Best options for air sealing & insulating 1960s raised ranch without spray foam
I live in EnergyStar Climate Zone 4A and I am working on trying to find insulation companies that will NOT use spray foam to air seal my rim joist and the attic of my 1960’s raised ranch house.
My main goal is to air seal my house so that it is less drafty in the winter time. I get a lot of air leaking behind the baseboards and through the windows. After air sealing inside the house, I’m going to get the crappy original wood single pane windows replaced and will make another post about that once the time comes.
I want to know:
1. What products that are NOT spray foam are the longest lasting and/or provide the most R-value for air sealing? I am talking with one insulator about tapes and mastics (airseal tapes, etc.) But I have NO idea what companies are good or what brands are good in terms of airseal tape/barriers, or what R-value to try aiming for with either one.
2. Is fiberglass blown in attic insulation better than cellulose? I have cellulose now and so far the companies I’ve talked to want to do blown in fiberglass. I have more insulation company appointments in October, that’s why I’m trying to ask for help now with finding out the best options before the different companies come to my house and give me their options.
My current thought is to have installed mineral wool/rockwool/roxul in the garage ceiling, as well as in front of the rim joist (inside the cavities). Also tape/foam board/mastic the rim joist and band joist in the basement and garage. Maybe rockwool the shared wall between the basement and garage that just has original pink fiberglass insulation in it now. Because it’s a raised ranch, the rim joist in the garage is inset several inches on each side, it is NOT flush with the garage walls. I don’t know if that makes air sealing more difficult or not.
My attic underside is NOT insulated and I’m not planning to change that, because I don’t get snow melting on the roof. The only attic change I’m considering is air sealing for sure and possibly more blown in cellulose or fiberglass. I don’t know how much blown in cellulose there is right now. I’m going to guess between 4 and 6 inches. According to one insulation person, he thought it had started out at 10 inches and wants to make it equal out to between 14 and 20 inches (the estimate doesn’t say and I’m going by memory).
The only estimate I have wants to add baffles to the attic, air seal with foam and add blown in fiberglass to make it equal an R value of 49. It does not break out the cost for each of these options. Would I do better with blown in cellulose and something besides foam on the can light penetrations and vent penetrations?
Please let me know if there’s anything else I haven’t considered and your thoughts and questions. Thanks!
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Replies
This is arguably the best blog GBA has on whole house air sealing:
https://www.greenbuildingadvisor.com/article/old-house-air-sealing-basics
If you really want to do a good job in the attic, you need to air seal first. This will require exposing the top plates, electrical boxes, plumbing vent penetrations, and any ductwork that have created holes in your ceiling air barrier. Someone will need to either shovel insulation away from these areas or remove all the existing insulation to gain access (there are insulation vacuum systems for this). Usually, air sealing in the attic is done with canned foam or caulk/sealants. Don't forget about sealing the attic hatch. Once all that work is completed, then you can blow additional insulation. The R-49 you mentioned is a good goal.
As far as the rim joists, the rigid foam insulation will work, but EPS and XPS technically needs to be covered with an ignition barrier unless the basement ceiling is covered with drywall or other approved fire-resistant finish. Certain foil-faced polyiso (Thermax) is allowed to be left exposed. This piece of information is not included in the article.
Thanks for the info. After the rim joists are insulated, they're going to be drywalled over. Unfortunately I can't seem to find an insulation company that also does drywall work, which doesn't really make sense to me because I'm sure I'm not the only one who has a finished basement with an uninsulated rim joist behind the drywall.
You might want to do a cost comparison between adding the drywall, with the additional labor and the cost of Thermax. The cost might not be much higher. Your insulator should be able to supply that product.