Another garage insulation thread

[razmaspaz]

Sorry to start yet another, but it seems that these get pretty specific to each situation so here goes:

I live just north of Chicago. Current temp this evening is -6F, thats pretty cold for here, but not uncommon lately.

I just bought a new to me house with a 3 car garage. I'm in the process of fitting it for a woodworking and bicycle repair space, but it is currently 20 degrees in the garage. I punched a hole in the already drywalled exterior wall today to find that there is no insulation in it. I haven't been in the attic yet to know if it is void of insulation, I'm probably doing that tomorrow, but that is the lesser concern, as I'm sure all options are available for insulating the attic space. Some of that space is under the master bedroom, and some is open to the attic space.

My big question is what options do I have for insulating the walls? After drywalling my entire basement in my old house I promised myself I would never do drywall again, so if I have to take the drywall off I'm paying someone to put it back. I've read I can get spray foam done by using the expanding foam, so is that the best option? I assume the other option is blown in insulation, both of which require holes in the wall. Is spray foam better even when installed in an existing wall? Will taking the drywall down be more than marginally better in r-value, assuming I use a competent installer?

Thanks in advance.

Other notes, I will be heating with a forced air type natural gas heater and will be running wiring which I'm happy to have as exposed runs of conduit. Same for the gas lines, I don't feel they need to be covered by drywall. This is a garage after all. Budget isn't unlimited, but I have the funds to "do it right" lets say. In other words i don't need to cut corners to save $ if there is long term savings in doing it right, but I don't want to incur the cost of drywall replacement if all i get is a pretty wall. Also I considered the idea of plywood for walls, but my wife balked at that idea for some unknown reason that I'm not interested in debating.

 

[pablo94sc]

I have osb on my garage walls and ceiling. That may not be code in your home, but it's easy to hang and painted white makes it good for lighting. Plus, easy to hang small things. Just a thought.

 

[CKS1955]

I was in your situation. I removed the drywall, insulated, then installed T1-11 plywood (5/8" x 4' x 8'). My wife also objected to installing plain plywood or OSB. I don't mind hanging and finishing drywall, but like the durability of the T1-11. In my area it is priced at about $32 a sheet. The ceiling remained 5/8" drywall. Of note none of the walls in the shop are adjacent to the living space. Most building codes will require 5/8" drywall on the ceiling and walls adjacent to living space.

Jay

 

[razmaspaz]

Does anyone have thoughts on spray foam behind existing drywall?

 

[Stuart in MN]

Blown in cellulose or fiberglass may be the easiest solution. You have to cut holes in the drywall for each stud bay and them patch them afterwards but that's less work than replacing it all.

 

[IlliniJeeper]

You may be interested in this post:

http://www.oldhouseweb.com/blog/adding-wall-insulation/

Here's a notable quote:

For example, I was at a seminar that presented a study using an average size home in Minneapolis, MN. The cost of blowing insulation into the walls would be over $4000.00. The annual savings would be around $160.00. Math wasn’t my best subject but I know if I invest four grand, I’d want to break even before a quarter of a century passes.

It's probably not worth doing, especially in a garage where you're not going to have a need to have such a large temp difference to the outside like you would in the whole house.. Insulate the ceiling because it's easy and cheap, leave the walls alone.

This doesn't even begin to get into moisture barriers, voids, etc.

 

[DC73]

Not sure that spray foam is viable behind existing drywall but you could check with a spray foam company to be sure. Spray foam uses a chemical reaction which is hot. They make multiple passes of thinner layers (especially with closed cell foam) to keep the foam from spontaneously burning. There have been houses burn down due to improper spray foam techniques. It also expands and could easily bulge your drywall.

I'm not a fan of blowing insulation into existing wall cavities although it can be done. The problem is that you frequently end up with voids due to obstructions within the wall. There could be fire blocks, wiring, plumbing, nailing blocks etc hidden in the wall that would make it more difficult to get the job done correctly. I can't find the link at the moment but there used to be an article online that showed before and after thermal images of a house that had insulation blown into the existing walls and you could see everywhere the insulation was missing. If you have access to a thermal camera, you could blow the insulation and then check later for voids to address.

DC

 

[razmaspaz]

Blown in cellulose or fiberglass may be the easiest solution. You have to cut holes in the drywall for each stud bay and them patch them afterwards but that's less work than replacing it all.

Blown in cellulose is what I did in my old basement, cut the holes and rented the blower. I would pay to have it done this time, as I'm not 100% sure it didn't settle after I did it. Thats why I'm interested in foam, I know it won't settle after the fact. I've seen demonstrations of it done behind drywall, but I haven't heard any real world experiences with it.

 

[machsnell]

I saw them do the spray foam behind existing drywall and cellulose also. Both on TV and read online. One had the drywall removed after sprayfoam and the whole cavity was filled. Both are possible. I am not sure about the #'s of r value per si. But I am pretty sure you get quite a bit more out of the sprayfoam. I am about to sprayfoam my garage which is just studs now. It's more than double regular but my trusses ar 8" bottom chords for attic and I want the best r value I can get for the 6" walls and 8" ceiling. Garage will be conditioned but I wanted to have the most comfort possible when I work in there which is mainly night and or winter. I am weird and like drywall and want a cleaner look than osb although much more durable. Talk to an insulation company but drywall is cheap and If I buy drywall guys will hang tape and mud for 15 to 18 per sheet. But I like to do it, at least in moderation!

 

[DC73]

Insulate the ceiling because it's easy and cheap, leave the walls alone.

This has merits. You could probably make a case that if you could do all the work yourself, that insulating the walls would have a reasonable payback, especially if you're going to be in the house for the long haul. I took this approach and did not go to the trouble of insulating my garage walls but I live in a more moderate climate.

Comfort may be a more driving issue than energy savings and wall insulation will help, especially in your cold climate.

If you do forgo the wall insulation, the best bang for the buck in energy efficiency and comfort is sealing all points where air can move through the walls and ceilings. Caulk around electrical junction boxes, where pipes penetrate walls, where electrical cables come through the top plate (if accessible), etc.

Do the air sealing whether you install wall insulation or not.

DC

 

[Kamn]

Spray foam can be done when there is existing drywall, they will inject it through a hole at the top of the wall......its done here in Canada with older homes that have plaster walls, it is pricey though. Better off taking the drywall down and putting in batt insulation and vapour barrier if you have plans on heating the space then get it drywalled.

Its all what you can afford and the level of work you feel like doing

 

[IlliniJeeper]

This has merits. You could probably make a case that if you could do all the work yourself, that insulating the walls would have a reasonable payback, especially if you're going to be in the house for the long haul. I took this approach and did not go to the trouble of insulating my garage walls but I live in a more moderate climate.

Comfort may be a more driving issue than energy savings and wall insulation will help, especially in your cold climate.

If you do forgo the wall insulation, the best bang for the buck in energy efficiency and comfort is sealing all points where air can move through the walls and ceilings. Caulk around electrical junction boxes, where pipes penetrate walls, where electrical cables come through the top plate (if accessible), etc.

Do the air sealing whether you install wall insulation or not.

DC

I agree, DC. Although being a born-and-raised Midwestern boy, I don't think the comfort factor is worth the investment of time and money to do it. It's a garage. It's not like you're going to be sitting out there in your underwear for long stretches of times. Having a drafty house is a nuisance because of how you use it. A drafty garage? Meh. Let the heater do its job, set the thermostat at a reasonable temperature, and give up your lifelong dream of woodworking in the ****.

But that's just me.

 

[razmaspaz]

Talk to an insulation company but drywall is cheap and If I buy drywall guys will hang tape and mud for 15 to 18 per sheet. But I like to do it, at least in moderation!

10ft ceilings means 3 panels to get to the top. I have a 20 ft wall and a 34 ft wall that would need to be redone. 12 ft panels are $12 at the big box. You really think I could get the whole thing re-rocked for less than $600? 15*(12+28). Rounded your 15-18 up to 28 as a hedge for Chicagoland.

 

[razmaspaz]

I just confirmed that there is no insulation in the attic space either. It is also drywalled and is truss construction at 24" OC. I imagine blown in or spray is the most effective method here. I'm toying with the idea of doing the ceiling and filling any gaps in the garage door weather stripping as well as any visible gaps in between the slab and the wall and leaving it at that.

 

[razmaspaz]

I got my estimate back today from the HVAC company to add the heater. They are saying $3700 to install a 75k BTU heater ($600 retail). There is a roughly 40' run of gas line that has to go through my basement sill plate, and it would need to be spliced via a T into the main line and have 3 bends to reach the heater. Beyond that it would require the standard hole in an exterior wall to vent it. The electrical will already be in place. I expected the cost to be half what it came to. For reference I'm in the Chicago suburbs. I'm getting another estimate tomorrow, but I'm just looking for some verification that either they are insane, or I am.

 

[Kamn]

Wow! thats pricey
with the heater and gas line it will be around the $1000-$1200 then the rest is labour
That needs to be a little cheaper or do it your self

 

[razmaspaz]

I just got a 2nd quote that was even more to put in a Reznor type unit. The guy who quoted it said the gas line install was only $900 of the price but he wouldn't do the line alone. I do have a quote now for a $895 gas install from a plumbing company I have a lot of trust in. I think that is reasonable for a 45' run for my area. $20/LF seems quite average. If I have the gas line run and charged, and I feel comfortable putting holes in my walls, is this a complicated install? I would plan to just vent it right out the rear wall, turn 90 degrees and go up. My biggest concern to be honest is getting service on the unit after I've installed it myself.