Garage insulation - opinions needed

Opinions needed please....

I am doing a new build...I have a 30x40 attached garage (only 13' of shared wall with the house though) with a 30x40 full story above it, to be used as a workshop. Garage will be insulated with fiberglass in the walls....I believe he is doing R-13, but potentially could be R-19. I'll have to ask.

My plan is to install a minisplit in the workshop area. The actual garage area will be unheated - I'll just use a space heater or something when needed. For the workshop, I just want to keep the humidity out in the summer and drop the temp a little, and keep it at 55-60 in there in the winter. Basically, to make it tolerable to be in there.

I don't ever expect to finish the workshop space for liveable area, but I always liked that I have 1200 sq ft available as an option in case I need it for elderly parents, kids that move back in someday (they are 4 and 7 now), etc.

Builder normally puts in R-19 in a garage ceiling, so that is included in my base price. He can put R-30 fiberglass in the garage ceiling (so, between the garage and workshop) for ~$300 as an upcharge. That is a no-brainer. I will at least do that.

The house is actually being spray foamed, and I can have them spray foam the space to R-30 (again, garage ceiling/workshop floor joists area) for $3500.

I completely understand the cost - it's a big area. That being said, it's a lot of cost. Do you feel that in the floor of the workshop, R-30 fiberglass would do just fine, or would you cough up the $3500 to have it foamed. Is it really worth it?

For a little bit of added sound barrier along with the insulation benefits it might provide, i would have it done.

I didn't insulate my garage at all when I built it. I figured I wouldn't be out there in the winter so I wasn't too worried about it. And it hasn't bothered me the times I had to change my oil in January or stuff like that. The thing I have learned, though, is that it gets to almost 100 degree in there in the summer. You need to keep a good seal between the area you park/work in and the roof vent area. I would think R-30 would be fine if you are not heating or cooling it. I have to get mine drywalled now so that the shredded newspaper spray in guy can come out. I looked at doing the pink type stuff and it would super expensive.

-Geoff

I should clarify - the 2nd story, over the garage, is a workshop. It's not part of the house. So, noise is a non-issue. I am wondering if it's worth $3500 to go from fiberglass to foam in the floor of that workshop - unheated garage is below it.

The only downsides I can see are the upfront costs, & if later on you need to run-repair any wiring/plumbing/duct in those cavities...

What is the R-value of the spray foam?

I have an attached garage with no attic so it vented to the outside and was not insulated. Its 2x4 construction. I installed an insulated garage door and that helped a ton. This summer I built a drop in the ceiling and ran plastic soffit vents to the roof vents. The walls are R13 and the ceiling is R30. It stays about 30 degrees cooler in the summer than it did, humidity is lower. I am waiting to see how this winter goes. I have an electric DeLonge oil filled radiant heater that did ok thru last winter (with the heat being vented straight to the outside) so this year it should be pretty nice.

If I were in your situation I would possibly do the fiberglass batts rolls of R13/R19/R30 now and if you decide that it wasnt great, then cough up the $3500 later (dont drywall anything until you make your mind up, if its not too late)

I would be the same - R30 - but R values seem to be BS when comparing the two products. The real advantage of the foam is it's a vapor barrier too - theoretically the same R-value but foam performs much better, especially in very cold environments.

At the end of the day, though, is that advantage worth $3500 given the planned usage of the space?

He would be drywalling, and honestly, I'd rather it be drywalled now instead of doing it later. I am thinking I'll go with R-19 in the walls (he just confirmed that's what he does as a standard) with R-30 in the ceiling. I think that'll give me a very nice garage space, and I think it sets me up well for the workshop above it.

Quote:

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Originally Posted by Atrus

I would be the same - R30 - but R values seem to be BS when comparing the two products. The real advantage of the foam is it's a vapor barrier too - theoretically the same R-value but foam performs much better, especially in very cold environments.

At the end of the day, though, is that advantage worth $3500 given the planned usage of the space?

He would be drywalling, and honestly, I'd rather it be drywalled now instead of doing it later. I am thinking I'll go with R-19 in the walls (he just confirmed that's what he does as a standard) with R-30 in the ceiling. I think that'll give me a very nice garage space, and I think it sets me up well for the workshop above it.

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If it is just a workspace, I think you can get away without the vapor barrier, but don't run cars for a long time. Maybe add an exhaust fan if you are running it with the doors closed.

Do an insulated door or doors too. I had to insulate mine on my own. You loose a ton thru the door.

Personally, I'd spend the $3500 and spray foam the garage ceiling now. 1) You're probably getting a slight discount on it since the contractor is already onsite doing the house.... vs. waiting 5-10 years and calling that same contractor back to just to do the garage ceiling as a standalone job. 2) It sounds like the probability of the upstairs turning into an apartment is pretty good. Spray foam will provide the necessary air barrier between the garage and apartment. Fiberglass batts, regardless of R-value, will not stop air leakage. I'd spray foam it and drywall/tape everything... and be done with it.

With all of the stuff that's in a typical garage -- carbon monoxide, fuel vapors, landscaping chemicals, etc. etc. -- I wouldn't think twice. If $3500 is too much, have them spray 1" across everything... and then back fill it with fiberglass.

I've owned several buildings. The one I now have at my home property is a
stand alone 30'x40'. It has Fiberglass batts in the walls, foam & foil panels
for ceiling. I also have full drywall on all sides.

It is more than sufficient. I simply can't see spending that extra $3,500 on
more insulating. I would think that money would be much better served
somewhere else.



Attachment 83799

my 2 cents worth.... if your building from the ground up put radiant heat in the garage floor
https://www.youtube.com/watch?v=uVkSKh2gefA

When I built my shop I did all spray foam in the walls and batts with blown in the ceiling (R-48) equivalent. All 3 garage doors are 2" thick insulated as well. It was the best money I ever spent. I leave the thermostat on 50* all winter and turn it up when I'm out there working. I have a radiant tube for heat, costs me $25/mo.

The biggest advantage of spray foam is that it creates a complete barrier......you get zero air leaks. Batting or blown in will always have air leaks around outlets, against studs, corners etc.

--Joe

Quote:

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Originally Posted by soap

When I built my shop I did all spray foam in the walls and batts with blown in the ceiling (R-48) equivalent. All 3 garage doors are 2" thick insulated as well. It was the best money I ever spent. I leave the thermostat on 50* all winter and turn it up when I'm out there working. I have a radiant tube for heat, costs me $25/mo.

The biggest advantage of spray foam is that it creates a complete barrier......you get zero air leaks. Batting or blown in will always have air leaks around outlets, against studs, corners etc.

--Joe

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That is the best part about the foam. You can seal all of the outlets and suspect problem areas with caulk/spray foam etc and save a ton of cash. Your heating bill is pretty impressively low though.

Thanks guys - really good ideas. I'll ask about a thin layer of foam just to act as a vapor barrier.

For the garage, walls will be R-19 batts, with insulated doors. I am thinking I'll end up with the R-30 batts in the garage ceiling (workshop floor) due to the cost, but will ask about foaming as a vapor barrier. The entire garage - ceiling and all - will be drywalled.

Workshop (2nd story), I will figure out...at this point, it's going to be studs. I'll do blown-in in the attic space there eventually, and I am undecided as to what I'll do on the walls. I plan on installing a DIY (MrCool) mini-split up there. I didn't even think of a vapor barrier - just reached out to the builder to see what his plan is for that. Makes sense that I need something.

I'll look into the radiant as well - I think that'll throw us way over budget. We're going a bit out of control, so I need to reign it back in.

One thing not to forget about though, especially in the winter time with a garage that has constant cars covered in snow and wet coming in for the night, you can seal a building too tight too. I'd vapor barrier just the ceiling between the garage and work shop area, and use normal fiberglass with paper backing in the walls, it'll allow the building to breathe and dry out, instead of holding all that moisture and humidity. It'll still hold plenty of heat that way.

In my eyes the only downside of foam is if you have to do any electrical or plumbing work later, but chances are you could add/route whatever you needed in the walls instead. The vapor barrier seems like a good reason to spend the $$$ in this case. Also, let me know how the mini-split setup turns out, i want to put one in my 2 car garage myself.

when i just built my house i had them not insulate the garage and i'd do it myself. Bad choice. totally wish i would have just had them do it as i already had them do all the electrical and everything in it except the heating system. i did ti with fiberglass and they would have spray foamed it. for roughly 1.5 times the amount. but it would have been well worth it to me. the foam is way better.