Duct Leakage and Retrofit Duct Sealing in MN Commercial & Institutional Buildings

Duct-sealing-report-(2).pngIntroduction/Background

Air leakage from distribution ductwork wastes energy by increasing fan power and discarding conditioned air. In Minnesota commercial and institutional (C&I) buildings, HVAC fans consume about 2,800 GWh of electricity per year (EIA 2008). Assuming about 5% duct leakage, approximately 380 GWh of fan power are lost on duct leakage per year. Duct leakage also results in significant heating and cooling energy penalties when conditioned air leakage is discarded from the envelope in exhaust or relief air systems. Duct leakage has traditionally been framed as a performance issue rather than an energy efficiency issue. However, a significant body of research developed over the last 20 years suggests that duct systems are not particularly tight and may be a major energy inefficiency in building HVAC systems. This discovery coincides with the development of a novel, patented sealing process (Aeroseal) that makes it possible to tightly seal ductwork in retrofit applications. The Aeroseal method requires significantly less access compared to traditional methods, and it may represent a path toward cost-effective energy savings from retrofit duct sealing. The growing recognition of duct leakage as a major cause of HVAC energy waste provided motivation to explore the possibility of retrofit duct sealing as an energy efficiency opportunity in Minnesota. This project characterized duct leakage in several types of Minnesota C&I buildings, completed retrofit duct sealing on a subset of C&I duct systems, and estimated the energy savings and cost effectiveness of retrofit sealing measures. The project then analyzed the results to develop screening criteria that displace cost-prohibitive leakage measurements and tested the criteria in a short pilot program to identify cost-effective duct sealing opportunities.

Full Report (PDF)
Duct Leakage and Retrofit Duct Sealing in Minnesota Commercial and Institutional Buildings

This project supported in part by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program.