Looking for input regarding insulation "plan" for detached

[CarCrazyRDM]

So below are a few pics to help better illustrate anything I might fail to describe correctly or in enough detail. I have pretty much finished off all electrical, I'm finalizing plumbing now, and other than some hardline airlines I plan to put in the wall I'm nearing being ready to insulate and drywall. I'm mainly looking for input on how to insulate the garage without going overboard, keeping in line with my "goals" and intented use for the garage, and an attempt to keep costs "reasonable." I plan to do the work myself unless I find the difference between doing it myself and hiring the work to be minimal.

A couple things to keep in mind, it will not be continually heated or cooled. I will have a propane heater at times in the winter and a window unit that I may run in the summer but ultimately I'm just looking to insulate it enough to keep it maybe 15 - 20 degrees hotter or cooler at the peak of each season. Also, the upstairs will never be finished so no need to go crazy. I will mainly be working on cars and doing general "shop work" on weekends etc out there.

The walls are 2x4 construction 16" OC. The ceiling I-beams are 19" or 20" OC and I believe something like 14" deep but I need to check on that. For the time being I plan to just insulate downstairs but I am sure I will insulate the rafters and end walls upstairs in the not too distant future.

With the above goals in mind:

1) Would you recommend just sticking with R13 or will the additional cost of R19 be felt given my intended use and region of the country?

2) I'm leaning towards using faced rolls of insulation unless you guys convince me using unfaced combined with a full wall vapor barrier is better.

3) I'm not yet sure what will be best for between the ceiling joists. Being that they are so deep and/or will have so much space between the back of the drywall and the insulation, does that change what is best to use?


Thanks in advance for any input,
Ryan


The garage -



General look of the walls and layout -



The only reasonable shot I can find of the ceiling/floor joists right now -



The upstairs -

 

[DC73]

Nice looking place.

Don't use R19 batts in the walls. It's a waste of money to compress batt insulation into a smaller space than it was designed for. Just select an insulation that is designed to fit in 2x4 walls. You can get both R13 and R15 fiberglass batts. R13 is readily available but you may have to order the R15s.

I used R15 mineral wool (Roxul brand) batts in my shop and I am really happy with the choice. A bit pricier than fiberglass but mineral wool blocks the flow of air much better, blocks sound transmission very well and is very fire resistant. Shop around. Lumber yards that cater to builders had much better prices around here than did Lowes.

I used the R15 mineral wool batts in the ceiling next to the drywall but to get the additional R-value (R30 at least for my climate), I put R19 fiberglass batts on top of the mineral wool because I got an extremely good deal on it and already having one layer of mineral wool seemed sufficient.

I can't tell from the map but it looks like you are near the border of climate Zone 3 and climate Zone 4. Recommended wall insulation for either zone is R13 to R15. Recommended minimum attic insulation for Zone 3 is R30 and for Zone 4 is R38. More is better depending on how often you will be heating and/or cooling the space.

Two good sources for research are GreenBuildingAdvisor.com and BuildingScience.com

Post your vapor barrier question in the Q&A forum at GBA to get the best feedback. This is one detail you want to get correct.

DC

 

[CarCrazyRDM]

DC73, thanks for the compliment and the info. I'll check out the two sites you listed as well.

 

[dshop]

you will never regret the initial added cost of professionally installed spray foam insulation. It fills every air gap void...any and all, no misses.
seriously check into this, it works well.
All the TV show guys in Canada use this for a reason, it is super effective.

 

[dave67fd]

I did R30 in the I joist ceiling/floor (Owens Corning Comfort Touch/no vapor barrier). You want at least R25. I also did foil foam board along the rim I joists, sealed with spay foam and then cut 16" batts to go over those before running the full back and forth length.

 

[CarCrazyRDM]

you will never regret the initial added cost of professionally installed spray foam insulation. It fills every air gap void...any and all, no misses.
seriously check into this, it works well.
All the TV show guys in Canada use this for a reason, it is super effective.

I know the stuff works but it's also very pricey. And for my intended use of the garage I think it might be a little over kill. I plan to get at least a couple quotes to have someone else do the job before I do it myself and I may ask them to just give me a ballpark idea on the spray foam but I'm almost certain it will be way more than I'm looking to spend.

I did R30 in the I joist ceiling/floor (Owens Corning Comfort Touch/no vapor barrier). You want at least R25. I also did foil foam board along the rim I joists, sealed with spay foam and then cut 16" batts to go over those before running the full back and forth length.

Looks good Dave. I imagine something like this is what I will end up doing. Thanks for the pics.

 

[BadgerBoilerMN]

If you use the proper fiberglass bat and a 1/2 inch of rigid insulation on the inside the thermal bringing loss--about 25% of the wall stack-up will be cut in half.

 

[CarCrazyRDM]

Badger, are you recommending such for the ceiling or are you talking everywhere?

 

[BadgerBoilerMN]

I use it everywhere. It worked wonders in my shop above the R-50 cellulose. No measurable solar gain from the steel roof. If you vault the ceiling, it is a must, but much thicker and foiled such as Thermax, an isoproyl rather than polystyrene.

Expensive but DIY friendly and worth it.

 

[d.swanson]

I'm no expert, but I thought the reason for not using paper backed fiberglass insulation was because:
1) The paper may mold over time
2) Paper is not as good a vapor barrier as plastic
3) In bulk, non-backed fiberglass insulation + plastic sheathing is less expensive than paper backed fiberglass insulation.

BTW - I did not see if you were planning on heat & AC?
Having lived in the Raleigh area basically all my life, if you can afford it, I would recommend both heat and AC.

 

[CarCrazyRDM]

d.swanson, I'm actually in Holly Springs as well. I just put Raleigh because on a national forum no one knows were HS is. But my HVAC plans are mentioned in the original post. Summary, no full-time heat or A/C, just secondary systems used in the peaks of each season.

I've gotten a couple of quotes and so far it looks like I can have the stuff installed for right around the same amount of money it'll cost me to buy just the materials. So seems silly not to just let them do it. And they'll knock it out a lot faster than I will.
None have suggested a plastic barrier at this point. I plan to call the company I am leaning towards using back on Monday and ask this specific question. But the current plan is R30 in the I-joist downstairs (and between the rafters upstairs if I do that now) and R15 in the walls.

I'm hoping to be ready for insulation in 2 - 3 weeks. I don't have that much more to do but there just never seem to be enough hours in the day or weekend to get as much done as I plan/want. Welcome to life right? Just need a plumbing vent run to the roof, a few more airline connections made and some extra "blocking" in the walls in few areas and we'll be ready to rock 'n roll!

 

[Angelfire]

DC73 is correct in recommending the proper vapor "retarder". Most think a sheet of visqueen is the right answer but there is so much more to be considered. In many parts of the country, a sheet of visqueen may actually be more detrimental than good. For myself, I went with a retarder that "adjusts" to the humidity within the wall and adjusts it's permeability accordingly. For some, paper faced batts are appropriate, and for others a full thickness of visqueen is. It deserves a bit of research to make sure you get it right for your climate.

Regarding the insulation, I used mineral wool on my home addition and will do so again on my detached garage....love that stuff compared to fiberglass and a side benefit is the sound attenuation that comes with it. I work late at night so blocking sound is quite helpful. I did seal all cavities with caulk before insulating which, while not as effective as spray foam, seems to have worked quite well and was a helluva lot cheaper. I do however like the idea putting fiberglass over the mineral wool as a cost savings. I may pursue this given I won't be living in the garage and will only be heating/cooling when I'm in there.
Cheers.

 

[d.swanson]

CarCrazyRDM - Wow, I don't know how I missed the propane heater/window A/C in in your first post, I must be more senile then I realized...

I hope a window A/C will be enough to make you happy; I found that a window unit for my 22 x 22 partially insulated (roof and wall adjoining the house) didn't seem to cool it down any, but did make it more comfortable if I was able to work near it where the cold air was blowing.

I had a similar situation with a portable heater.

From what I have heard others on here say, I wonder if a ductless mini-split ac/heat pump would be the way to go; I just wish I knew someone local with first hand experience.