I’ve built a gambrel roof barn, the loft of which is 2×10 steel on 16 inch centers. I plan to spray-foam the interior of the loft for living space, end walls and ceiling to four inches. I’ll use stand-offs to put an air channel between the roof sheeting and the foam to maintain a cold room. The question: will I gain anything by putting fiber-glass batts inside of the foam?
Thanks for your input.
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Sure you will...
itchy arms
;)
There is a bit missing from your overall. You do not insulate a building by just doing the roof and end walls.
There is a floor system to consider.
Infiltration prevention includes the whole package.
If you control the rest of the climate in there, I don't see much benefit from adding FG
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Thanks Piffin,You're right, I didn't tell the whole story. The lower level of the barn is concrete in foam forms with Hardy Panel exterior siding. The interior will be receiving metal siding. The lower floor (full eight inch slab) has radiant tubing in it and will be solar heated.The floor of the loft will be solar heated with under floor radiant and 10 inches of fiber glass on the under side. Metal siding will be used on the ceiling of the lower floor also.Thanks again for the prod, Piffin.
Shouldn't be any infiltration with that setup!Ther eis another thread around here someplace where a guy is worried because he hear that Hardiepanels should not be used over ICFs. I think he was talking direct contact.
Did you use strapping screwed to the ICFs first and then the siding?
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Good evening Piffin,Nope, we screwed the Hardy panels right to the connectors. It's stood well for five years. That doesn't say they won't fall off tomorrow.I am planning on putting in air exchangers. Properly done, the spray foam will make the place like the inside of an ice chest.I'll go look for the discussion on Hardy Panels.Thanks again./s/ Rich
Boy a 8" radiant slab is gona take a long time to get up to temp. Why so thick?
"The lower floor (full eight inch slab) has radiant tubing in it and will be solar heated."With solar heat, you do not think in terms of "bringing it UP TO temperature" You think in terms of a heat sink for storage, to coast through those rainy days. The thermal mas provides that.
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Piffin,I found the other thread on insulation. The analysis seems to be 4 inches of foam and call it good.
When I ran the numbers, with four panels at 4 x 8 angled for this latitude the 8 inches of concrete provides me with about three days of carry over. Three days is about typical for the cloud cover in a winter storm. I also looked at over-production on the part of the panels. With much less than 8 the slab may reach shut down temperature and shut down the circulation pump. I've also factored in a 1500 gallon water storage tank that will be available to heat the slap, the loft under floor radiant as well as supply the domestic hot water for the building. Thanks for your interest./s/ Rich
with infiltration controlled by the spray foam, why do you seem to think the R-value of the fiberglass wouldn't be of any benefit?Depending on the r-value of the assembly, he might not gain a lot, but if he's got R13 foam and adds another R13 fiberglass, that's significant benefit, for example.-------------------------------------
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You used that great big word <IF>;)I was responding to his first post wherein he stated pretty clearly that he plans 4" of the foam which provides him with a good R28. I have seen charts showing a great fall-off in return on insulation added, making it questionable in some climatic areas to add more than 3" of foam. Once he gets to 4", the payback on any FG batts added would be out there about fifteen years, more or less.Now if you wanted to make an argument for only using 2-3" of foam to save money and then adding the FG bAtts, I don't think I would disagree with you.When I was doing most of the foam work, I was paying about seventy cents a board foot. I just talked to a guy the other day who got an estimate that looked like about $1.30/bd ft!
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I see; he never specified the foam he was using though. Could be anything from R3 to R7 per inch, and he's in a real heating climate, so that's a big range to consider.-------------------------------------
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Ooops, you are right. I had the impression he had mentioned closed cell poly.
Probably I assumed because he is in the heart of Corbond territory
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