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Feel More Comfortable, Breath Healthier Indoor Air, & Help Mother Earth (and your wallet) for $15

Written by Aaron Martin, Building Energy Analyst and HERS Rater

According to the Environmental Protection Agency, roughly 25% of the air moving through you HVAC system's ductwork is loss through leakage. Aside from the resulting comfort issues inside the home, increased inefficiency for your heating and cooling system, and financial and energy losses, indoor air quality is also adversely affected. If your ducts are located in unconditioned space (crawl spaces, attics, basements) return duct leaks are pulling hot or coldLeaky duct Environmental Solutions Group contaminated air into the duct system and introducing this into your indoor environment. On the other side of the coin, supply leakage can also be insidious. The negatively-pressurized (i.e... too much return and insufficient supply) environment can be flat-out dangerous if you have gas combustion appliances within your home's thermal boundary: back-drafting can occur, as well as scarier events life flame roll-out. Thus it can be seen that duct leakage is more than just energy loss and is a big part of the "house as a system" mindset.

We purchased our 1955 brick ranch earlier this year and one of the bonuses of the house was its HVAC system, a dual-fuel heat pump installed in 2013. Though the supply ducts were replaced at the time of the installation and were insulated to Code levels (R-8 duct insulation), the return ducts were probably 20 to 30 years old and looked quite leaky; they were also uninsulated for the most part. One hundred percent of this ductwork is located in the crawl space. Moreover, a visual inspection from inside the house showed plenty or dust, dirt, and pet dander. Promptly after moving in, we had a licensed HVAC contractor replace the return ducts, insulate them to code, and add a high-quality media filter to the system. We were quite comfortable throughout the cooling season (which is fairly surprising considering that the house is mostly uninsulated).

Now that we are into the heating season, I decided to assess the performance of the ducts at my house. Using the tools of the trade, I was shocked and disappointed to find that nearly half of the air moving through the ductwork was lost to leakage. Even more concerning was the fact that the three return ducts (which go to two return grilles) were quite leaky. Donning my coveralls, a respirator, and a head lamp, I was able to find gaps between the sheet metal box just beneath the home's main return grille and the floor joists to which it is attached. One gap was so large, I was able to put three fingers through. Not good.

Mastic Sealant Ducts Environmental Solutions GroupThe solution: a bit of effort, a cheap paint brush, and a bucket of mastic, a water-based sealant used for ducts that creates an air-tight seal. Mastic can be purchased at home improvement stores or HVAC supply stores for around $15 for a one-gallon bucket. I applied this from inside the house at the two returns (indeed, at one point my head and shoulders were inside the home's main return as I painted on the mastic) while an HVAC technician sealed from the crawl space side. I had the benefit of being able to blow air into the duct system using a duct tester, which helped the technician determine where the leakage was happening. He was also nice enough to address the connections of flexible ductwork to sheet metal duct boots at a couple of the leakier supplies.

The results: duct leakage was reduced by 67%! I am incredibly pleased and, though we have not bee in the house long enough to see financial gains of the duct sealing, I can breath easier (quite literally, in this case) in knowing that we are no longer pulling contaminated crawl space air into the house, our system is working more efficiently, our hard-earned dollars are not flowing out of the house, and we are helping the planet to boot. Not a bad return (pun intended) on an investment of $15!

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