Heating a detached garage with room above

[pfettig77]

Hi all,
I'm in the finishing stages of building a cape style garage with a room above. I'd like to heat it this winter but there are some factors that complicate it a bit vs. heating a regular garage. The 2nd story will be a storage area but also a rec room for the kids. I'd like to keep the garage and attic at about 45ish all winter and crank it up when I have a project or the kids want to hang out. I suppose sometimes I would like the attic to be warm but won't need the garage part to be warm and vice versa. Has anyone had any experience with propane vent free wall heaters? I thought maybe I could put one downstairs in the garage and one in the attic.

There are plenty of ways to heat the garage, but this seemed cheap and simple. I'm definitely open to other ideas. I've already gone way over budget on this project so money is definitely a consideration.

Here are some details:

-I'm in NW Wisconsin - winters are cold - below 0 is common
-The garage is 24x30 with the same size attic above. The ceiling in the garage is 10'4" (between the I joists).
-It will be insulated with fiberglass insulation (2x4 walls). Not sure if I'll do the ceiling.
-The garage is 14' from the house and I have hydronic baseboard in the house.
-There is a 3' x 9' hole in the ceiling for the stairs

 

[red94chev]

I tried a ventless propane heater a few years ago, never again. The condensation it caused was insane, the fumes were bad, and it still wasn't that warm.

I settled on a 80k Big Maxx on a 120 gallon tank and it's been excellent. No fumes, great heat, no condensation. I keep the grage at 45 when I'm not out there and it has no problem getting it warmed back up quickly.

It's definitely costly compared to a ventless heater but still not terribly expensive. But completely justifiable by me for the quality of heat.

 

[pfettig77]

I tried a ventless propane heater a few years ago, never again. The condensation it caused was insane, the fumes were bad, and it still wasn't that warm.

I settled on a 80k Big Maxx on a 120 gallon tank and it's been excellent. No fumes, great heat, no condensation. I keep the grage at 45 when I'm not out there and it has no problem getting it warmed back up quickly.

It's definitely costly compared to a ventless heater but still not terribly expensive. But completely justifiable by me for the quality of heat.

Ok. Thanks. I see I can get it for $445 locally. What else would I need to buy to make it operational (venting, etc.). I wonder if that would heat both floors if I let it ooze up the stairwell?

 

[Prospecter]

Ok. Thanks. I see I can get it for $445 locally. What else would I need to buy to make it operational (venting, etc.). I wonder if that would heat both floors if I let it ooze up the stairwell?

My shop is 24x30 with a second floor in Mid-Coast Maine. Maybe not quite as cold as northern Wisconsin. My insurance company objected to a ventless heater. I went with a Ryobi vented heater. Easy, through the wall vent and air intake. Propane fueled. I am R35 walls and R50 ceiling. I only heat when out there, and go from cold to comfortable in about 20 minutes, even on the coldest days. I use a stairwell cover to separate the two floors, since we do not go to the second floor much.

In your situation, I would set up the second floor so I could close it off when not using it. Let the heat flow up when using it. I think I would also consider a mini-split if I was starting over.

 

[rmanrman]

Ok. Thanks. I see I can get it for $445 locally. What else would I need to buy to make it operational (venting, etc.). I wonder if that would heat both floors if I let it ooze up the stairwell?

I have a direct vent propane wall heater in upstairs rec room/office above the garage
You’ll need to have it on an exterior wall for the vent. The unit uses outside air for combustion therefore no heat loss from room
I had a vent free unit too much condensation and if you use any spray cleaners ex brake clean the fumes are heavy. The direct vents are about 3x cost $. You’re going to need at least a 100 lb propane tank it uses fuel quickly

 

[pfettig77]

My shop is 24x30 with a second floor in Mid-Coast Maine. Maybe not quite as cold as northern Wisconsin. My insurance company objected to a ventless heater. I went with a Ryobi vented heater. Easy, through the wall vent and air intake. Propane fueled. I am R35 walls and R50 ceiling. I only heat when out there, and go from cold to comfortable in about 20 minutes, even on the coldest days. I use a stairwell cover to separate the two floors, since we do not go to the second floor much.

In your situation, I would set up the second floor so I could close it off when not using it. Let the heat flow up when using it. I think I would also consider a mini-split if I was starting over.

I was thinking about some sort of trap door for the stairwell - maybe pink foam board (made to look nice) or something. Or maybe enclose the stair area and use a regular door. That would also keep car fumes and bugs, etc. out. What kind of cover do you use?

 

[pfettig77]

I have a direct vent propane wall heater in upstairs rec room/office above the garage
You’ll need to have it on an exterior wall for the vent. The unit uses outside air for combustion therefore no heat loss from room
I had a vent free unit too much condensation and if you use any spray cleaners ex brake clean the fumes are heavy. The direct vents are about 3x cost $. You’re going to need at least a 100 lb propane tank it uses fuel quickly

Thanks. Sounds like vent-free is not the way to go. I have a 500 gallon tank, so I should be good.

 

[Prospecter]

I was thinking about some sort of trap door for the stairwell - maybe pink foam board (made to look nice) or something. Or maybe enclose the stair area and use a regular door. That would also keep car fumes and bugs, etc. out. What kind of cover do you use?

Trap door is what I use. Masonite glued to foam. The Masonite is smooth, brown, and a little shiny. Good enough for me.

 

[Old Moparz]

I have a similar sized garage & faced with the same issue of wanting to heat both floors. I looked at two different styles of heating systems. For the first floor garage space I'd like a ceiling mounted radiant heater that runs on propane & vented to the outside. My propane supplier said they have one in their shop that I can come look at if I want. For the second floor I was considering a split system, A/C & heating unit.

 

[pfettig77]

I have a similar sized garage & faced with the same issue of wanting to heat both floors. I looked at two different styles of heating systems. For the first floor garage space I'd like a ceiling mounted radiant heater that runs on propane & vented to the outside. My propane supplier said they have one in their shop that I can come look at if I want. For the second floor I was considering a split system, A/C & heating unit.

I was thinking about a mini too. I installed one in my house last summer (MrCool) and I love it. However, it's not one of those that can heat when it gets real cold outside. They make ones that do, but I think they're really expensive (if anyone has info on this, I'm all ears). If I had A/C in my garage I'd feel like the king of ht world.

 

[BrianS]

I have a 24x32 with bonus room above in SW OH. I did a 2 head DIY Mr Cool mini-split with one head downstairs and one upstairs. I also have a direct vent propane heater for when the mini-split can't keep up in the winter. I keep it 50* in the winter and the propane has only kicked on during one really cold week last winter.

The big issue I see for you, unless I'm misunderstanding, is you only plan to insulate the walls? If you aren't insulating the roof/ceiling, you are going to spend a fortune in gas trying to keep it even 45*.

 

[red94chev]

Ok. Thanks. I see I can get it for $445 locally. What else would I need to buy to make it operational (venting, etc.). I wonder if that would heat both floors if I let it ooze up the stairwell?

Heater, propane tank, exhaust piping, stuff to hang it, mines on a dedicated electrical outlet, and I had a HVAC guy run the propane supply.

Heat rises so that would be your friend for the upstairs. Maybe consider some fans to either help push the heat down up blow it upstairs.

 

[pfettig77]

I have a 24x32 with bonus room above in SW OH. I did a 2 head DIY Mr Cool mini-split with one head downstairs and one upstairs. I also have a direct vent propane heater for when the mini-split can't keep up in the winter. I keep it 50* in the winter and the propane has only kicked on during one really cold week last winter.

The big issue I see for you, unless I'm misunderstanding, is you only plan to insulate the walls? If you aren't insulating the roof/ceiling, you are going to spend a fortune in gas trying to keep it even 45*.

I'll be insulating the attic ceiling too (not between the floors though). Should have made that clearer. I built rafters from 2x12s so I should be able to insulate it pretty well. Which MrCool did you use? How cold can the outside temp be and still heat efficiently?

 

[Innovate1]

I say your a little light on insulation space with 2 x 4 walls and 2 x 12 roof (and you need to leave some air space for ventilation above) in your climate. You also need to keep in mind that some furnaces/heaters condense in places not designed for it when run at low indoor temps of 45F which causes early failure of the equipment.

 

[pfettig77]

I say your a little light on insulation space with 2 x 4 walls and 2 x 12 roof (and you need to leave some air space for ventilation above) in your climate. You also need to keep in mind that some furnaces/heaters condense in places not designed for it when run at low indoor temps of 45F which causes early failure of the equipment.

I haven't insulated it yet - do you mean the framing just won't allow for very substantial insulation?

 

[BrianS]

I'll be insulating the attic ceiling too (not between the floors though). Should have made that clearer. I built rafters from 2x12s so I should be able to insulate it pretty well. Which MrCool did you use? How cold can the outside temp be and still heat efficiently?

I have the 36k BTU multi-zone condenser with a 24k head in the main garage downstairs and a 12k head upstairs. The upstairs head rarely runs in the winter, the heat from downstairs flows up easily. I don't have insulation between floors. It has no problem heating when it is in the teens outside. The forced air propane only kicked on when it was in the single digits for an extended time (2-3 days).

 

[pfettig77]

I have the 36k BTU multi-zone condenser with a 24k head in the main garage downstairs and a 12k head upstairs. The upstairs head rarely runs in the winter, the heat from downstairs flows up easily. I don't have insulation between floors. It has no problem heating when it is in the teens outside. The forced air propane only kicked on when it was in the single digits for an extended time (2-3 days).

I have a similar one in my house but I was under the impression that the efficiency dropped way down once it gets down to 40 degrees outside.

 

[Innovate1]

I haven't insulated it yet - do you mean the framing just won't allow for very substantial insulation?

Yep. Limited space for insulation. There are more expensive options such as spray foam that give more R value per inch but the cost is higher. What type are you planning to use? It would be fairly easy to estimate BTU needed with the details of wall area, window area, door area and R value, etc. We did 2 x 6 for house and 2 x 4 for for attached garage walls but we have much milder climate than you.

 

[pfettig77]

Yep. Limited space for insulation. There are more expensive options such as spray foam that give more R value per inch but the cost is higher. What type are you planning to use? It would be fairly easy to estimate BTU needed with the details of wall area, window area, door area and R value, etc. We did 2 x 6 for house and 2 x 4 for for attached garage walls but we have much milder climate than you.

I had a guy come over and give a quote for spray foam but it was outrageous. I don't think I'd ever make up for the extra cost with the extra efficiency - not in my lifetime.

 

[Innovate1]

The easiest way to get some idea of how much to heat the place and how many BTUs needed is to get some quotes on heating equipment.

 

[BrianS]

I have a similar one in my house but I was under the impression that the efficiency dropped way down once it gets down to 40 degrees outside.

That was true of old school heat pumps, these modern mini-split systems are much more efficient. There are some models that have a "hyper-heat" mode that will provide heat at even colder outside temps.

It was something I was concerned with, hence the back-up propane heat, but I've been pleasantly surprised with how well it does. Bonus, you get cooling in the summer as well.

 

[CraigStu]

We used a ventless propane heater in a 1500 sq ft house for 18 years. It worked great. We also had a typical heat pump and used the propane heater to make sure the emergency heat never came on and to make the living room super comfortable. Maybe a house vs a garage w/ all it's hard smooth surfaces deals w/ humidity better? I don't know because I never measured humidity. We liked it enough though that our current 2019 build house has two of them. We don't use them as much as the other house but they sure make the living room and wife's sewing room nice to be in even when it is in the 20s outside.

 

[dcg9381]

Has anyone had any experience with propane vent free wall heaters? I thought maybe I could put one downstairs in the garage and one in the attic.

Yes. I own two of them. They're for "emergency use" when the Texas grid takes an all-too-common **** in the middle of winter. Or as a money saving measure when it's really cold and our heat pumps try to go to resistive heat. A 30K BTU unit put at the bottom of the stairs in my "walk out basement" can heat the entire 3000 sqft house when it's 20 degrees out.

If I run it for 12+ hours, I do notice condensation on the glass garage door in my office.

We also use these for "supplemental" heat in the shop. When it gets cold our ductless splits drop capacity and cannot keep up. I've never seen moisture problems in the shop.

I think how well it will work for your case is going to depend on how humid it gets there and how long you're going to be running these. If you're just heating for a few hours, I'd use 'em just due to the economics.

You could always go resistive heat (240v) in the garage and as heat rises, see how that does above the garage.

 

[dcg9381]

That was true of old school heat pumps, these modern mini-split systems are much more efficient. There are some models that have a "hyper-heat" mode that will provide heat at even colder outside temps.

Just pay attention to their temp/performance curve. You can still buy some that don't heat very well below 30 degrees. And you can get others that are efficient when it's really cold.

 

[pbon]

I have a 24x30 with same size upstairs. Have a Big Max 50k. I hear just the down stairs but if I opened the door at the top of the stairs it would heat upstairs. Heat rises. First year I had an 18k through the wall AC with built in 12k heater and it heated the garage. Insulated — that helps a lot.

 

[pfettig77]

The easiest way to get some idea of how much to heat the place and how many BTUs needed is to get some quotes on heating equipment.

If I have to have an HVAC guy come over and give me a quote then it's game over before it starts. I won't have thousands to spend to heat the place once I'm done building. I came here to learn about alternatives to calling a pro and shelling out thousands.

 

[Innovate1]

If I have to have an HVAC guy come over and give me a quote then it's game over before it starts. I won't have thousands to spend to heat the place once I'm done building. I came here to learn about alternatives to calling a pro and shelling out thousands.

I never said you had to follow through. It costs nothing to get a quote.

 

[pfettig77]

I never said you had to follow through. It costs nothing to get a quote.

That's true. I kinda feel bad about wasting people's time though. I do have an acquaintance in the business. I'll pester him.

 

[pfettig77]

I just installed a minisplit last summer and I really love it. The change in my electric bill is almost nothing. Now you guys have got me thinking of getting one for the garage (with some backup of course). I read a thread on this forum from 2015 where most people seemed to tell a guy from WI to avoid a mini split because they don't work well in real cold climates. Seems like there are a lot that heat nowadays when the outside temp goes down to -22. What about a ducted minisplit. Anyone do that?

 

[Jackfre]

A Rinnai EX38 will do it and with the possible exeception of running the gas line, you can easily install it yourself. They are not inexpensive, but come with the vent kit, programmable stat, modulating burner and fans. Buy it where you can, install it and if needed, call the LP company to hook it up.

 

[Ak Jim]

Yep. Limited space for insulation. There are more expensive options such as spray foam that give more R value per inch but the cost is higher. What type are you planning to use? It would be fairly easy to estimate BTU needed with the details of wall area, window area, door area and R value, etc. We did 2 x 6 for house and 2 x 4 for for attached garage walls but we have much milder climate than you.

With only a 2x4 wall your best option would be to add 2” of bluebord on the outside and then put your siding over that.

 

[dcg9381]

If I have to have an HVAC guy come over and give me a quote then it's game over before it starts. I won't have thousands to spend to heat the place once I'm done building. I came here to learn about alternatives to calling a pro and shelling out thousands.

I tend to agree with you. If I ask an HVAC guy, those quotes have always come in at at least 300% of what it cost me to do a mini-split.
If you know your budget will simply get you the equipment, no sense in calling a pro.

There is an "in-between" option. If you're not willing to learn to install ductless splits yourself and you're currently running low on construction funds, simply provision for a future unit. I've still got a disconnect behind my garage that's fully wired, it's just not plugged into a breaker. If and when I ever get around to installing a ductless system in the garage, it's a lot easier to do now.

Same thing with ductless propane heat. Just run the lines. If you don't use them, your out the cost of that plumbing. If you decide to add the units, you're just out additional costs on the units and some minor adaptation to the propane lines.

Install blocking for the heaters / ductless systems now. Take pictures with measurements of where everything is..

 

[WisJim]

I'm in western Wisconsin, east of St Paul/Minneapolis, and we had 2 Fujitsu XLTH (Extra low temperature heating) 15k minisplits in our old farmhouse, and they did well heating that space most of the time. They were both downstairs so we had some resistant heat in the upstairs bathroom that was used only when my wife was bathing. When it got really cold, January and February, we used the wood burning furnace to provide more heat, but that was more because of how our utility credited us for our solar electric production. Our minisplits did fine in low temps and we used them exclusively, no wood backup, a couple of winters ago. Mitsubishi and Fujitsu both make minisplits that do well to minus 15 degrees or so.

 

[pcmeiners]

Check out the low temp minisplits, full rated heat down to -26 F. Propane is expensive compared to an efficient minisplit. My electric runs $.11/kw, so for me propane is just under 4 times as expensive

https://www.goodlifehvac.ca/images/Fujitsu_LZ_Series.pdf

Below is a spreadsheet link, download, then open. You need to replace present day fuel costs variable in the spreadsheets cells. If you go with a very efficient unit use 400% in the "air source heat pump " "approx efficiency (%)" cell otherwise use 300%

Heating Fuel Comparison Calculator​

 

[pfettig77]

I'm in western Wisconsin, east of St Paul/Minneapolis, and we had 2 Fujitsu XLTH (Extra low temperature heating) 15k minisplits in our old farmhouse, and they did well heating that space most of the time. They were both downstairs so we had some resistant heat in the upstairs bathroom that was used only when my wife was bathing. When it got really cold, January and February, we used the wood burning furnace to provide more heat, but that was more because of how our utility credited us for our solar electric production. Our minisplits did fine in low temps and we used them exclusively, no wood backup, a couple of winters ago. Mitsubishi and Fujitsu both make minisplits that do well to minus 15 degrees or so.

Small world - I'm one zip code north of you - Boyceville (closer to Prairie Farm though). This is very interesting info. I do have a guy that can help me install one of these. I looked up the system you had. I think they've updated them because it says they go down to -15 but a lot of new ones go down to about -24.

 

[dcg9381]

Check out the low temp minisplits, full rated heat down to -26 F. Propane is expensive compared to an efficient minisplit. My electric runs $.11/kw, so for me propane is just under 4 times as expensive

This is the strangest performance curve I've seen published. Seems like someone in marketing managed to play with some numbers:



This thing is rates to 123% at -26C. I mean that's great. But that's also a substantial reduction in it's heating capacity compared to how it does at zero. It's like the intentionally "underrate" the heating capacity so they can claim it's super efficient at -26C.

 

[lmg]

Hi all,
I'm in the finishing stages of building a cape style garage with a room above. I'd like to heat it this winter but there are some factors that complicate it a bit vs. heating a regular garage. The 2nd story will be a storage area but also a rec room for the kids. I'd like to keep the garage and attic at about 45ish all winter and crank it up when I have a project or the kids want to hang out. I suppose sometimes I would like the attic to be warm but won't need the garage part to be warm and vice versa. Has anyone had any experience with propane vent free wall heaters? I thought maybe I could put one downstairs in the garage and one in the attic.

There are plenty of ways to heat the garage, but this seemed cheap and simple. I'm definitely open to other ideas. I've already gone way over budget on this project so money is definitely a consideration.

Here are some details:

-I'm in NW Wisconsin - winters are cold - below 0 is common
-The garage is 24x30 with the same size attic above. The ceiling in the garage is 10'4" (between the I joists).
-It will be insulated with fiberglass insulation (2x4 walls). Not sure if I'll do the ceiling.
-The garage is 14' from the house and I have hydronic baseboard in the house.
-There is a 3' x 9' hole in the ceiling for the stairs

Building codes prohibit openings directly from garage to sleeping space.

 

[pcmeiners]

This is the strangest performance curve I've seen published. Seems like someone in marketing managed to play with some numbers:



This thing is rates to 123% at -26C. I mean that's great. But that's also a substantial reduction in it's heating capacity compared to how it does at zero. It's like the intentionally "underrate" the heating capacity so they can claim it's super efficient at -26C.

Yes the units produce far more than than the advertise rating, no issue for me, especially since a 12K unit cools my 30X36' garage and temporarily my 1350 SQFT attached home until I finish installing (3) 9K minisplits for my attached home.

"It's like the intentionally "underrate" the heating capacity so they can claim it's super efficient at -26C."

They are NOT stating the units are super efficient at -26, just that it can produce at least full rated output at -26. So is there something wrong when the units put out the full rating or more at -26, and far more than the rating at all other temperatures with a much higher than average SEER and HSPF.

That is why I purchased all extra low temp, high efficiency Fujitsu splits

 

[pfettig77]

Building codes prohibit openings directly from garage to sleeping space.

I figured that. No one will be sleeping up there for a while. When they do, I'll enclose the stairs.

 

[pfettig77]

This has been a very helpful thread. Here's what I think I may do:

In the garage part I'll have some sort of LP heater and upstairs I'll do a minisplit. That way if it gets really cold - too cold for the minisplit - I can let the heat from the garage ooze up the stairs. Also, if it gets really hot in the garage in the summer I can let the cold ooze down the stairs and cool down the garage in the summer. I might also just do a minisplit with two zones and have some sort of cheap backup for when it gets below -20. Thoughts on that?

Anyone have experience with one of these (or similar)?

Rinnai 22,000 BTU Propane Gas Vent-Free Fan Convector FC824P - The Home Depot

For a room or area that needs extra heating, Rinnai Vent-Free Fan Convectors are the perfect solution. They're simple to install, thanks to their vent-free design. They're also designed to be safe and

www.homedepot.com

Why is it 5X the cost of a wall ventless with a blue flame?