insulation recommendations?

[Mike]

Evening,

I purchased a 12'x16' structure (shed). I have paid the builder to insulate the floor as part of the construction. I need to insulate the walls and gambrel roof. The three things I'm considering are fiberglass (pink) batts, rigid foam, and spray foam. The first to I can do myself. The third I would like to do myself, but I know the installation is critical to the proper functioning of spray foam so I should have someone with experience do the installation.

Fiberglass insulation would be the cheapest of the prices I have looked found. Spray foam (closed cell) would fill gaps and form another barrier inside the outer sheeting. Rigid foam I would either do two layers or would create a "box" with a hollow core that I would push between the studs. Fiberglass and rigid foam would have gaps between the outer surface and the outer sheeting that I'm concerned would allow mold growth.

Seems to me spray foam would be best for my situation. I'm concerned about off gassing (another reason to have some do this so the 2" installation depth is not exceeded) and the R value seems to be about the same as rigid foam.

Oh, also seems that gravity would cause fiberglass to lose loft, compress, in the gambrel sections since I must apply the insulation from below.

I know there is significant prep work before foaming, and I don't mind doing the prep work.

Thoughts?

Thanks again for your help.

Mike

[Ed Pawlowski]

I'd go with rigid foam and DIY If you have an EPS (expandable polystyrene) fabricating shop near you, they will make it to the thickness you need so there is no gap.

[gregz]

I question whether a complete seal is good. What's going to be in the shed.

Greg

[Fat-Dumb and Happy]

Fiberglass insulation is NOT what it's cracked up to be,

[Stormin Mormon]

I'm also been wondering what's the purpose of insulating a shed. Seems like a lot of extra bother. Fiberglass from below is fine, for the roof. Doesn't lose all that much, over time.

[trader4]

It's interesting to watch, but not sure exactly how much of that translates into an application of the insulation in the real world. He's deliberately forcing air with a fan through the insulation. If you have fiberglass batts laying between joists in at attic, there is no fan forcing air through it. The insulation is even covered with a vapor barrier, then by drywall under it. So, I'm sure you'd get some thermal movement of some small amount of air, but it's nowhere near having a fan force air through it.

Also if this were an inherrent problem with fiberglass insulation, wouldn't it be reflected in the R ratings?

[gregz]

It should be reflected. It's not linear. The greater the differential temperature, the more the air wants to flow. We all know what the fibers look like. Cellulose forms a more continuous barrier.

Greg