Opinions needed - insulation

[Atrus]

Opinions needed please....

I am doing a new build...I have a 30x40 garage with a 30x40 full story above it, to be used as a workshop.

My plan is to install a Mr Cool minisplit in the workshop area. The actual garage area will be unheated - I'll just use a space heater or something when needed. For the workshop, I just want to keep the humidity out in the summer and drop the temp a little, and keep it at 55-60 in there in the winter. Basically, to make it tolerable to be in there.

I don't ever expect to finish the workshop space for liveable area, but I always liked that I have 1200 sq ft available as an option in case I need it for elderly parents, kids that move back in someday (they are 4 and 7 now), etc.

Builder normally puts in R-19 in a garage ceiling, so that is included in my base price. He can put R-30 fiberglass in the garage ceiling (so, between the garage and workshop) for ~$300 as an upcharge.

The house is actually being spray foamed, and I can have they spray foam the space to R-30 (again, garage ceiling/workshop floor joists area) for $3500.

I completely understand the cost - it's a big area. That being said, it's a lot of cost. Do you feel that in the floor of the workshop, R-30 fiberglass would do just fine, or would you cough up the $3500 to have it foamed. Is it really worth it?

 

[Atrus]

Should also add - I am in MI....so, we do see bitterly cold days in the winter, and 90*+ for stretches in the summer.

 

[ddawg16]

$300 upcharge to go to R30 is a good value. But $3500 to get the same R30? Naw.....

Just do the R30 Fiberglass. But also make sure you cover it with drywall and a proper vapor barrier.

 

[Atrus]

Thanks - will definitely be covered with drywall.

From what I have read, the R-value comparison is sketchy at best. I think the foam outperforms fiberglass in every way except cost.

I do tend to agree though - given the cost, it just seems like the R-30 should suit me fine.

 

[matt_i]

So, just to be sure its not an attic space with the roof directly under...because those get HOT.

Imo the ceiling is where you lose the majority of heat, so the R-30 is definitely something I would look at. I'm curious why they are not quoting loose fill cellulose, that seems to be the easiest way to get the R-30 to me. Fiberglass is OK but its going to pack down and lose R-value and I personally think that its more susceptible to heat loss due to slow air currents in the attic that are driven by winter winds thru the soffit and ridge vents.

 

[rodder98]

To upgrade to R-30, Yes, definitely.
But, not to have it foamed. That's REALLY expensive.
Also, check with the foam contractor about whether the foam is combustible. Some building departments
won't allow it unless it is treated after foamed, with a chemical to make it non-combustible. I saw someone once take a scrap piece of the foam and made it burn with a cigarette lighter.

 

[aardquark]

I would use Roxul instead of fiberglass. It is a little denser, more resistant to packing down, you get a slightly better R-value, and (in my opinion), it is more resistant to rodents, which love to tunnel through garage walls, leaving their little presents. Yeah, it's a little more expensive than fiberglass, but not excessively.