[ponjohn]

If I used Polyiso or EPS do I need an air gap?


This is the front half of the garage at 22 x30.



Would I be disappointed with simple R19 and an air gap.



75k hot dawg heater.


Thanks.

[unruhjonny]

I'm pretty sure the air gap is the key component;
without an air cavity, heat or cold will conduct through your roof.

I believe around here for tight ceilings (eg: narrow scissor trusses) spray foam is used - but it doesn't vridge the bottom chord to the top chord...

[TAKerry]

First, not sure what you mean by vaulted. If you have scissor trusses, which have a pitched ceiling rafter at a different elevation the roof rafter with a space in between, then you can insulate to that and the air space will be above. If the roof line rafters are the same that you are putting ceiling against then you should at least put some Styrofoam baffles in to let air flow from the bottom to the top at the ridge, then insulate. R19 is ok for walls but in Conn I would spend a couple more dollars and put in at least R30 in the ceiling. Code calls for much higher Im sure (in MD we now need R40 min) but we used R30 for years, and it will be fine for a garage. Also, have you purchased the heater yet?, There may be a better option for that as well.

[ponjohn]

Originally Posted by TAKerry

First, not sure what you mean by vaulted. If you have scissor trusses, which have a pitched ceiling rafter at a different elevation the roof rafter with a space in between, then you can insulate to that and the air space will be above. If the roof line rafters are the same that you are putting ceiling against then you should at least put some Styrofoam baffles in to let air flow from the bottom to the top at the ridge, then insulate. R19 is ok for walls but in Conn I would spend a couple more dollars and put in at least R30 in the ceiling. Code calls for much higher Im sure (in MD we now need R40 min) but we used R30 for years, and it will be fine for a garage. Also, have you purchased the heater yet?, There may be a better option for that as well.

I am insulating and covering the highlighted rafters.

[TAKerry]

You need to get the foam vents. They are kinda u shaped, slightly less narrow than the joist bay. Staple them to the bottom of the plywood then add your insulation. It doesn't look like you have enough room for r30, so in your case go with the r19, or the highest r value you can get for the depth you have. Pretty sure you can get all the stuff from HD. Then you can put your ceiling right on the bottom of the rafters. It would be ideal if you had a vented soffit and a ridge vent on the top of the roof as well to allow positive airflow, even if you dont still add the foam vents, the outside stuff can be changed at a later date. Reason I asked about the heater, my brother had one in his shop in MD and when he moved to Canada he put in a gas radiant heater. He said the radiant worked so much nicer. That is what im planning on putting in mine.

[ponjohn]

Originally Posted by TAKerry

You need to get the foam vents. They are kinda u shaped, slightly less narrow than the joist bay. Staple them to the bottom of the plywood then add your insulation. It doesn't look like you have enough room for r30, so in your case go with the r19, or the highest r value you can get for the depth you have. Pretty sure you can get all the stuff from HD. Then you can put your ceiling right on the bottom of the rafters. It would be ideal if you had a vented soffit and a ridge vent on the top of the roof as well to allow positive airflow, even if you dont still add the foam vents, the outside stuff can be changed at a later date. Reason I asked about the heater, my brother had one in his shop in MD and when he moved to Canada he put in a gas radiant heater. He said the radiant worked so much nicer. That is what im planning on putting in mine.

I do have a ridge vent, so I m not going to bother with sheet insulation then. R19 it is.



Thanks.

[indymanjoe]

I had r-19 in my ceiling like the OP. Worked just fine,no snow melted on the roof at all. Michigan.

[TAKerry]

R19 is fine just a little light for ceiling insulation. If that's all you can fit its definitely better than nothing. Especially in a garage.

[stags]

ponjon, don't want to rain on the parade but doesn't look like you have room for R19 either. Check rafter depth - look like 2x6's, which would be around 5 1/2" at best. R19 is 6 1/2" so you're either gonna crush the rafter vent (no air flow) or the insulation (loss of R value). If they are 2x6's you might want to go with R13 or R15 (both 3 1/2") and then nail 1" or even 2" foam boards underneath. This will give you a tighter job and brighten up the ceiling if you use foil or white faced foam. Keep in mind code calls for foam or paper faced insulation to be covered with a fire barrier like drywall or thermoply but this shouldn't matter unless you plan to sell in the near future.

[TAKerry]

I did a 'cheapy' ceiling in a guys lawn mower shop years ago with foil faced foam board (guy wanted something quick and cheap). We were careful and neat with the installation and taped all of the joints with foil tape. Turned out half decent and it did reflect a lot light, as well as heat back into the space. Also, locally we now have to build with 2 x 6 ext walls to allow for r 19.

[stags]

Right I've done a few like that too - good bang for the buck. Side note - R19 batts do Not yield R19 in a 2x6 wall. Read the fine print on the bag - it an R17 when compressed. Not a big issue unless you run into a rather picky customer or inspector

[ponjohn]

Originally Posted by stags

Right I've done a few like that too - good bang for the buck. Side note - R19 batts do Not yield R19 in a 2x6 wall. Read the fine print on the bag - it an R17 when compressed. Not a big issue unless you run into a rather picky customer or inspector

I will check that out. As noted better than nothing.



Besides sheetrock what has everyone used for a garage ceiling?

[Stuckinda60s]

I'd rethink the salamander for a heat source. They need to be vented to be safe. They consume a lot of oxygen which can be a double whammy, Low oxygen can cause you headaches and also cause poor combustion due to a rich condition. That means carbon monoxide output will increase. Not a healthy combination. I know a lot of people use them in garages, but that doesn't mean it's a smart thing to do.

I'm actually uncomfortable if it's too warm when I work. Twelve years ago, I built a 54x32 garage gambrel-roofed garage with an upstairs which is like a full attic with 10' ceilings. Downstairs has a man door and two 10x12 insulated roll-ups and 12' ceilings. The bottom is fully insulated, including from the upstairs. I bought a trailer type hot-air furnace and never installed it. We've had several stints of single-digit temps but the floor is such a great heat sink that water has never frozen there. I'll start out wearing a long-sleeved flannel shirt when I'm working there but end up in a tee shirt most of the winter. I'm not saying that's for everyone, but I'd advise that you work out there for a while during cold weather without heat to see how much you actually need. You might find that you're more comfortable after you've worked for a while than you thought you would be. Don't get me wrong, I've never spent a lot of time down there when we've been in low single digits. Most of the time it's been in the 20's-30's

[TAKerry]

We used to use the salamanders all the time in new construction. They are a life saver in sub zero temps but the house is usually uninsulated and open at every crevice as possible. I agree that they are bad in an enclosed environment and will probably never buy another. They also put a tremendous amount of moisture into the air. They are ok to run on a burst for say 10 minutes then let them sit for a half hour so your not building up the fumes too bad, but I think there are much better ways to heat now that are just as inexpensive.

[Formulabruce]

Propane gives off a bunch of Moisture, The kero ones smell.
Here are the vents I used. Plastic, staple in place. Then insulate below them. Make suire you have a sofit vent
The sheets stacked on the firebird below the vents are about 1 inch thick, they are reflective on one side, styrofoam, and have a sheet of plastic on the roof side. They have little R value, but are cheap, and have the water barrier you want and the reflectivity of light and heat back down. 10 bucks at Home depot.

[TAKerry]

Vents are perfect, the foam sheets typically are about R-7 per inch. Not a lot like you mentioned but so much better than nothing. For a garage would be fine.

[FirebirdHank]

The "hot dog" heater is a ceiling mounted and vented type heater. The only draw back I have found is that they are noisy. If I had a high enough ceiling I would have gone with a radiant heat tube type. In floor heat is another option but has to be planned into the initial design.

[TAKerry]

My brother had a hot dawg heater in his garage here in MD and it worked pretty good. It was gas powered with an outside vent to get rid of the co2

[Stuckinda60s]

Originally Posted by FirebirdHank

The "hot dog" heater is a ceiling mounted and vented type heater. The only draw back I have found is that they are noisy. If I had a high enough ceiling I would have gone with a radiant heat tube type. In floor heat is another option but has to be planned into the initial design.

That sounds like a viable option. I've heard Salamanders referred to as hot dogs and thought that was what was meant by the OP. My mistake.

That being said, though, I do think that the issues with Salamanders needed to be brought up for those considering garage heaters. It ain't getting any warmer out there.