My house is about 30 years old and I am about to replace the siding on my house and I was thinking then once the old siding is ripped off, should I take the wrap as well as the plywood off to do a thorough insulation job? I was thinking of using spray foam. Of course I would be spraying the foam from the outside and it would be adhering to the sheet rock backing. Is this a good approach? Any suggestions would be greatly appreciated.

Thanks.

Question:
What color is a cucumber?
Where is Singapore?

Choices:
Green
In the Far East

 

the "poll" option is bogus. I'd vote for "ring shank nails" myself.

you'll never be able to open up the drywall for any fixes if you foam without putting in a plastic isolation sheet. also check your local code official... some areas require more insulation than you can get within the studs (!) which means you have to apply foil-faced foam outside.

spray foam is 2 to 3 times the cost of anything else. it's Cadillac treatment.

You say the foam would stick to the back of your drywall. (?)
Do you not have a vapour barrier between your drywall and the existing insulation (if any) or between the drywall and the studs?

If it wuz me, and you have the stud cavities open from the outside, I would buy slabs of extruded polystyrene foam, cut those to a little undersized with an ordinary hand saw, stick the 3 1/2 inch thick foam slab into place and hold it there temporarily by shoving shims between the foam slab and the studs, then caulk all around the foam slab with expanding foam. Once that expanding foam sets up, cut off the excess foam and fill in the spots where the shims were with more expanding foam.

Extruded polystyrene insulation (like "Roofmate") is closed cell foam, so it's not permeable to air or moisture. So, it doesn't need a vapour barrier. If you do use extruded polystyrene foam, you'd do well to remove the vapour barrier before installing the foam from each stud cavity to avoid having two impermeable barriers that water could get between.

This message has been edited. Last edited by: Nestor,

Nestor, you made the same recommendation to me as well. It does sound good in theory. Do you know anyone who has actually insulated as you described? Also, I haven't seen "Roofmate" in my area. Are you familiar with any other manufacturers?

Sturdy:

No, I pretty much tend to my own business running my property, so I don't know of anyone who's used polystyrene in their walls, but if you can use it as insulation and install it from the inside, I can't see why it wouldn't be equally effective installed from the outside.

So far as I know, there are only two manufacturers of extruded polystyrene insulation in North America, Dow and Owens Corning.

Dow makes "Styrofoam" and their line of "Styrofoam" includes a variety of of both expanded and extruded polystyrene insulations for various uses, and that line up includes "Roofmate" made specifically for insulating flat roofs. Expanded polystyrene is the stuff that looks like it's made of styrofoam "beads" whereas extruded polystyrene just looks like rigid foam.

Click on this link to see some pictures of what Dow's "Styrofoam" extruded polystyrene insulation looks like:

http://www.glasscellisofab.com/en/polystyrene.html

Dow's web page for their extruded polystyrene is here:

http://building.dow.com/na/en/...gidfoam.htm#Building

Call 1-866-583-BLUE (2583) to talk to someone at Dow about using it to insulate your stud cavities from the outside. Also, they should be able to tell you who sells it in your area and whether my game plan is appropriate (and possibly give you some ideas on how to improve on that gameplan).

Owens Corning makes "PINK", which is an extruded polystyrene that's pink in colour.

http://www.owenscorning.com/wo...tyreneInsulation.pdf

Just dial 1-800-GET-PINK, and you'll talk to someone at Owens Corning wanting to sell it to you. He'd be able to tell you whether my game plan is a good one or not, and also who retails the various extrusions Owens Corning produces in your area. Those companies should have people on staff who can tell you whether or not it's a good gameplan as well, and if they know anyone who's done it.

The people answering the phones at Dow and Owens Corning are going to give you far more reliable advice than I can.

But, I don't see any reason why insulating your stud spaces from the outside wouldn't work as well as insulating them from the inside with fiberglass. And, people do that all the time. If you use extruded polystyrene, the only difference should be that you're getting 60 percent more insulating ability per inch.

Also, so far as I know, both Dow and Owens Corning make equally good extruded polystyrene insulation, and the only difference between them is the colour. So, see what both offer and chose the product that's most suitable. And, phone everyone who sells Dow's or Owens Corning's extruded polystyrene in your area for prices. Just because different places are selling the same thing, doesn't mean they're selling it for the same price.

I know that Dow's "Roofmate" has been used on flat roofs for over 20 years because I was considering using it instead of expanded polystyrene when I had my roof redone over 20 years ago now. So, if there are any health concerns with extruded polystyrene insulation, they most likely would have come to the medical community's attention by now.

This message has been edited. Last edited by: Nestor,

Thanks Nestor.
That will keep me busy for a while

Here's a video of a guy doing what Nestor described:
http://howtohomeinsulation.com...mans_spray_foam.html

This message has been edited. Last edited by: SturdyNail,

SturdyNail:

It seems to me that there'd be enough people wanting to do what you're doing that either Dow or Owens Corning would make a 3 1/2 inch thick slab 14 1/2 inches wide to fit between wall studs that are 16 inches on center.

If either one does, that would save you a lot of cutting work.

Why wouldn't you just cut everyone to fit snug and use the foam wherever the boards studs were bowed.warped or you did cut an air-tight fit? Seems like an extra lot of work for nothing...

Can't talk about SturdyNail's walls, but my experience with the studs in my building is that they can be anything but straight, all in a nice straight row and on 16 inch centers.

Some of them will twist, some of them will have split since they were installed, some of them bow this way, some of them bow that way, some of them will bow AND twist at the same time, Some of them will have one straight side and one curved side cuz they were cut from a smaller tree, you name it.

My wall studs look OK from a distance or if you're not really paying attention. Once you get out the tape measure and start taking measurements, you find out how unique and individual each stud can be.

This message has been edited. Last edited by: Nestor,