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Shop Ceiling/Roof Insulation Upgrade

Bib Overalls

Well-known member
Joined
Dec 4, 2006
Messages
3,318
Location
Jonesboro, Arkansas
I built my shop ten years ago. At the time it was all that I could afford and I was quite pleased. But over the years my needs and desires have changed and I need to upgrade to a fully heated and insulated structure with good lighting. I can not afford to do it all at once so I will start with the ceiling and the lighting. End and side wall will be done later.

I used an Adams Truss metal frame with wood purlins and girts. The roof and walls are clad with 1" "AgBoard" and a metal skin. All of the joints in the AgBoard were sealed with tape. This

When you look up at the ceiling you see the white underside of the AgBoard and horizontal bays formed by the 2" x 4" roof purlins.

Weight is a big consideration. The ceiling/roof is not engineered to take the load that comes with drywall or OSB sheathing.

My plan is to use the white 28 gauge metal that I used on the exterior of the building.

This will, in effect, create almost air tight chambers between the purlins. I want to insulate this dead space. Can I use unfaced fiber glass bats (the cheapest alternative) or should I use a closed cell foam material in blocks or sprayed in?
 
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fefarms

Well-known member
Joined
Jan 25, 2007
Messages
186
Fiberglass insulation and water do not mix. It soaks up moisture like a sponge and its insulation value drops to zero once wet.

With metal on both sides, and no venting, the roof/ceiling assembly will not dry out easily. In a humid place like Arkansas, I would fear interior air getting into the cavities, and the humidity condensing out on the cold underside of the roofing metal.

If you can handle the cost, I would suggest foam insulation sprayed onto the underside of the ag-board. This will be impervious to moisture, and also act as a good air barrier to prevent condensation.

A second option would be rock wool batts. These are as easy to apply as fiberglass, and not too much more expensive. Rock wool deals with moisture much better than fiberglass.
 
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Bib Overalls

Well-known member
Joined
Dec 4, 2006
Messages
3,318
Location
Jonesboro, Arkansas
Thanks, fefarm.

You have captured the essence of my concerns. I'm going to talk to an insulation contractor on Monday. He offers spray in foam and traditional insulation. I'm hoping he can set me straight.
 
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blossom2347

Member
Joined
Sep 30, 2011
Messages
15
Agree with fefarms. These should not be used at once. Bib if you want any guldens you can visit us. :)
 
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