How do I insulate an existing, finished garage?

[williaty]

We recently moved into a new house and the existing attached garage is going to be my shop. Unfortunately, when it was built in 1979, the walls and ceiling of the garage weren't insulated and the whole thing was finished with interior dryway and wooden shingles on the exterior walls. It gets shockingly hot in the summer and freezes in the winter. Insulating the ceiling I think should be relatively easy because there's a ceiling trapdoor access to the attic, so blowing insulation or even putting batts down should be straightforwards. The walls are what vex me. Since the walls are already nicely finished in drywall, I'd prefer not to rip it all down to insulate. Additionally, one wall has lower cabinets and a counter from one end to the other, complicating access even if I were to rip the drywall down.

Does anyone have a suggestion for how to proceed?

I remember when I was a kid, it was common to see houses with rows of dots along every exterior wall where a hole had been drilled and insulation inserted into each stud bay. What was this process called? Is suitable for solving my problem if I have them do it from the inside (since I don't want the shingle siding messed with)?

 

[strength_and_power]

Drill a 4” hole at the top of the inside wall. Blow insulation in. Rinse and repeat in every stud bay. Install a 5” trim board when done to cover the holes.

 

[NostraThpmas]

First, check to see if you have fire blocking. Those are horizontal members between the studs to stop fire from spreading. They are common in attached garages.

 

[thammel]

My house has a 20x20 attached garage. The ceiling was uninsulated and the front wall, one side wall and half of the rear wall were also uninsulated. I tore down the drywall for those areas, ran some electrical for more outlets and switched over head lights, and put in fiberglass insulation. Then I put up new drywall and painted whole garage which was previously unpainted. I also put foam board insulation in the doors and pull-down stairs to the attic overhead. It definitely helped a lot with temperature control. Of course, after that I added a 32x28 attached garage perpendicular to that one which is a whole lot better!

 

[kngelv]

Pictures would help.

James

 

[DGersic]

Does anyone have a suggestion for how to proceed?

I remember when I was a kid, it was common to see houses with rows of dots along every exterior wall where a hole had been drilled and insulation inserted into each stud bay. What was this process called?

You’re looking for blown in cellulose insulation. You’ll drill a hole in each wall cavity. Blow in insulation, it packs the cavity full. Then you get to patch and paint.

 

[Stuart in MN]

It's possible to remove some shingles on the exterior, then drill the hole for blowing in the insulation, then replace the shingles. You need a tool called a shingle puller - it basically a flat bar with hooks on the end, you drive it up between the shingles, hook on to the nails holding the shingle in place, then drive it back out and it pulls the nail out.
That's an oversimplified description, but you can find pictures of the tool online along with more detailed descriptions how to use it. I think it was demonstrated on This Old House years ago.
My house has wood shingle siding and I have a shingle puller, I've used it a number of times for making repairs. It's not all that difficult but it does take some time.

 

[matt_i]

If you did cellulose, it will compact/settle over time. I would not make the "patch" permanent as it would be adviseable to go back in a year and continue filling the open space at the top.

Or, you could make a bigger project of it, tear off the drywall and possibly increase electrical wiring, then fit roxul (with better R-value and no-settling) and re-drywall.

I think a stud finder would tell you if blocking was going to be found. Or a smaller test-core at the bottom of the cavity to verify that the cellulose pack is making it all the way down.

 

[Ultradog MN]

People are terrified of drywall. Dont be.
As said above, use a hole saw and cut out a 4" hole in each cavity. Save the disks you cut out. Blow the cavity full of insulation.
Cut a piece of 1x3 about 6" long. Screw it as a backer behind each hole then screw the discs you saved to to the backer.
Mud as required.
Drilling through the exterior is nuts! SO much harder to patch the holes.

 

[kaehlin]

I had cellulose blown in. They accessed from the inside due to siding on the outside, drilled two holes (high and low) in drywall between each stud bay, blew cellulose, andcapped with a white plastic piece. I've been looking at the dozens of plastic hole plugs for years now, and the work to fix each hole / patch / paint is not trivial. If I had to do it over again, I would tear out the drywall, insulate, then re-drywall.

 

[loganb]

Drill a 4” hole at the top of the inside wall. Blow insulation in. Rinse and repeat in every stud bay. Install a 5” trim board when done to cover the holes.

Did this myself...I think I ripped my trim to like 8" due to how far down off the ceiling I had to put the hole but worked great...minus me not having all the trim up and it's 4 or so years after I did the work.

 

[Citation]

Do the walls have a proper vapor barrier? I would be concerned if they don't that you will get moisture trapped in the wall. I could be wrong about that but I would at least look into it.

 

[Ultradog MN]

Do the walls have a proper vapor barrier? I would be concerned if they don't that you will get moisture trapped in the wall. I could be wrong about that but I would at least look into it.

In a garage a vapor barrier is not required by code - at least not here in the Twin Cities.
There generally isn't all the people breathing and expelling vapor, taking showers and cooking.
I wouldn't worry about it.

 

[Skooterj]

You really have 4 options.
1. Remove the drywall and start over with the insulation of your choice (Spray Foam, Fiberglass, Rock Wool, Sticky Cellulose)

2. Drill holes and blow in cellulose. I have seen this done with one large 4" hole at the top of the wall, or two smaller 1 inch holes at the top and mid point of the wall. These holes can be interior, requiring drywall repair or hiding behind crown molding and chair rail trim, or simply just plugged with plastic plugs they make just for this process.(I think the plugs are super ugly, but they work). Or they can be exterior, requiring either drilling through your siding and plugging or removing your siding temporally. This can get difficult if you have any blocking in the walls, and it always settles a few inches, leaving a small gap at the top of the wall and possibly another at the blocking mid point.

3. Drill small holes and inject slow rise foam. These holes can be pretty small, but you still need one or two every stud cavity. Again, these can be from the inside or the outside. But with the proper amount of foam, it will completely fill the cavity and work its way into any crevices and act as a wind barrier. This will need done by a professional.

4. I have heard about this, but never seen it actually done. If there is room and no blocking is present in the walls, it is technically possible to go up in the attic, drill holes through the top plate of each stud cavity and blow in cellulose or inject in foam. You then fill these holes with Fire blocking Caulk. If you go that route, I would do the walls before you do the ceiling.

 

[theoldwizard1]

Most heat loss/penetration comes through the roof/ceiling. Insulate there first. Minimum 6". More is better.

Also, make sure the area between the ceiling and the roof deck is well ventilated. You may even want to consider powered ventilating in summer.

 

[dcg9381]

3. Drill small holes and inject slow rise foam. These holes can be pretty small, but you still need one or two every stud cavity. Again, these can be from the inside or the outside. But with the proper amount of foam, it will completely fill the cavity and work its way into any crevices and act as a wind barrier. This will need done by a professional.

I was thinking about mentioning this option. I've never done it and it's probably not cheap. But could it be done via drilling small holes in the header, so you don't have to deal with drywall repairs at all?

 

[Skooterj]

I was thinking about mentioning this option. I've never done it and it's probably not cheap. But could it be done via drilling small holes in the header, so you don't have to deal with drywall repairs at all?

See option 4 in my post. I've never seen it done, but it is possible. I mean, I've drilled through a top plate to drop a wire down to install a new outlet in a wall. But you are going to have the same problem, if there is mid blocking, you are still going to need a second hole below the blocking. Could that be behind the baseboard? Maybe.

 

[MikeC55]

Unless you have a pretty steeply pitched roof, and/or large rafters (2 x 12, etc.), drilling holes in the wall header may be pretty difficult, especially if the ceiling is already in place. Access will be a real pain. I'd much rather drill holes in wall and deal with a little drywall patching.

 

[Chris Stapley]

There's two way to do it honestly, the mickey mouse " might get some in the cavities way" or take down the drywall and
insulate properly once... you can benefit with the open walls as a few have suggested too ,great time to add additional
wiring etc..

 

[Higgins]

Drill a 4” hole at the top of the inside wall. Blow insulation in. Rinse and repeat in every stud bay. Install a 5” trim board when done to cover the holes.

Paint the "cover board" a contrasting color! Then hang some not used every day items from it!

 

[MichaelP]

I'd definitely remove the drywall to have a good access for inspection, electrical, plumbing/compressed air work and insulation. Then I would put either OSB or ply instead of drywall.

Make sure you install baffles above the attic insulation, soffit intake vents and some kind of exhaust for attic ventilation (properly proportioned).

 

[Ultradog MN]

So to the guys who are suggesting he tear out the drywall, are you SURE you've thought that idea through???
What will it cost to tear it out, haul the debris away, buy new sheetrock and install it. Then, because you won't even TRY to do a little patching you'll hire someone to do 10 times the amount of labor to tape the whole garage again.
Does that make any sense??
It sure doesn't in my world.

 

[tarmy]

There's two way to do it honestly, the mickey mouse " might get some in the cavities way" or take down the drywall and
insulate properly once... you can benefit with the open walls as a few have suggested too ,great time to add additional
wiring etc..

I thought that too…

Until I had it done and tested to see if the insulation fully penetrated and thoroughly filled every bay. I did it last year on a 70 year old summer vacation home that gets used year round. It is quite a system and it is indeed very good at filling every small nook and cranny. They sealed all the various top and bottom of exterior and interior wall finishes too. They used two 2 1/2” holes (no fire blocking) one in the mid height and one at the top. The material they used packed very evenly and tightly. Worked out great in my case. I had the holes from the outside as I also wanted rigid exterior insulation in voids as well. Topped it off with Hardiplank siding to reduced maintainance.

 

[dcg9381]

So to the guys who are suggesting he tear out the drywall, are you SURE you've thought that idea through???

Depends on where you are, could be that drywall replacement is a cheaper option than paying someone to slow rise foam.
1979 garage, I want to "adjust" some electrical anyway...

I do like OSB panels though, that's what I use in the shop. If I ever need to get behind the wall, I just drop a 4x8' panel. Not fireproof, but painted, they don't look horrible.

 

[ludakris04]

Insulate the attic. Insulate the door.

Since it is attached, you only have two walls left. (assuming they insulated between garage and house in 1979)

See how it does, you might be surprised.

Pulling drywall down, throwing up bats, and new drywall or slatwall is probably the easiest.

 

[99MPower]

if the garage is already empty, IMHO, im ripping down the drywall. Fixing ALL the electrical, with multiple breakers, a 220 outlet on both sides, 12/2 20amp outlets everywhere, front outlets for jack screw garage door opener, pull out electrical cords from ceiling, and more lights. Cant do the wiring, with all the drywall in the way.

Its a garage, so Id tape/mud myself, it doesnt need to be perfect, and good practice.

If you dont need to do electrical, then i'd rip a 6-10" strip around the top of garage, all the way around. Keep the pieces, to put back up after blowing in/settling/etc.

Lots of options, just a matter of money, time, and how "nice" you want to upgrade the garage while you do it

 

[Ultradog MN]

My garage is done entirely with 5/8" type X - fire rated drywall. Three reasons i went that way. It's cheap, it's probably the most fire proof covering and it is by far the easiest to repair.
I simply can not understand everyone's fear of of taping and mudding.
All my wiring is on the wall in thinwall conduit that's easy to make changes to.

 

[firebirdparts]

I will just throw out here that I'll bet you can see fire blocking using an IR camera. I bought one earlier this year that plugs into the phone, not a lot of money. You can see studs in an insulated wall quite easily. We have an upper half story, upstairs you can see nails. Just from the difference in thermal conductivity vs. a rafter.

 

[Dumber than lumber]

You’re looking for blown in cellulose insulation. You’ll drill a hole in each wall cavity. Blow in insulation, it packs the cavity full. Then you get to patch and paint.

I think you need two holes per "cell". One at top of cavity and one at bottom.

 

[DGersic]

I think you need two holes per "cell". One at top of cavity and one at bottom.

We didn’t. This was blown in ~20 years ago.

 

[Dumber than lumber]

We didn’t. This was blown in ~20 years ago.

That is interesting.
Now, did you just tear off the drywall to prove me wrong?
Or is there more to the story?
Did they blow in the faced batts at same time? (That was a joke.)

 

[dcg9381]

I think you need two holes per "cell". One at top of cavity and one at bottom.

I think I'd take an IR camera to it before I'd assume that, if you're talking about "blocking". Or are you talking about that's what you need to make sure the insulation fills the cavity when you blow it in?

Insulate the attic. Insulate the door.
Since it is attached, you only have two walls left. (assuming they insulated between garage and house in 1979)
See how it does, you might be surprised.

Honestly, as he's got to do the attic anyway, that's not a bad idea. ~75% of the heat loss/gain is going to be out the top. Might not have to do the remaining 2 walls.

 

[Hank11]

Honestly, as he's got to do the attic anyway, that's not a bad idea. ~75% of the heat loss/gain is going to be out the top. Might not have to do the remaining 2 walls.

I have this situation and it’s not ideal, but it’s also not bad. In the winter, the room feels just a little bit chill even when it’s warm in there. The mini split keeps it pretty nice otherwise. In summertime it’s less bothersome because the walls that are maybe 3/4 uninsulated are not exposed to hot afternoon sun. If I had a west facing wall, and it was uninsulated, I think I would insulate it.

It seems incredible that anyone would put up drywall without putting up Insulation, but they do it.

 

[Dumber than lumber]

I think I'd take an IR camera to it before I'd assume that, if you're talking about "blocking". Or are you talking about that's what you need to make sure the insulation fills the cavity when you blow it in?

Honestly, as he's got to do the attic anyway, that's not a bad idea. ~75% of the heat loss/gain is going to be out the top. Might not have to do the remaining 2 walls.

Blocking is what I was thinking. But wires and other trash (you know how wacky subs can get?) could also prevent a thorough fill.
Insulated garage door Is something to consider. Maybe it is already done or in process.

 

[DGersic]

That is interesting.
Now, did you just tear off the drywall to prove me wrong?
Or is there more to the story?
Did they blow in the faced batts at same time? (That was a joke.)

20 years ago, we removed the top course of cedar siding and blew in insulation. The 1950 ranch had none in the walls.

Earlier this year, we gutted the bathroom for a remodel.

Most of the house is plaster over rock lath. The bathroom had previously been remodeled with sheet rock, poorly.

So it was interesting to see how the cellulose had held up when the inside walls were opened up.