Seeking insulation advice for planned build

[tjsmk8]

I've been lurking here for years, and it's finally time for a post. Excavation should be done in 3-4 weeks, so it's decision time. I don't have an exact footprint yet (waiting on the clearing/dirt work), but I anticipate an enclosed area somewhere between 30x40 and 40x50. The entire area under roof will be larger due to "outdoor" camper storage, likely a porch, etc. The building will be post frame regardless of size.

Anyhow, I want to keep the enclosed space reasonably comfortable here in SW Indiana (hot and humid summers, cold and dry winters). I don't plan to condition the area full time (well, maybe in the winter), but I want to be able to in the future. I've talked to several builders, barn owners, and one spray insulation place (so far). All have suggested different ideas.

- 1/2" foam/radiant barrier under all sheet metal. Suggested by one of the barn building companies. This was quoted with the barn price, so I don't have an exact cost. I doubt it's money well spent if there will be any serious heating or cooling.

- I recently visited a barn built by the same company above, but the owner requested no insulation, wrap, VB, etc. (it may have something under the roof sheet metal, but definitely nothing else). Following construction, the walls were studded with 2x6s, r19 batts installed, and sheathed with OSB. The ceiling is sheet metal with thicker batts rolled on top. I've considered something similar, but I was thinking housewrap under the metal and bookshelf girts would be improvements?

- A spray foam place was contacted and given assumed dimensions of 30x40x14. The guy seemed knowledgeable and recommended 3" of open cell on the walls and 4" of open cell on the roof. He only recommended the open cell on the walls if it was to be covered. I had a few questions about closed cell (which this company does), that he seemed to answer confidently. The open cell price wasn't much more than diy batts.

Given the above, what direction would you take? Spray foam sounds good, but I have doubts about the open cell. If not foamed, I question my own ability to insulate and seal the place properly considering the seasons, conditioning or not, etc. I don't have a price to load it up with closed cell foam, but I seriously doubt it's reasonable for this project. I'm certainly open to any ideas not mentioned as well.

Thanks for any advice.

 

[Voi]

I say skip the 1/2" foam. Not worth the extra labor unless it's thick enough for your climate zone to control dew point.

Does you builder say you can skip the regular girts if you go with bookshelf girts? Framing in between columns in addition the regular girts seems silly to me. But bookshelf girts create more paths for thermal bridging. How do you want the interior finished?

Pole barns are leaky and spray foam is a great way to overcome that. I'd get some firm prices on open cell and compare it to fiberglass. Flash and batt might be a compromise depending on price.

I'd talk to other spray foam installers, particularly about the ceiling. It's long been thought closed cell was necessary for an unvented ceiling but it seems like some are softening their stance on that. I'd read up on building science type sites as well as talk to installers.

I assume you're not putting in an attic?

 

[DougWil]

If you plan on eventually having a well insulated, well lit, with a finished interior, wiring, heat,, etc.... I wouldn't suggest a pole barn.

Because by the time you pay for and add in all those expenses, and use some not rotting alternative such as perma columns, the economy of a pole barn is significantly diminished.


At the end of that 40-50 year life of many polebarns a conventional building should go another few hundred years if well built and well maintained.

 

[NUTTSGT]

I'd suggest atleast put a ceiling in and insulating it. Create an attic space and properly ventilate it. Once I lowered the ceiling in my garage and insulated it, it dropped the inside afternoon temps by 10-15°.

 

[theoldwizard1]

You need to start with a vapor barrier and 2" of solid foam board BELOW your concrete ! Even if you never "condition", it will be more comfortable.

Pole barns are leaky and spray foam is a great way to overcome that.
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I say skip the 1/2" foam. Not worth the extra labor unless it's thick enough for your climate zone to control dew point.

I think the point being made here is, YES, spray foam, but at least 1"-2". With closed cell foam, this is also a vapor barrier.

Flash and batt might be a compromise depending on price.

This is generally considered the best "bang for the buck" ! The nice part about it is you can do the spray foam at build time and add more insulation later.

With careful planning you have a full range of insulation options, blown fiberglass or cellulose, to "wet" cellulose, to fiberglass roll or batts.

 

[Jess]

I would suggest that you consider a building wrap before the metal, regardless of what you decide. It will reduce air infiltration and if you decide on spray foam, will keep it separate from the metal. Flash and batt will tighten it up and you can add as much batt insulation as you feel you want for your location and climate. On my conventional framed shop, we did just did batts and vapour barrier. The exterior was sheeted in plywood, building wrap and then metal sheeting. In my mild climate, we don't need to heat other than for a few weeks in the winter. Good insulation will have long term benefits, regardless of what type you choose.

 

[tjsmk8]

Thanks for the responses everyone. It’s obvious I have some more research to do and phone calls to make. I’ll try to respond to everyone’s comments/questions here.

Voi – I agree, the ½” rigid foam/radiant barrier can probably be skipped if I’m planning on more serious insulation. I think it’s typically used to make buildings more comfortable when they won’t be conditioned in any way.

I haven’t discussed the bookshelf girts with a builder, it’s just something I thought might make things easier if I’m going to fiberglass the place myself. I see thermal bridging mentioned in most discussions concerning this style, so I need to read up on that. Interior walls will likely be finished with painted OSB. Ceiling will be determined after the insulation decision is made.

I’ve called two spray foam places, with two very different recommendations. The first suggested open cell with 3” on the walls, 4” on the roof. The second preferred closed cell with a minimum of 1” all around, and 2” if I was considering full time conditioning. The price of 1” closed cell was nearly identical to the 3-4” of open.

DougWil – While I desire everything you mention, post frame construction seems to be the way to go in my area, and I’m willing to compromise. I haven’t made a price comparison myself, but I’ve talked to a few that did. The basic structure (no insulation, electric, etc.) prices weren’t comparable.

NUTTSGT – If I decide to go with a ceiling, a ventilated attic space is planned. If spray foam is selected, I’ll probably leave the trusses exposed. Either way, I don’t plan on any usable attic storage space.

Theoldwizard1 – thank for the input, but I almost wish I could un-read it! If I’m going to the expense of 2” rigid foam under the slab, it would seem foolish to not add the pex for possible radiant heat. I’ve already talked myself out of this option once, and now I’m considering it again.

Jess – I’m definitely thinking the wrap will be a good idea if going with fiberglass/loose fill/blown/etc. I’m not sure of its usefulness with spray foam though. I’ll have to look into that more. Thanks for the suggestion.

Hopefully I’ve answered some questions and cleared things up a bit. Maybe not though, since I’m still thoroughly confused. Please keep the suggestion, questions, and comments coming. Thanks.

 

[DougWil]

DougWil – While I desire everything you mention, post frame construction seems to be the way to go in my area, and I’m willing to compromise. I haven’t made a price comparison myself, but I’ve talked to a few that did. The basic structure (no insulation, electric, etc.) prices weren’t comparable.

That is correct, as a shell a pole barn is much cheaper,it is the finishing of that shell and the much diminished lifespan where the initial low cost loses it's economy.

 

[theoldwizard1]

I would suggest that you consider a building wrap before the metal, regardless of what you decide.

I disagree ! 1"-2" of closed cell spray foam is an EXCELLENT vapor barrier.

 

[theoldwizard1]

I’ve called two spray foam places, with two very different recommendations. The first suggested open cell with 3” on the walls, 4” on the roof. The second preferred closed cell with a minimum of 1” all around, and 2” if I was considering full time conditioning. The price of 1” closed cell was nearly identical to the 3-4” of open.

I'm with #2 !

Theoldwizard1 – thank for the input, but I almost wish I could un-read it! If I’m going to the expense of 2” rigid foam under the slab, it would seem foolish to not add the pex for possible radiant heat. I’ve already talked myself out of this option once, and now I’m considering it again.

Tough decision without hard and fast decision on future heat/cooling.

Do you have natural gas available ?

Radiant heat is the MOST COMFORTABLE heat you can get. I don;t think the cost of operation is that much different than other heat sources.

If you are on a tight budget, at LEAST do the vapor barrier.

 

[tjsmk8]

That is correct, as a shell a pole barn is much cheaper,it is the finishing of that shell and the much diminished lifespan where the initial low cost loses it's economy.

The shell is where I hope to save as much money as possible. I intend to finish everything else myself (except spray foam if chosen). If I had more time, I'd consider stick built doing more of it on my own. Lifespan isn't a huge consideration, as we don't plan to stay here forever (10-15 years). I do want a good solid building though, and I want the future owners to enjoy it as well.

I should add some detail concerning what we plan to do with the place. It will obviously be storage for some things year round. At times it will be a work shop with an in ground scissor lift being considered. We definitely plan to use the open space as an area to entertain as well. A portion of the building will also be a fitness room. If the whole place where conditioned, I'd consider leaving this exposed. At present, I'm leaning towards a smaller, well insulated room with maybe a mini split just for that space.

I guess it's the time we want to use the building to entertain that I'm most concerned with. Spray foam sounds great, but I don't know if it will ever be worth it only heating or cooling a small percentage of the time. When I do put heat into it though, retaining it would be great (as well as condensation control at all times).

I guess I'm just looking for the best bang for the buck. I'm still looking at options, but three have been priced so far. DIY R-19 batts, open cell foam (3" on the walls, 4" on the roof), and closed cell (1" all around). Given the intended use and options, what would you choose? DIY batts is cheapest, but the foam options are close enough that I'll seriously consider them if worth it.

Again, I thank you all for your opinions and thoughts.

 

[tjsmk8]

Ok, after a week of vacation, another week getting the lot cleared and leveled, and a ridiculous amount of time spent thinking about how I want to do this, it’s time to start making decisions. At this point, I’m pretty set on installing a metal ceiling with blown in insulation on top. I also plan to have the soffits/ridge vented when the building goes up. With that as the plan, the local builders still suggest a barrier at the roof sheet metal for condensation control. I’m not sure if it’s necessary or not with the attic area vented, but I guess it won’t hurt anything?

The problem I have is that I’m still indecisive when it comes to the wall insulation. I have found another local spray foam installer that will do 2” of closed cell at $1.40/sq. ft. While this is tempting, it’s still the most expensive option. Interior walls will be finished with painted OSB regardless of insulation choice. Given the space that will be available in the wall cavity if I go with spray, should I plan to install anything else (more $$$) or just live with the air gap?

As a second option, the building has been quoted with ½ foam with a reflective surface on both sides (3Ht is the product) under the wall sheet metal. With this stuff claiming to be a vapor barrier, am I asking for issues if I add more insulation on the inside (I’ll never be content with ½” of foam alone). If it is ok, would this be a case where bookshelf girts would be ok due to the break created by the foam?

A third option – we have a place close by that sells reclaimed and factory seconds of polyiso pretty cheap ($12 for a full sheet of 1.5”). The guy that runs the place recommended reflective wrap under the sheet metal, polyiso in between or on top of the girts, and possibly another layer of polyiso if I really wanted it in there thick. This seems easy enough, but I’m not sure what I think of the multiple layers and air gaps, and additional framework will still be required prior to sheathing.

Last option (I know, sorry for the long post) – have it built uninsulated with house wrap only, stud it vertically, roll in R-19, vapor barrier (if needed?), and hang the sheathing. Price to do this is acceptable and I’m sure the result will be ok, but it will be the most DIY and will take a while with my current schedule.

That pretty much sums up where I’m at now. Open cell has been ruled out along with a couple of spray contractors that have quoted closed cell. The one closed cell contractor I’m still considering is probably the best option I have, but I need help ranking the remaining possibilities. If that can be accomplished, I should be able to weigh the cost vs. benefit and finally make a decision. Thanks again for the help.

 

[HRJoe]

I think you want the roof vapor barrier. Now that you're separating from what's above the ceiling (with blown in) from below, then it just comes down to what to do about walls. My metal pole barn guy doesn't like closed cell foam on the metal. And I don't really see the benefits of the open cell.

So I guess I'd just bat the walls (this can be done horizontally, too, right) and forget it. TI'm at a similar decision point as you and the only place I'm considering some foam is just to seal the concrete to the walls...just as a seal along the perimeter, with closed cell.

 

[matt_i]

In my mind it comes down to this. Go with a less expensive pole structure with a metal skin and spray foam it, or pay more for a stick building in the framing & sheathing but then a relatively easy job to roll out fiberglass or mineral wool into the nice regular framed cavities.

 

[DougWil]

In my mind it comes down to this. Go with a less expensive pole structure with a metal skin and spray foam it, or pay more for a stick building in the framing & sheathing but then a relatively easy job to roll out fiberglass or mineral wool into the nice regular framed cavities.

Yeah, that is what people don't consider. A pole barn "shell" doesn't have any framing to attach insulation, sheeting, electrical boxes, cabinetry, etc. All that has to purchased an installed later.

The more you spend trying to make a pole barn shell into a fully slabbed, low air infiltration, insulated and finished shop the smaller the savings.
All while those buried wood poles, quietly rot.

 

[homebuilt burner]

I was told the reason for the vapor barrier under the metal roof skin is to prevent condensation from the underside of the roof. Not really for insulation but to protect the insulation.

 

[MagKarl]

Frame the walls with commercial girts on 2 foot centers, wrap the walls before the tin goes up, insulate with fiberglass or foam board at your leisure.

 

[pmiranda]

No matter what, I have seen folks recommend a wrap before the exterior tin goes on so that when you have to replace a panel, the insulation won't come off with it.
If you spray foam, it will have to be covered with something on the inside to protect it from UV degradation and sparks or other sources of ignition. Unless something is different about the foam you can get vs. what I've seen.

You definitely want something to prevent condensation under the roof panels. Dunno if just a wrap is good enough since "I ain't from around there"

 

[tjsmk8]

Frame the walls with commercial girts on 2 foot centers, wrap the walls before the tin goes up, insulate with fiberglass or foam board at your leisure.

The idea of simply rolling in insulation and adding the sheathing sounds great, but every time I see commercial/bookshelf girts mentioned, thermal bridging due to the framework is brought up. If a wrap under the sheet metal is an adequate break, what material/thickness is necessary?

 

[tjsmk8]

No matter what, I have seen folks recommend a wrap before the exterior tin goes on so that when you have to replace a panel, the insulation won't come off with it.

Thanks, that's something to consider and will be discussed with the builder (if I ever chose one) and the insulator.

 

[MagKarl]

The idea of simply rolling in insulation and adding the sheathing sounds great, but every time I see commercial/bookshelf girts mentioned, thermal bridging due to the framework is brought up. If a wrap under the sheet metal is an adequate break, what material/thickness is necessary?

It's my opinion that people worry unnecessarily about these topics. I'd look at conventional stick framing/insulation for homes as an example. Is a "thermal break" required in your area to meet energy code for stick framed homes? It's not in mine.

Commercial girts are pretty similar to horizontal studs. Yes studs do lower the average R value of a wall compared to the ideal cavity, but so do doors and windows for example and a 2x6 still has a higher R value than most windows.

 

[65cayne]

I wouldn't worry about thermal bridging at all. MagKarl is spot on.

The foremost things on my mind would be 1) controlling/venting moisture to prevent condensation, and 2) preventing drafts and airleaks/infiltration, and then 3) type/method/amount of insulation.

 

[Jess]

I disagree ! 1"-2" of closed cell spray foam is an EXCELLENT vapor barrier.

Building wrap is not a vapour barrier. Think Tyvec or similar. Putting wrap on under the metal sheeting will allow for panel removal if and when its damaged or changes to the building require removal of the metal. Try it with spray foam on the back...

 

[Jess]

I was told the reason for the vapor barrier under the metal roof skin is to prevent condensation from the underside of the roof. Not really for insulation but to protect the insulation.

The building wrap usually used under any sheathing is a Moisture Barrier, not a Vapour Barrier. Using a building wrap under metal will reduce air flow and if its insulated with spray foam, provide a separation in case the sheeting needs to come off.

The confusion comes with Moisture Barriers and Vapour Barriers and where you are located. In my marine climate, roughly the PNW, we place moisture barriers in the form of a 'rain screen' system immediately under the exterior finish. This allows the building frame to dry outward. Vapour barriers in my climate are usually 6 or 10mil poly on the warm side of the insulation. This is normally just under the drywall or whatever interior finish you are using. Your area may be different depending on location.