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4 Dec ’16
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Hi
This is my first post, but I've been lurking here for a while. I just moved from the city into a 150 year old farm house in northern Illinois, so I expect to be spending considerable time on this forum.
I'm currently trying to insulate a small barn (16'x'24 with a hayloft) so my band can practice in it. So it doesn't need to be as warm as a house, it just needs to be tolerable nine months out of the year. Since the previous owner accidentally burned down the original barn, this 2x4, OSB and vinyl siding is only six years old. Besides the cracked cement floor (from the heat of the fire) it's in good shape.
I've already insulated the stud walls with R13 fiberglass rolls, and covered them with OSB, but the roof is going to cause some problems. It's a corrugated sheet metal roof, with 2x4 studs, spaced at 2' intervals. It has soffit vents and a ridge vent so I'm going to have to allow airflow, but since the studs are 2x4s and not 2x6s, if I put 3.6" thick insulation up there'll be no room for those foam vent baffles which are typically about an inch thick.
I'm hoping that the corrugation of the roof(see picture) will allow enough airflow (there are a couple of ridges per stud, about a half inch wide), especially since the extra 2x4 cross stud holds the metal a couple inches away from the back of the insulation, but I won't want to leave the fiberglass exposed, so I'm wondering what I should use as a moisture barrier before I put up the insulation.
Should it be totally water proof and air tight like Poly Film? Or should it be breathable, like Builder Board or rosin paper?
Am I making any sense? Have I left out any vital information? Am I missing something really obvious? Thanks in advance.
15 Feb ’12
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you could use 2 inch dow board instead of bats and it should give you enough spacing for airflow, I wouldn't put a moisture barrier under the insulation, to be honest since it is a barn I probably wouldn't put any up, I don't think it will be much benefit.
27 Aug ’14
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KVR's method will be the fastest and relatively easy to install. If you're concerned about enough spacing for air flow you could put some cross purlins spanning the 2x4s (something cheap, 1x2) before you put in the rigid foam board.
Speedfunk's roof was done like this (full photo credit to speed, here's the link to his build):
4 Dec ’16
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Thanks for the replies already. Here's the pic that didn't post with the original post so you can see the 'vents' that the sheet metal roof provides.
I thought about foam board, but decided against it because a) the R values on that stuff were much lower b) it was much more expensive than fiberglass and c) since the studs aren't perfectly spaced I'd be cutting an inch off the side of one board, half an inch off the next etc. While 23" fiberglass roll would just smush in there and staple to the studs.
It may just be a barn, but I'm going to spend a lot of time in there.
18 Jan ’16
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icanreachit said
KVR's method will be the fastest and relatively easy to install. If you're concerned about enough spacing for air flow you could put some cross purlins spanning the 2x4s (something cheap, 1x2) before you put in the rigid foam board.Speedfunk's roof was done like this (full photo credit to speed, here's the link to his build):
I don't feel like reading 21 pages 🙂
do you how how much his entire build (house + land) cost ?
27 Aug ’14
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Jl, I'm not sure off of the top of my head. I believe he goes into it in detail throughout his post. Might even consider pinging him here on thehomesteadingboards as I know that he's a member here as well.
The following users say thank you to icanreachit for this useful post:
jl4 Dec ’16
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Just to give myself a bump before I actually do this, I wanted to quantify why I prefer fiber glass roll to foam board and throw some numbers out there.
Because the studs are 2x4s and not 2x6s I'm limited to 3.5" thick insulation, and in the 23" wide variety, there's not many options, but lets say I go with this stuff:
http://www.menards.c.....3001887880
R-13 and only 28 cents a square foot
where as R-13 foam board like this:
http://www.menards.c.....5728609215
is a $1.25 per square foot, and will require cutting to size.
Since I have about 500 square feet to cover that's $140 vs $625, so you can understand why I'd want to go for the fiberglass.
My main question is what to put behind it, and since I'm all about the Menards links tonight, how about this:
http://www.menards.c.....0984092916
Or should I use something more breathable, bearing in mind there's a 2" gap behind that and the tin roof (see pic above).
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