Ever notice a breeze in older buildings even when it is not windy? Many buildings leak air, which means their owners are losing money. The Charlotte Mecklenburg School System (CMSS), the 19th largest in the U.S. with a $1.3 billion operating budget, recently decided to take action to identify school system buildings that might be exhibiting air leakage.
In 2014, CMSS approved an architectural/engineering guideline change proposal to incorporate air barrier testing for all new buildings, additions, and major renovations. Using this guideline, CMSS’s plan was to decrease the air leakage from 0.25 cfm per square foot of exterior enclosure for buildings built in 2014 to 0.15 cfm per square foot of building enclosure for buildings built in and after 2018.
To help the school system determine sources of air leakage in one school built in 2015, Terracon performed air barrier testing in general accordance with the U.S. Army Corps of Engineers (USACE) Engineering Research and Development Center’s (ERDC’s) Air Leakage Test Protocol for Measuring Air Leakage in Buildings using a proprietary (Retro-Tec) Blower Door Testing system.
For effective use of test equipment, the building had to be divided into five areas to be tested separately. Splitting up the building into separate areas proved challenging due to the amount of ducts and air transfers which crossed firewalls and had to be sealed. All doors and mechanical ducts were sealed to prevent extraneous air leakage, which can disproportionately alter the results of the test. The flow through the building enclosure was recorded at 10 different pressure points. These points were placed on a graph which created a straight line that was then used to calculate the flow through the building enclosure at 75 Pascals, a unit of pressure in metric units.
Smoke pens, devices that emit a constant stream of smoke that can be used to show air movement, were used on the interior of the building to focus…