Blow-in Insulation for Garage/House Wall: Dangerous?

[Psychstache]

So my house was remodeled before I purchased it and in that process, the kitchen was rearranged. The pantry became this large cavern that backs up to the wall of the garage AKA the pantry and garage share a wall. The garage is obviously unairconditioned and lacks insulation, including this wall. The result is that during Texas summers, where it is currently approximately 16 kajillion degrees outside, the garage gest very hot, which in turn causes the wall to get quite hot, which in turn leads to things melting/spoiling/molding in the pantry.

My plan has always been to go rent an insulation blower and fill in the wall cavaties on the garage/pantry wall. In getting ready to execute this plan, I began reading online and saw some articles that mentioned a concern about a fire hazard with using blown-in insulation with a garage and recommended something fire resistant like mineral wool. This would require removing the drywall to install and then reinstalling, increase the labor and cost.

Is this a real concern?

[Fishindude]

I do not think blown insulation is a fire hazard.   If all you have to do is one wall of a pantry, I would not mess with blown in insulation.   The hassle of getting the blower equipment set up and ready to go, then cleaned up and returned is more work and cost than it's worth.

For a small wall like that, I would tear off the finish material (drywall) on one side or the other, insulate the stud cavities with fiberglass, them replace the finish material.   A simple fix, if it's a wall in back of a closet and you don't care about looks, would be to simply glue or otherwise fasten foam board to the surface of that wall to keep the closet cooler.

Big picture - I'd get the entire garage insulated including an insulated overhead door(s).   If will help keep the whole house cooler and save energy.

[lthenderson]

Modern blown in insulations are treated to resist things like fire so I wouldn't worry about that. I'm guessing you were reading about the shared wall between a garage and a home should be constructed as a fire barrier which is why certain types of materials should be avoided.

I personally would never put blown insulation in a vertical stud bay application. It settles with time and you would still end up with hot spots at the top of the pantry wall. Also like Fishindude said, for the effort and cost of renting a blower outfit, you could get enough drywall, screws, mud and probably the bat insulation necessary to do the same job two or three times over and you won't end up with compressed blown in insulation.  If the inside wall of the pantry is visible and in nice condition, do consider removing the drywall to insulate from the garage side where it might not be so important. I also agree that a good long term goal should be to insulate all the garage walls. Not only does is save energy but it gives you a buffer in the summer so your car isn't so hot to get into until the A/C kicks up to speed.

[BudgetSlasher]

As others have said there are more effective insulation systems than blown in and you may wish to investigate them a little further.

That being said, if you have investigated them and have settled on blown in for your application and accepted its trade offs.

I would be 0% worried about a fire risk. There are two types of blown in, that I am aware of, fiberglass and cellulose. Fiberglass is essentially the same stuff used in the bats that are one of the most common insulations still today; if your house is already built using these I would feel the difference in risk is negligible. The other kind, cellulose, is essentially shredded newspaper and is treated with a fire retardant; with the fire retardant and meeting flammability standards (Class 1 I think) I would not worry.

A garage wall should have a thermal barrier, drywall counts, to delay the spread of heat and ignition of the contents of the wall. (I think I am getting the term and purpose right, thermal barrier and ignition barrier always get confused in my mind). If that is overcome ... well more than likely your wall is framed with wood which will also burn.

One last thing, I do not too much about it, but I know that injection foam exists as a form of insulating closed walls. You could look into that.

[Papa bear]

Agree with everyone here.

But if you really want to go with blown in, the workaround is to buy enough insulation to get the free rental for the blower/hopper.  Then return the rest of the insulation back to the big box store when you’re done. 

It’s more hassle, but you get the machine for a free rental.


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[Psychstache]

Agree with everyone here.

But if you really want to go with blown in, the workaround is to buy enough insulation to get the free rental for the blower/hopper.  Then return the rest of the insulation back to the big box store when you’re done. 

It’s more hassle, but you get the machine for a free rental.


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Yeah, that was kind of my plan. I think the free blower option could be worth it because my idea was to insulate the entire wall on the garage side, not just where the pantry is (since the rest of the wall is opposite our breakfast table/nook area). I haven't measured it but the space is a little under two car lengths in width, so maybe it is still worthwhile? I will measure the space later today.

[Psychstache]

So I measured the wall that I am targeting for insulation at it is 15' by 8'. Still not worth the blow in plan?

[zolotiyeruki]

Personally, I *would* go for blown-in insulation.  Yes, it's possible for blown-in insulation to settle, and you see that all the time in attics.  However, batts have similar or worse qualities--they can also settle, are a hassle to fit around plumbing and electrical, take more work if your studs aren't 16" on center, and more often than not will have all sorts of voids.  If you loosely blow cellulose in your walls, then yes, you'll get settling.  What you want is "dense pack cellulose" in your walls--it'll completely fill the cavity, including the odd-shaped areas (like around electrical boxes), and it won't settle.  It'll insulate better than batts, and provide better sound isolation as well.

There's a great video demonstrating the difference here: https://www.youtube.com/watch?v=ce-mM7R11Lo

[Fishindude]

So I measured the wall that I am targeting for insulation at it is 15' by 8'. Still not worth the blow in plan?

Correct, not worth it.
Doesn't pay to get involved with blown in insulation unless you are buying a whole bunch of bags of material (truck load).

It's also a crummy solution in vertical walls as someone mentioned.   Go with fiberglass or foam.
Blown in insulation is best used in attics.

[sonofsven]

I'm confused. Drywall is up on both sides of the wall in question, right?
Were you planning on filling each stud bay with blow in and then patch the drywall holes?
To install batt insulation you'll need to demo the drywall on one side.
Seems like the first option is easier and less expensive, although drywall on the garage side is often not finished to the same level as the house side.
The system I use on new construction is called BIBS, blown in blanket system. It's fabric stapled to the studs, insulation blown in through small holes in the fabric, then install and finish drywall.
It's really nice.

[Psychstache]

I'm confused. Drywall is up on both sides of the wall in question, right?

Yes, that is the current situation.

Were you planning on filling each stud bay with blow in and then patch the drywall holes?

That was my original plan, yes.

To install batt insulation you'll need to demo the drywall on one side.

Yeah, I don't really want to do that. Seems like a big PITA

Seems like the first option is easier and less expensive, although drywall on the garage side is often not finished to the same level as the house side.

I agree. My primary concern is the question of safety. If BII is not a fire hazard in a garage wall, I imagine that is what i will end up doing.

The system I use on new construction is called BIBS, blown in blanket system. It's fabric stapled to the studs, insulation blown in through small holes in the fabric, then install and finish drywall.
It's really nice.

I'll keep that in mind should I end up taking anything down to the studs.

[Psychstache]

Personally, I *would* go for blown-in insulation.  Yes, it's possible for blown-in insulation to settle, and you see that all the time in attics.  However, batts have similar or worse qualities--they can also settle, are a hassle to fit around plumbing and electrical, take more work if your studs aren't 16" on center, and more often than not will have all sorts of voids.  If you loosely blow cellulose in your walls, then yes, you'll get settling.  What you want is "dense pack cellulose" in your walls--it'll completely fill the cavity, including the odd-shaped areas (like around electrical boxes), and it won't settle.  It'll insulate better than batts, and provide better sound isolation as well.

There's a great video demonstrating the difference here: https://www.youtube.com/watch?v=ce-mM7R11Lo

Yeah, this is the 1st video I originally found when I realized that I needed to do something about the wall. This is definitely where I lean right now.

[nereo]

Blown-in cellulose insulation has a class 1 fire rating - it’s written right on the bag.  As others have pointed out, what you want is dense-pack, which will ultimately give you better insulation and better fire protection and better sound-deadening than fiberglass batts. Given your situation it will be a lot less tearing out of drywall.

I’ve had good luck getting the blower for free even when I’m buying less than the minimum, but you can always do the ‘buy and return’ strategy.

You can watch what happens when different insulation materials are put under a blow-torch here:
https://youtu.be/8NC79e0oztM
Blown cellulose won’t ignite. 

[Model96]

I would forget about blow-in insulation and patching drywall. If the garage side of the wall is clear and losing an inch or two of space is ok,, just line the wall with an insulating plasterboard such as 'Kooltherm' which comes in various thicknesses. Quicker, easy, simple, cleaner, and will be a far far superior insulating result to loose fill which will settle.

[sonofsven]

I'm confused. Drywall is up on both sides of the wall in question, right?

Yes, that is the current situation.

Were you planning on filling each stud bay with blow in and then patch the drywall holes?

That was my original plan, yes.

To install batt insulation you'll need to demo the drywall on one side.

Yeah, I don't really want to do that. Seems like a big PITA

Seems like the first option is easier and less expensive, although drywall on the garage side is often not finished to the same level as the house side.

I agree. My primary concern is the question of safety. If BII is not a fire hazard in a garage wall, I imagine that is what i will end up doing.

The system I use on new construction is called BIBS, blown in blanket system. It's fabric stapled to the studs, insulation blown in through small holes in the fabric, then install and finish drywall.
It's really nice.

I'll keep that in mind should I end up taking anything down to the studs.

Ok, thanks for clarifying.
Cost of blower/blown in plus drywall repair vs
Cost of demo, install batts, new drywall
Seems like an easy decision-blown in.
Can't quite believe someone would drywall a garage wall without insulation first?
Cheap ass contractors...

[Jon Bon]

Blow

But yeah this is marginal either way. You would also be fine to tear off the drywall and fill it with batts.

Renting and using the blower is a good skill to have. I have likely used it maybe 10 times now? Every time I am glad I did. Its a tremendous bang for your buck. Most houses the pay back is measured in months and not years.

Honestly it's amazing IMO that more people don't use it.

What is in your attic currently? I would do the wall and put a few excess bags in the attic unless its already very well insulated.

[TomTX]

I've done cellulose blowing into a wall and it was NBD. Just get a hole saw approximately the same size as the blower nozzle. After you have obtained materials and tools:

1) Use hole saw to make a hole in the drywall at the top of each stud bay. Set plugs aside.
2) Blow in cellulose to rejection (ie, you can't stuff in any more)
3) Use drywall mud and plugs to fill the holes in the drywall.
4) Sand and repaint if desired.

[Dicey]

I've done cellulose blowing into a wall and it was NBD. Just get a hole saw approximately the same size as the blower nozzle. After you have obtained materials and tools:

1) Use hole saw to make a hole in the drywall at the top of each stud bay. Set plugs aside.
2) Blow in cellulose to rejection (ie, you can't stuff in any more)
3) Use drywall mud and plugs to fill the holes in the drywall.
4) Sand and repaint if desired.

This great as far as it goes, but the walls should have fire blocks, which means one hole will only fill half of each bay.
You will need to bore a second hole below the fire break to fill the entire cavity.

Insulating a garage against the blistering Texas summers is a great investment!

This tip won't help in your specific situation, but it's related, so I'll share it here. We did a studs-out remodel on a house that was close to a roadway, so sound dampening was important. We decided to use something called Eco-batt on the whole house, including the garage and interior walls. We're DIYers, but DH decided to check with a pro after we'd priced out the material only. To our absolute delight, it was cheaper to hire a pro because they get a much better price on material. The guy was quick and clean and fast. He used the exact material we wanted.

Also, if anyone ever has the opportunity to insulate interior walls, do it, it makes a noticeable difference.