Adding Insulation in an Attic
LESLIE: Gene in Louisiana has an insulation question. What can we do for you?
GENE: Yes, my question is I live in an older home with no insulation except what I have rolled in myself; I just rolled it in. I’m considering putting in blown-in insulation and I wish to know if I need to keep using rolled-in or if I have to put a moisture barrier down to go underneath the blown-in insulation.
TOM: So right now you have insulation batts, correct?
GENE: Just what I have put in; about a third of the house and the rest of it is just nothing in there.
TOM: And you want to use blown-in because it’s just easier?
GENE: Correct. It’s easier …
TOM: Well, you don’t have to put – then I’ll tell you what. If you don’t have a vapor barrier down, I’m not going to tell you to put one in now. It certainly would be difficult to do that at this point in time. If you had no insulation and you had easy access and you could put down insulation that has a vapor barrier that faces down to the ceiling, so to speak – I assume we’re talking about the attic here – the rule is that the vapor barrier always goes toward the heated side.
But if you’re going to go blown-in, typically you don’t use a vapor barrier. The amount of insulation you need is 22 inches of blown-in. I think 19 inches of batt insulation and 22 inches of blown-in insulation is what is recommended for your part of the country. But make sure, make sure, make sure, Gene, that you have enough attic ventilation. That’s really critical because if the attic doesn’t breathe, that insulation will get humid and damp and not work very well.
GENE: And I’ve got way high ceiling and it’s a 12-on-12 pitch, the roof, so I …
TOM: Well, man, if you’ve got a 12/12 pitch, why don’t you get up there and put down some batt insulation? You don’t need to use blown-in. You can use a faced, batt insulation with a vapor barrier on the bottom; lay it against the ceiling. And you’ll only need 19 inches of batt insulation because you need more when you use blown-in. And if you put the first layer down and let’s say you use like 10-inch insulation the first time and you want to put a second layer down, the second layer would be unfaced and that would be laid perpendicular to the first layer.
But if you’ve got a 12/12 pitch and then plenty of room to walk up there, I would definitely do that because, frankly, it’s going to be easier for you to get around and do anything you need to do in that attic without having the blown-in. Blown-in is OK if you have an attic that’s really hard to work in like an attic that’s built with a truss roof or something of that nature.
GENE: Exactly. Thank you very much.
TOM: You’re welcome, Gene. Thanks so much for calling us at 888-MONEY-PIT.