How To Choose And Use Insulation | This Old House

If you have an open stud bay, then you can use any one of these insulations. Okay, so let's talk about insulation in general. We all know that its primary metric is the R-value, and it talks about how it either slows or stops the transfer of heat. Right. We either want to keep the heat in the house during the winter, or we want to keep the heat outside of the house during the summer. Right, because heat always wants to go to cold. Okay, so R-values. All right, this is cellulose right here, and this is about 3.6 per inch. So an R-value of 3.6 per inch. Right. It's blown into the wall cavity. This is called a wet blow or sticky blow where they blow it through a gun and there's a mist of water that actually mists the insulation and sticks it together and dense packs it into the wall. All right. And it's really just chopped up newspaper, right? Chopped up newspaper. You can see it right here. It's treated with a boron and that's a fire retardant and also an insecticide. Gotcha. Okay. And this guy right here in the middle? All right. This is a closed cell insulation. That is really hard and rigid. Very rigid. Now the R factor of this is six per inch. Wow. So that's pretty high. Gotcha. All right. And this guy right here? This is an open cell. Again, 3.6, 3.8. Courage. All about the same. And all of the other insulations that we're going to look at are about the same, except for this one right here. And we blow this in, it very quickly expands, and now we've just shaved it off to fill this entire stud. Right. It goes in as a liquid, six seconds, it expands, you shave off the excess. Gotcha. Okay. And what are we looking at right here? All right. This is a ground-up blue jeans. It's made into a bat, and you just put it into the wall, the same as you would put in fiberglass insulation. Gotcha. All right. And everyone knows fiberglass. This is very common all across the country. Right. Now, fiberglass insulation goes into the stud bay. It should be put into the stud bay loosely, not packed in tight. Because this is all about trapping air, and so actually compacting it in there means that we're trapping less air. So you want to actually leave it sort of fluffy. Now, because air moves in this wall cavity, sometimes you want to put on an air barrier on the outside, and that will stabilize the efficiency of the insulation. Actually, it will stop the air from moving inside the wall cavity so that the R factor is stable in cold, windy conditions. Gotcha. Okay. So let's also talk about the movement of air, because air can contain vapor. So we have to think about which way the vapor is going and how we either stop that, Let's try to slow it down. Right, that warm air, think of it as filled with moisture, and it's trying to get to that cold side back here on the sheet. Warm goes the cold, gotcha. So a vapor barrier right here, this is a polyethylene, you staple it to the wall, and that stops the moisture from getting into the wall cavity. Now, you've always told us that you want to see the vapor barrier on the warm side of the wall. So down in Florida, put it on the outside, up in Alaska, keep it on the inside. That doesn't work for us here in New England, because we've got both a heating and a cooling system. In the winter, we're making We're taking heat in the house, and that's going to want to go out in the summer air-conditioning, obviously. Right. Well, what can happen is the vapor in the summertime can collect on the backside of your drywall. And it can't breathe or dry out if you have a vapor barrier. But this is a vapor retarder, and it basically puts up just like the poly, but it actually allows the stud bay to breathe so that in the summertime, the moisture that does collect back on the backside of this... Retarder can actually dry out because it breathes. It's not a full barrier. It does want to work in one direction. Slow the vapor transfer on this side, but allow it to breathe on this side. Now, this is a sheet. You can also get it on the insulation itself. Gotcha. Okay. So, some pretty good lessons right there. Obviously, all these are going to need a vapor barrier or a vapor retarder. What about this wall right here? Well, because of the makeup of the open cell and the cellulose, it's dense, and air can't move in it. quickly so it doesn't need an air barrier but it depends on where you are in the country to establish whether or not you need a vapor retarder or a barrier. So depending on what climate you live in you may have to figure it out. In terms of the closed cell do we need a vapor? Closed cell doesn't need a vapor retarder or a vapor barrier. So this sounds like a really good option. It sort of begs the question why don't we see it used pretty much everywhere? Well I think the biggest drawback to this is cost. This is four times the cost of of this or even a fiberglass insulation. Wow, so it can get really expensive. Double the cost of this foam. Gotcha, okay. Now, everything we've looked at right here is in an open stud bay, so we know that they can go, if you've gutted all the way down to the studs, or if it's new construction, what about a retrofit application? All right, a retrofit, you can take this cellulose right here, not wet blow it, but blow it through the machine through a small hole in the wall, usually two holes, one in the center and then one at the top, and blows through the machine and actually dense packs it into the wall cavity. Okay. Now, the fiberglass insulation Over here, you can actually have a product that instead of it being in batts, it comes in individual pieces like this and it goes through the same kind of machine, sucks it in through a bigger hole. Like a two or three inch hole, and dense packs that into the wall cavity also. Again, a double blow is important. Halfway up and about a foot down from the top. So also good for retrofit. What about the blue jean? Can we blow this in in the retrofit? No, that's a batts system. It has to go into an open wall cavity. Gotcha. And how about our foams? On the open cell, we've seen you actually pour this in through little tiny holes. This is actually flowable or pourable. It's a faster set time. When you spray it, it's six to eight seconds. When you pour it into the wall cavity, it's five to eight minutes. It goes in as a liquid. It sits on the bottom, five minutes, and then grows up inside the wall. And then our closed cell foam, can we retrofit this? You cannot retrofit it. It has to go into an open stud. All right, Thomas, that's some very good information. Quite a bit of it there, but we've got questions coming, so hopefully that'll straighten some people out. Thank you. I hope so.