Duct Leakage to Outdoors

If the heating and cooling duct distribution system is located in unconditioned space (e.g., a vented attic or crawlspace), test the ducts for air leakage to the outdoors (i.e., into unconditioned space) in addition to testing total duct leakage.

Use a testing protocol approved by Residential Energy Services Network (RESNET) . This testing is typically done by a home energy rater certified by RESNET.

  • Test duct leakage after all components of the system have been installed and air sealed, including the air handler, the ductwork, the duct boots, and the register grilles atop the finished surfaces (e.g., drywall, carpeting, flooring).

  • If there is more than one system in the home, assess leakage on a per-system, rather than per-home, basis. 

  • Visually inspecting ducts prior to drywall installation allows for easier corrections.

  • Either visually inspect or duct blower test ventilation ducts (e.g., ducts used for a separately ducted ERV or HRV system). 

  • Testing to outdoors is not required by ENERGY STAR or codes if the ducts are located completely within the conditioned space of the home and if certain other conditions exist, as described in the Compliance tab.

Figure 1 - Building Right - Boot has been covered with insulation and sealed with mastic.

Figure 1 - Building Right - Boot has been covered with insulation and sealed with mastic.

Figure 2 - Building Wrong - Insulation does not cover boot and is not sealed.

Figure 2 - Building Wrong - Insulation does not cover boot and is not sealed.