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Wednesday, January 18, 2017

Roof Venting in the Tiny House

Alisha McDarris

Venting the roof of our tiny house was a point of much research and deliberation. We'd look up what we were supposed to do, think we had an idea, then come across someone who said the complete opposite. We had heard roof venting was absolutely necessary and not so much. So we dug deeper, asked some people who knew a lot more about roof venting and building than we did, and came up with this: Yes, you need to vent the roof of your tiny house.

But why? And how? Well, first, whether or not you vent the roof of your tiny house largely depends on the shape of your roof and the insulation you are using. Our tiny house roof is a simple slanted roof and we used fiberglass insulation and as it turns out, in those situations venting is absolutely necessary. The most definitive text we found on the subject was this website. It's based on conventional building principles, but the facts remain. We double checked with some guys at our local building supply store and they confirmed our suspicions: yes, vent.

But How?! Lots more research later here's what we came up with: yeah we have a bathroom vent fan and a kitchen vent fan, but those aren't keeping all the hot air being pushed upward every day from creeping into the cavity between our ceiling and our roof sheathing, causing mold, mildew, even rot to form. No good. So the solution for us was baffles. Or vent chutes. Whatever you call them they keep the fiberglass insulation from pressing directly up against the roof sheathing and they allow air to flow all the way from the lowest point in the ceiling to the highest. And on that highest point we created a protected gap between the exterior walls and the roof drip edge that allows that warm, damp air to escape so it's not trapped up there forever, wreaking havoc on our wood and ruining and our ability to breathe uncontaminated air.

Baffles are super easy to install and really cheap. We purchased polystyrene chutes for about $1.68 a piece and placed them in between every roof joist all the way from the low to the high point of the roof. They are held in with about 3 staples each and the insulation just goes in right after. Easy peasy lemon squeezy.

Creating the actual vent openings on the outside of the roof line was a bit trickier. Metal vent grates would make it hard to attach the drip edge and wouldn't keep out bugs. We found a sort of plastic woven mesh that's supposed to keep leaves out of gutters which we considered using, but it was going to be a bit more expensive and we'd have to cut it. What we ended up with -- and this was Josh's idea -- was a cheap, short, long strip of corrugated plastic that we could easily cut to size. The corrugations allow air to flow through and a bit of weed mat attached via spray adhesive keeps insects and debris from getting into the ceiling. Slide that stuff under the drip edge, screw it down, and we have our roof venting solution!



Alisha McDarris / Author & Editor

Alisha has been a writer and photographer forever. OK, maybe not forever, but at least for more of her 20-something years than she hasn’t been those things... [Read More]

2 comments:

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  2. Wonderful illustrated information. I thank you about that. No doubt it will be very useful for my future projects. Would like to see some other posts on the same subject!
    Pergolas

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