Conflicting info on foam and batt insulation methods

[OptionalStop]

I'm planning the insulation on my spring build here in upstate NY and I'm getting different opinions on how to insulate with my chosen method of polyiso foam and fiberglass batts. I have some sheets of reclaimed 1" polyiso foam that will go between my outside girts underneath the steel, then 8' wide R19 fiberglass blanket rolls to fit perfectly between the posts, and finally OSB over that. I should get a total of R25 with this setup. I've read that some suggest the opposite with polyiso underneath my interior OSB (or drywall) then fiberglass batts. Wondering which method I should go with.

 

[Black Oak]

I would go with foam sheets between the girts , fiberglass inside . A poor mans flash and batt method is to seal the foam sheets on the INSIDE with a diy spray foam , great stuff in a can , or hire it done . Stopping the air infiltration is most important. A vapor barrier on the ceiling and blow in all you can . Also, if you are still planning, I would also have 1ft. vented soffits on the sides , w/ unvented on the ends, and a vented ridge. Just my 2 cents.

 

[b-boy]

I'm in WNY, and you just described my building.

I'm using 2" XPS (R10) against the girts, foamed all gaps, and adding unfaced R11 batts. The foam board and spray foam really made a difference for air infiltration.

For the ceiling, I'm going with R38 batts instead of blown in insulation. It was easier to just do that myself. It cost a little more, though.

 

[OptionalStop]

Great, good to know some others local who did the same with good results. I forgot to add that I'll be leaving a gap between the foam to fill with spray. What about a plastic vapor barrier on the walls? Should I use plastic between the foam board and steel siding or skip this since the foam will provide my vapor barrier?

Blown cellulose will be going in the attic along with 1' vented soffits. I chose blown in because I want to do it in my house attic while I have the free machine rental.

B-boy I'm in Rochester and buying my building from House Of Steel are you familiar with them?

 

[b-boy]

I'm in Pendleton, right outside of Buffalo. I'm not familiar with House of Steel.

Your foam board/spray foam should act as a vapor barrier and insulation. You don't need another one, or you'll probably get moisture in your fiberglass.

Blown-in is a lot cheaper. My insulation cost way more than I expected, but I didn't want to deal with doing blown-in. The batts are easier to work with, and can be removed without creating an avalanche of material.

I used some local Amish workers to build my pole barn, and a local guy for concrete. I got several estimates for my build, and the Amish guys were a lot cheaper (~10k less). They showed up when they said they would, and they finished on time. I think they did pretty good work. There are a few spots where the screws holding the metal aren't lined up perfectly, but I can live with that. They offered to finish the inside as well, but I decided to do it myself. After adding up everything I spent, I probably should have let them do the work.

 

[tonyciambrone]

I'm in WNY, and you just described my building.

I'm using 2" XPS (R10) against the girts, foamed all gaps, and adding unfaced R11 batts.

Why not use unfaced r13 or r15 batts? Cost? You'll lose money in the long term I would think

 

[1redTA]

not all foam board acts as a vapor barrier, I was researching this the other day, as some are permeable

 

[b-boy]

I used XPS, which does act as a vapor barrier.

 

[b-boy]

Why not use unfaced r13 or r15 batts? Cost? You'll lose money in the long term I would think

No reason not to go with R13/R15. I got the R11 bundles pretty cheap, and I was having a hard time finding unfaced in stock anywhere when I ordered it.

 

[stm317]

Polyiso Foam with all seams sealed will be the only vapor barrier needed. Do not add another vapor barrier if it's fully sealed with polyiso/spray foam.

 

[Black Oak]

Do your research on insulating your ceiling/ and or/ roof deck. Assuming you'll have metal screwed down to purlins. Different methods in hot vs cold regions. The goal is to know the dew point in your area, and to not have condensation dripping up top. Lots to read on this out there , so learn all you can. Will you have any decking up top ( OSB ), What will the venting be , if at all? Ask your builder his thoughts .

 

[walta]

Putting insulation between the steel framing is all but pointless as the steel conducts heat so well. R19 between steel studs every 16 inches gives you an R4 wall.

The only affective way to insulate a steel building is on the outside.

Walta

 

[Black Oak]

Are you building a traditional "pole barn " , or an all steel structure ? Wood posts in the ground or steel anchored to the slab .

 

[OptionalStop]

Do your research on insulating your ceiling/ and or/ roof deck. Assuming you'll have metal screwed down to purlins. Different methods in hot vs cold regions. The goal is to know the dew point in your area, and to not have condensation dripping up top. Lots to read on this out there , so learn all you can. Will you have any decking up top ( OSB ), What will the venting be , if at all? Ask your builder his thoughts .

I'm going to be running blown cellulose in the attic with vented soffits and a ridge vent. Steel ceiling panels, plastic vapor barrier on top of that attached to the bottom of the trusses, and then insulation.

Its going to be a traditional pole barn wood structure with laminated posts in ground and steel siding.

 

[BucketTruck]

I’m doing something similar in my pole building. I used R-7.5 1.5” foam board between the girts and I used 2x4’s to frame the wall cavity and used kraft faced R-19 batts for a total R value of 26.5. I didn’t spray foam around the foam boards, just cut them to fit snug. It can breath a little bit but that’s ok because the faced insulation is my vapor barrier. I like the idea of using the 2x4’s to frame the wall cavity because they don’t touch the girts so there is no thermal bridge. I framed the walls 24” OC and plan to use OSB for the walls and ceiling. I’m going to use R-30 faced insulation for the ceiling. I would go with R-38 but I have an attic so I can only fit the R-30.

 

[Blazinzuk]

I did what bucket truck did. Except 1" foam. Then framed up interior with 2x4s, then R19 Batts. Nothing in my shop has frozen yet and all I have is a electric space heater in there right now.

No thermometer out in the shop but I leave a tiny bit of water in a small glass to make sure. Been down to 2° outside. Nothing has frozen yet

 

[OptionalStop]

84 Lumber carries 8' wide R19 batts and gave me a quote for the walls. It's a little more than 24" or 16" batts but I won't need to frame in with 2x4's so I'll save money there. I am going to run horizontal 2x4's before my OSB though, for strength and so I have solid studs for hanging cabinets or whatever.

 

[Marctrees]

READ this to understand WHY the foam HAS to be a certain min thickness depending on climate zone to not have condensation troubles - --

Marc

https://www.google.com/search?q=fla...rome..69i57.9720j0j1&sourceid=chrome&ie=UTF-8

 

[Marctrees]

In upstate NY OP needs to put vapor barrier Poly on the inside of the building side of the insulated wall.

Like right directly behind his proposed OSB, or any other permeable inside finish.

In far South, it would be opposite.

In, very roughly speaking, about 60% of the center band of 48 states, current Scientific opinion is possibly NO Low perm barrier anywhere in wall.

Don't take my word for it, Google "Vapor barrier heating climate"

Upstate NY being primarily a "Heating climate"

AKA Zone 6.


Marc

 

[OptionalStop]

Good info there thanks. Since I'm going to run horizontal 2x4 on the inside of the walls after insulation so I have something to hang my OSB to, I will have a 1.5" open air gap between OSB and insulation. I'd be inclined to install the vapor barrier poly BEFORE the 2x4's and right against the insulation but not sure if it makes a difference?

 

[bullnerd]

OS, take a look at my build, link in the sig.

pages 1-3 I think, shows the insulation and plastic.

I put the plastic on over the 2x's on the inside, more to staple to.

Look at those big sheets of insulation! Looks so cozy! lol!

Also, if your going to hang stuff from the 2x's, use real screws, not drywall screws or nails. Use structural screws or ledgerlok style.

 

[Marctrees]

Everyone has an opinion, few are technically correct.

READ the link tech info....

Not from Houzzzz or some BS site, but from the Science "Building envelope" community.

Marc

 

[Marctrees]

Study to UNDERSTAND WHY it should be done a certain way...

Marc

 

[b-boy]

Good info there thanks. Since I'm going to run horizontal 2x4 on the inside of the walls after insulation so I have something to hang my OSB to, I will have a 1.5" open air gap between OSB and insulation. I'd be inclined to install the vapor barrier poly BEFORE the 2x4's and right against the insulation but not sure if it makes a difference?

I think that they key is don't have a vapor barrier on the outside and the inside.

If you're using foamboard or spray foam, make sure it's enough of an insulator to prevent condensation of water vapor. If it's too thin, water will condense. Also, make sure to use unfaced batts. You don't want to trap water.

if you don't want to use foamboard you're better off just going with a plastic vapor barrier on the 2x4s and batts on the outside of the vapor barrier.

 

[Marctrees]

b-boy made a good post above, but the last sentence is confusing -

""if you don't want to use foamboard you're better off just going with a plastic vapor barrier on the 2x4s and batts on the outside of the vapor barrier.""

Again, w OP living in the northern zone, poly needs to be put immediately on backside of OSB, sheetrock, or whatever is the finish on inside of room.

Marc

 

[Marctrees]

b-boy -- You have a good grasp of the principles..

Please restate that sentence to avoid confusion.

Thank you, Marc