertight exterior cladding assembly.

The non-structural panel assembly consists of:

  • EPS insulation;
  • optional air barrier;
  • basecoat;
  • mesh; and
  • finish.

The EPS insulation has a furring channel embedded in the foam with a sleeve on each end to allow for a mechanical attachment to the substrate. This type of panel is attached to the substrate with a mechanical and adhesive attachment. The lightweight panel type can be installed on virtually any type of project; an advantage in its use is there is no need to modify an existing structure for retrofits and remodels. This panel uses a ship-lap design as one method for joining the panels. A silicone sealant joint can also be placed between the panels to provide a watertight exterior cladding assembly. Non-structural panels are ideally suited for existing low-rise buildings where disruption of the existing business is critical.

This photo shows a brick stencil applied to the substrate prior to the application of the EIFS finish. The stencil is removed before the finish dries to replicate the look of traditional brick. Photos courtesy Sto Corp.

This photo shows a brick stencil applied to the substrate prior to the application of the EIFS finish. The stencil is removed before the finish dries to replicate the look of traditional brick. Photos courtesy Sto Corp.

A closed-cell backer rod is required, and the typical width for an expansion joint is 19 mm (3/4 in.). A 22.2-mm (7/8-in.) closed-cell backer rod is installed in a 19-mm wide joint—the specification for the preferred width to depth ratio is 2:1. The sealant joint would have an hour-glass configuration and the backer rod helps to maintain the correct ratio.

The decision to use panels should begin early in the stages of design development. The design professional must determine whether the project is suited for prefabrication. However, not all areas of the project will be panelized—there may be some areas where there is an in-place application depending on tie-ins and connections.

A case study on panelization
The Mayfair Renaissance, a 36-story tower built in downtown Atlanta, was constructed to match an existing precast concrete tower onsite. The panels were built offsite in a controlled environment in Lexington, Kentucky. The controlled environment enhanced quality control, and no days were lost due to inclement weather. Since the panels were manufactured offsite, there were fewer disturbances to the site and reduced construction waste. The lightweight panels reduced the amount of structural steel as compared to the precast, and the panels were also more energy-efficient with a blanket of continuous insulation to reduce heating and cooling costs. Panelization has been a popular method for construction in the hotel industry over the last 30 years since the reduced construction time allows the owner to receive revenue more quickly when compared to a stick-built project.

Specialty finishes
A new development in the EIFS industry was the introduction of finishes with super-hydrophobic self-cleaning properties, rinsing clean with rainfall. A major advantage of the finish is its high resistance to mold, mildew, and algae which reduces maintenance costs. The finish is offered in various colors and textures. A smooth coating is also available to apply over existing EIFS surfaces and other exterior substrates.

EIFS offer specialty finishes that replicate brick, granite, limestone, metal panels, and precast. These finishes are easier to install and can require fewer specialty trades than traditional cladding materials. Specialty finishes offer a cost-effective aesthetic option, increase energy efficiency, and moisture protection. The finishes offer an identical look to the natural cladding, but are less heavy, allowing the creation of a lighter building.

Deflection criteria is the extent to which a material can bend or flex during its lifetime. A cladding with a deflection of L/240 is more flexible than a cladding with a deflection of L/360, L/480, or L/600. Claddings with a higher deflection criteria require a heavier structure to support the weight of the cladding and are less flexible. In other words, since EIFS requires deflection criteria of L/240, and other claddings such as brick and limestone need L/600, an owner can also save on the cost of the structural steel.

The Homewood Suites project in Nashville, Tennessee (currently under construction), is using an EIFS brick and limestone finish. The project was over-budget with traditional brick and natural limestone due to the cladding’s cost and the structure required to hold its weight. Specialty finishes replicating the look of limestone are gaining in popularity due to the cost savings and the ease of application.

The exterior cladding on the Norton Road project is an EIFS System featuring an air barrier, continuous insulation, and a finish replicating the look of natural limestone.

The exterior cladding on the Norton Road project is an EIFS System featuring an air barrier, continuous insulation, and a finish replicating the look of natural limestone.

Construction Specifier - Dec. 2013 - Norton - 2EIFS with a metallic finish—designed to replicate metal panels—offers an expedient and cost-effective solution to metal panels since the material can be installed onsite and adjusted to allow for any changes in framing. The material does not have to be pre-ordered and is offered in various colors. Unlike traditional metal panels, EIFS with a metallic finish has continuous insulation, and there are no penetrations through the cladding for attachment to the substrate.

EIFS testing and research
One of the most important features and benefits of EIFS is the result of independent testing to demonstrate its long-term performance compared to other claddings.

In 2003, DOE contacted EIMA proposing a thorough hygrothermal evaluation of EIFS alongside numerous other commonly used claddings.2

EIMA worked with Oak Ridge National Laboratory to design and construct a specific facility dedicated to this purpose. Testing was performed in two phases, from January 2005 to May 2006 and June 2006 through June 2007.

The Natural Exposure Test (NET) facility, located in Hollywood, South Carolina, is a fully conditioned enclosure designed to accept completely instrumented wall sections. Phase One of the DOE/EIMA study—lasting 17 months—evaluated 15 individual wall sections, including barrier EIFS, EIFS with drainage, stucco, brick, and siding.

In Phase Two, which lasted 13 months, additional wall sections of all claddings were placed on the northwest side of the building, and flaws added to their construction. These flaws allowed water to enter the wall, behind the cladding, in order to test more rigorously the water-resistive barrier components. This data was also monitored and analyzed by the Oak Ridge National Laboratory.

The picture is an example of a specialty finish replicating the look of granite using a ceramic bead, mica chips, and clear binder. This installation is on the Spring Hill Suites in Alexandria, Virginia.

The picture is an example of a specialty finish replicating the look of granite using a ceramic bead, mica chips, and clear binder. This installation is on the Spring Hill Suites in Alexandria, Virginia.

The ORNL testing at the NET facility demonstrated the following key conclusions:

  • EIFS with a liquid-applied WRB, performed better than any other tested cladding assembly—15 individual wall sections that included barrier EIFS, EIFS with drainage, stucco, brick, and siding were also tested;
  • EIFS assemblies had superior drainage capability compared with the other claddings as evidenced by the lower relative humidity (RH) values through the various wall components; and
  • the best overall performance was an EIFS with 101.6 mm (4 in.) of ci applied over a liquid-applied WRB with an empty (no batt insulation) stud cavity.3

Conclusion
Over the last 50 years, exterior insulation and finish systems have demonstrated they are versatile, lightweight, energy-efficient claddings that can be installed over various substrates. Independent third-party testing has shown EIFS can outperform other types of exterior cladding. Whether field-applied or a pre-fabricated panel, such assemblies can be considered for existing, new, or retrofit projects.

Notes
1 View the Oak Ridge National Laboratory study results at www.ornl.gov.sci/roofs+walls/research/EIFS/eifs.htm. (back to top)
2 View the study results at www.ornl.gov.sci/roofs+walls/research/EIFS/eifs.htm. (back to top)
3 The full report is available at www.ornl.gov/sci/roofs+walls/research/EIFS/eifs.htm. (back to top)

Michael A.DeLaura, LEED AP BD+C, is a 28-year veteran of the EIFS and coatings industry, and is currently an exterior cladding specialist for Sto Corp. DeLaura is an active member of the U.S. Green Building Council (USGBC), and a member of its education review team. He has reviewed proposals for the last three GreenBuilds. He is a board member of the Hampton Roads Green Building Council, and serves on the education and programming committee. He can be reached at mdelaura@stocorp.com.

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Claddings and Entrapped Moisture: Lessons learned from early EIFS

 

All images courtesy Masonry Technology Inc.

All images courtesy Masonry Technology Inc.

by John Koester

While some building science concepts can be difficult to grasp, there is nothing new or complex about the relationship between temperature and moisture management. The phrases ‘wet and cold’ or ‘warm and dry’ are ingrained in the minds of the public for good reason.

The law of physics dominating this phenomenon is thermal conductivity. Dense materials transmit temperature more efficiently than less dense ones because the molecules are closer together. Water is denser than air and transmits temperature 25 times more efficiently. When a person is wet, the ambient air temperature can be received more readily and the body loses temperature to the surrounding ambient air more easily if the latter is colder. A practical example can be found in the kitchen—moving one’s hand into a 200-C (400-F) oven, without touching any surfaces, is quite different from plunging a hand into boiling water.

Controlling the temperature relationship of a building from inside to outside (or outside to inside) means insulating the exterior building envelope.

Controlling the temperature relationship of a building from inside to outside (or outside to inside) means insulating the exterior building envelope.

Good thermal insulators—sprayed polyurethane foam (SPF) and rigid boardstock, for example—have a lot of air molecules in proportion to other dense molecules; further, the former is effectively positioned between the latter to make this separation. A good example of this is the cardboard sleeve that slides around a paper cup of hot coffee, allowing someone to comfortably hold a steaming beverage.

The clear takeaway for the building industry is to have an impact on a temperature relationship of a building from inside to outside (or outside to inside), one must insulate the exterior building envelope—the walls, floors, and roof (Figure 1).

Another critical requirement is keeping the insulation material dry. Wet insulation is not an insulator, but rather a conductor. Different types of insulation materials absorb moisture at different rates. In many instances, an exterior building envelope with no insulation is preferable to one with wet insulation. Of course, the problems of wet insulation in a wall do not end with just poor insulation values. They also include mold, pest infiltration, and building material degradation.

As shown in Figure 2, there are many causes of wet insulation in the exterior building envelope. Examples include:

  • uncovered insulation stored in an exposed location on a jobsite can be installed in a damp/wet state;
  • liquid water can egress into the exterior building envelope during and after the construction phase;
  • moisture (in the form of water vapor) can enter the building envelope from the exterior and interior;
  • liquid water can leak from faulty plumbing; and
  • poorly insulated plumbing or HVAC ductwork can condense and drip water.

Moisture problems with EIFS are often in areas where the system abuts other materials such as wood trim, at the top wall, at roof flashing, around wall openings, and where other items penetrate the cladding’s surface. EIFS can also develop penetrations over time—foundations move, walls crack, storms can blow debris into façades, etc. There can often be installation issues. Even though manufacturers of EIFS products have recommended best practices and procedures, onsite labor does not always follow them; components like flashing can be improperly installed or omitted.

As the National Institute of Building Sciences’ (NIBS’) Whole Building Design Guide states:

Problems observed with in-service EIFS installations are primarily related to moisture intrusion. EIFS provides protection against moisture infiltration at the base coat; however, moisture migration through openings for windows, flashings and other items, or holes and cracks in the EIFS itself, have allowed leakage to occur on EIFS clad buildings. With barrier EIFS installations, or where weather barriers and flashing are improperly installed in conjunction with wall drainage EIFS installations, moisture has entered the wall system at these locations and caused damage to the wall sheathing and framing. The extent of these occurrences on wood frame structures has led to class action lawsuits.1

There are many causes of wet insulation in the exterior building envelope.

There are many causes of wet insulation in the exterior building envelope.

EIFS and entrapped moisture
There are additional scenarios that have caused a great deal of problems. For example, issues occur when board stock rigid insulation is layered against other rigid insulation or exterior sheathing, or when decking traps moisture between the layers of material. This phenomenon first happened on a wide scale in early exterior insulation and finish systems (EIFS). Moisture entered these systems and became entrapped behind the rigid insulation and in front of the wall sheathing on the backup wall, deteriorating the water-resistant barrier (WRB), sheathing, and structural studs (Figure 3).

In early exterior insulation and finish systems (EIFS), moisture occasionally entered and became trapped, deteriorating the water-resistant barrier (WRB), sheathing, and structural studs.

In early exterior insulation and finish systems (EIFS), moisture occasionally entered and became trapped, deteriorating the water-resistant barrier (WRB), sheathing, and structural studs.

Moisture entering these early EIFS assemblies (through any of the methods previously mentioned became held for an extended period in the pockets/voids in the exterior building envelope created by the variations between the rigid insulation surface and the wall sheathing surface. This negative scenario was amplified by the composition of the two layers of materials involved.

The EIFS industry started addressing this problem by incorporating a 3.175-mm (1/8-in.) drainage plane between the back side of the board stock rigid insulation and the exterior face of the sheathing or the WRB installed over the sheathing. Created through vertical adhesive patterns and/or strips of manufactured drainage material (Figure 4), this void became the accepted solution because it caused the least decrease in R-value while maintaining effective drainage characteristics. It also allowed accumulating moisture to effectively drain down and out the wall.

Additionally, this size was chosen because anything smaller could have allowed capillary action. When a wet layer is in close proximity to a dry one (i.e. less than 3.2 mm [1/8 in.] of separation), moisture moves between them. As the Whole Building Design Guide states:

Once wetted, capillary transfer within, or between, layers of an exterior wall assembly can also occur, and can be further exacerbated by moisture loads inherent to an exterior wall product or material shortly after initial installation.2

These voids are not widely promoted features of EIFS because the cladding systems qualify, under the International Building Code (IBC), as “barrier systems.” In other words, they are not supposed to allow moisture to penetrate into the building envelope and accumulate. The following information comes from an International Code Council Evaluation Service (ICC-ES) report of a major EIFS manufacturer’s product:

Compliance with the following codes:
● 2012 and 2009 IBC; and
● 2012 and 2009 International Residential Code (IRC).
EIFS: IBC Chap. 14, IRC Chap. R7
Weather resistance: IBC Chap. 14, IRC Chap. R7
Weather protection: complies with IBC Section 1403.2 and IRC Section R703.1

Granted, in a perfect world, EIFS would indeed work as a barrier system. However, walls do leak because of contractor error or issues with the installation of other products used in conjunction with the system. Therefore, since evidence showed moisture penetrated these systems, the EIFS industry’s decision to add a drainage plane to overcome the entrapped moisture problem is important. As this information was at one time proprietary and not widely disseminated, the requirement for and effectiveness of a drainage plane as a remedy for entrapped moisture is not fully appreciated by the construction industry.

It is important to note this article is not intending to single out and disparage the EIFS industry. In fact, it should be seen as just the opposite—EIFS manufacturers have made significant strides in successfully remedying the entrapped moisture problem by adding a drainage plane. Further, it is critical to remember the entrapped moisture problem is not exclusive to just one type of building envelope system.

Voids created through vertical adhesive patterns and/or strips of manufactured drainage material maintain effective drainage, without overly decreasing R-value.

Voids created through vertical adhesive patterns and/or strips of manufactured drainage material maintain effective drainage, without overly decreasing R-value.

Many are specifying rigid board stock insulation to be applied outside the wall sheathing, but this may create a system remarkably similar to early EIFS—and without the benefit of the drainage plane.

Many are specifying rigid board stock insulation to be applied outside the wall sheathing, but this may create a system remarkably similar to early EIFS—and without the benefit of the drainage plane.

The problem with two barriers
Enter the new energy code requirements: the 2009 International Energy Conservation Code (IECC) for residential buildings and American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-2007, Energy Standard for Buildings Except Low-rise Residential Buildings, for commercial buildings. (The 2012 IECC, requiring even stricter standards, may soon be adopted in some locations.) To comply, the building industry is specifying rigid board stock insulation to be applied outside the wall sheathing.

In so doing, the industry may be unwittingly creating a system remarkably similar to the early EIFS, but without the benefit of the drainage plane. There are numerous ongoing discussions in the construction industry related to this application (Figure 5):

  • Should the WRB be installed over the rigid insulation (Figure 6)?
  • Should the exterior sheathing and rigid insulation (with taped seams) be installed atop the WRB (Figure 7)?
  • Does rigid insulation with taped seams qualify as a WRB?
  • Is rigid insulation with taped seams a vapor retarder?

This author sees most types of board stock rigid insulation with taped seams as ‘vapor retarders.’ If this is the case, then the consequences of two or more vapor retarders as components of the same exterior building envelope system are very real.

There is nothing wrong with two or more vapor retarders in one exterior building envelope—provided no moisture is trapped between them. Similarly, there is nothing wrong with moisture being trapped between two or more vapor retarders in an exterior building envelope—provided the amount is small, and there are no other construction details involved that could rot or harbor microorganism growth. Of course, both of these scenarios provide potential problems given the criteria.

Whether there are issues with installing the WRB over the rigid insulation is a discussion ongoing within the industry.

Whether there are issues with installing the WRB over the rigid insulation is a discussion ongoing within the industry.

Should the exterior sheathing and rigid insulation (with taped seams) be installed atop the WRB?

Should the exterior sheathing and rigid insulation (with taped seams) be installed atop the WRB?

 

 

 

 

 

 

 

 

 

Conclusion
When it comes to claddings and entrapped moisture management, denial and ignorance are rife. “I do not have to worry about moisture being trapped in the exterior building envelope because it cannot get there” is the former, while “I didn’t know that material was a vapor retarder” is the latter.

Holistic building is critical to ensure the envelope functions as intended.

Holistic building is critical to ensure the envelope functions as intended.

While a sense of denial is inexcusable for design/construction professionals, the ignorance can be more understandable. There are many choices for exterior building components that may qualify as vapor retarders under various conditions and configurations:

  • rigid insulation (and other types of insulation);
  • certain veneers/rainscreens;
  • both interior and exterior sheathings;
  • interior vinyl wallcoverings;
  • some paints and coatings;3 and
  • polyethylene sheets and other products specifically billed as ‘vapor retarders.’

Knowing how the wide range of components in the exterior building envelope interacts with each other under various conditions is not easy. Nevertheless, it is the responsibility of the specifying professional to research and determine what components and configurations will function properly. The term ‘holistic building’ is not just a catch phrase—it is a requirement that allows an exterior building envelope to function effectively in the long term (Figure 8).

Notes
1 Visit www.wbdg.org/design/env_wall.php. (back to top)
2 See note 1. (back to top)
3 Vapor retarder paints typically have a perm rating of 0.8 to 0.45, but the actual perm in the field depends on the number of coats and the degree of coverage. For more information, read the Journal of Light Construction article, posted at www.jlconline.com/paints/q-a–vapor-retarder-paints.aspx. (back to top)

John Koester is the founder and CEO of Masonry Technology Inc. With construction experience dating back almost 40 years, he has been a card-carrying mason and cement-finisher, and for many years operated his own masonry construction business in the Minneapolis-St. Paul area. Koester has extensive background in waterproofing systems in the areas of forensics, design, and installation oversight—both in restoration and complete re-roofing projects. He can be contacted via e-mail at john@mtidry.com.