Understanding duct sealing in a new home…

Sounds pretty mundane, but in the MN building industry it is a pretty hot topic. As code continues to be understood by us all, the best and most cost effective ways to build a home always seems to filter to the top of the list. One of the major code changes we saw in this past cycle was the sealing of the duct systems within a new home. To many it seems strange why we would worry about losing airflow in our home when it is still staying within the house envelope.   There is much more to this logic than meets the eye. Moving forward, I have decided to spray seal all of my new homes ducts from the inside with a spray sealant vs how many builders plan to do it by basically bondo sealing the ducts together with a thick mastic type sealant. My decision to do so came after seeing results first hand on my own home. I figured what a better way to test something out than myself on my personal home that I recently finished. Being new but built in the previous code, I automatically assumed everything was working the way it needed to and all of the rooms had plenty of air flow to either heat or cool. My heating/cooling guys are some of the best in the business and this too gave me comfort in knowing what I should be dealing with. I was definitely proved wrong with my logic when the preliminary testing came back to show me how much air was flowing from each duct in my home. I had ducts ranging from 1 cfm all the way to 55 cfms. Basically meaning no air coming into some areas of the home and lots of air coming from others. I often preach to my new home customers not to shut vents completely down to avoid hot/cold spots in a home as well as high/low pressure areas of the home. Little did I know this was happening even when the systems ducts were fully open. The fun began once the company fully sealed the duct system and started to spray in the sealant. Basically they pressurize the entire duct system in the home to force an airborne chemical in to seal each and every joint in the ducts system. As they sealed, you could watch the computer read out showing just how much tighter the home was getting. Upon completion, my homes supply system had a 98.1% reduction in air leakage. Meaning the air was now all flowing to the exit points in each room vs inside the ceiling spaces of the house possibly or other rooms in the house. What does all this mean to the homeowners we are now going to build homes for? It means that you WILL have much more even heating/cooling in a home despite one room being a foot away from the furnace room and one room being all the way upstairs and across the house. Your thermostat will call for hot or cold less often if the entire home is more evenly balanced as well. The bottom line is a new home will now push more air, more evenly, and do it with the same type of heating system.   I’m happy to be your guinea pig and hope this helped you understand what is on the horizon for us all when looking at new homes!

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