Thursday, October 11, 2012
I did inspect the ducts and other than some minor leakage here and there I was unable to find any severe leak.
I cut the drywall well back to expose the entire duct and taped up the tabs to make it air tight. I will repair the drywall with the opening right over the duct this time.
The mysterious 67% duct leakage problem revealed itself on inspection of the attic. There is a chase running vertically right beside this return air duct that follows all the way to the crawlspace.
I accidentally discovered this when I shined a light down the chase and could see spray foam insulation at the bottom. At one time before the knee wall in the crawlspace was foamed, there was about a 2x4's width at the bottom of the chase that was open to the crawlspace. The foam insulation crew inadvertently sealed this gap when the foamed the knee wall. This open chasm would have shown massive airflow during the blower door test. This is where I think the 67% air loss was coming from. Besides air and moisture having a clear shot up from the crawl to the attic, anything else that could climb could have also found it's way up into the attic and in the wall. There was a rats nest in the attic behind the same wall above the kitchen.
Most of the old loose insulation in the attic was black from moisture and condensation. The dust and the dirt was awful. We have re-mediated most of the old loose insulation and vacuumed up there with a modified shopvac. The air quality is noticeably better and it's still dirty up there! It 's getting better though. We hauled out about twenty bags of old nasty insulation.
I also found a couple of gaps in the spray foam between the attic and the garage or at least my cat did. I knew if she could get into the attic space above the garage from the attic in the house we had an issue. Sure enough I found two pretty substantial holes underneath some furring strips in the attic. They were hard areas to get to. I've sealed them up with Great Stuff.
New drywall with cutout in the proper location.