Study: Sealing ducts in conditioned space saves energy, reduces leakage
A new study indicates that leaks in ductwork in conditioned spaces can have a significant impact on energy savings.
The study, conducted by Comfort Institute in combination with the Greater Cincinnati Energy Alliance (GCEA), showed that the amount of conditioned air seeping through the building envelope and escaping to the outside of a single- or multifamily home was reduced by an average of 11.4 percent after the ducts were effectively sealed, according to a release.
Energy modeling conducted by the Greater Cincinnati Energy Alliance showed an average total heating and cooling cost of $2,010 per year, with $202 per year in savings or a 10 percent reduction in energy costs.
“We now have some initial data which contradicts the common opinion that duct sealing only saves energy if the leaky ducts are located in unconditioned spaces,” said Rob McCracken, director of operations for GCEA. “We can begin to see that, based on individual home situations, homes with duct systems located inside the house can see a reduction in energy consumption between 5 percent to 15 percent.”
“There is an erroneous belief among many building professionals that leaks within ductwork located inside the home, have little effect on overall energy use,” said Comfort Institute co-founder Brendan Reid. “Earlier studies only addressed the impact of sealing duct leaks which were readily accessible for hand sealing – those in unfinished basements. What those studies neglected to evaluate was the impact of sealing the hidden, inaccessible duct leaks – which routinely do leak to outside.”
In the joint study, 11 Cincinnati-area homes with duct systems inside the thermal boundary had their ducts sealed using Aeroseal, a highly effective aerosol-based patented duct-sealing technology. Duct sealing was the only procedure conducted in these homes.
Multiple tests, including blower door tests administered before and after the duct sealing processes were completed, were used to determine the amount of conditioned air escaping through the building envelope. Blower door tests before and after the duct sealing measured whole house CFM50 leakage reductions, averaging 11.4 percent or 347 CFM50.
According to Reid, in one home, where aerosealing the ductwork reduced overall building envelope leakage by 10 percent, an analysis showed the duct sealing resulted in a 16 percent reduction in heating and cooling costs.
In the study, two-story homes showed greater reductions in envelope leakage than single story homes, presumably due to many openings in the thermal envelope. This data confirms that ducts “inside the house” are often connected to outside.