A properly sealed duct system in a house is one of the most important weatherization measures to make during an energy efficiency retrofit. By sealing the ducts, especially when they are located in unconditioned space, such as attics, basements and crawlspaces, conditioned air is prevented from being lost to the non-conditioned air. In addition, the system is less likely to suck pollutants, such as dirt, dust, small pests or fiberglass insulation particles into the house. A dirty duct system will not only reduce the life of the entire air conditioning system by clogging the system but by also affecting the indoor air quality. For these reasons Posigen Energy Efficiency upgrade teams prioritize sealing duct systems.
In an average U.S. house the amount of air traveling through the duct system that is lost to cracks and gaps can be up to 30%. Since this air is already conditioned, these leaks can cost more than leaks elsewhere in the house even if they are not as big. As most houses have ducts in non-conditioned areas, the areas where cool and hot air meet are top priority.
The upgrade crews always use proper materials in order to ensure not only that the job is done correctly, but also that it stays correct for years after. Many tapes and adhesives will break down in the heat of the summer, so a putty-like material called mastic is used to make sure that the ducts get sealed and stay sealed for a long time. If there are more serious problems such as a disconnected duct or pinched section preventing airflow, these can also be addressed to ensure savings, comfort and safety.
Posigen emphasizes duct sealing as an upgrade that delivers in multiple ways.