Insulation - Saving Green and Being Green

Before we broke ground, I had it in my head that we would invest in insulating the entire house with foam rather than using fiberglass batts. That, of course, was prior to a number of surprises that have eroded away at the available funds to invest in energy efficient techniques. When the time came to get bids for foam insulation, the prices were an unpleasant surprise. This was disappointing since we invested a large amount in the geothermal system and don't want those gains minimized by par or sub-par insulation.

The obvious answer is to just bite the bullet and pay for the foam. The price for Icynene insulation in the entire house was well over $10k. That's a big pill to swallow considering fiberglass batts throughout would only be $3k or less. We also received a bid for a soy-based foam as an alternative to Icynene. This was around $8k; a much more palatable number, but still a bit steep.

I started digging into the differences between these foams to better understand the price and performance deltas. Icynene boasts an R-value of 3.7 per inch. BioBased's soy foam boasts an R-value of 3.7 per inch. Old fashion fiberglass boasts a value of...3.7 per inch. Huh? The fact of the matter is that fiberglass's r-value is a theoretical value that doesn't consider the effects of outside air entering the wall cavity. Foam insulation doesn't have this problem since it seals as well as insulates. This how foam manufacturers are able to achieve better real world performance and why they claim higher r-values that fiberglass. So if I can just figure out how to seal the wall cavity inexpensively, then perhaps we can just use the fiberglass and save some green.

It turns out this is fairly common especially in colder climates. I came across a few sites of companies up north that use a combination of caulk and foam to seal up the house. This is something I could do myself and save even more money. Basically, the idea is to use expanding foam anywhere inside the wall where air can enter and then use caulk where 2x6s meet, between the bottom 2x6 plate and the sub-floor, around door and window headers, etc.

Here's what it required:

Oh, and a really tall ladder!

The Great Stuff foam is awesome. This was easily applied and didn't take long. I recommend buying the pro gun shown above. The cans at Home Depot are not appropriate for large scale applications and you can't adjust the flow rate like you can with the gun. The gun cost about $50. I bought four large cans of the foam and it was enough for the whole house. The caulk was the most expensive part. I bought GE's Silicone II since it allows for 2x expansion. This should hold as the wood expands and contracts with temperature changes. I went through almost 40 tubes of caulk. A word of advice on caulk guns: buy the nicest one you can find. The $3 gun at Home Depot or Lowe's will have you cursing 15 minutes into the work and you'll be icing your hand when you get home. Why do you think I took 2 months off from this blog! ;)

For the foam, I applied it between the 2x6s and the external OSB at places where an OSB seam met the 2x6. I also applied between 2x6s where there was a small gap that wouldn't get much fiberglass. The caulk was applied at every seam where two or more 2x6s met as well as around all 2x6 seams at door and window headers. The hardest part was the clerestory where I had to use a 20' extension ladder to get all the seams. This was a bit nerve racking, but I managed to stay on the ladder. In the picture above, you'll notice a small nylon rope tied to the foam gun. This went around my wrist so if I needed to drop the gun to catch myself, it wouldn't go plummeting to the ground and get damaged. I never dropped it, but it was convenient to be able to let go of the gun to move the ladder or get around.

It took me 3 weekends to do the whole house. I expect I spent about 40 hours total. After it was all done, one of the HVAC contractors mentioned that they do that service and it probably would have cost between $2k and $3k. I spent about $450 on materials so I think doing this myself was worth it. Here's how some of it turned out.

Cross braces have an OSB seam behind them

Plug any holes you see

In the end, we went with Icynene in the roof and in the bands. The bands are where the floor rafters and the OSB meet. This area is difficult to foam or caulk and fiberglass doesn't do well here so it was worth the cost. The total cost of the Icynene was about $3600. Formaldehyde-free fiberglass batts were put in the walls. The cost of the batts which including sealing all floor penetrations and putting non-expanding foam around the windows was just under $2k. So we ended up spending less than $6k on insulation and we got more than I had originally planned. I hadn't even considered caulking everything which wasn't included in any of the foam quotes we got.

Foam in the roof of the clerestory

Foam, Batts, and Caulked header