Can anyone give me their experiences (positive or negative) with dense-packed cellulose?
shm_helene1
| Posted in Green Products and Materials on
We are building a new house and in research insulation options I decided on dense-packed cellulose. My builder seems very opposed to it. He uses blown-in fiberglass. He said he had problems in the past with settling. He also thinks the R-value is probably higher with blown-in. Any advice would be really appreciated.
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Friends in Alaska live with their double walled, dense packed walls and love them. BUT, you do have to find a capable outfit that can dense pack correctly. There is a great video here on GBA that defines dense pack. When correctly done it will not settle. Rental blowers will not do the job. This will take professionals with a hopper truck and powerful blower. Best if you can have an open raised heel truss above with continuous cellulose.
See more details at CCHRC;
http://www.cchrc.org/
A great u-tube about cellulose in extreme cold;
https://www.youtube.com/watch?v=Xen_VWyDezY
Cheers,
PK
Ditto on getting the right installer. I've tried to switch entirely to cellulose because there's less embodied energy, no itching, and rats don't seem to like it. We've done a number of dense-packed floors as well as walls. There tends to be some airborne fine dust as material is going in, so it's a little more hassle in a remodel, but not an issue in new construction.
Sounds like your man is inexperienced. DP cell installers worth their salt always use IR cameras to monitor and prove the quality of the blow. Perhaps they cannot get the right machine in your area. There are excellent instructions on the internet; its not that hard. 3.5 to 4 lbs per ft sq will not settle.
Thanks all for your answers. I think the builder wants to use his guy and his guy isn't experienced with it. I will share your answers with him and hopefully this will continue to sell my point.
Shannon,
If you (or your insulation contractor) wants more information on this topic, I would suggest this article: How to Install Cellulose Insulation.
Dense pack is messy, expensive, fussy around penetrations, hard to do small sections (one wall that wasn't ready when the truck was there). It did make my very drafty 150 year old house pretty cozy, but next time I will save the money and instal rock wool myself.
JM Spider fiberglass insulation is well liked. Search Chandler on this site.
Both fiberglass and cellulose will settle if not installed at sufficient density. The required density for cellulose not to settle is a function of it's seasonal moisture content changes, and thus climate dependent. In most US zone 3 locations 3.2lbs/cubic foot would be enough, but in climate zone 6A it would take at least 3.5lbs per cubic foot.
The air-retardency of fiberglass is pretty lousy at the minimum densities that it won't settle (which is not as climate sensitive) but is pretty good at 1.8lbs per cubic foot and up. New-school blowing wools like Spider, Optima, and L77 are higher-R than cellulose, but not by enough to really matter in typical 16" o.c. framing that typically has a ~25% framing fraction thermally bridging the insulation. The higher R can make a difference on double-studwall and Larsen Truss assemblies though.
Whatever you choose for fiber type, specify the installed density, and try to verify it by multiple methods (eg counting the bags and multiplying by weight, and estimating the wall cavity volumes, etc.)
We used double wall construction with dense packed cellulose in our new house. Depending on where you live it is hard to find experienced installers. They originally wanted to blow in behind the sheetrock but I insisted they use the netting. We did have some problems and the sheet rockers weren't really happy when they overfilled some areas. It was the most cost effective of all the options we looked at. I like the fact that it is recycled material and can be easily removed if necessary unlike spray foam.