Airtight Buildings Equal Significant Savings

By using simulation software to study the building envelope, the National Institute of Standards and Technology (NIST) has evaluated the energy impact of air barriers in commercial buildings. The study was conducted in three typical non-residential buildings in five cities, each located in a different climate zone. The findings reveal how significant savings on annual heating and cooling energy costs can be reaped by improving the airtightness of a commercial building’s envelope, predicting the potential for 37-percent cost savings each year.

Using the baseline energy, climate, and building data from each city, researchers were able to model each building with wood frame and masonry construction. Building wraps or coatings were among the methods applied to increase airtightness in masonry block construction.

A combined annual gas-electric cost savings resulting from improved airtightness in frame construction buildings in Bismarck, ND, would be 33 percent for a hypothetical office building, 22 percent for a retail building, and 31 percent for an apartment. The predicted savings would be higher in Minneapolis (37 percent for an office, 26 percent for a retail building, and 33 percent in an apartment).

The study, which was sponsored by the U.S. Department of Energy's Office of Building Technology revealed that buildings in warmer climates which improved airtightness were less likely to see savings as significant, but could reap the benefits over time. For example, the estimated cost savings for Phoenix were 10 percent, 16 percent, and 3 percent for the office, retail, and apartment.

According to the Oct. 7, 2005, NIST Tech Beat newsletter: “Although not evaluated in this report, improving building envelope airtightness also reduces the potential for problems caused by air leakage such as poor indoor air quality, thermal comfort, and degradation of building materials due to moisture damage.”

To review the complete research study, titled “Investigation of the Impact of Commercial Building Envelope Airtightness on HVAC Energy Use (NISTIR 7238),” visit (http://fire.nist.gov/bfrlpubs/build05/art007.html).