I recently raised a small carriage barn frame, about 20 foot square, that will serve as a small garage/shop. Originally I had planned on not insulating, and to date have boarded and shingled the roof and sheathed the sides with 1" pine shiplap, and was planning to add windows and finishing with clapboards come spring.

I'm located in NH and now that the weather's cooling off, I'm rethinking the insulation thing: specifically, adding enough insulation to help retain some heat while I'm out there, just for the first floor and not in the attic/storage.

My overhangs are only 4" on the gable ends, so wrapping and strapping with foam panels, etc., probably won't work too well, plus I'm on a bit of a budget. I'm considering using 2" foam panels on the interior cut to infill the spaces between posts & braces (foil to the inside) and covered with 1/2" sheet rock, and likely the same foam panels on top of the attic floor.

My main concern with this approach is a vapor barrier or lack thereof, and do I really even need one? The building won't be kept heated year round, so basically I'm looking at a buffer to temperature swings.

Should I be OK with this basic approach? I'm familiar with the "proper" way to wrap and strap a frame that is to be fully insulated and heated year round, but need some advice when it comes to changing things up.

Thanks,
Audi

Could you insulate on the outside of the eve sides and inside on the gable end wall? 1" or finished 3/4" boarding is not much to attach a wrap and strap to, inside or out.

No vapor barrier needed. There is no place for moisture to be trapped, it can dry to the inside or outside. Heating with wood?

Thanks for the reply, Tim.

Actually I might be able to insulate the inside of the gable ends and outside the eave walls; I know I overhung the eave walls a bit more than the gables. Would there be an advantage to doing it this way do you think?

I realize 1" boards are not a whole lot to attach to; I used 2x4s horizontally on the flat as nailers throughout, and no board goes more than 4' without being nailed to something.

If I used the infill approach that I first considered, I was going to cut the 2" foam to fit the recesses between posts, connectors, braces, etc., followed by a same shaped piece of sheet rock covering the foam, held in place by 3/4" trim to cover any gap and allow for movement. I've gotten some advice suggesting using spray foam to fill any gaps between the foam and the posts, etc., but I'm wondering how effective it will be as the posts shrink and swell. As there's only 6 posts in the frame, I figured it would be a pretty quick, rudimentary insulation job.

I'd like to heat with wood, but am leaning towards using something like a ceiling-mounted propane garage heater - the main advantage being it wouldn't permanently take up any valuable floor space (it's only 20x20). I really don't think I can sacrifice any floor space (plus clearances) for a woodstove, unfortunately.

I was thinking I could get away without a vapor barrier in my case, but you hear and read so much about the damage caused by missing or incorrectly applied vapor barriers that I wanted to throw it out there for some feedback.

Thanks again,
Audi

The advantage it one continuous layer of foam, easier to install, no cutting and fitting, it leaves the bulk mass in side as a heat sink, it makes a thermal break where your studding will conduct cold, and as a solid sheet on the outside it acts as a better air barrier, air leakage is a major factor. On the cost side you will use less can spray foam.

Understanding you have 2xs on the flat you can fit additional foam in this space and dry wall over that. When you cut to fit foam into that space set the table saw at a slight angle so the foam wedge fits into the bay, tighter.

When heat sources come up I always think that wood is the simplest and cheapest as it has to possibility of "free" attached. When fossil based fuels come they can in no way be gained free. So I usually insert "use more fossil based foam" here, it is like purchasing your fuel once, just thinking longer term. You can really bake yourself in a wood heated space, so much so you may want to vent the building at times by opening a window.

How is the ceiling insulated?

When using vapor barriers you want to be careful that you don't use two, one inside and one outside where you could possible build up trapped moisture, it will leak and moisture will get into the space and it won't come out as easy as it goes in. I don't see where the system you are thinking of using acts in this way. The only place in question would be the ceiling.

Vapor starts to get complicated in the area of dew point and how much insulation you need to void this factor out so that moisture does not condense on the exterior face of any warm foam. 2" of foam is not enough to stop this. So on the outside the foam should be strapped and then the new siding added over the strapping giving it an air space to dry out. One more benefit to insulating outside the structure.

Great feedback, thanks!

The ceiling would be pretty easy to insulate and add a vapor barrier to. The frame uses English tying joints with floor joists that set into the tie beams; I left a space of about 3 or 4 inches between the outermost joists and the roof plane, so it would be easy enough to have the second floor's insulation wrap down over the outer joists and tuck into the wall space, helping to seal that off.

As far as what to use for ceiling insulation, I'm still undecided. The second floor framing uses 4x6 joists on 2' centers, so I was considering covering that with either rough sawn pine or OSB, then a vapor barrier, and then using either foam panels or fiberglass, topped with OSB. There would be an insulated trapdoor at the top of the access stairs, and the space would only be used for storage. What are your thoughts on this, would one way be better than another?

As to the walls, I should be able to use a continuous layer of foam panel on the outside of the eave walls, then strap and side them easily enough, using foam infill on the interior as well. Even without using foam on the outside of the gable ends, I'm guessing it would make sense to strap before siding anyway, to allow an air space? I might be able to use 1" foam panel on the exterior of the gable ends (up to the tie), then add studding above that to the roof. It would minimize the overhang, but I'm OK with that, my house was built in 1790 and has hardly any overhang, so it would match, I guess. As long as I include an airspace to let the walls dry out, I'd still be OK without a vapor barrier?

Vapor does indeed start to get complicated, ack.

Audi

Hi Audi;

How much time is the building going to be heated and to what temperature?

I am questioning the cost-benefit of insulating at all. Most of the cost of heating a house is the 24 hour a day 70 degree temperature. The fuel needed to occasionally heat a small space to a 60 degrees may not justify the cost of insulating.

I have an unheated, uninsulated, part-time shop, but I admit the cold temperature discourages me from working if I have a choice. I can run a kerosene heater as needed. I take the work to my basement (55 degrees) if I need to glue or paint it.

My point is that it does not take nearly as much energy to temporarily heat a space than to heat it full time so the need to insulate a shop/garage may not be justified.

Jim

Check out this information too.

http://www.greenbuildingadvisor.com/blog...pact-insulation

Jim

Very reasonable information, Jim. I sure wish they could prove one way or the other this issue of " spay agents". What makes me wonder either way is the Blogger says "I have to note here that I’m not 100% sure that XPS is made with HFC-134a; ". I see the comparisons to pay back, but it is based on this unsure aspect. The hearsay I have been exposed to says they have stopped using the bad spray agents.

There is a lot of questionable practices going on these days, are they hype or seriously real, I know not. Fracking for natural gas, and/or in oil sands is one in question, is it really worth it? Trying to chase all the attached energies to a product is near mind boggling. Keep It Simple Sally.

Those are some good points.

My first decision was to not insulate the barn, largely because of the reasons you mention, Jim. Then, as the weather started getting colder, I realized I'm really not going to be out here much at all if I don't insulate it - proving that decisions about whether or not to insulate should not be made during the warmer months.

I do know that I will definitely spend more time out there if there's a way to maintain a reasonable temp, and honestly I'm tired of freezing cold tools, rust forming in the spring when the weather starts to warm, etc...at this point I feel the benefit of heating/insulating outweighs the cost, and wish I had seriously considered the subject earlier.

I agree that foam panels may or may not be the best thing from an environmental standpoint, so I'm off in just a few minutes to check out what they have available at an outfit that sells used foam panels - it keeps them out of landfills, they're 50-70% cheaper than new, and by continuing to use them I'll give them a better shot at "paying back". At least I'm not buying new, and I feel good about that.

Thanks for the replies guys,
Audi

Hi Audi, I have a 28'x36' barn/house which is insulated with used foam as well. It came off some flat roof from somewhere. Some of the sheets were tapered, some 4'x4', some 4'x8', some still had large washer still stuck to the sheets. I also get foam as factory seconds, with voids or slightly the wrong size. All things that make the installation a bit more time consuming. For my own project and money I am happy to use these types of materials. For clients I tend to go with new product, as it installs quicker and so cheaper for them. Or it turns out to be a wash cost wise. I would have no issue using used or seconds if the client so desired.