FAQs for Building Envelope and Air Barrier Tightness Tests

Q: What is an Air Barrier?

A: An Air Barrier is defined by the Air Barrier Association of America as an assembly to “control the unintended movement of air into and out of a building enclosure.”

Q: Why has Air Barrier Tightness become a USACE certified requirement?

A: The reasons why air barrier tightness has become a requirement is due to the many ways air may escape from the building envelope. Over 40% of the nation’s energy expenditure stems from the operation of buildings where the majority of this energy is used to condition the indoor environment. Because wind is constantly changing the positive and negative pressures on the building envelope, a proper enclosure is vital to reductions in energy consumption.

Q: What are some common causes of air leakage?

A: There are three common causes of air leakage:

  1. Improper sealing and climate changes: In warmer seasons, the air rises to the top of the building, and since buildings are not totally sealed, the air escapes through open windows and/or ventilation openings. In turn, the rising warming indoor air reduces the pressure at the buildings base which then causes cold air to be drawn through openings near the building’s base. During coolers seasons, the adverse occurs.
  2. The Buoyancy Force or Stack effect: Is the movement of air into and out of the buildings, chimneys, flue gas stacks and other containers. The movement is driven by buoyancy that occurs because of a difference in indoor-to-outdoor air density that stems from temperature and air density. Thus, the greater the thermal difference and the height of the structure, the more air moves in and out of a building
  3. A third force is the design of a buildings mechanical system where heating and ventilation systems promote either positive or negative pressures within the building.


Q: What is the USACE?

A: The USACE (United States Army Corps of Engineers) is a federal organization and the world’s largest design and construction management agency. Their mission is to “provide vital public engineering services in peace and war to strengthen our Nations security, energizes the economy, and reduce risks from diseases.” The Corps vision is to breed a “great engineering force of highly disciplined people working with partners through disciplined thought and action to deliver innovative and sustainable solutions to the Nations engineering challenges.”

Q: What are the benefits of the USACE regulations?

A: The USACE regulations on Air Barrier Tightness support the Energy Independence and Security Act of 2007. The air barrier is an important addition to optimize the HVAC’s system performance. The regulations on air barrier tightness improve smoke and fire control and reduce energy consumption.

By reducing the amount of air from entering and exiting a buildings envelope energy consumption decreases by way of lowering cooling and heating costs as well as allowing designers to reduce the building envelopes HVAC demands.

The 2008 regulations on air barrier tightness also improves Indoor Environmental Quality (IEQ) by reducing drafts in the building that causes occupant discomfort as well as decreases noise pollution by patching leakage paths.

The air barrier system also eliminates degradation of the building’s materials caused by interstitial condensation. Interstitial condensation is condensation that is hidden in cavities and gaps that if undetected can accumulate and lead to mold and decay where its cause is due to the leakage of uncontrolled air flow. A more efficient building envelope will help decrease condensation in a building’s cavities which leads to a reduction in the amount of microbial growth, or bacterial growth.

Air Barrier tightness also improves poor air quality by decreasing the amount of fumes, dust, and other toxic particles from entering the buildings air circulation systems. Moreover, air barrier tightness also eliminates a buildings inability to balance pressure conditions as well as improve its control and balance of its HVAC systems.

Q: Why hire a Registered Roof Observer (RRO)?

A: Systems Building Envelope Consultants has had the RRO designation through the Roof Consultants Institute (RCI) since 1997. USACE projects are beginning to require the presence of an RRO to perform daily oversight and quality control on all roof work. We have met that challenge using our staff’s credentials well in advance of any requirements from the USACE.

Our other roofing specialties include designing, specifying repairs/replacement and managing roofing, waterproofing and exterior wall systems. Our senior building science consultants also specialize in forensic investigation, expert witness testimony and construction document preparation.

Our RRO’s operate without conflict of interest, and are not connected with any manufacturer or product. They strive to be unbiased and are governed by an established code of ethics. We keep a working knowledge of the latest industry technologies and methodologies. We are committed to maintaining annual requirements for continuing education.

Roof consultants plan roof design solutions, perform evaluations of existing roofs, prepare construction documents, perform forensic inspections, monitor construction and serve as expert witnesses. Roof consultants possess a broad base of practical knowledge about the roofing industry at large. Many choose to focus their work and become experts on specific roof types and materials.

Roofing Quality Assurance Observers monitor the construction process. They strive to make sure the roof is built to code and specification. They work to assure proper application procedures are followed and that criteria for validation of manufacturer’s warranties are met.