R-11 Insulation

[Blownchevelle68]

Hello all

I have a attached garage i'm starting to renovate. Currently drywalled and insulated with R-11, but taking all the drywall out and replacing. Couple years ago I wrapped and re-sided the house, using vulkem on the end siding to seal the gaps.

The R-11 insulation I have in the walls looks great and I plan on putting a 6-mil plastic sheeting over the entire wall. Will I benefit from taking the current insulation out and replacing with R-13 or will it not be a huge difference?


Right now the garage is unheated and the coldest temps inside have been around 20 degs (that was with a negative actual temp) and high wind. We plan on installing a furnace and using the garage more like a lounge/shop this year.

Thanks !! Jason

 

[Falcon67]

I would not think the effort and expense worth it for "2-R". Making sure the walls are done right and the insulation tight to the studs, air movement eliminated,etc would allow the existing to perform quite well. I only have R-13 in the shop walls and attic here and I don't have any issues cooling or heating for the times I'm in the space even with roof deck temps over 140F or the attic cold enough to see your breath.

 

[James-W]

If you were to remove the current insulation and use spray foam insulation, that would seal everything up and would insulate the garage a lot better. I am not saying you should do that, I am just saying it would be an improvement that may be quite beneficial for you and something you MAY want to consider.

 

[Blownchevelle68]

I would not think the effort and expense worth it for "2-R". Making sure the walls are done right and the insulation tight to the studs, air movement eliminated,etc would allow the existing to perform quite well. I only have R-13 in the shop walls and attic here and I don't have any issues cooling or heating for the times I'm in the space even with roof deck temps over 140F or the attic cold enough to see your breath.

Thanks-Anything I should be spraying in there now? Should I get some of the cans of spray foam and pull each roll of insulation out, spray the perimeter around the 2x4 then reinstall insulation, followed by plastic sheeting?

 

[BruceMc]

Assuming the R-11 was installed carefully and correctly, you won't see any real world difference with R-13. You'll be a lot farther ahead putting the same time and money toward getting a proper seal at any penetrations (outlets, garage door, windows, etc.) and weatherstripping.

 

[Falcon67]

What Bruce said. You could spray the edges if you like but it'll run into money pretty quick as those can's don't hold much. I would consider caulk maybe, but I didn't do any of that - just walled it up and caulked the interior seams (OSB).

 

[DonPowers]

The calculation for heat loss is Q=U x A x ∆T
Where:
Q= BTU per Hour
U= 1/R
A= Area in sq ft
∆T= Temperature Difference between inside and outside

So if you have R=11 and you and you want to upgrade to 13 or higher, run the calculation for other R values to see how many BTU per hour that you gain.

There a lot of other considerations to factor into a heat loss calculation but this will give you a ballpark idea of your heat loss. If you set it up on a spreadsheet you can model options.

 

[NUTTSGT]

Since the R11 is already there, I'd leave it alone.

What's in the ceiling ? Does that have R11 in it also ? If it does, I'd roll another layer (of something thicker) perpendicular across the trusses to blanket the attic. Just make sure you do not block the soffit vents, if you have them.

Is your garage door insulated ? If not, take care of that too.

 

[larry4406]

I tend to agree on making sure the existing R11 is proper vs removing and changing to R13. Spend some time using a quality latex caulk to provide air seal of the wood framing (caulk sill to stem wall, seams in the double top plate, any ganged studs, etc). Pull the insulation down slightly at the top and inspect for any wiring penetrations at the top plates and make sure these are fire stopped and then restore insulation.