Increasing Wall Depth To Add Insulation...

[The Shat]

Live in Minnesota, where it's cold as hell in the winter, and pretty damned warm in the summer, too. I'm in the middle of a garage remodel (26' x 20' attached). It has three exterior walls which are 2x4 construction (16" o.c.). Is it possible and/or cost efficient to face-nail/screw 2x2 strips to the existing studs to make the equivalent of a 2x6 wall? I would then be able to increase my exterior insulation from the r-13-15 range to r-21. The cost of the 2x would be about $100, and I would imagine that cost would be recouped relatively rapidly in my gas bill. What say you guys?

 

[green.bubbly]

You are only going to spend $100 so it certainly would not take much to recoup your investment.

 

[Randy in Maine]

Why not just use foam board. I am using 2" and 1 1/2" to do mine with spray foam around it. R=21 and low infilatration value. Vapor barrier over that.

 

[sickjuice]

Yep certinaly can do. If you got the place gutted its a no brainer, but if your garage is already finished and your thinking of gutting it just to add the 1.5" inches of insulation I'm not so sure its worth it

 

[The Shat]

Yep, it's already gutted to the studs, so it won't take more than a day of work to rip down some studs, glue, and screw. I do have to look into what Randy has done, though. How much more costly is the foam board? I was unaware that I could get r-21 out of a 2x4 cavity.

 

[Boomer343]

You could cut down foam insulating board and tack/glue that to the studs and plates then use longer drywall screws to attach the drywall. That would give a good thermal break.

If you want to do it with dimensional lumber then I would get a roll of thin closed cell foam that is used between concrete and a sill plate and put a layer between the pieces. Not as good of thermal break but still worth the effort.

 

[markvfr]

Or, if you want to spend some money but save time, get closed cell foam sprayed in your existing walls. 3.5" of closed cell foam=R20 and you don't need to hang poly. Thats probably the best insulation you can do, but it is expensive. Check with a local contractor and maybe its within your budget.

 

[bcoke]

The least expensive way would be rip 2x4's into 2x2's nail and glue or screw to the existing 2x4's, use 2x6 size insulation than wallboard.......now the most important fill all cracks, exterior wall seams , holes [wireholes,knots, old nail holes,the sill joint etc.] with spray foam insulation [rattle cans] and or caulking. Insulation as with most jobs is all in the details ,sloppy workmanship will cost you a lot of BTU's a crack or hole has 24/7 by 365 days to leak your heat out. Take your time it will be worth it!

 

[Falcon67]

As above - I would rank things for climate control as 1) seal out air movement 2) thermal break 3) thicker insulation. 1 and 3 are probably the most cost effective since you are buying insulation anyway. The #2 1" foam board would go quicker since it's less work and easier to cut and fit. Problem there is using old work boxes to add your outlets, so you'd want to seal those inside and around to keep the air out.

 

[Gary S]

I think you are wasting your time. Your existing 2x4 wall can take R13 blankets, and you can easily add another R5-7 with outside sheathing. That puts you around R20. Once you reach R20, your heat lost through the walls is hardly measureable, and you are wasting money trying for more.
Get your ceiling to R40-50, and the walls near R20, and after that, your doors and windows will be almost all your heat loss. Remember that a 2 pane Energy Star window is only R3, and a 3 pane Energy Star window won't hardly make R5. That is where your heat is lost, not in a R20 wall.
The ceiling is more important because heat rises, so you want about R50 up there to stop it.

And, all these nice energy efficient garage doors with the nice advertised high R values all assume that the door is 100% tight with no loss around it. If you believe that your door fits that tight, I can sell you cold hardy bananas to grow in Minnesota

 

[DynoDave]

A friend of mine, who is a member here, used this system on his garage here in Michigan, and is very pleased with the results.

http://www.builditsolar.com/Projects/Conservation/MooneyWall/MooneyWall.htm

 

[Randy in Maine]

Why not just use foam board. I am using 2" and 1 1/2" to do mine with spray foam around it. R=21 and low infilatration value. Vapor barrier over that.

I got my foam at a commercial insulation place that mostly deals with commercial applications. It is not the stuff you get at Home Cheapo, and is actually less money for it and there is no foil exterior. I am using construction adhesive that won't disolve the foam to hold the foam to the 2x6 roof rafters (R34 4" and 1 1/2"= 5 1/2") or for the 2x4 wall (2" and 1 1/2"= 3 1/2") and taping the joints. I plan to cut it to fit pretty tightly also on my tablesaw. I will put a 6 mil poly vapor barrier over it and finally the wood ceiling/drywall walls nailed into the 2x framing lumber. I have a new roof already on and log siding on my exterior walls, so I chose not to dink with that.

 

[NUTTSGT]

Since your walls are already gutted, I would add the extra 2x2 to the face and go with a thicker insulation. Simple and done.

One thing I might consider doing is trying to block the air infiltration at the sill though. I have thought about doing this on my house (old country home) if open another exterior wall. Staple some plastic at the bottom of the wall, 4-5" tall. Then rip down some scrap OSB or plywood and screw it to the wall like a kick plate over the plastic. Let the excess plastic drape over the kick panel. Fill that area between the studs, exterior wall and kick plate with expanding foam. Once it sets up, remove the kick plate, and tear off the plastic. The sole purpose of the plastic is to keep the expanding foam from sticking to the kick panel. Then put your fiberglass batts in like a normal wall.

It's all theory in my mind but having a home built on a 10-12" beam sitting on a stone foundation, I think it would work as I feel plenty of air filtration coming from that area or used too.

 

[justanengineer]

Something you might keep in mind depending on your goals for the garage is that you dont necessarily need a ton of "insulation" to keep your garage warm, even in a cold environment. Outside materials like stucco or brick and inside materials like plaster are some of the best insulation/thickness you can get. Granted, theyre expensive, but if you/the wife want the place to look like a million bucks eventually they might be a consideration. My current house is inch+ thick plaster on the inside, a regular stick wall, then laid brick (not brick fascia/brick tiles) on the outside. There isnt a lick of insulation in the walls but its by far the warmest house Ive ever lived in and holds the heat for days.

 

[theoldwizard1]

It might be cheaper to rip down 2x4 if you have a table saw.

I would use long drwall screws to attach them. Drywall screws are thin and you can drive them with a drill it that is all you have.

 

[Cobra6]

It might be cheaper to rip down 2x4 if you have a table saw.

I would use long drwall screws to attach them. Drywall screws are thin and you can drive them with a drill it that is all you have.

That is exactly what I did - but I did get some of the 2" x 2" pieces they had on sale at HD instead of ripping 2x4s - it was almost the same cost.

I also ran the #2 Phillips drill tip completely through my hand while putting the strips onto the studs. I would advise against doing that.

 

[The Shat]

Damn, hope your hand is alright!

First, let me thank everybody for the awesome suggestions. I think I've buttoned up my plan for the next phase of the project, and more importantly, have added a new project to further improve things.

I'll compare cost of 2x2 strips of either pine or foam board. If it's close, I'll probably try the foam board. If it isn't (and I doubt it will be), I'll just use studs (probably make drywall installation easier, anyways). That'll give me a 2x6 cavity which should take r-19 relatively easy. I never would have thought air infiltration is as big a deal as it is, so I'll be sure to be meticulous with my vapor barrier and buy a few rolls of tape and spray foam.

What I didn't mention is that the siding (if you can call it that!) is hopefully coming off in the next year or two. As of now, it's this **** fiberboard stuff (can't be more than 3/4" thick) with the texture of lap siding on the outside. It comes in 4'x8' sheets, and is cheap as hell. That's literally all that is on the outside of the studs. In fact, mice have chewed through the bottom, and I can see daylight through the hole! When I spring for new siding, I'll look into some 3/4" or 1" sheathing and at least a 2" layer of foamboard on top of that. I'll likely due that all the way around the house, too. At least other parts of the house have some planking on the outside studs, but still no housewrap, and certainly nothing air tight. Hopefully that will go a long way towards improving things around here, and should be far more accessible than taking out interior walls!

 

[Krodad]

Why not just use foam board. I am using 2" and 1 1/2" to do mine with spray foam around it. R=21 and low infilatration value. Vapor barrier over that.

^^^^^ excactly!

As you have already said and know, infiltration is your biggest killer, whether it's obvious like around doors, or not so obvious, like inside the cavity. If you have any leak at all in the wall cavity somewhere, no amount of batt insulation is going to do any good. Not sure how often you heat the area, or how big the differential is, but I don't give batt insulation much credit at all.

Since you have it down to the studs already, I'd consider rigid insulation between the studs, as thick as your pocketbook will allow...don't worry about making it super tight between the studs. Let little gaps happen, then come back with spray foam and seal the entire perimter. Maybe this is 1", maybe it's 2"...not really that big of a deal in the long run. Then, before you sheet the interior, add another layer of 1/2" or 3/4" rigid board again, over the studs, and tape the joints (with housewrap tape). Now you have a thermal break over the studs, another "gasket" seal on the wall, and a truly dead airspace in between. That airspace also gives you the advantage of having some room for wires.

Of course it would be even better to completely fill the cavity with the foam board, but that is really not practical from a wallet standpoint...just too expensive and really not that much more effective. Getting caught up in maxing out the R-value number makes no sense if it's really not going to be effective...and effective R value is what makes the difference. If the heat is incedental...meaning you warm it up when you are out there working and shut it down the rest of the time, then this argument is even more true as the insulation effectiveness has a time and temp. differential associated with it.

The ceiling insulation is a little different animal though...you want quite a lot up there, but assuming this is a pretty tight ceiling, the R Value gives you more benefit in the summer months resisting the very consistent high attic temps.

 

[theoldwizard1]

A friend of mine, who is a member here, used this system on his garage here in Michigan, and is very pleased with the results.

http://www.builditsolar.com/Projects/Conservation/MooneyWall/MooneyWall.htm

Very cool !

Cellulose insulation is very cost effective and you can rent the blower from HD or other home improvement centers. The translucent insul mesh make it easy to see the each stud cavity is properly filled.

Another advantage of cellulose is almost ZERO waste. It the floor is clean of debris when starting, and inuslation that falls out is just recycled !

 

[Arctic Taco]

I would go with the blown cellulose and use you ripped 2x horizontally, and rigid foam in between, minimizes thermal breaks that go all the way through the walls. Of course you would have to do the box extensions, and seal really good around them to the foam(tape?) and vapor barrier, then put up 1/2" ply, on the bottom course and sheet rock up top, gives you something to hang stuff from with out the guessing game of where are the studs. Not the cheapest route. Another option, maybe shift the foam to the outside next year when you do the siding, horizontal tape seams house warp and nail up some stickers to attach your siding to, gives some space for condensation to drain away from your wall.
Have seen that work quite well up home-Alaska

 

[Iggi]

Radiant barrier keeps the 110 degree south Texas heat from turning my garage and shed into an oven. Its amazing how cool it is compared to my buddies sheds with tons of insulation. In the winter, the radiant barrier traps the heat in the room so i can heat the entire garage with a tiny space heater. Our electric bill during the summer went from $200 down to $120. The heater does not come on as much during winter as well. We love it and it only costs us $130 for a 1000 sq ft roll. I got it from a company out of dallas called attic foil or something like that.