LESLIE: Rob in California is on the line with an insulation question for a Cathedral Ceiling. What could we do for you?
ROB: Well, I’ve heard about this spray-foam insulation. And I’ve heard about – from you and others – that when we’re applying insulation in a cathedral-ceiling situation, we have to provide for ventilation between the insulation batts – in a traditional fiberglass-batt insulation, we have to provide for ventilation between the insulation and the roof sheathing.
TOM: That’s correct.
ROB: So I’m wondering – yeah, so …
TOM: But not with spray foam, only with fiberglass.
ROB: OK. That’s what my questions is, is do I have build that in on – somehow with spray foam? Sounds like no.
TOM: No. No, because it’s a different system. So the – when you insulate with fiberglass, you have an unconditioned attic space, so to speak, OK? When you insulate with spray foam, you now have a conditioned attic space. The difference is that when it’s unconditioned, you have to ventilate it to carry the moisture out. When you use spray foam, there’s really no – the moisture is really no longer an issue.
So in my house, when I go up in my attic, my attic is pretty much the same temperature as the rest of the house, within a few degrees, even though it’s not heated or cooled up there. It’s just an old-house attic.
ROB: Right.
TOM: And it never used to be that way. Like most attics, it was screaming hot in the summer and freezing cold in the winter. But now it’s steady.
In fact, we’ve actually started to use it in new ways. This past holiday season, I was frustrated because the LED strands, even though they were perfect the year before, half of them work and half of them don’t when you take it out again.
ROB: Yep.
TOM: And I was spending a lot of time fixing them. And I figured – this year, I got some new lighting. I was just going to put it up in the house attic – as opposed to the garage attic, where it’s always cold – because I figure the temperature being stable is less likely to impact it. So that’s kind of the way we – another way we used it.
But we think the spray foam, for our family, has worked really well because it’s super comfortable compared to the fiberglass we had before. It’s not for everybody but I would highly recommend it.
And if I had a cathedral ceiling, I would definitely, definitely use it. Because with a cathedral ceiling, the problem is that you don’t have much depth in the rafter bay, right?
ROB: Yeah. Right.
TOM: So you can’t put much insulation in there. Plus, you have to leave it sitting back an inch-and-a-half or so for ventilation. So if you use spray-foam insulation, you can fill it up and it’s going to have a higher R-value per inch than the fiberglass, anyways.
ROB: Yeah.
TOM: So that’s – those are some of the reasons I think it’s a good idea.
We wrote an e-book on it. It’s called The Money Pit Guide to Insulation. It talks about all the different insulations and the pros and cons of each. And that’s on our website at MoneyPit.com.
ROB: Oh, great.
TOM: If you click under the section about Listen & Watch, there’s a section there of books. And you can download or read it right there online.
ROB: Excellent. I will go check that out for sure. It sounds like the spray foam is a much better deal and I didn’t realize that you could spray it right on the back of the roof sheathing. It sounds like it seals it up tight and that sounds wonderful.
TOM: It does. And that’s the other advantage of it because it both air-seals and it insulates at the same time. So we used Icynene. I’m very happy to recommend it. It’s a great product.
ROB: Great. Thank you very much.
was wondering if the spray insulation in a non vented room would also work with a room that has can lighting in it?
would it also become a conditioned space?
Yes, but if we are talking about ceiling fixtures and especially recessed lights, you’ll need to maintain the required air space around each fixture to prevent overheating.