As more high-performance buildings are constructed, increased focus is being paid to the building envelope – the buffer that surrounds and protects the central structure. There’s good reason for this heightened concern. Buildings need a reliable building envelope assembly to provide protection from the elements for every portion of the building’s outer structure – from the roof and exterior walls to the basement.

All of these components are vulnerable to water intrusion and weathering, air leakage and premature deterioration of construction materials. These problems often result in costly maintenance and repair, inflated energy costs, poor indoor air quality and shortened lifespan for the building.

Causes and Results

There are several causes to building envelope failures and the problems that result from it. They include:

  • Design defects
  • Material failures
  • Poor workmanship
  • Weather related issues

Several issues result from a failed building envelope:

Water Intrusion

This is by far the most destructive result of building envelope failure. According to Building Design + Construction Magazine, 50 percent of the cases they’ve investigated around the country involve moisture penetrating the building exterior or becoming trapped within the envelope system during construction or occupancy. Moisture leads to mold growth or can degrade the envelope of the building and ultimately cause a structural failure.

Air Intrusion

Leaks in the envelope waste energy. According to Oak Ridge National Laboratory (ORNL) a lab managed for the US Department of energy, common fiberglass batts result in a 28 percent decrease in labeled R-values. Small voids of 1-2 percent allowing air intrusion result in 25-40 percent loss of labeled R-value. Moisture laden air currents account for 90 times more moisture vapor transfer into a wall than that caused by diffusion. Air leakage thus has the potential for damage caused by condensation, increasing the load on HVAC systems and negatively impacting the comfort of occupants.[1]

Structural Integrity

Issues arise when buildings are not constructed to original design specifications or when the design itself is flawed. Another cause of structural failure is the use of substandard materials during construction. Any of these can result in either the failure of the building envelope, or the entire structure itself.

[1] Best Practices – a Tighter building envelope, presentation by Jeff Seabold, AIA, NCARB, LEED Green Associate, Seabold Architectural Studio.

The devastating effects of a failed building envelope can be avoided early in the construction by instituting an effective testing process. Heading off problems has resulted in a greater focus on testing using standards like the National Environmental Balancing Bureau’s Procedural Standards for Building Enclosure Testing, the U. S. Army Corps of Engineers Air Leakage Test Protocol for Building Envelopes, and ASTM E779 and E1827.

Here are some best practices to follow when developing a comprehensive building envelope testing program.