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Attic Air Sealing - How important is it?

Friday, February 19th, 2016 by Tyler Tetreault


Last Thursday, I went out with one of our crews to do an attic air seal and insulation job in Sandston, VA. I first did a Blower Door Test to calculate how much air leakage the home had. This is the first set of test numbers you see below.Attic Air Sealing  How important is it - Image 1

It calculated out to be .79 Air Changes Natural (ACHn). This means that roughly 80% of the air in this home is leaking out every hour! Crazy! We got to work right away and started removing all the fiberglass batts that were originally installed in the attic many years ago.

Attic Air Sealing  How important is it - Image 2 

They were full of mice droppings and other sorts of trash / debris. Gross! We exposed all the top plates ( tops of the walls that can be seen from the attic), plumbing and electrical penetrations, and duct work penetrations.

Attic Air Sealing  How important is it - Image 3

 All were then sealed with spray foam to ensure we reduce the amount of air escaping into the attic.Attic Air Sealing  How important is it - Image 4New R-38 cellulose was blown in after air sealing to create a nice continuous blanket of insulation.Attic Air Sealing  How important is it - Image 5 We closed out our day with another Blower Door Test to see how much improvement we made to this house just by fixing the attic.Attic Air Sealing  How important is it - Image 6The post-work numbers calculated out to be .56 Air Changes Natural (ACHn) or 56% of the air leaking outside every hour. That's roughly a 24% improvement! Just goes to show how important it is to air seal before adding new insulation! Next major things that could be done to improve this Sandston home even more would be a sealed crawl space and replacing the old wooden windows!

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The Drying Co./ThermalTec
236 Industrial Blvd
Suite A
Toano, VA 23168
1-757-645-0270


The Drying Co./ThermalTec
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P.O. Box 637
Toano, VA 23168
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