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Metal polebarn - Ridge vent AND spray foam?

mattlikesbikes

Well-known member
Joined
Jun 9, 2009
Messages
76
Location
Austin TX
We just signed the contract on a metal building (36x46) which will double as a garage/workshop and one bedroom place while we wait to build a bigger house at our farm.

We are going with pole barn construction and the company recommended we have a ridge vent installed. They know we plan to spray foam the interior and gave us advice about how to protect the vent during that (stuff pool noodles into it). But I cannot help but think we don't need a ridge vent if we are foaming. Much like traditional construction where you turn your attic into a conditioned space.

I'll have a window unit for the shop portion of the garage, but don't plan to otherwise condition the shop when not in it. The 26x26 apartment will have a mini split and will have spray foam on the exterior walls and pink stuff on the interior/to the shop walls. That unit will be set to run enough to control humidity when we are not there.

This is central texas where it gets mighty hot but humidity isn't too bad. I have a smart window unit, which I could setup to run daily for a little bit to add some conditioning of the space, if need be. Which would be useless with a ridge vent.

So do I save the $900 and skip the ridge vent or keep it? They did also imply that the ridge vent did a better job rain sealing the ridge than their non-vent option.
 
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mattlikesbikes

Well-known member
Joined
Jun 9, 2009
Messages
76
Location
Austin TX
https://www.energyvanguard.com/blog/71851/Beware-of-Roofers-in-Homes-with-Spray-Foam-Insulation

I believe this has come up before here on Garage Journal but I wasn't able to find the thread.

So they quoted $900 for the ridge vent? And said it would keep rain out better than no ridge vent?

I think they were saying that the ridge cap option that wasn't vented was not as good at keeping out rain as the ridge vent is. Doesn't make a ton of sense to me, as I assume the ridge cap should have enough overhang.


The article is consistent with what I was thinking. But for clarification, if we don't plan to condition the garage space, should we have the vent to allow for passive airflow? Or should we plan to condition the space, just to a limited degree (humidity control - 3 20 min cycles a day or something).
 

rerod

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Joined
Jan 30, 2015
Messages
376
Location
North English Iowa
Cathedral ceilings are tricky to ventilate and have been known to collect condensation and rot out in heating dominated areas, but I'm not sure about texas. Usually a un-ventilated flash with foam, and then batt with fiberglass is recommended, but along with 3" of ridged board insulation over the roof deck to achieve >R49. Or if you have 24" of truss space you can fill 20" of cellulose and have a 4" ventilation space. Either way you should have a air barrier between the conditioned garage space and the insulation..

https://www.greenbuildingadvisor.com/article/is-using-closed-cell-foam-worth-the-trade-offs
 
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