Heating a detached garage - Forced air v. Infrared v. Hydronic slab

[benyl]

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If all your loops are to conditioned spaces, why even run glycol at all?

Glycol boils at 197C. Same idea as antifreeze in your car. You don’t run straight water due to boiling point.

Also, if your boiler fails, you don’t want burst pipes. Glycol mixtures over 60% don’t freeze / burst until past -40C.

[ThePenIsMightier]

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If all your loops are to conditioned spaces, why even run glycol at all?

The more I think about this, the more a unit heater (i.e. NG forced air) seems to make the most sense. Best bang for the buck. Smallest footprint. Easiest to maintain. Like many of the folks sharing experiences here, I've been surprised by how capable my little 5000W electric heater is for my 20x20 detached today.

Likely going 32x24 or some kind of staggered combo, 26'deep x 10'wide adjoined with a 22x20, so giving up a bunch of floor space for mechanicals seems kind of lame.

It's not technically the best bang for your buck in the short term. The 5kW heater kicks its ass down the street (in the short term) and it works great, as you've seen.
Gas > electric as long as you're confident that the only way you're leaving that house, is in a body bag. It's definitely better, but dumb to sink that money in and then leave in 5 years.

[prae]

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Glycol boils at 197C. Same idea as antifreeze in your car. You don’t run straight water due to boiling point.

Also, if your boiler fails, you don’t want burst pipes. Glycol mixtures over 60% don’t freeze / burst until past -40C.

Yeah I grok the physics and understand glycol's purpose in lowering the freezing point. I meant- if you're just doing hydronic in a conditioned space (i.e. basement or attached garage) glycol feels really counterproductive. It increases viscosity and arguably reduces pump life. I always assumed you'd only want glycol for something like a snowmelt loop in the driveway.

I'm not sure I understand your comment about boiling point- why on earth would you want to run 100+C liquid in a heating loop. If you need to exceed boiling point of water at the start of a hydronic loop; something is seriously incorrect.

All of this comes from someone who's never installed, owned, or maintained a boiler so; could be a learning moment for ol' prae.

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It's not technically the best bang for your buck in the short term. The 5kW heater kicks its ass down the street (in the short term) and it works great, as you've seen.
Gas > electric as long as you're confident that the only way you're leaving that house, is in a body bag. It's definitely better, but dumb to sink that money in and then leave in 5 years.

Fair.

[Tik-Tok]

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Likely going 32x24

Mine is 33x26 (inside footage), if my garage got hit by a tornado, and I had to start from scratch, I'd go 33x28.

At 26' and with 2' of cabinets lining the back wall, there isn't much room to walk around a crew cab, short box truck.

[Perfect Dark]

24'x35' attached garage with 2 bedrooms and a bonus room above. I initially was going to go with IR as I have a 14' ceiling but after talking to the contractor ended up going with a 80k BTU forced air unit instead. It works great, garage stays nice and warm and when the heater is running it's actually very quiet (can't hear it at all in the rooms above). They used aircraft cable to hang it from the ceiling which helps with noise due to reverberation I'm thinking.

[tha_bandit]

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I did the same thing. I already had 220v in the garage. 6000w heater in my triple garage is more than enough to keep my triple garage at 20C when it's this cold outside if I need it. I usually just keep it from 10-15C. Minimal addition to my monthly bill. I went with Dr. Infared heater off amazon for $250.

exactly what i have in my detached, using a wifi thermostat with a contactor to control the 240v, working great.



Disclaimer: Do the above at your own risk

[imranm]

I went nat gas forced air. I have a triple with 16” ceilings. Kids bedrooms above.

It’s loud when it’s on but in my kids room it only sounds like a murmor.

Two reasons I went this way - again garage is huge cubic footage so when it got cold (with glass doors no less) it got really cold and my kids floors would get cold. So now I have a warm garage and warm floors in the kids room above.

Install costs are higher than electric but operating costs are basically $5-7 a month in the dead of winter.

Paid $3600 all in with permits for a 45,000 btu unit.

Great investment any way you go, but thought I’d share my experience!

[killramos]

Serious but odd question. I know we talk a lot about dedicated overhead forced air or in slab etc. Heating for garages.

But if you are building from scratch is there any reason you wouldn’t just heat your garage with normal central HVAC? Either plumbing in your existing ducting or on its own dedicated zone/furnace?

Is it just the substantial delta in BTU’s that a garage would consume?

If your utility room is adjacent it seems to me like this would be pretty simple to pull off and presumably cost less to a comparable amount? Figure you could even integrate dehumidification this way.

[ExtraSlow]

1) This thread is about Detached garage
2) For attached, cant mix garage air and house air, against code. Will CO poison your entire family (and disrespect them too)

[killramos]

No one was talking about detached anyway haha.

Definitely wasn’t suggesting bringing air into the house from the garage but I can see how that seemed like what I said. I guess to loop back. Second furnace on its own loop for garage in adjacent utility room, any reason why that isn’t a good idea?

Would certainly solve the “noise” problem, and I like the idea of integrating dehumidification.

[BerserkerCatSplat]

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1) This thread is about Detached garage
2) For attached, cant mix garage air and house air, against code. Will CO poison your entire family (and disrespect them too)

Bingo. Can't run ducting from main HVAC to garage and meet code, regardless of attached or detached. Needs to be a completely separate air system. Not sure if having an isolated circuit on a separate furnace is allowed, seems like an edge case. At that point, what's the advantage over a self-contained ceiling unit?

[ThePenIsMightier]

You have brought shame to your family.gif

[ExtraSlow]

well, second dedicated "real" furnace is a great option. People do that. usually just in the garage itself though I think. Used furnaces are cheap as heck too.

[killramos]

I’m just day dreaming of how I want to setup hypothetical garage heating, and the way things are laid out my Utility room would be right next to the garage.

At that point the question is just why not stick a second furnace in there to service the garage rather than plumb in dedicated gas and vent lines to hypothetical ceiling mounted garage heaters (also noisy).

[ExtraSlow]

I think, your going to run into code problems having both furnaces in the same utility room. Although an HVAC expert could confirm.

[killramos]

*insert Ron Swanson gif*

[Darell_n]

If you force air into the garage, air has to exit in the same mass. Return air ducts take care of this inside the home but having a return from the garage is not a good idea in any scenario.

[ThePenIsMightier]

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If you force air into the garage, air has to exit in the same volume. Return air ducts take care of this inside the home but having a return from the garage is not a good idea in any scenario.

Pfffttt!! Someone show this guy a compressor curve.
I'll get my stamp(s) from under this Lego blueprint.

[Darell_n]

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Pfffttt!! Someone show this guy a compressor curve.
I'll get my stamp(s) from under this Lego blueprint.

Corrected for your pleasure.

[ThePenIsMightier]

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Corrected for your pleasure.

Trying to tell me I can't run my garage at about 30psi...


That reminds me... I've recently had the intense pleasure of working with a PhD Process Engineer who wanted us to design her 500 barrel, hydrocarbon tanks for 30psi... For fuckin serious.
Yeah, this 3/8" plate roof that's 12 feet in diameter should easily handle that.