Help me determine the best heating method for my shop

[olytdi]

I'm trying to figure out what method of heat would be best and most cost efficient. The details:

36x36 post construction shop with 12 ft walls and 18 ft at the peak. Slab not insulated. All open inside with trusses. Plywood and felt under standing seam steel for the roof, and 2 inch wrap insulation sandwiched between the steel siding and the girts. Two 10 x 10 insulated overhead doors. R value is about 7 throughout. There are two largish clear poly panels at the gable ends that serve as windows.

Before I get slammed for building such an poorly insulated building, note that I live on the Salish Sea and the winter temps here are generally in the 30's and 40's. We average about 6 inches of snow yearly and we get freezing weather for a couple of days to (rarely) a couple of weeks per year. My last building was similarly built and required heat only occasionally in the winter.

I have electricity and propane at my disposal. A ceiling fan or two will be installed. I don't usually sequester myself in the shop for long periods of time in winter so heating it is something that I'd need to do only intermittently.

I suspect that my best options are either propane tube infrared overhead heaters or a propane unit heater but I don't know for sure.

Resistance heating would be unrealistic. Heating with a torpedo or anything not vented is a non-starter for me. It's wet enough here as it is! I don't want to go with wood or pellets.

Lastly, I don't need it to get warm. I run hot anyway when I'm working so bringing the space relatively quickly to the upper 50's would be just fine.

So what am I looking at -- unit heater or infrared? If so, which?

Any feedback appreciated!

 

[Jackfre]

I think if you check the utility rebates in your area that minisplits will be your best bet. If going propane I think you could easily do this with a Rinnai EX-38.

 

[olytdi]

Thanks for replying, Jack! I will check out the Rinnai. I'm thinking a minisplit might take too long to heat up the space and with that level of insulation, not suitable for keeping it on all the time. I also worry about dust -- I saw an elaborate filtering setup on another thread but I'm not sure about that for my application. I do heat my house with two minisplits and they work awesomely!

 

[woodfirenewbie]

Can confirm the Rinnai. We have an ex22ctn in our four-season room for heating duty in MN. I wouldn't have used anything else... they're an incredible piece of kit. The venting AND thermostat are included in the price, and it is miserly on fuel while remaining very quiet with few on/off cycles.

The only downside is that they need to be situated on an exterior wall as the included venting comes straight out the back of the unit to the exterior. (edit: there is a kit to route the intake/exhaust lines to the left or the right of the unit inside the wall too, but they are not common) Ceiling mount unit heaters don't take up wall/floor space and have roof or wall venting, so there is more flexibility in where they're installed.

If we had a good place to mount a Rinnai in our garage I'd buy another one.

 

[Showkey]

OP what is the cost per KW delivered ?
Cost propane? Yes, that is variable by time, season, amount purchased etc.

 

[theoldwizard1]

With your temperature range, the most cost efficient heating/cooling would be with a mini-split heat pump. The problem is with your size of a building you will need at least 2 air handlers to get any kind of reasonable heat distribution. Initial cost will be high, but it should pay back quickly.

 

[4x4Pete]

If cooling is not required I would probably go with an infrared tube heater. Minimal maintenance for dust. Straight along the 18' peak, air inlet and exhaust on the gable ends. If you can maintain a comfortable temperature with such little insulation it can be left on for the cold spells and won't fry your head. I have one- mind you it in a much colder climate and I have way more insulation. It keeps it comfortable and doesn't run enough to burn or overheat anything. I also have natural gas- annual cost is about $250 for a 30x32x12.5 in Canada. Heating season runs from early November to mid May. I keep it set to 70° the whole time.

 

[olytdi]

Can confirm the Rinnai. We have an ex22ctn in our four-season room for heating duty in MN. I wouldn't have used anything else... they're an incredible piece of kit. The venting AND thermostat are included in the price, and it is miserly on fuel while remaining very quiet with few on/off cycles.

The only downside is that they need to be situated on an exterior wall as the included venting comes straight out the back of the unit to the exterior. (edit: there is a kit to route the intake/exhaust lines to the left or the right of the unit inside the wall too, but they are not common) Ceiling mount unit heaters don't take up wall/floor space and have roof or wall venting, so there is more flexibility in where they're installed.

If we had a good place to mount a Rinnai in our garage I'd buy another one.

I don't mind the exterior mounting need but it doesn't look like they make any with significant BTU output. I do need something that can heat up the space on demand more than keep a temp ongoing, hence why I was thinking probably unit heater or infrared tube. I don't see heating the space when not using it. If i have any of that wrong, please let me know! I appreciate the feedback!

 

[olytdi]

OP what is the cost per KW delivered ?
Cost propane? Yes, that is variable by time, season, amount purchased etc.

Looks like I get my first 600 kwh for $0.0092 per kwh then it's $0.0112 after that. So probably 11 cents per on average as I used 678 kwh last month and any additional heating would be at the higher rate.

Propane is a wildcard, of course. I did just top off my 500 gal tank this week for $2.09/gal which is the most I've ever paid. Last year it was $1.19/gal. I would think the cost of propane would be more likely to elevate unpredictably than the price of electricity...

 

[olytdi]

With your temperature range, the most cost efficient heating/cooling would be with a mini-split heat pump. The problem is with your size of a building you will need at least 2 air handlers to get any kind of reasonable heat distribution. Initial cost will be high, but it should pay back quickly.

Yes. I heat/cool my home with two minisplits and they are awesome! But like you said, the up front cost is high. I think my two home units cost me around $10k or so when I had them installed 4 years ago. But they are da bomb. Kept my interior at 70 last year when it was 113 degrees outside! I also worry about the recirculation of dusty air being a challenge. All of that said, having cooling as well as heating would be great in the shop -- just not sure it's justified price-wise and maintenance-wise.

 

[olytdi]

If cooling is not required I would probably go with an infrared tube heater. Minimal maintenance for dust. Straight along the 18' peak, air inlet and exhaust on the gable ends. If you can maintain a comfortable temperature with such little insulation it can be left on for the cold spells and won't fry your head. I have one- mind you it in a much colder climate and I have way more insulation. It keeps it comfortable and doesn't run enough to burn or overheat anything. I also have natural gas- annual cost is about $250 for a 30x32x12.5 in Canada. Heating season runs from early November to mid May. I keep it set to 70° the whole time.

Thanks Pete, that's kind of where my mind is currently. I cannot get a firm handle on whose units are best/most affordable and how to size them. Heck, I'm having problems figuring out how many BTUs I would need in any context but it's probably at least 80K for a unit heater and I don't know in terms of a radiant heat system.

One of the most compelling aspects of the infrared radiant tubes is what you mentioned -- spanning the whole upper section of the peak from gable-to-gable is entirely doable.

You mention positioning it at the top of the peak - what about truss wood, light fixtures, and such that might be near the tube or more closely placed? Is that a problem with being too close to the heat source?

Interesting that no on is recommending a unit heater! I appreciate the diversity of ideas.

 

[4x4Pete]

There are clearances to combustibles that need to be adhered to as well as clearance to cars on lifts and the like. The unit I bought is a Superior Radiant Systems UX60 with a 30' tube. Their install manuals are available online. They have distributors in Canada and the US.
The ceiling in my shop is flat so I have it mounted across the back furthest away from the overhead doors, mounted at a 45° angle. The clearances at the corner of the reflector was listed at 4" mounted in this way. I put it at 6" and have no issues with heat damaging anything. I have a 52"tv mounted 36" below it with no problems there either. This saves the middle ceiling area for a future lift. The whole shop is evenly heated with no real difference between the front or back. You can shorten the tubes a bit to satisfy the installation which I took about 2' off. I have a 60k btu unit which could have been a 40k without a problem. The online sizing calculators put my shop at about 35k which I thought was too little. I used to do gas and refrigeration work for a living and figured that I wanted a good recovery so I went up one size. I keep the shop heated all winter and there was no need to up size at all. It runs often enough to maintain the temperature but with a short enough cycle to not really notice the heat when you're directly below it.
Radiant tube heaters do put out more heat at the burner end so it can be positioned to take advantage of that. Superior Radiant Systems pride themselves about their reflector which they claim to have great projection. It seems to work but I can't say whether it's better than their competitors.
The biggest draws for me were the facts that there is no air movement, it heats the objects in the room and the floor is warm too. My attached garage (my old shop) has a furnace installed up above a mezzanine and ducted down through the mezzanine floor which works good but blows the dust around and doesn't heat as evenly as the tube heater. For that reason I didn't care for the minisplits either. A/C would be nice but not really needed in my climate.

 

[Fueler]

I have a 32K mini split cooling a 40 x 40 superbly. Went over 100 degrees for a couple of days. Stayed at 70 inside with no humidty.
Humidity control is a big thing for me. No flash rust anywhere. My insulation isn't great but it sounds like it is better than yours.
Also does well in the winter until the wind gets too high and the temp below 20. Then my tube heater kicks in to take up the slack.
if I had to do it again I would use 2 mini just due the large and awkward size of the 32K. Might even be less expensive.

 

[olytdi]

Thank you Pete and Fueler -- that's very helpful information!

 

[Firebrick43]

I wouldn't hang a radiant heater in the trusses. I would also highly suggest putting a ceiling on the bottom of the trusses like a metal r panel liner even if you don't insulate it. But even a 1" celotex layer between the ceiling and truss will make a huge difference, in heating and in the summer.

The shop I grew up in had a massive barrel stove to heat it until insurance made it go bye bye
My father and i then put in a 140k propane furnace. This was only used when we were in the shop to warm to a point to wear a sweatshirt.

After the first year the propane bill was enough my father had me nail up clothes board to the rafters and the difference was huge in propane usage and general comfort.

Heat rises. Why waste it up in the rafters when your down low.

 

[pcmeiners]

With an efficient heat pump you would use 3x less electric than electric resistance, Propane is expensive compared to that and like any fuel it will continue to go up. If you spend a lot of time in the shop I would go heat pump, You need to do something with 12' walls, 18' peak. I am finishing up an install of (2) 12000 Btu very efficient Fujitsu heat pumps in my 36 by 30 shop, with the units I have I will be running cheaper than natural gas.

• cooling Capacity 12,000 BTU
• Heating Capacity 16,000 BTU
• SEER 29.3
• HSPF/EER 14.0 / 15.2

 

[Farmer29]

With an efficient heat pump you would use 3x less electric than electric resistance, Propane is expensive compared to that and like any fuel it will continue to go up. If you spend a lot of time in the shop I would go heat pump, You need to do something with 12' walls, 18' peak. I am finishing up an install of (2) 12000 Btu very efficient Fujitsu heat pumps in my 36 by 30 shop, with the units I have I will be running cheaper than natural gas.

• cooling Capacity 12,000 BTU
• Heating Capacity 16,000 BTU
• SEER 29.3
• HSPF/EER 14.0 / 15.2

My shop has 18ft walls with 3 overhead doors biggest being 16X20. I usually set temp at 68 degrees and leave it there.
Coldest we usually get here is - 10-15 but we have seen -24 this winter. Are you using air to water or air to air?

 

[pcmeiners]

Air to air, had (1) going when it was 7° F, kept the shop at my setting of 65°, and the unit outside only starts up intermittently; likely I could heat/cool with 1 unit but I wanted a second as a backup, wall mount unit (9 ft up) provided nice even heat, very quiet
Wish I could have done a geo loop but my property is on shale about 2 ft down.
KW cost here is 12 cents. Heat pump COP is averaging about 4, so basically I am getting a KW of heat/AC for 3 cents, sure bets my baseboard heat/AC window unit cost. As a note, I purchased "extreme low" temperature units so I do not have to worry about minus temperatures, which is very rare anyway.

Still to be done on the garage.... I need to install really good seals around the garage doors and I plan to add a couple feet of cellulose blown insulation above the ceiling, previous owner installed thick fiberglass already. The cellulose will form an air seal, which the fiberglass thoroughly ***** at.

Lastly, for anyone installing mini splits in snow country, mount the outside units high off the ground. I placed mine about 24" of the ground, perpendicular to the prevalent wind direction.

 

[Highbeam]

Looks like I get my first 600 kwh for $0.0092 per kwh then it's $0.0112 after that. So probably 11 cents per on average as I used 678 kwh last month and any additional heating would be at the higher rate.

Propane is a wildcard, of course. I did just top off my 500 gal tank this week for $2.09/gal which is the most I've ever paid. Last year it was $1.19/gal. I would think the cost of propane would be more likely to elevate unpredictably than the price of electricity...

Better check again, our utility just jacked up rates so the first 600 is 11 cents and above that is 13 cents per kwh. Nice.

 

[pcmeiners]

Don't feel bad, if you lived in NYC the stated rate in December 2022 was $ .231

 

[olytdi]

I did end up putting in a 40,000 btu electric unit heater. When it's 30 degrees in the shop, it takes an hour and a half to get it comfortable. It's about $1.25/hr on high but once it gets comfortable, it cycles on low. Haven't had it a month yet so don't know the impact to the bill yet.

I also just installed a 10 ft fan and with that running, it cuts the heating time in half! Really makes a difference getting the air at the peak mixed in to the floor.

 

[nadogail]

My recommendations will depend on your local cost per BTU.