Insulating garage ceiling under living space

[HeyMick]

Hi all…

I have a two bay garage under living space. When we moved in, I knew I would need to deal with insulating the ceiling. Currently, it has R-9 Kraft faced with the barrier facing down. The garage is not currently heated/cooled. The rafter bays are 9.25” deep. I’m planning to replace all the insulation. My question is what’s best practice. I’ve read a lot of different opinions. Not in the budget to do closed cell foam. Planning to use foam board and spray foam on the rim joists and over the garage doors. Is fiberglass, barrier up the first step? What should I cover the bottom of the insulation with? It’s part workshop and parking and I don’t want to continually be exposed to breathing fiberglass dust.

The block walls are not insulated, but mostly below grade. The heat runs are wrapped. The pipes will be covered by the end of the day. Planning to add a mini-split next year.

 

[billconner]

If I understand it, 2x10 joists. I'd leave fibreglass, drywall it, and blow in cellulose. I'd try to figure out a way to blow it in on top of fibreglass but might slash paper and blow below. You could get good insulation - probably over r3 per inch - at low cost.

Not only does code - albeit for new - require the drywall, I'd feel much better living in the house with that separation.

If you wanted a little more insulation, sheath joists with 1" of foam - foil coated polyiso - before sheetrock.

 

[HeyMick]

Yes, 2x10 joists. Any concern with the existing insulation having the VB facing down? The drywall, even painted, is still breathable, to my knowledge.

 

[acer66]

I would also leave the insulation in there and cover it with drywall.

Maybe insulate the walls instead?

Where are you located?

 

[HeyMick]

I’m in East TN

 

[AC-WC]

I would pull the current R9 and replace with R30 with vapor barrier facing down (it's 10"thick). At the time it was originally built it was likely code to have vapor barrier facing the garage side so hard to go wrong in that respect. If possible save the R9 for the walls. Definitely use fire proof/resistant drywall when you get to that stage.
As long as you have vapor barrier I would not worry about fiberglass dust. You will probably want to wear a dust mask while you install the insulation.
Billconner isn't wrong but I struggle with putting holes in my new drywall. That's just my preference.

 

[acer66]

Every more current insulation I have installed said faced side towards conditioned space.

Besides that I would take mineral wool over fiberglass.

 

[Hank11]

With conditioned space above I would not worry too much about the ceiling. More so because you are going to install hvac in the garage. Your floor upstairs and the ceiling below then only separate two conditioned spaces. I’d insulate the exterior walls, and make the garage door seal as well as possible. Absolutely dry wall the walls and ceiling.

 

[billconner]

Billconner isn't wrong but I struggle with putting holes in my new drywall. That's just my preference

When I did it, I left of a 8" or so strip of drywall continuous at one end of joists, and snuck the tube in and blew. When I was near end. I stopped, held a piece of wood with a hole just tube size, and finished the cavity. Was amazed how perfectly the cellulose stayed in place and was easy to add last trip of drywall.

NOTE: Whom ever pointed out vapor barrier is on wrong side - thank you! I had a brain fart. I would slash the existing paper and add insulation below it. Either cellulose as I described or another batt - probably a 6" - unfaced. Not easy but doable and economical as well as effective.

Of course, you could sheetrock and heat the garage.

 

[HeyMick]

Thank you, everyone! I really appreciate your help.

 

[NUTTSGT]

I would pull the current R9 and replace with R30 with vapor barrier facing down (it's 10"thick). At the time it was originally built it was likely code to have vapor barrier facing the garage side so hard to go wrong in that respect. If possible save the R9 for the walls. Definitely use fire proof/resistant drywall when you get to that stage.
As long as you have vapor barrier I would not worry about fiberglass dust. You will probably want to wear a dust mask while you install the insulation.
Billconner isn't wrong but I struggle with putting holes in my new drywall. That's just my preference.

This is probably what I would do, tear out the old and put in new to fill the space completely.

I'd make a couple of suggestions first. Cut a section of some rigid foam board and nail (plastic cap nails) in the ends at the rims joist. Then I would use some Great Stuff to completely seal around it to seal it up.

Secondly , buy an electric stapler and a 5K box of staples. Trust me on this one.

Next, insulate your overhead door. Depends on door type as to how I would do it. Then move to the walls, all CMU block ? Tap con some either firring strips or 2x4s flat to the walls. Firring strips, you can add 3/4" rigid foil, the latter you can add 1.5" of foam board. Then cover the walls.

Lastly. I know you don't get terribly cold in Tn, but keep the O/H door shut during the winter and when it gets cold.


BTW, I'd also suggest adding your location "I’m in East TN" to your profile. It will help others in the future give you better advice.

 

[nicks78camaro]

I just went through this in western PA.

1950s house had old flattened down insulation in the garage ceiling (2 bedrooms and a bathroom above). Bedrooms and bathroom were very cold in the winter, compared to other parts of the house. Garage door is newer/better insulated type.

I ripped down the plaster ceiling, replaced all insulation with R19 faced fiberglass (paper down).

Installed new 5/8" fire rated drywall. Taped and mudded the seams.

Took the opportunity to run wires for additional outlets and lighting.

It made a HUGE difference in the temperatures in the upstairs rooms.

I'd do the exact same thing again.

You could fit even more R-value as my joists are only 2x8.

 

[acer66]

I just went through this in western PA.

1950s house had old flattened down insulation in the garage ceiling (2 bedrooms and a bathroom above). Bedrooms and bathroom were very cold in the winter, compared to other parts of the house. Garage door is newer/better insulated type.

I ripped down the plaster ceiling, replaced all insulation with R19 faced fiberglass (paper down).

Installed new 5/8" fire rated drywall. Taped and mudded the seams.

Took the opportunity to run wires for additional outlets and lighting.

It made a HUGE difference in the temperatures in the upstairs rooms.

I'd do the exact same thing again.

You could fit even more R-value as my joists are only 2x8.

What is the reasoning to put paper side down in your climate?

 

[nicks78camaro]

What is the reasoning to put paper side down in your climate?

I have extreme hot and extreme cold here so it was a coin flip. Either way I could be considered "wrong". Plus the old stuff was paper down.

 

[AC-WC]

What is the reasoning to put paper side down in your climate?

Vapor barrier is supposed to be on the heated side. In the northern states that means on the interior, in the southern states it should face the exterior. TN is kind of in the middle but since it was originally VB down hard to go wrong with repeating.

 

[acer66]

Vapor barrier is supposed to be on the heated side. In the northern states that means on the interior, in the southern states it should face the exterior. TN is kind of in the middle but since it was originally VB down hard to go wrong with repeating.

You are right in milder climates, 1-3 iirc, its installed face out and the face down in basements I would argue is done mostly because it’s easier to install that way.

Not that I have ever done that.

How important which way
the face is installed really is anyway is another question.

The reason why I asked nicks78camaro is that because he is western PA.

 

[andyvh1959]

I just went through this in western PA. 1950s house had old flattened down insulation in the garage ceiling (2 bedrooms and a bathroom above). Bedrooms and bathroom were very cold in the winter, compared to other parts of the house. Garage door is newer/better insulated type. I ripped down the plaster ceiling, replaced all insulation with R19 faced fiberglass (paper down). Installed new 5/8" fire rated drywall. Taped and mudded the seams. Took the opportunity to run wires for additional outlets and lighting. It made a HUGE difference in the temperatures in the upstairs rooms. I'd do the exact same thing again. You could fit even more R-value as my joists are only 2x8.

Well thanks a bunch! Another project to add to my list. My 1973 tri-level here in Green Bay is exactly the same, almost. Two bedrooms, main hall and the main bath above the 24x24 2-car garage. The ceiling in the garage is drywalled, but 52 years of various owners has aged it. Now I feel I should do likewise and tear down all the old drywall, upgrade the insulation and new drywall nicely finished as I see in many homes on the market around here. Great, another project to lodge in my brain at night until I get to it.

I said the same, almost, because in my house the ceiling over the garage is 2x12 construction. So I could get up R38, installed like shown:
https://ww2.owenscorning.com/litera... (for 2x12 Cathedral Ceilings) Data Sheet.pdf

I do know there are leaks in the HVAC ducting that route through the garage ceiling structure as I can feel some heat in the winter and cooling AC in the summer. So its best I tear the whole ceiling out, remove the dryer vent ducting that was across the entire ceiling span of 24' (another dumb *** installation in this house). I could also make sure any gaps are sealed/closed to make sure mousy critters cannot find a path into the house as had happened in the past. Finally I'll mount steel angle strips across sections of the ceiling for hanging items like bicycles, lawn chairs, etc. Right now I have many screw hooks into the ceiling joists through the drywall.

 

[75gmck25]

The facing is there to provide a vapor/moisture barrier, and that usually means it is on the house side unless it is in the basement. In a basement there is usually more moisture coming through the cement walls than there is coming from the basement room.

Could you glue up closed cell foam panels under the floor (not always that easy on ceiling), and then use spray foam to seal around the edges? That would provide a vapor barrier and air seal, and then you add rockwool or fiberglass to fill in the joist bay, and sheetrock over that. Having a good air seal to keep out cold air infiltration from the garage is very important, and most blown in and batt insulation does not do a good job of air sealing.

 

[NUTTSGT]

What is the reasoning to put paper side down in your climate?

If I had a living space above my garage, I would also do the paper down.

My simple reasoning is when winter comes, I want the moisture from the melting snow (off the vehicles) to stay in the garage. It'll get vented out when the doors are opened and closed. Same reason I used exterior grade paint on the interior garage walls.


My simple train of thought through experience. When it's wintertime and snowy, do you ever get frost build up on the inside of your car or truck windows ? Where does that moisture come from as the air is normally "dry" during the winter ? The melted snow off your boots or shoes. Try knocking the snow off them before you climb in.

 

[Hank11]

I think OP is going to condition the garage —- “Planning to add a mini-split next year.” If that’s right, there’s no need for more insulation in the ceiling between the garage and the upstairs.

 

[acer66]

If I had a living space above my garage, I would also do the paper down.

My simple reasoning is when winter comes, I want the moisture from the melting snow (off the vehicles) to stay in the garage. It'll get vented out when the doors are opened and closed. Same reason I used exterior grade paint on the interior garage walls.


My simple train of thought through experience. When it's wintertime and snowy, do you ever get frost build up on the inside of your car or truck windows ? Where does that moisture come from as the air is normally "dry" during the winter ? The melted snow off your boots or shoes. Try knocking the snow off them before you climb in.

Yes, I sometimes forget that people use their garage for their intended purpose and actually park their cars in it.

 

[acer66]

I think OP is going to condition the garage —- “Planning to add a mini-split next year.” If that’s right, there’s no need for more insulation in the ceiling between the garage and the upstairs.

Did not see that which then raises the question what is going to happen in the garage.

If it will be a workshop or a place to hang out I would put sound proofing into the ceiling.

 

[CraigStu]

Well thanks a bunch! Another project to add to my list. My 1973 tri-level here in Green Bay is exactly the same, almost. Two bedrooms, main hall and the main bath above the 24x24 2-car garage. The ceiling in the garage is drywalled, but 52 years of various owners has aged it. Now I feel I should do likewise and tear down all the old drywall, upgrade the insulation and new drywall nicely finished as I see in many homes on the market around here. Great, another project to lodge in my brain at night until I get to it.

I said the same, almost, because in my house the ceiling over the garage is 2x12 construction. So I could get up R38, installed like shown:
https://ww2.owenscorning.com/literature/pdfs/21151-D EcoTouch R-38C (for 2x12 Cathedral Ceilings) Data Sheet.pdf

I do know there are leaks in the HVAC ducting that route through the garage ceiling structure as I can feel some heat in the winter and cooling AC in the summer. So its best I tear the whole ceiling out, remove the dryer vent ducting that was across the entire ceiling span of 24' (another dumb *** installation in this house). I could also make sure any gaps are sealed/closed to make sure mousy critters cannot find a path into the house as had happened in the past. Finally I'll mount steel angle strips across sections of the ceiling for hanging items like bicycles, lawn chairs, etc. Right now I have many screw hooks into the ceiling joists through the drywall.

Yep you just talked yourself into a big project didn't you. But at least it sounds like it should net you a big improvement.

 

[andyvh1959]

Yeah, that's the part that makes the project much more likely. The east end of my house has always been less comfortable in the winter than the west end. Inadequate old insulation over the garage is the likely cause.

 

[HeyMick]

The facing is there to provide a vapor/moisture barrier, and that usually means it is on the house side unless it is in the basement. In a basement there is usually more moisture coming through the cement walls than there is coming from the basement room.

Could you glue up closed cell foam panels under the floor (not always that easy on ceiling), and then use spray foam to seal around the edges? That would provide a vapor barrier and air seal, and then you add rockwool or fiberglass to fill in the joist bay, and sheetrock over that. Having a good air seal to keep out cold air infiltration from the garage is very important, and most blown in and batt insulation does not do a good job of air sealing.

I have been considering doing this exact thing. Need to run the numbers and determine if it’s going to be worth it as we would like to move in about five years, if possible.

 

[andyvh1959]

Back on this discussion because for my 1973 trilevel house with the garage directly under the bedrooms, fire code mandates I have drywall for the garage ceiling. Fine, got that right now though it needs to be replaced and the insulation above should be improved. But, the east and north walls of the attached garage also have living spaces on the other side, and those walls are not currently covered with drywall.

I'll likely be selling this house within the next five years. Now I'm wondering if those walls in the garage will have to be redone with drywall to meet current code? Or does current code not apply for a house built in 1973? As it is, I'm pretty certain the north and east walls have practically nothing in them for insulation. So it may be best for me to take off the current 1/4" thick dark paneling anyway, insulate and then apply new drywall. Damn, yet another project.

 

[75gmck25]

Is the garage used as a garage or as living space? There is usually no requirement to bring an entire house up to current code at the time of sale, but if the purchaser hires an inspector its possible that code compliance issues may come up for discussion. Sometimes it can stop a sale.

Tearing off the paneling is probably not that hard, and a drywall crew can hang new 3/8" drywall really quick. It wouldn't need more than a quick once-over tape and float if its only garage space. The big question might be how much money you want to put into insulating the walls before you install the drywall. For the cheapest solution I think I would focus on air-sealing any wall penetrations (foam around receptacles and pipes, etc.) and then use batt insulation to fill the stud cavity.

 

[billconner]

The existing work only has to comply with the codes in effect at the time it was built. Previous poster is correct - a house inspector may try to make it an issue. They'd be wrong but still troublesome.

Vertical surfaces need 1/2", horizontal 5/8". Includes columns and all structural support.

I probably would not do it unless I wanted it for some reason, like appearance.