Should You Ventilate a Spray Foam Attic?

Key Points

Spray foam insulation is a great choice, but some homeowners aren’t sure what it means for ventilation in the attic. Here are some things to know:

• With open-cell spray foam insulation, the attic becomes a conditioned space, so traditional ventilation methods like ridge vents or soffit vents are not necessary.
• Spray foam insulation helps keep the attic at a stable temperature, similar to the rest of the house, preventing extreme heat in the summer and cold in the winter.
• The spray foam expands and seals all cracks, gaps, and crevices, effectively preventing drafts and improving energy efficiency throughout the home.
• Having air-conditioning equipment in a spray-foamed attic is beneficial because the stable temperature helps the system work more efficiently.

Transcript

LESLIE: Joe in Rhode Island, you’ve got The Money Pit. What’s going on with your spray foam attic?

JOE: Well, we built a new home.

TOM: Yep.

JOE: And it’s 2×6 construction with a truss roof.

TOM: OK. Yep.

JOE: And I used open-cell, spray foam attic and they come in and then they shave it all down to the studs.

TOM: Yep. Yep.

JOE: So, we have a completely sealed envelope of the structure itself.

TOM: OK.

JOE: Now, when – it’s a truss roof, so there’s really no attic. But there is a space up there.

TOM: OK.

JOE: When you sheetrock the whole ceiling and close that off, do I need to be concerned with some sort of ventilation in the spray foam attic space?

TOM: No, not at all. Not at all.

Where did they insulate in the attic? Did they insulate under the roof itself or …?

JOE: They insulated the roof, right to the plywood roof.

TOM: Yeah. Nope, you absolutely do not need to ventilate a spray-foam house, and here’s why: because, basically, now that attic is a conditioned space.

I have a spray-foamed attic. It’s terrific because it’s pretty much the same temperature as the rest of the house all the time. It used to be that it was, you know, super hot in the summer and really cold in the winter. Now, it’s pretty much even-steven. And the fact that you used spray foam means that it expanded and sealed all the little cracks and gaps and crevices, so you’re not going to have any problems with drafts getting in there.

JOE: OK.

TOM: So you do not need to ventilate that roof.

JOE: Oh. How about – we have mechanical equipment up there. I have the air-conditioning unit up there.

TOM: Yep. Mm-hmm.

JOE: No concerns with that, in that space, either?

TOM: No. It’ll even work better because now, when it’s trying to cool in the summer, it’s not going to be doing so in an attic space that’s 110 degrees.

JOE: Alright. I was concerned because there’s absolutely no ridge vent, no soffit vent, and no …

TOM: Yeah. No, that is done correctly. And we have to start thinking differently. Now, we use attic ventilation when we use products like fiberglass because we have to manage the moisture. But with spray foam, ventilation is not an issue. That is now a conditioned part of your house, just like any room in your house.

JOE: OK.

TOM: You may not have heating ducts up there but it does not need to be ventilated.

JOE: Fantastic.

TOM: Alright? That’s a good choice.

JOE: Alright. Alright. Very good.

TOM: Good luck, Joe. Thanks so much for calling us at 888-MONEY-PIT.