What blown insulation to use?
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| Posted in Energy Efficiency and Durability on
I’m a contractor and in the process of finding the best, safest, and most energy efficient blown insulation to use for my customer. The asbestos siding was just removed revealing that there is no insulation in the walls and I simply would like to know what is the best insulation overall. I read that cellulose can corrode metal over time and doesn’t fill the cavities. There are so many pros and cons to this question of the best insulation I decided to pose this question to the Green Building Advisor. I’ll wait to hear back and thanks in advance for your help!
Mike
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Replies
Mike,
There is no single "best" insulation. The most common insulation used for filling the empty stud bays of existing houses is cellulose. It will not corrode metal, and if it is installed with the dense-pack method at a density of at least 3.5 pounds per cubic foot, it will not settle.
Blown-in fiberglass can also work, although fiberglass has a much higher embodied energy than cellulose, and is therefore considered less "green."
For more information on blown-in cellulose and blown-in fiberglass, see Blown Insulation for Attics.
Michael,
My personal favorite is not blown but pumped: Air Krete wall foam. It is a cementitious material which is inherently non-combustible, has zero outgassing and good r-value (4 per inch). Air Krete has been around for years and has a very good track record. We have installed it since 2006 and it is my preferred retrofit product.
Torsten: I have read that the Air Krete is good, but tends to crumble at the edges over time, as houses "wiggle" (from wind, heavy traffic, seismic activity, etc). Have you noticed any of that? Too, does Air Krete fill in very small voids? Thanks. john
Still not sure what to go with. The general consensus seems to be cellulose is good for attic floors and foam is best for walls, but which foam is the question...
Mike
Michael,
I don't know where you live, or the origin or your information. But I strongly disagree with your conclusion that "The general consensus seems to be ... foam is best for walls."
In New England, almost no one uses spray foam to insulate the empty stud bays of existing homes. Almost everyone uses dense-packed cellulose.
The important thing is where are you?
You have the options of internal, external, what does your customer expect?
More important what do you expect.
External insulation means that the occupier will have to pay to heat the frame of the home and the spaces between the frame.
Internal, uses less insulation, costs a lot less to run the heating system, one will recover the cost more quickly, makes rooms smaller, easier to do to obtain an air tight fit, you can ignore the weather.
Only filling the spaces between the frame, leaves a lot of wood to conduct the heat from the home.
The area where I work is lower Westchester County in New York. The insulation contractors in my area seem to push foam insulation. My quest is to now find one who uses dense-packed cellulose. I need to get this done asap so we can tyvek the house before the rains come. Thanks all for your help! Much appreciated!
Mike
It sounds like you are working from the outside and there is already drywall on the interior that you are not disturbing. Cellulose is a good choice and what I'd do is find some of the weatherization agencies or contractors in the area and get some referrals to companies that can come out and do the job. There is an entire market segment that does nothing but retrofit work, and if you do some Googling for "westchester county weatherization" you should start finding the right people. If it was my job I'd wrap the exterior now, and let the insulator do what he has to do when he shows up. Leaving the house unprotected exposes you to a lot of risk. There are ways to temporarily batten down the wrap so that it can be pulled out of the way later. CYA!