Insulating an already insulated garage

[jonnyboy]

So I just had a 30x60x14 post frame shop built. I had the builder install 2” vinyl back insulation between the metal exterior and the girts. I am regretting my decision and would like to add something with a higher R value but don’t want to run into an issue with the moisture barrier being on the wrong side (I am in southern Virginia so will be heating 4 or so months out of the year).

I feel like these are my options:

Add batts (faced)
Add batts unfaced (no vapor barrier since there’s technically one on the outside)
Add batts unfaced (plastic vapor barrier on interior)
Add batts unfaced (plastic vapor barrier on interior and pierce/slash existing vinyl back insulation to prevent a double vapor barrier)

Any suggestions?

 

[AC-WC]

For your area I think you're going to be unfaced and no plastic vapor barrier.

 

[jonnyboy]

For your area I think you're going to be unfaced and no plastic vapor barrier.

That’s what I leaned towards at first but worry that while heating would trap moisture in the walls. I thought about doing rock wool thinking it would be less susceptible to holding moisture if that did happen.

 

[theoldwizard1]

Heat rises. Additional insulation should go in the ceiling or under the roof deck.

 

[jonnyboy]

Heat rises. Additional insulation should go in the ceiling or under the roof deck.

For the ceiling I have R38 blown in and a vapor barrier installed on the interior just behind the metal ceiling.

 

[flippin]

I am certain the bill will be huge but would spray foam be an option?

 

[jonnyboy]

I am certain the bill will be huge but would spray foam be an option?

Spray foam is out due to cost.

 

[theoldwizard1]

For the ceiling I have R38 blown in and a vapor barrier installed on the interior just behind the metal ceiling.

Adding insulation in the walls is not going to help much. You need to find and plug air leaks.

 

[racecougar]

So I just had a 30x60x14 post frame shop built. I had the builder install 2” vinyl back insulation between the metal exterior and the girts. I am regretting my decision and would like to add something with a higher R value but don’t want to run into an issue with the moisture barrier being on the wrong side (I am in southern Virginia so will be heating 4 or so months out of the year).

I feel like these are my options:

Add batts (faced)
Add batts unfaced (no vapor barrier since there’s technically one on the outside)
Add batts unfaced (plastic vapor barrier on interior)
Add batts unfaced (plastic vapor barrier on interior and pierce/slash existing vinyl back insulation to prevent a double vapor barrier)

Any suggestions?

I'd go with door #4

 

[mdg]

So I just had a 30x60x14 post frame shop built. I had the builder install 2” vinyl back insulation between the metal exterior and the girts. I am regretting my decision and would like to add something with a higher R value but don’t want to run into an issue with the moisture barrier being on the wrong side (I am in southern Virginia so will be heating 4 or so months out of the year).

I feel like these are my options:

Add batts (faced)
Add batts unfaced (no vapor barrier since there’s technically one on the outside)
Add batts unfaced (plastic vapor barrier on interior)
Add batts unfaced (plastic vapor barrier on interior and pierce/slash existing vinyl back insulation to prevent a double vapor barrier)

Any suggestions?

Just wondering what you ended up doing? I'm closing on a home with a 60 x 40 metal building with 16' ceiling height. It's stick built with 24 on center studs with vinyl backed insulation on walls and roof. It's in central Tennessee. I'd like to use the building year round and be semi comfortable with heating and cooling. Was thinking of putting up a metal ceiling with blown in cellulose and unfaced batts for the walls. From whatI understand, it's not the best idea to do closed cell foam over the vinyl. Pretty confused on what's the best way to go.

 

[nadogail]

IMHO, Insulation is like money in the bank, it’s almost impossible to have too much of either.