Air Sealing and Insulation - The Week of Weatherization

This week has been all about air sealing and insulation.

In my previous post, I wrote about air sealing and insulating the main house--a drafty and uninsulated house, built in 1906. In the weatherization project, that house wall assembly's R-value increased from R-1 to R-12-- a huge improvement that will dramatically effect the comfort of the house, and decrease the energy bills.

This post is about air sealing and insulating the ADU. It was far easier and cheaper to air seal and insulate the new ADU construction than to weatherization retrofit the 1906 construction. In contrast to the retrofitted R-12 walls, the ADU's walls are now R-33. After much consideration, I decided to use Certainteed blown-in fiberglass insulation. This cost $2,700 for about 1400 sq ft of wall cavity (9" deep), and 900 ft of ceiling cavity (10"deep).

Blown-In Fiberglass Insulation

For those of you who are new to this, R-value is a measure of the heat resistance of a material assembly. You know how metal or glass feel cold when one side is facing cold air? They feel cold because those materials conduct heat very quickly. Conversely, Styrofoam does not conduct heat well, which is shops sometime use Styrofoam cups to contain the heat of hot liquids. The best kind of insulating building product is called closed cell spray foam, but it is 2-3 times more expensive than blown in insulation. It's also super ugly---to me, it looks like alien puke--just look at the picture of it in my main house basement ceiling and you'll see what I mean. But, it's effective as an air sealer and insulation material and it's en vogue. It's very important to air seal and insulate buildings to reduce their energy demand- and there's a number of ways to accomplish this. 

Closed cell spray foam looks weird, but it does a great job insulating and sealing

Below are three videos that show the air sealing and insulation process that we used. This was a neat process to watch in person--the third video is best one to see the insulation being blown.

Installing cardboard baffles to create a vented roof cavity


Installing netting for insulation


Blowing in insulation in walls and ceiling (aka. BIBs- blown in blanket insulation)



A video of the completed insulation a day later.