Pole Building Insulation Question

[bray101]

Hey all. Been reading the site for awhile, but this is my first post.

I’ve searched and searched...and then read and read some more, but I can’t seem to find someone with the exact question I seem to be obsessing over.

Recently had a 32x40 pole building constructed. Storage space in the house is limited, so I framed in two small rooms inside the garage for storage that is out of sight, as well as studded out the rest of the building. 24” o.c.

My question comes with as the winter approaches in Ohio, I want to insulate the building this year or next. On the two 32’ walls, the 4x6 posts are facing in a direction that has traditional 2x4 framing. On the 40’ walls, the post face in the direction so that the 6” side frames the wall.

My question is...when I insulate, should I use R-13 on the 2x4 walls (4” cavities) and R-19 on the 6” deep cavities? Also, the horizontal purlins that attach to the posts will stop the batts from direct contact with the plywood sheathing. I’ve read a few posts that have put 1.5” foam in those cavities to even everything up behind the stud walls prior to insulation. I’ve read what seems to be a thousand posts, and it’s a 50/50 split on the air gap between the insulation and the sheathing. Sheathing is plywood wrapped with Tyvek, and then vinyl siding. Slab is already poured inside and the bottom framing plate was attached directly to the concrete.

Thanks!

 

[Firebrick43]

The air gap that is needed has already been taken care of by the style of construction you have chosen. The vinyl siding has air slots on the bottom edge and ventilates between the siding and tyvek. Hardieplank, smart side and cedar lap should have a rain screen built outside of the sheathing.

The issue with most pole barns is the metal panels on the outside and no sheathing. You don't want to block the vertical webs as they are the air channels to ventilate the back of the wall. Insulation such as fiberglass is fine to touch the back of the metal panel, you just don't want to press it in hard enough to block the channels. Other insulation methods such as cellulose or spray foam should have sheathing, tyvek, or netting applied before insulation so again the channels are not blocked.

1.5 xps would be wonderfull for air sealing and increased insulation but not neccessary per say in your situation. If you already have framed vertical studs it may be difficult to install now.

 

[bray101]

Thank you! If I just use batts that go up to the horizontal purlins and create an additional air gap, would that be a problem? Or am I taken care of due to the vinyl/tyvek/plywood sheathing combo already?

Thanks.

The air gap that is needed has already been taken care of by the style of construction you have chosen. The vinyl siding has air slots on the bottom edge and ventilates between the siding and tyvek. Hardieplank, smart side and cedar lap should have a rain screen built outside of the sheathing.

The issue with most pole barns is the metal panels on the outside and no sheathing. You don't want to block the vertical webs as they are the air channels to ventilate the back of the wall. Insulation such as fiberglass is fine to touch the back of the metal panel, you just don't want to press it in hard enough to block the channels. Other insulation methods such as cellulose or spray foam should have sheathing, tyvek, or netting applied before insulation so again the channels are not blocked.

1.5 xps would be wonderfull for air sealing and increased insulation but not neccessary per say in your situation. If you already have framed vertical studs it may be difficult to install now.

 

[Firebrick43]

I would try to fill that space with some kind of insulation for no other reason of improve energy efficiency. It's going to be a effort vs reward question your going to ask yourself.

A flash layer of spray foam would be doable and seal everything well but is expensive. I don't know if fiberglass is available in 1.5 or 2"???

It might be worthwhile to also fill to somewhat deter rodents. They love hidden open spaces.

 

[Aquamoose]

I’d frame with 2 x 6 on the 32” walls with them installed so it’s protruding inward about 1 1/2” - 2” then install thicker batt insulation. My shop was done similar to yours only I specified that the 4x6 be oriented to allow for thicker space for the insulation.


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[like2wheel]

The issue with most pole barns is the metal panels on the outside and no sheathing. You don't want to block the vertical webs as they are the air channels to ventilate the back of the wall. Insulation such as fiberglass is fine to touch the back of the metal panel, you just don't want to press it in hard enough to block the channels. Other insulation methods such as cellulose or spray foam should have sheathing, tyvek, or netting applied before insulation so again the channels are not blocked.

Is this true? I was going to spray foam the bottom (commercial girts) where I can see some daylight where the panel meets the bottom trim. But I did wonder if it was a good idea to leave it to ventilate the wall. Kind of like a mini version of the soffit/ridge vent.

I also thought about sealing the bottom, but not the top to maybe let it passively vent without all the air movement behind the fiberglass.

 

[bray101]

Any idea on what to use outside of a spray application? I didn’t think of the 1.5” foam, and it may prove quite difficult/impossible to slide those behind the framing at this point without snapping the foam in half...

I would try to fill that space with some kind of insulation for no other reason of improve energy efficiency. It's going to be a effort vs reward question your going to ask yourself.

A flash layer of spray foam would be doable and seal everything well but is expensive. I don't know if fiberglass is available in 1.5 or 2"???

It might be worthwhile to also fill to somewhat deter rodents. They love hidden open spaces.

 

[Dragfluid]

OP, you're in Ohio? If you want that shed to be comfortable, you need more than R13 in the walls!

Take a look at my build thread for some ideas.

 

[Firebrick43]

Any idea on what to use outside of a spray application? I didn’t think of the 1.5” foam, and it may prove quite difficult/impossible to slide those behind the framing at this point without snapping the foam in half...

I really don't know other than spray foam. 1.5" xps foam would have been easy before framing the walls but as you surmised is going hell now. Call your local insulation supply house and see if 1.5 or 2" fiberglass batts are available.