Choices in Insulation
LESLIE: Next up, we’re going to take a call from Kevin who’s calling us from Alabama with some insulation questions.
Kevin, how can we help?
KEVIN: Well, my wife and I bought a home on 80 acres that was a two-story house that was dried in, so we’ve kind of been building on it ourselves. We’re to the point where we’re starting the insulation and I’ve been reading about this BIB system, the blow-in blanket insulation.
KEVIN: I kind of wanted to get you folks’ opinion how good it is because I’ve seen it done two different ways: one’s with netting and you blow it inside the netting; or the other, they just kind of blow it on like you blow on cement and then they shave it down so it’s even with all the joists. And is it worthwhile to put on the interior walls and do you know how much more expensive it would be than the batting insulation?
TOM: I think it is going to be more expensive. Some of my friends from This Old House I know swear by that. I talked to Tom Silva not too long ago about that spray-on insulation and they’re really having great success with it. It is going to be a little more expensive, though, and you’re really talking about two separate systems. One is a foam system that sprays on and hardens and then you have to saw it flush with the studs. The other kind, that uses the netting system, is the kind that they typically use inside existing wall cavities for, say, older homes that have no insulation where they drill small holes and blow it inside. Either of those works well. They’re both, though, going to be more expensive than fiberglass batts.
LESLIE: Tom, what is the advantage over the blow-in and the fiberglass? Does one have a longer life span or is it pretty much the same?
TOM: You’re not going to get any settling. You’re going to get probably better insulating capability because there’s going to be no space in that bay that’s uninsulated. Every little piece of that bay will be insulated. And so those are the main advantages of it. It’s a better r value, too.
KEVIN: Is it recommended, though, for new construction? I mean can you still use it that way?
TOM: Absolutely. There’s no reason you couldn’t.
KEVIN: But it is definitely worth it. Even though we’re in the southern area here, I’m not so much worried about heat loss as I am sucking the cool air out because I do have an attic fan. I have a large attic and we built a third-floor room for the grandkids, but I do have an attic-type fan – not a whole-house but an attic fan – and I worry about it sucking all the way up through the walls up there and this will supposedly make everything tighter.
TOM: Well, it will and let me straighten you out on that attic fan. Disconnect it. Alright? Don’t use an attic fan because an attic fan will draw air through your interior walls as well as your exterior walls right through your outlets and other places you have holes in the wall and the attic fan will rob – especially in a well-insulated, well-sealed house, it will rob the air conditioning out of the interior conditioned space.
A better option on this is to have passive roof ventilation – so vents at the ridge and vents at the soffit – where you use natural ventilation to cool off the roof. But attic fans are usually real insulation robbers – I mean real energy robbers, I should say – because they will reach down into the house and take out the air conditioning.
KEVIN: And I heard you say that last week and that’s why I got to thinking about it that maybe it’d be better to put this blow-in insulation …
TOM: It’s OK for that but remember, even if you were to perfectly seal the outside wall cavities, Kevin, you have all the internal wall cavities. So where all those wires go down through the interior of the walls, the attic fan can still depressurize those cavities and pull the air conditioning out there as well.
You know, you were saying before that you’re down in the south so you don’t worry about heat loss. But some of the leakiest homes in America are in the southern area of the country because people don’t think about – they don’t feel the cold draft and they don’t realize how much of that air conditioning money is leaking out through the house. So it is wise to have a well-insulated house whether you live in the north or the south.
KEVIN: OK, well I’m definitely going to give this BIBS system a look at then. And I just, before I started trying to track people down, I just did want to get your opinion on it to see what you think, so I think I’ll go ahead and give it a shot, at least, and look at it.
TOM: Well, we appreciate you calling. Thanks again, Kevin.
This is The Money Pit Home Improvement Radio Show. The number is 1-888-MONEY-PIT.