Architectural Record BE - Building Enclosure

A New Era of Exterior Sealants

New technologies allow sealants to provide better adhesion to the wide range of building materials used in modern construction, and they are longer lasting for improved durability
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Sponsored by OSI
By Andrew A. Hunt
 
Continuing Education
 

Learning Objectives - After this course, you should be able to:

  1. Explain the building envelope and the role it plays in improving energy efficiency, indoor air quality, and durability.
  2. Discuss how modern sealants play an important role in creating a successful building envelope.
  3. List the different attributes, characteristics, and classifications associated with high-quality sealants.
  4. Compare the advantages of modern sealants over traditional sealants relative to shrinkage, UV resistance, and protection against dirt and dust collection.

Credits:

1 AIA LU/HSW
0.1 IACET CEU*
AAA 1 Structured Learning Hour
AANB 1 Hour of Core Learning
AAPEI 1 Structured Learning Hour
MAA 1 Structured Learning Hour
NSAA 1 Hour of Core Learning
OAA 1 Learning Hour
SAA 1 Hour of Core Learning
NLAA 1 Hour of Core Learning
NWTAA 1 Structured Learning Hour
 
This course can be self-reported to the AIBC, as per their CE Guidelines.

The building envelope is the vertical, horizontal, and sloped plane where the interior and the exterior of a building meet. This includes floors, crawl spaces, ceilings, windows, doors, the wall and roof assemblies (consisting of framing and insulation), and areas around plumbing pipes and electrical wiring. The building envelope is a comprehensive system that, when properly designed and installed, protects the building from unwanted water intrusion, controls air movement between conditioned and unconditioned spaces, and greatly improves the energy efficiency of the building.

Photo of a house.

To properly seal a building envelope, the key is to treat the entire structure and building envelope as if it is one system. If any part of the system is compromised, the seal of the entire structure can deteriorate and cause serious and costly damage.

The building envelope most commonly consists of the following five critical barriers:

  • a deflection barrier to deflect water and elements away from the structure;
  • a water protection barrier, which is an integrated assembly of materials to seal out and drain water from the building envelope;
  • an air barrier to stop the movement of air from going in and out of the structure;
  • a vapor retarder to slow the movement of humidity and moisture; and
  • a thermal barrier to control the temperature variations between the exterior and interior conditions.

When working as expected, these five components help keep the occupants safe by improving indoor air quality (IAQ) and creating a more durable structure free from the risk of mold and mildew through water intrusion. They also improve the thermal qualities of the building, reducing energy use, which saves money on utility bills and helps conserve resources.

The design and execution of this complex systems approach varies by building, area, and climate. However, one truth is constant across all climate zones and regions—like a chain, a building envelope is only as good as its weakest link. The most vulnerable areas of the building envelope are gaps created where either different building materials meet or where joints or seams are located. For example, where window frames interface with exterior siding or where building wrap overlaps.

According to the California Energy Commission, approximately 40 percent of air that infiltrates into a residential building comes from doors, windows, and plumbing penetrations. Properly sealing the areas around these openings can significantly decrease air and water intrusion.

Other major areas where air infiltration occurs is at floors, walls, and ceilings. According to the same report, approximately 36 percent of air infiltration happens in these locations. Another 16 percent of air infiltration occurs around fireplaces. Five percent of air infiltrates through fans and vents, and 2 percent infiltrates around electrical outlets.

During construction, layers of the walls, floor, and subfloors are sealed when they are installed to protect the interior of the building against the elements. Attics and ceilings are insulated and sealed using various materials to ensure that conditioned air does not escape into the attic or allow unconditioned air to enter through vents or chimney penetrations. Siding also must be adequately sealed so that water doesn’t permeate through, introducing the potential for mold growth and possibly causing walls to rot. While these main structural components of the building are sealed during installation, gaps around these areas can allow air, dust, moisture, and humidity to penetrate the opening, thus allowing contaminants to seep into the walls and floors, creating an unhealthy living space, costly repairs, and strain on the HVAC system.

moisture penetrates the building envelope.   moisture penetrates the building envelope.

When moisture penetrates the building envelope and gets inside the walls of a building, it may not be noticeable at first. This water intrusion can cause serious wall damage as well as toxic mold and mildew.

One of the greatest potential problems that can arise from a poorly sealed building envelope is water intrusion. Water damage that could have been prevented by properly applying a small amount of quality sealant can cause hundreds, even thousands of dollars in structural repairs if left untreated. This can happen as water penetrates doors and windows, but it also can occur when water penetrates through gaps in the siding and seeps into the walls. It’s important to seal gaps between dissimilar cladding transitions as well as areas around chimneys and air vents. Often attics contain batt insulation that, when it gets damp or wet, can lose its ability to insulate while also becoming a breeding ground for harmful contaminants.

Additionally, a leaky building envelope can increase the amount of energy required by the building’s HVAC system to keep the conditioned air at a comfortable temperature year round. This can lead to increased energy costs and unnecessary wear and tear on the HVAC system.

All of these potential issues can be prevented with the proper application of quality sealants. Since gaps are often between two very different types of building materials, it’s important to make sure the sealant can properly adhere to both materials. For example, a brick wall could have an opening for a wooden door. The gap between the wall and door would need to be sealed with a material that would properly adhere to both building materials as well as maintain its rigidity and flexibility as needed. We’ll discuss these sealant materials, their characteristics, and application techniques throughout this course.

 

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Originally published in Architectural Record

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