Another Insulation Question

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Forum topic by Chas7715 posted 03-06-2019 04:52 PM 464 views 0 times favorited 15 replies Add to Favorites Watch
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41 posts in 1805 days

03-06-2019 04:52 PM

So…I share my work space with cars. I have one bay of a three-car garage for my “shop”. The garage is fully dry-walled, taped, mudded and painted but uninsulated. In the winter it gets too dang cold for my old bones and in the summer it’s too hot. If it matters, I’m in central Oklahoma. My time is limited to the more temperate times.
I want to insulate. I need to do two walls, east and west. The doors are already insulated and the back wall adjoins he remainder of the house and the wall is insulated. My question is this: Should I tear out the drywall on the east and west walls, put in batt insulation and re do the drywall or attempt to add blown-in insulation? Which would be more cost effective?


-- Perfection is highly overrated!

15 replies so far

View fivecodys's profile


1674 posts in 2554 days

#1 posted 03-06-2019 05:08 PM

Hi Chuck,
I have the same situation as you. I spoke with an insulation company and they said that the blown in insulation is marginal because they can never really get the stud bays full due to electrical wires, screws we have put into the wall and dealing with the fire blocking. This was just one company so take that into consideration.
If I were to strip off the drywall, I would not replace it with drywall. I think I would use plywood. Then I could mount things wherever I wanted.
I’m not sure how the fire marshal feels about that though. :)

Please let us know what you decide to do

-- A bad day woodworking is still better than a good day working.

View jonah's profile


2133 posts in 4217 days

#2 posted 03-06-2019 05:29 PM

If you do blown in right, it is definitely the better way to go. All you need is one or two holes per stud bay and make sure you fill it up all the way to the top so it’s dense packed. Getting an insulation company to do it might be a challenge because it’s such a small job. You might be better off renting the machine and doing it yourself. You can blow the insulation in from either the inside or outside of the wall.

View Chas7715's profile


41 posts in 1805 days

#3 posted 03-06-2019 05:30 PM

I know two things:
(1) There are no wires in the walls that would interfere with the blow-in nor is there any fire-blocking (I watched the house bring built)
(2) Building codes require a minimum of 5/8” drywall, taped and mudded, on walls and ceiling in all attached garages to retard the spread of any possible fire. Thus your use of plywood would not be in compliance with current building codes unless your garage is detached. But, you’re free to do what you want.

My starting point is to get some estimates from insulation contractors. Depending on the cost, I was exploring possible DIY approaches.

-- Perfection is highly overrated!

View clin's profile


1125 posts in 1914 days

#4 posted 03-06-2019 06:45 PM

I’d certainly look into blown-in insulation at this point. With no wires etc in the walls, it should work pretty well. If done right it can be better than batts.

-- Clin

View BlueRidgeDog's profile


740 posts in 698 days

#5 posted 03-06-2019 07:36 PM

Well, if the drywall is up, then by all means the blown in is the way to go.

View OnhillWW's profile


271 posts in 2151 days

#6 posted 03-06-2019 07:54 PM

Just a thought, blown in is the way to go in your situation – HOWEVER…..
You are most likely gaining / losing more heat from the garage doors. If insulated that’s a plus but air infiltration top bottom, edges and between the folding panels is a big issue. Also , you do not say what is above the ceiling. If living space that is good but if it is a roof you need to insulate there as you will gain a lot of heat in the summer and lose more heat in the winter from the ceiling than the exterior walls.

-- Cheap is expensive! - my Dad

View bilyo's profile (online now)


1198 posts in 2021 days

#7 posted 03-06-2019 08:01 PM

Do they still inject foam or is it no longer used? As I recall, it had/has excellent insulating qualities.
Don’t overlook insulating the ceiling. It is more important than the walls. The walls already have a dead air space that insulates pretty well.
Is your shop bay walled off from the other two bays? If you can, that would be the first thing I would do.

View Knockonit's profile


725 posts in 1120 days

#8 posted 03-06-2019 08:04 PM

Rj in az

-- Living the dream

View Woodmaster1's profile


1565 posts in 3505 days

#9 posted 03-06-2019 08:44 PM

I used fiberglass bat insulation before putting up drywall. I have r19 in the walls and r30 in the ceiling. I use a bigmaxx 50,000 BTU natural gas furnace. The cost to heat the 30×33 detached garage at 68 degrees for the northern Indiana winter is $120.00 extra a year

View corelz125's profile


1778 posts in 1894 days

#10 posted 03-06-2019 09:31 PM

5Codys what is you use fire rated plywood? Would it be up to code then?

View fivecodys's profile


1674 posts in 2554 days

#11 posted 03-06-2019 09:43 PM

5Codys what is you use fire rated plywood? Would it be up to code then?

- corelz125

Good Question. I know that there are specific rules when dealing with garages here in my city.

Is there such a thing as fire rated PW?

-- A bad day woodworking is still better than a good day working.

View corelz125's profile


1778 posts in 1894 days

#12 posted 03-06-2019 10:12 PM

Yes there is. On the commercial construction jobs here they use it all the time. I see the 3/4” and it has a stamp on it.

View tomsteve's profile


1093 posts in 2137 days

#13 posted 03-06-2019 11:44 PM

dont forget ceiling insulation.

View CWWoodworking's profile


1146 posts in 1097 days

#14 posted 03-07-2019 01:47 AM

With drywall already up, blown in would be pretty easy.

Someone would have to pay me a lot of money to tear the drywall down just to insulate.

View ibewjon's profile


2150 posts in 3711 days

#15 posted 03-07-2019 01:47 AM

I see commercials for injected foam insulation all the time. It should fill in around wires, ect. There is open cell and closed cell, I think closed is better. Just a couple small holes per space to patch, and better R value than fiberglass or blown in paper.

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