Stack effect discussion
I find it interesting and a little frustruting that in all the discussion on stack effect I have not been able to find one article discussing the contribution of leaky ducts located in attics to stack effect. I have a home owner who reported excessive dust in her home. She lives in a 22 year old two story home in central California built before the requirement for sealed ducts. I noticed she had about 12 can lights in the ceiling of the upstairs rooms which were not air tight and with the other typical air leaks inthe upper portion of the shell of her home I suspected some duct leaks. She has 3 HAVC systems all with ducts in the attic and in portions of the interior walls. Testing the duct systems I found her duct leaks averaged 21% of nominal air flow which is fairly typical of some 22 year old homes here in the Valley. She has a natural draft fireplace on the first floor and no other gas appliances within the envelope. I recommended duct sealing and replacing the can lights, together with weather stripping attic access and exterior doors. She allowed me to seal the ducts reducing the duct leaks to less than 6% of nominal air flow and no other work. She would not pay for blower door testing. She now complains that I have caused air to flow down her chimney introducing an ash smell and creating a health hazard. I cannot help her to understand that because I have reduced the flow of air out the top of her home I have esentially imporved the condition of the air within her home.
Rare Service Heating and Air Conditioning, Inc.
Inactive BPI Building Analyst
A/C and HP Professional