*
Before blowing cellulose into wall cavities of my balloon framed old house, I am trying to understand the danger of not having a vapor barrier on the warm side. I think the insulating qualities of cellulose are fine, but conventional wisdom says condensation will occur on outer wall sheathing with vapor flow into walls.
I read CIMA technical bulletin #2 and I’m not sure this helped. Section 9.2.1 states that vapor retarders are unnecessary unless temps are below -15F and then vapor barrier paint is recommended. But then in section 11.5 homeowner is cautioned that R.H. should be below 40% inside when outside temps fall below 32F. Retarding vapor flow into walls of existing homes seems difficult – don’t know if vapor retarding paint really works. Anyone have experience with this?
Confused as usual.
Mike
Replies
*
I've seen problems and I've seen successes. Whether the job was cellulose or fibeglass.
1 i think cellulose is your best choice.
2 Research is confussing to me too
3 Moisture transported through Air leakage is probably more of a danger than vapor diffusion through painted wall surfaces.
4 go for it, do a depressurisation of the house after insulating and seal the leaks
5 hope for the best.
*
FREDL; Explain dense packed cellulose insulation, I thought that cellulose insulation was blown in, that it would stay lightly packed. The reason for the question, I just moved into a 60 yr. old house and I'm wondering about how to insulate. I live outside St.Louis, Mo. and right now its 4 degrees, plus it gets rather hot here in the summer.
*
Bill - I've followed Fred's advice and am pleased with results (so far - not done yet). One issue to address in ballon frame is wall cavity to joist bay bypass at second floor joists. I was repairing siding on that wall and removed enough claps and one sheathing board to dam up joist bays. Then I blew from attic to first floor - 20' - and it dense packed all the way to attic floor.
If you're diy, plan a weekend of experimenting and learning. The particular free loaner blowing machine I had had no damper to adjust product-to-air mix (lean-ness being required for dense pack) and I had to fabricate a damper from cardboard. Then it worked like Fred said it would.
*Bill. I just wanted to add to Fred's usual good advice. Just blowing cellulose into a wall is no guarantee that it will not settle. It must be blown in to some density, usually 3.5 pouds per cubic foot (PSF). Properly blown in cellulose does not settle.If you plan on doing this yourself--a good, invaluable experience--get back on this page and ask for more information before you start blowing. Gene L.
*
FredL
Thanks for the info,you explained it clearly,now I understand, I remember many years ago a friend had cel insulation blown in, a few years later there was a line around the top of the wall in two bedrooms, water stains, the only thing we could come up with was the insulation settled. And as luck would have it the contractor was no longer in business! Bill
*Gene LThanks for taking time to reply, I will probably be doing this myself in the distant future, to many other things to do to this old house first, so I will be back looking for more advice.Bill
*Bill ConnerThanks for the reply, I will be a diy, I will be in the future looking for more good adviceBill
*Fred,The use of DP cellulose to stop convective heat loss and convective vapor transfer has attracted me to the concept. I have been trying to figure out what to do with old house walls for many years and this seems like the best concept. I am not that concerned with conductive heat loss thru walls except that maybe higher wall temps will reduce radiative heat loss for inhabitants. I am still a little concerned with moisture diffusion. Maybe this can be reduced with the right wall treatment but lets assume I cannot due a good job of this and diffusion still exists. I still don't have a clear picture of the concept of moisture storage in the cellulose. Say that the hygroscopic nature of cellulose causes the moisture content to increase during the heating season. The outer framing would be drier and then wouldn't the concentration gradient cause the diffusion to continue from the cellulose to the outing sheathing?I live where winters are severe and summers are humid. I don't have a clear picture of when the cellulose dries out.I have seen statements made that this has been tried and there were no problems but I have to wonder how one knows there are no problems. Are samples of sheathing moisture levels being taken. Will the framing still be dry 50 or 100 years from now?I would love to silence the complaints from my wife in the winter but not if I compromise the longevity of the house.Mike
*Fred,The use of DP cellulose to stop convective heat loss and convective vapor transfer has attracted me to the concept. I have been trying to figure out what to do with old house walls for many years and this seems like the best concept. I am not that concerned with conductive heat loss thru walls except that maybe higher wall temps will reduce radiative heat loss for inhabitants. I am still a little concerned with moisture diffusion. Maybe this can be reduced with the right wall treatment but lets assume I cannot due a good job of this and diffusion still exists. I still don't have a clear picture of the concept of moisture storage in the cellulose. Say that the hygroscopic nature of cellulose causes the moisture content to increase during the heating season. The outer framing would be drier and then wouldn't the concentration gradient cause the diffusion to continue from the cellulose to the outing sheathing?I live where winters are severe and summers are humid. I don't have a clear picture of when the cellulose dries out.I have seen statements made that this has been tried and there were no problems but I have to wonder how one knows there are no problems. Are samples of sheathing moisture levels being taken. Will the framing still be dry 50 or 100 years from now?I would love to silence the complaints from my wife in the winter but not if I compromise the longevity of the house.Mike
*I got a quote from an insulation contractor to do the walls of my ( soon to be) 220 year old house in NH. Is it safe to assume that all cellulose insulation is installed in the dp method or should this fact be specified?
*
Before blowing cellulose into wall cavities of my balloon framed old house, I am trying to understand the danger of not having a vapor barrier on the warm side. I think the insulating qualities of cellulose are fine, but conventional wisdom says condensation will occur on outer wall sheathing with vapor flow into walls.
I read CIMA technical bulletin #2 and I'm not sure this helped. Section 9.2.1 states that vapor retarders are unnecessary unless temps are below -15F and then vapor barrier paint is recommended. But then in section 11.5 homeowner is cautioned that R.H. should be below 40% inside when outside temps fall below 32F. Retarding vapor flow into walls of existing homes seems difficult - don't know if vapor retarding paint really works. Anyone have experience with this?
Confused as usual.
Mike
*
Specifiy it. Safe to assume and contracts are mutually exclusive concepts.