Impact of Changes to Building Airtightness on HVAC Costs

Air leakage is generally the most significant factor in small-building energy consumption. This study determined if reducing air leakage in preengineered metal buildings would be cost-effective. The effects of air-retarder treatments on owning and operating costs were examined for two different sizes of buildings that were thermally modeled using a building energy analysis computer program, BLAST. The annual energy consumption and peak loads were then produced by BLAST to find the fuel consumption for each building and the system sizes needed for adequate climate control. A detailed cost estimate was done on the mechanical system based on the required equipment size for each air-retarder treatment used. Life-cycle costs were determined for two types of air retarder and one case without an air retarder at four locations in cold and hot climates, and for five air exchange rates. A payback analysis illustrated the cost-effectiveness of the air-retarder treatments. Both air-retarder treatments proved cost-effective for both buildings. They provide immediate savings in system first cost because of the reduction in heating, ventilating, and air conditioning (HVAC) system size, as well as long-term energy and operation cost savings. Furthermore, even if the HVAC system size was not reduced, use of air retarders still had a short payback period in both warm and cold climates.