When our attic renovation was still in the planning stages, I began researching insulation options. It made my head spin: closed cell foam, open cell foam, blown-in cellulose, venting or not venting the roof…

I knew for sure that I didn’t want to use fiberglass batts. From my own research, unless the batts are installed correctly, the R-value can be greatly compromised (and supposedly many contractors don’t take the time to install them correctly). It also may contain formaldehyde and it doesn’t address air leakage, such as gaps around electrical receptacles, which is a big factor in energy loss.

When we had our energy audit last fall, they recommended using dense-pack blown-in cellulose for the attic rafters. To add an additional R-value of about 6.5, they said we could add an inch of rigid foam insulation over it and under the drywall without losing much in square footage.

The rafters are only 2×6s, so getting the most bang for the buck is important. Not having to beef up the rafters with 2×2s would also be most desired.

It seems everyone has differing opinions and puts their own sales and marketing spin on it, so it’s hard to figure out what is fact and what is hype, but it seems there is no clear-cut answer as to what will work best in your situation.

I’ll briefly describe the options we considered, tell you what we decided to do, and why. Maybe you’ll disagree, but I’m not putting it up here to start a debate.

We sought estimates for several types of insulation: blown-in cellulose, open-cell sprayed-in foam and closed-cell sprayed-in foam. Our contractor also included fiberglass in his initial quote, which we eliminated.

Fiberglass insulation would be the cheapest option. It would also mean, however, that additional steps would have to be taken to seal up air gaps and vent the roof using ridge and soffit vents, thereby eliminating some of the savings.

Blown-in cellulose was the second-most economical; maybe 30% higher than fiberglass. Made from pulverized newspapers and treated with borate for insect- and fire-resistance, it’s more eco-friendly than fiberglass. It also wouldn’t address the venting and air gap issues, so there would still be additional expense.

Open-cell (low-density) foam costs about twice as much as cellulose. While there are several choices in this market, we received quotes for a non-descript brand of open-cell foam and Icynene®. From my understanding, these are the basic options:

• Soy-based foam, such as BioBased Insulation® uses soybean in place of some of the petroleum and contains no CFCs or VOCs
• Icynene® contains no formaldehyde and is water-blown, so like soy-based foam it doesn’t contain ozone-depleting HCFCs. They offer one version of their product which uses castor bean (in place of soy). Their rationale is since soybeans are a food source, castor beans are a greener alternative.

  Whether soybean or castor bean, from what I can tell the total percentage may only comprise 5-7% of the product, so you’d have to decide for yourself if the cost is worth it to you.

• Other open-cell foams will likely contain HCFCs if they are not blown in with water (in addition to potentially containing formaldehyde), so be sure to find out.

The last estimate we received was for closed-cell (medium-density) foam. While touting the highest R-value rating, it was also twice as much as open-cell and almost 5x as much as cellulose. The cost was one of the main reasons we chose not to go with closed-cell — it just was not in the budget, for one, and based on the information we had, we were skeptical that we would ever recoup the additional cost in energy savings.

In the end, we decided to go with Icynene® for these reasons:

• Up to 40% of energy loss is caused by air leakage. Icynene® (and other open-cell foams) would seal gaps and holes while also providing at least the same amount of R-value as fiberglass and cellulose
• Icynene claims to be hydrophobic and will allow water to pass through it. Closed-cell foam proponents claim this isn’t a good thing and their product prevents water from passing through. If we have a leak in our roof, I want to know the roof needs repairing before it gets really bad.
• Whether or not you go with their castor bean version, it’s still widely reported to be a green product: no HCFCs, no VOCs like formaldehyde, and it contributes to green building certifications (LEED)
• Open-cell foams have superior sound absorption properties over closed-cell
• Tom Silva, of This Old House fame, recommends open-cell foams in most situations (in my book, if it’s good enough for TOH, it’s good enough for Bungalow Chronicles!)

Insulation installation is tomorrow! I’ll let you know how it goes.

Tags: attic renovation, decisions, eco-conscious, eco-friendly, insulation, research