Install Radiant Barriers to Remove Excess Heat
LESLIE: John, you’ve got The Money Pit. What can we do for you today?
JOHN: Hi. I just want to ask you guys a quick question on radiant barriers.
JOHN: I’m wanting to do a radiant barrier underneath my rafters in my attic.
JOHN: I’ve got soffit vents already cut.
JOHN: I’m going to redo my roofs. I’m going to put a cupola up top.
JOHN: And I was wanting to put the radiant barrier to exhaust all the heat before it gets into the house. Do I need to use solid or do I use a perforated? I live in a very dry climate, too, (inaudible at 0:27:28).
TOM: OK. First of all, do you intend the cupola to be the exhaust venting for the attic space?
JOHN: Yes, I do.
TOM: I mean a cupola is a good-looking piece of architecture but it’s not necessarily an efficient exhaust vent. The soffit vent is the right idea, because you open up the overhang. But the best exhaust vent is a ridge vent that goes down the entire peak of the roof; not just sort of the center where the cupola is.
So you could still do the cupola but I would definitely couple that with a ridge vent because then what’s going to happen is, as wind blows over the roof, it will depressurize around the ridge area and the cupola area; it’ll draw the heat out of there. But at the same time, it’ll pressurize the soffit area so it’ll push air in the soffits up underneath the roof sheathing and exit at the ridge. And that cycle will repeat 365 days of the year and that’s what’s going to keep it as cool as possible.
JOHN: OK. But would I use solid or use the perforated type of aluminum?
TOM: For the radiant barrier? So you want to press that up underneath the roof sheathing?
JOHN: Yeah. No, I’m going to put it to the bottom of the rafters inside the attic.
TOM: OK, I don’t – well, the thing is, you don’t want to obstruct the airflow. I think I’d probably go with perforated.
TOM: Because otherwise, you’re basically creating a channel where the ventilation would have to go between the radiant barrier and the underside of the roof sheathing; almost like a finished attic, you know what I mean? So I think I would use perforated.
JOHN: Just use the perforated?
JOHN: Because I was wanting to draw the air from the soffits straight up to the …
TOM: Yeah, exactly. And it’ll pull more heat from the attic space that way, too.
JOHN: OK. I appreciate that.
TOM: Alright. Good luck with that project. Thanks so much for calling us at 888-MONEY-PIT.
That kind of improvement will definitely cut his air conditioning bills down.
LESLIE: Oh, absolutely.