Heating a detached garage with room above

[Old Man Roger]

Sorry if I’m repeating anyone, I just scanned the thread.

Heat rises, if you let it passively heat the upstairs, it won’t do a great job of heating the downstairs.

Maybe a vent from downstairs to up, to meter the amount of heat that escapes? Or maybe some sort of circulation to push the hot air back down stairs?

 

[pcmeiners]

Needless expense running the propane, the minisplits as in my other post will definitely heat/cool to your needs, at a much lower utility cost. two low temp 9k unit should do it, one unit for down stairs, one for upstairs (if desired), two 12k guaranteed .

I stated just under 4x, that is with an electric cost of $.11/kw. A high efficiency heat pump produces 4x the amount of heat than a standard resistance heat (electric baseboard) for the same amount of electric . So you get 4000 watts of heat/cooling from every 1000 (one kw) watts used on average; that is with a high efficiency unit, not cheap standard minisplits.

 

[pfettig77]

Sorry if I’m repeating anyone, I just scanned the thread.

Heat rises, if you let it passively heat the upstairs, it won’t do a great job of heating the downstairs.

Maybe a vent from downstairs to up, to meter the amount of heat that escapes? Or maybe some sort of circulation to push the hot air back down stairs?

I thought of that. It's just really hard to know how much will flow up the stairs. I do plan on enclosing the stairs in the future, but maybe not for a couple of winters.

 

[Old Man Roger]

I thought of that. It's just really hard to know how much will flow up the stairs. I do plan on enclosing the stairs in the future, but maybe not for a couple of winters.

There a thread on this site recently talking exactly about the subject. He was trying to keep the garage warm but all the heat was going to the upstairs apartment through the stairwell. Let me see if I can find it.

 

[Old Man Roger]

Here it is, there is a lot of info, some that will probably not have anything to do with your problem, but some that I think might help you.

Contractor undersized mini split in garage, trying to figure out solutions

My spray foamed building is cooling about 1200 sq feet with 18,000 btu central ac unit. Either the insulation/air sealing is inadequate or that unit isn't working right.

www.garagejournal.com

 

[pfettig77]

Needless expense running the propane, the minisplits as in my other post will definitely heat/cool to your needs, at a much lower utility cost. two low temp 9k unit should do it, one unit for down stairs, one for upstairs (if desired), two 12k guaranteed .

I stated just under 4x, that is with an electric cost of $.11/kw. A high efficiency heat pump produces 4x the amount of heat than a standard resistance heat (electric baseboard) for the same amount of electric . So you get 4000 watts of heat/cooling from every 1000 (one kw) watts used on average; that is with a high efficiency unit, not cheap standard minisplits.

I would love to be able to just do the minisplits and be done with it. Seems too good to be true - why would anyone heat with propane? We do get the occasional -25 or -30 around here. What would I do then?

You recommended the Fujitsu - I can't seem to find if they have a unit that does the heating down to -15 with multiple zones. Also, I noticed a lot of other brands can heat in even colder weather. Do you like any other brands? I have a Mr. Cool and even though it's not high end, I really like it and it's supposed to heat down to -13.

 

[pfettig77]

Here it is, there is a lot of info, some that will probably not have anything to do with your problem, but some that I think might help you.

Contractor undersized mini split in garage, trying to figure out solutions

My spray foamed building is cooling about 1200 sq feet with 18,000 btu central ac unit. Either the insulation/air sealing is inadequate or that unit isn't working right.

www.garagejournal.com

Thanks for the link. Makes me think I really need to do something about the stair opening.

 

[pcmeiners]

"We do get the occasional -25 or -30 around here. What would I do then?"
That is already answered in the link....

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

The XLTH, are under rated in the brochures, they will heat sufficiently at those temperatures. The LZ designation is in the middle of the model name, on page 20 of the 2023 Catalogue you can download from the Fujitsu site,or in the link above . Yes there are a number of minisplits that can heat down to minus degrees, but at what BTU rate, and at what efficiency.

Two single zone minisplits are far more efficient than any two zone minisplit

Sorry but I am not repeating anymore info I have given in previous posts or links.

 

[toyotadriver]

I think it has been covered but the OP should NOT do a vent free unit. They do make heat fairly cheaply but the moisture they produce is a big negative ESPECIALLY for the OP’s climate. In a dry, not long term cold climate like Tx, they can work ok. Never great but ok. The OP will absolutely HATE the moisture build up in his super cold climate and will likely cause mold.

Vented gas/propane downstairs and a mini split upstairs seems to be a good solution. Another option would be gas/propane downstairs and an electric resistance heater upstairs but only use the one upstairs when people will be up there.

 

[pfettig77]

I think it has been covered but the OP should NOT do a vent free unit. They do make heat fairly cheaply but the moisture they produce is a big negative ESPECIALLY for the OP’s climate. In a dry, not long term cold climate like Tx, they can work ok. Never great but ok. The OP will absolutely HATE the moisture build up in his super cold climate and will likely cause mold.

Vented gas/propane downstairs and a mini split upstairs seems to be a good solution. Another option would be gas/propane downstairs and an electric resistance heater upstairs but only use the one upstairs when people will be up there.

So I've been learning. Looks like this might end up being a very expensive project.

 

[pfettig77]

Ok. This might be worthy of an entirely new thread, but does anyone have opinions/experiences about the different brands of mini splits with hyper heat type heating (thinking -20 and bleow)? That's the route I think I'll go. Maybe just one 12k BTU one in the garage for now then another upstairs next summer depending on how I like it. I'd like the Fujitsu, but this project is already violently over budget and they're twice as much as the other ones I'm looking at (like Senville and Pioneer). Not off the table though.

 

[lmg]

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

Thank you for responding to my concerns on the openings to the sleeping space, I was afraid it would be ignored.

Another issue is the fact that the garage has to be separated from the house by fire rated assemblies. So walls, ceilings, doors, etc need to be fire rated. Sounds like you may have a pull down stairway, I am guessing that it does not have any fire rating.

Lack of fire separation may be an insurance company issue in the event of a fire.

 

[pfettig77]

Thank you for responding to my concerns on the openings to the sleeping space, I was afraid it would be ignored.

Another issue is the fact that the garage has to be separated from the house by fire rated assemblies. So walls, ceilings, doors, etc need to be fire rated. Sounds like you may have a pull down stairway, I am guessing that it does not have any fire rating.

Lack of fire separation may be an insurance company issue in the event of a fire.

The garage is detached. The stairs are not pull down - just regular construction.

 

[lmg]

The garage is detached. The stairs are not pull down - just regular construction.

Great.