Putting in insulation where none exists?
MichaelNYC
| Posted in Energy, Heating & Insulation on
Hi,
I just bought and moved into a 1927 Craftsman bungalow in upper Westchester county, NY. I am working room by room, starting with the dining room, and ripped down all the old wall board (there was no lath and plaster, interestingly enough). There is absolutely no insulation between the wall studs on the exterior walls of the room. However, I can see a type of fiber board, upon which they put wire lath and then stuccoed the entire exterior of the house. Having said all that, is it prudent to put in fiberglass in the wall cavities before I sheetrock over it? Is rigid foam better? I don’t want to use the spray-on foam that expands for health concerns. Any advice would be greatly appreciated. Thanks.
Replies
What health reasons concern you about spray foam?
IMHO, insulations rank in this descending order: spray foam (either open or closed cell), cellulose, and fiberglass. If you go with cellulose or fiberglass, be sure to air seal any penetrations into the cavity before insulating. Foam air-seals as it's applied. The choice is really between foam and cellulose. If you've got the bucks now and can wait for the payback, go foam. If money is tight, but you still want good performance, blow cellulose. If you're moving in 6 months, use fiberglass.
Andy
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Hi,Is there a good way to install cellulose in the case where you are taking down the lath and plaster (ie compeletely removing the inside wall)?What holds the cellulose in place? Netting? or?Thanks
Gary
Cellulose can be installed several ways. You can blow it in behind a net, or a reinforced plastic vapor barrier. It can be blown into the open cavities damp and trimmed flush with the stud faces. It will hold its shape. Or you can install the drywall, leaving a strip out to provide access for the hose, and dense pack the wall. That's how my house was done, and it's been working well.Andy
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Did you also have a 6 mil plastic vaporbarrier under the drywall?
Thanks
'Nemo me impune lacesset'No one will provoke me with impunity
No. I don't believe vapor barriers are appropriate in mixed climates. I told the BI this, and even though it's code in CT, he was OK with it.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Agree with Andy. I just wanted to add that I think the Stucco situation makes the vapor barrier even less desirable than it would be otherwise.
This line of thinking is the root of many problems in the USA:
If you're moving in 6 months, use fiberglass.
That was me being facetious to drive home a point. I almost never advocate the use of lesser quality products.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
I was hoping so. The humor might get missed.
If you go with cellulose or fiberglass, be sure to air seal any penetrations into the cavity before insulating.
I meant to ask about this earlier but forgot. I've heard this many times. But I also hear that an advantage of cells over FG is that the latter permits convective air currents whereas cells do not. So surely cells, esp dense-pack cells, cut off air infiltration, so why the emphasis on sealing penetrations before blowing cells?
This is especially puzzling because there's no air-tight barrier on the outside of the house, even with building wrap. I thought that there might be something here about too much moisture infiltration if you don't seal, whereas cells can handle the little bit of moisture just from diffusion without a VB. But that argument wouldn't hold for AC in summer.
Cellulose absolutely performs better than fg in blocking air infiltration. But it's not perfect, and I like the belt and suspenders approach.
It's most critical to block the air leaks at the top and bottom off framing cavities. The stack effect - warm air rising - is probably the most powerful force driving air leaks in houses. If you cut off the air's path from low to high, preferably at the top, but the bottom is helpful, then you'll short circuit most air leaks. Another key to the puzzle is this. As the air leaks out the top, it must be replaced, and that happens with air drawn in from the lowest pressure area, typically the basement or crawlspace. Those tend to be damp places, so this replacement air is a common source for moisture in framing cavities and attics. I looked at a classic case last week. Damp, vented, dirt floor crawlspace. You could feel the air moving from there into the basement. The attic in that house had both a large, leaky hatch and a whole-house fan. The bottome of the attic sheathing was covered with frost. Textbook.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Thanks for your responses, they are very helpful.
There's nothing wrong with fiberglass when installed with care. It is a do it yourself job. You can purchase an extra dense fiberglass batting that is more resistant to air flow than standard fiberglass.
Install unfaced fiberglass insulation and go over the entire wall with a plastic vapor barrier.
Rigid foam would be near impossible to fit tightly.
I beg to differ WayneL5,
If you live in a dry climate that is always 45deg F outside and you keep it 70deg inside, you may have a good reason to use FG.
Foam (spray in place or cut to fit and sealed w/gun foam) work better per R value in cold climates.
Google "insulation r-value testing". Interesting reading.?!
Garett
http://www.energywisemortgage.com/r-value_myth.htm
I'm not sure which FHB articles directly reference this issue. Odds are they'd use Building Science as one of their sources, however. I'd also look to PATH, Home Energy magazine, and Energy Design Update for more info.
FG can work if it's detailed well. And so can a vb. But fg is rarely detailed well, particularly around obstructions, whereas blown foam or cellulose excell in complex spaces. As to vbs, well, far more moisture (like an order of magnitude more) can move with air infiltration than can diffuse through drywall. Vapor barriers deny water in cavities the chance to dry inward, as they are wont to do in the summer.
I have no argument with vapor barriers in the cold parts of Canada, where your experience comes from. That said, how well are the code required vapor barriers working out in Vancouver? Seems to me I saw lots of vb related issues causing walls to be torn out when I was there a few years back.
Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
But you feel that CT has enough of a temp. swing not to use VB? I'm not that far from you on L.I., so that's why I ask. As for detailing, yes I do cut very closely around obstructions and such to get the best fit. Back in Ontario the concern was too tight of a house, and often air exchangers would be installed to offset that.edit: are there any issues with blown in cellulose settling and leaving gaps at the top of a stud bay?
Edited 1/22/2006 9:23 pm ET by TGNY
Yes, I do. It gets pretty hot here for four months of the year, and pretty cold for four months. Not sure what happens with the remaining four months, 'cause it seems that the weather sucks, then, too. <G> Because I don't work there, I'm not quite sure how far north I'd go before wanting a vb. Somewhere around Piffin, I imagine. Certainly in most of Canada.
I don't worry about the cellulose settling in cavities. Mine was blown in to a density of around 3.5 lbs per cubic foot, which is greater than cellulose's normal settled density of about 2 lbs per foot. Consequently, the stuff stays where it's put. I have no open attic space, so there's no loose blown cellulose in my house. If there were, I wouldn't worry about settlement there either. The advertised R-values for loose blown cellulose are for the predicted settled depth of the nominal blown depth, if that makes any sense.
Cellulose has one great advantage in use without a vb. That is, it can hold a lot of water before saturation. So, if it gets a little damp, no big deal. It can dry the next time favorable drying conditions turn up. Use a vb, and the drying potential diminishes greatly.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Amen to what Andy said. Andy sure saves me alot of typing by almost always saying exactly what I would have said. He knows his stuff.
Got the check, I take it? <G>Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Since this started with a 1927 house....How do you stop cells blowing through the gaps in the 1x sheathing in an old house? Do you rely on the building wrap? And if it's not there, there's gaps between shingles in shingle siding..... Seems like dense-pack at least is not an option.....
That may be true in this case. If there's no building paper and gappy sheathing, then foam is probably the best option. On the other hand, if the windows and doors are properly flashed, it could work.
Old houses are tough. Sometimes, the best that you can reasonably do is air seal. I did a blower door test a few weeks ago on an old house, and at 50 Pascals of depressurization, which is equivelent about to a 20 mph wind, we had outside air flowing between the floor boards on the second floor. The homeowner didn't want to go to the expense of insulating the walls. In that case, the best resolution we could think of was to tear out the baseboards and install blocking both in the balloon framed studs and between the joists to seal out the outside. That's a case where air sealing would probably have at least as much effect as insulation, at a fraction of the cost. Low hanging fruit, as Fred Lugano used to say.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
If there's no building paper and gappy sheathing, then foam is probably the best option.
There was some talk on a thread not long ago about SPF in these kinds of walls gurgling through the gaps in the sheathing and pushing out the siding. Maybe this is not a problem, or less of a problem, with open cell foam. Any foamers reading this and want to comment? I'd also be worried about degradation of the foam from UV exposure.
On the other hand, if the windows and doors are properly flashed, it could work.
I assume you mean as long as there is building paper properly integrated with the flashing (if that is there.....).
Well, in theory, if the siding is expertly applied and the flashings properly integrated with it, no building paper should be needed. On my own house, I used #15 felt paper and a rain screen....Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Did you reside an existing house?Sounds like it would be advantageous to put in a drainage plane before blowing cells. But of course if you're going to reside, better to blow cells beforehand rather than screw up the siding later.As you say, old houses are hard.
No, I built new and blew the cellulose from inside.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
"I have no open attic space, so there's no loose blown cellulose in my house. "I don't think that this has ever come up. What kind of ceiling/roof systems do you have? Just packed cels over net and DW or pack cels with venting baffel (I think that is what Mike Smith uses)? Or Sprayed foam or ?
In about 2/3 of my attic, the 2 x 8 rafters are dense-packed with cellulose, no venting. In the remaining third, there's a plywood floor and the space between the 2x10 joists is dense packed. That part of the attic is vented. It's interesting to note that the frost patterns on the roof suggest that the side with unvented roof leaks less heat than the side with the vented roof.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom