Insulation

[DaveL.]

Need some advice/thoughts...
My attached garage (1200 sq ft) is heated with a cieling mounted Modine 75000 btu heater. My builder insulated the cieling with 6" of cellulose. Lowes recently had a great deal on rolls (15" x 40') of faced R-13 . With the price of natural gas I thought I'd roll some R13 to increase my overall R-value up there. I was going to remove the facing (vapor barrier) from the insulation as I layed it over the existing blown in stuff. After talking to freind who does remodeling,he suggested I just lay the insulation down with the barrier up since it was just over the garage and not over any living space. The trusses are 2' apart so the batts overlapp the trusses. I'm about 75% finished and am wondering if I might develop a moisture problem even if it is over the garage. Sorry for the long post but whats your thoughts?

P.S. In the winter months I keep the thermostat set at about 50 except when I'm working out there then I turn it up to about 60-65.

Thanks...Dave

 

[ChucksCrib]

I always thought..........as a rule of thumb...........that the vaper barrier faces the heat(of the room).

Is there a vapor barrier under the blown in stuff?

Thats alot of work to peel the vapor barrier off of the insulation. Why don't you just get it without the kraft paper on there.

I believe R13 is about 4" thick. If your gonna go through all that work why not go with the R19(6.25 ") or R30 (9.5" ) insulation

 

[DaveL.]

Chuck- Yes the the vapor barrier would normally lay towards the drywall. There is no vapor barrier under the blown in stuff. The reason I bought the R-13 with facing was I got it all for $140. There was no sale on the unfaced. I'm just wondering if I should start pulling all the paper off. In hindsight,I should have just spent $400 and got the R-19 or R-25 unfaced.
Garage budget is really tight right now so I took the best deal I could find. My main concern is moisture.

Dave

 

[mleichtle]

If your ceiling is drywall, paint it. Theres your vapor barrier, no worries.

 

[ChucksCrib]

Knowing that........

Ideally........if you use the painted sheetrock as a vapor barrier and also leave the kraft paper on the insulation......moisture between the two has got no where to go.


Realistically.........I'm sure any moisture trapped between the two mediums will find there way out before you run into any problems.

 

[trovato]

Check out this site: http://www.naturalhandyman.com/iip/infxtra/infinsul2.shtm

They say: When adding additional insulation to an attic that is already insulated, NEVER USE INSULATION WITH A VAPOR BARRIER!! If you do, there is a chance that moisture that has slipped by the first vapor barrier will become trapped by the second vapor barrier, decreasing the value of your insulation. If you have to use insulation with a vapor barrier because your Uncle Harry gave it to you, slice the vapor barrier in numerous places with your utility knife to allow moisture to pass through it. And then thank Uncle Harry!

That sounds a lot easier than peeling it all off!

 

[DaveL.]

If your ceiling is drywall, paint it. Theres your vapor barrier, no worries.

I've got 3 coats on the cieling...you think that will do the trick? Its not semi gloss however if that makes any difference.


Thanks guys..Dave

 

[trovato]

Different paints have different "perm" ratings, for permeability. If you know what brand/type of paint you used, maybe you can find out its rating from the manufacturer. From what I've read, oil based paints do a better job as vapor barriers.

 

[mleichtle]

Yep, I just read FHA says perm rating of 1 to be a vapor barrier. My thinking was, we paint siding why? to keep moister out, if it works there why not here. I was talking before thinking again. IMO the craft face paper wouldn't trap moister any more than say a plywood floor if just rolled out and not stapled. And the paint will stop enough vapor that you'd never have to worry about it.

 

[DaveL.]

Check out this site: http://www.naturalhandyman.com/iip/infxtra/infinsul2.shtm

They say: When adding additional insulation to an attic that is already insulated, NEVER USE INSULATION WITH A VAPOR BARRIER!! If you do, there is a chance that moisture that has slipped by the first vapor barrier will become trapped by the second vapor barrier, decreasing the value of your insulation. If you have to use insulation with a vapor barrier because your Uncle Harry gave it to you, slice the vapor barrier in numerous places with your utility knife to allow moisture to pass through it. And then thank Uncle Harry!

That sounds a lot easier than peeling it all off!

Yep I agree.Thats what I am going to do. The moisture can also pass through where the batts join together.
Thanks for all your help..

 

[jonkav]

As a side query, how much insulation for an attached garage? In our new house, they've only insulated and sheetrocked the adjoining walls--the rest are unfinished (as usual). Is there really a difference between R-13 and 15?

 

[DaveL.]

My attached garage cieling was insulated by the builder to R-19. I just added rolls of R-13 to give me a total of about R-30~32. Are you going to heat your garage? If so I'd insulate to at least R-30.

Dave

 

[jonkav]

What about the walls?

 

[NHCharger]

What about the walls?

What do you have for walls? 2x4 or 2x6. If 2x6 you might as well go with the R-19. For 2x4 the standard is R-11. You might want to check to see if there is a big price differance going to the R-13. Are you going to heat the garage?

 

[DaveL.]

They used R-11 on my 2x4 walls.

 

[jonkav]

Mine is 2x4. I was thinking of R-13, but was wondering about the worthwhileness of going to 15...

At this point, the only heating would be on an as-needed basis. But, it will be the primary entry point into the house, so having 30 degree air mixing with 69 degree (inside) air is not that desirable

 

[jonkav]

Another lame-ish query--why use batts vs roll? A batt only seems better if it is the same length as your cavity/bay... otherwise, you still end up cutting pieces, so might as well go with a roll... ??

 

[rdnkjeeper]

I personally like the rolls better, then I can cut it the size I want.

 

[MyMopar]

A quick question. My garage was an old arn that the guy had rebuilt and sided. He didn't add the 1" think silver faced foam 4x8 tiles if you know what I mean. The siding is installed directly over the barn wood.
I want insulate because I am heating the garage. It is a detattached garage heated by a Modine HD60. I was just going to put up insulation R-19 with the kraft paper facing in and then drywall. Would I have to do anything more or anything special due to the siding being installed directly over the wood? Is it worth it to caulk between the boards before putting the insulation up?
Also would I want to use a higher R- value for the ceiling?

 

[oldgoat]

Well now I'm comfused. The way I am reading this if you paint your ceiling then you don't need the vapor barrier. But on a house they put the insulation in with vapor barrier and then many times paint the walls. I'm planning on puting R19 at least in the ceiling with kraft paper and staple it to the rafters then puting the sheetrock up next. Would this present a problem?