How to Ventilate Your Roof
LESLIE: Charles in Florida has a question about installation. How can we help?
CHARLES: Well, wonderful. My wife and I are building a house here in Duval County and I was (audio gap) traditionally that every house I ever built before I used fiberglass. Well, I’ve found a website that said … gave a lot of the negatives of all the different kinds of insulation. And so I decided maybe I didn’t want fiberglass. And the builder said to use Isonene and spray it on.
TOM: Isonene is an excellent product.
CHARLES: And … well, it gives the negatives on Isonene, too. The bugs that bore in there and like to make nests – like yellow jackets and all the wood-boring animals that (laughing) … they like the Isonene. And then I found that the sun … if any sunlight – direct sunlight – gets on it that it breaks it down quickly. And every form – even the cellulose – supports mildew if it gets wet. And I haven’t found anything that I like.
TOM: Well, Charles, you’re … congratulations on doing all the investigation. Now, are you building this home from scratch?
CHARLES: Well, yeah. I’m the owner/builder.
TOM: So you’re not saddled with anything that’s partially-constructed? This is not a remodel in any way. It’s all totally new, correct?
CHARLES: New house.
TOM: Alright. Well, if it’s a brand new house, I mean I think Isonene is an excellent option and fiberglass is a fine option as well. It’s going to be very, very important that whichever material that you choose, you want to make sure that, for example, in the area of the attic – especially in Florida – that you have more than adequate ventilation. Because if you don’t ventilate that space, you’re going to have a lot of moisture problems. In the winter time, you’ll get condensation when it gets chilly out. In the summer time, it’ll overheat and drive up your air conditioning costs. But I think the most common insulation mistake that folks make when they’re building new is they don’t put enough ventilation in. In new construction, you want to have continuously open soffits and continuously open ridge vents to make sure you’re totally flushing that space with air all the time.
You know, if you’re concerned about health effects of fiberglass, if it’s up in the attic, it’s not in your breathing space – nothing to worry about. You mentioned Isonene; concerned about breakdown from the sun. Well, it’s not an exterior-graded product. It’s one that’s not going to be exposed to the sun; so that’s not a condition for you to … to worry about. Both of those are excellent products. Both of them will do a great job if they’re properly installed and properly ventilated. That’s the bottom line.
CHARLES: Yeah, we … the roof is on and it has got ridge vents. Everywhere there’s a ridge.
TOM: That’s excellent. And you have … do you have soffit vents at the overhangs? Are they perforated soffits all the way around?
CHARLES: Well, I haven’t put them on, yet. I got the overhangs but I’ve not installed the soffits.
TOM: Yeah, make …
CHARLES: I was going to make continuous vented and two or three people told me I need to break it about every other one or every third one and make it a solid one or …
TOM: No, it’s not necessary to have any solid soffit materials whatsoever, Charles. I would make it totally ventilated. The entire soffit space should be ventilated. And those panels that are available today that are made of vinyl or aluminum, can have thousands of tiny holes in them. And really, it looks solid from the eye … you know, from the street. But it’s perfectly ventilated; you’ll let a lot of air in. Because what happens is as the wind blows over your house, the air blows in the soffit, underneath the root sheeting and out the ridge. And that’s a cycle that repeats … it repeats 24 hours a day, 365 days a year and takes the moisture out in the winter – which makes the insulation more effective. It takes the heat out in the summer.
CHARLES: Well, I appreciate your time.
TOM: Thanks so much for calling us at 888-MONEY-PIT.