Options for Shop Heat

Planning stages for 24x36 shop/garage. My goal is to keep the area above freezing when not in use and getting it warm enough for finishing in winter (say 50-60) here in southern New England. If I go with wood frame it would be 2x6 insulated walls and considering insulated steel structures. I am in the planning stages with nothing carved in stone besides size. Structure is detached from house.

No natural gas available.

Possible energy sources. Electric (last resort), wood, pellet, oil, propane or something I haven't considered yet.

I was thinking pellet with auto hopper feeder for lower attention during off hours and lower ash vs wood.

Like to hear your thoughts, pitfalls, options

Thanks in advance for your sage advice.

Recommend propane. You can get extremely efficient furnaces and only need 2" pvc for both incoming air and also for the exhaust.
You can set thermostat to 35degrees and turn it up when you want it warmer.. It will warm up quickly if you put the correct size furnace in.

Run the duct work around under the ceiling, but in the heated area so you do not have losses to the outside.

I heat my entire house and included shop with a geothermal heat pump. The initial costs are higher but the payback is there if you plan to stay on the property. My house is maintained at 71 degrees in the winter and 74 in the summer. Depending on how much property you own there are various methods for collecting from the ground. Geothermal operating costs are much lower than propane and air source heat pumps. I reside in NW PA so we do see hot and cold extremes. This Old House has done a number of systems on their show.

My heated area is 1500 sq. ft of living/shop and a 1000 sq ft basement (slightly cooler than the living space) at an annual cost of $2190. This includes well pump, electric stove, dryer and water heater.

You mentioned a pellet stove. Best better check your insurance carrier. I had my detached shop built in 2001 and looked for an insurance carrier. All wanted know if I had a wood or pellet stove as they would not write a policy if the building had wood/pellet stove heating. In 2019, I changed my insurance carrier and those I queried about coverage told me the same.

Propane is very efficient. I don't know what your energy costs are, but a heat pump may be a good fit. I think you can save around 50% over the cost of electric resistance heat.

Another thing to consider is warm up time when you want to use the shop. I have a natural gas furnace in my shop, around 80,000 BTU, & keep it at 4.5 *C when not in use. If I want to use the shop after work, I turn up the setting to 18 & by the time I get home 1/2 hour later, its nice & toasty. Even 15 minutes of heat will get it quite comfortable. It will be easier to accomplish this with propane than with a heat pump.

Interesting option

A Rinnai EX38 will walk away with that space. You may be able to get utility rebates on a mini-split install.

I converted my house/attached shop from forced air to in-floor radiant heat. One of the smartest things I've done and I would suggest it if you can pull it off with your heat source. My shop is always warm and comfortable, even on -20 Wisconsin winter days. Because every object in the shop is warmed, and not just the air, it is much more comfortable than forced air heating. It also helps dry the wood piles I have in my shop.

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Originally Posted by Bob Falk

I converted my house/attached shop from forced air to in-floor radiant heat. One of the smartest things I've done and I would suggest it if you can pull it off with your heat source. My shop is always warm and comfortable, even on -20 Wisconsin winter days. Because every object in the shop is warmed, and not just the air, it is much more comfortable than forced air heating. It also helps dry the wood piles I have in my shop.

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My shop is detached and probably only around 1000 sf when built. What type of fuel and device do you use? My weather is probably very similar to yours, maybe a few degrees warmer on average.

BTW I already have an oil fired boiler (no natural gas available) for the house which will be pretty maxed out with 550 sf in-law appartment being added now. I sure like the idea of keeping the tools warmer avoiding condensation I get now in the unheated, unisulated, leaky as a tent shop I have now.

So normally, I'd immediately be recommending a MiniSplit...and 18-20K BTU unit would likely work nicely for the size of your shop (in general), especially if it's properly and well insulated. But you'd need a unit that has a better "low temp" limit than many of the most inexpensive units offer because of where you live and the kind of cold weather you get. My unit will work down to -5ºF, but that's not an issue here in SE PA other than once is a very, very long time with an unusual weather pattern. MiniSplits are heat pumps and while they do use electricity, the heat itself is extracted from the outside air. (Most also provide AC which is nice when it gets humid during the warmer summer months) Whether a heat pump type system will work well for you may or may not be the case where you live in Mass. From there, my recommendation would be to insulate the structure very well and use a propane powered furnace or overhead unit for heat with a thermostat that you can can control and monitor from your phone for convenience. I would never use resistance heat of any kind...it's hugely costly to run as I know from personal experience. Oil has its own challenges with storage, etc, so propane is easier and cleaner around that issue.

We heat both our home (1500 sq ft) and 2 separate workshops (His and Hers, each 600 sq ft) with natural gas fired boilers and in-floor radiant heat. Our yearly cost is under $1300 with the house at 71 F and the shops at 67 F. The best part of the radiant is the shop is warm no matter when I go to use it and the machines are warm to touch.

Where do you live in Massachusetts? In coastal areas, the weather is somewhat moderated temperature-wise (although the Nor-Easters are rough snow blizzards). We had oil heating when we lived North of Boston (hated it). I think the propane is a good choice. Mini-splits are great in the South and are heat pumps, but likely not going to use the AC that much in summer up there.

Of course, the added humidity from the propane heater is a definite drawback unless it's vented. And then you lose some of that heat going outside.

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Originally Posted by Bob Falk

I converted my house/attached shop from forced air to in-floor radiant heat. One of the smartest things I've done and I would suggest it if you can pull it off with your heat source. My shop is always warm and comfortable, even on -20 Wisconsin winter days. Because every object in the shop is warmed, and not just the air, it is much more comfortable than forced air heating. It also helps dry the wood piles I have in my shop.

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But that doesn't work so well if you don't want to pay for keeping the shop warm when not using it. Because of all the heat stored in the slab it will keep the shop warm all night. And when it finally does cool down there's a long wait to get it back up to a comfortable temperature. In-floor radiant is great for a house that is occupied almost continuously, but not for a space that is empty except for a few hours a day.

John, I had a natural gas boiler installed. I am no HVAC expert, but I think any system that heats water will work. What you would then need are manifolds, pumps, and other piping/hardware to control temp/water flow. Since you are detached, it would seem logical to design a system just for the shop. Perhaps an on-demand tankless hot water heater would work. They are relatively inexpensive and have been used for such applications. I would Google "radiant floor systems" or some such terms for your area and see if you can find someone to design a system. There is a lot of information on Youtube as well. I installed all the insulation/tubing myself (both in-slab and under floor), but had my radiant contractor install the boiler and all the hardware as that is pretty complicated. You will have to insulate under and around your slab (I used salvaged 2" and 3" foam board) You won't have condensation problems with a continuously heated shop. My shop is bone dry....as I said, I can bring air-dried wood in my shop and it will dry over the winter (albeit slowly). FWIW, I have bought various supplies from www.supplyhouse.com. Good luck!

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Originally Posted by Alan Lightstone

Where do you live in Massachusetts? In coastal areas, the weather is somewhat moderated temperature-wise (although the Nor-Easters are rough snow blizzards). We had oil heating when we lived North of Boston (hated it). I think the propane is a good choice. Mini-splits are great in the South and are heat pumps, but likely not going to use the AC that much in summer up there.

Of course, the added humidity from the propane heater is a definite drawback unless it's vented. And then you lose some of that heat going outside.

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I live near CT, RI, MA border below the snow line but 0 F happens as does 100 on occasion

Frank, your are correct. Every situation is different, but if you don't continuously heat you will likely get condensation on your tools.

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Originally Posted by Bob Falk

Frank, your are correct. Every situation is different, but if you don't continuously heat you will likely get condensation on your tools.

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Yes, if you live with high humidity that's a concern. Where I live the humidity averages around 50 - 60% & I don't get condensation on the tools. The shop is at 4.5*C when not being used.

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Originally Posted by John McKissick

I live near CT, RI, MA border below the snow line but 0 F happens as does 100 on occasion

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You may very well be fine with the better quality MiniSplit, then and they are super efficient energy use wise. You'll get both heat and AC/humidity control with one system. Initial cost can be a little higher, but the thrifty use of power can make up for it in reasonable time, IMHO. Mine has barely affected our electric bill...I keep it at a constant 64ºF all winter long and have it on AC at 76ºF for most of the summer. 750 sq ft or so with decent insulation.

Should you go with a mini-split you will be looking at the units with the -20*f capability. The typical models sold in your area, in most areas actually, are rated down to -5*f. An advantage of the mini-split is that you get excellent de-humidification. In your area you need the dehumidification more than you need temperature reduction.

A cabinet shop near me uses a wood fired boiler to drive in floor radiant heating. It’s a good outlet for their scraps, but their main fuel comes from local tree services. I’m really impressed with in floor radiant. once you get all that mass warmed up the flywheel effect keeps things very stable. It makes dust control much easier too.

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Originally Posted by Jim Becker

You may very well be fine with the better quality MiniSplit, then and they are super efficient energy use wise. You'll get both heat and AC/humidity control with one system. Initial cost can be a little higher, but the thrifty use of power can make up for it in reasonable time, IMHO. Mine has barely affected our electric bill...I keep it at a constant 64ºF all winter long and have it on AC at 76ºF for most of the summer. 750 sq ft or so with decent insulation.

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+1. Hopefully you have good insulation. If not, a definite to-do item.

The mini-split I have is somewhat challenged with de-humidification in Coastal Florida, but where you are, should work extremely well. I'm stunned how energy efficient my Mitsubishi is.

I installed infloor radiant heating when I built my shop 20 yrs ago. I used a 60 gal NG hot water tank, four zone manifold, pump, relay switch, and a thermostat--in slab tubing too!!

Full disclosure--good buddy is a plumber and gave wholesale costs on material and helped install. Biggest expense was the tubing. The slab is 1000 sq ft and we divided into 3 zones(one left over for the 2nd floor which I haven't needed yet). Cold season stays in the 40s and dips into the 30s sometimes here in the PNW and I keep the temp 55-60 deg unless I'm spraying finishes. Very comfortable and it doesn't take long for the temp to come up when needed. I would try to avoid any forced air system for dust issues and a propane hot water heater is much less costly than a tankless heater. Not sure of other cost comparisons but the infloor radiant system has been great for me. Good luck

John,

I live very near you. Last year I installed 6 minisplits in my house and I am still overwhelmed with how well they work. I plan to add one to my shop in the future when finances allow. I currently have a 220v electric heater which keeps the shop above freezing and will get it up to the 50s on most winter days. You could get one of these for very cold days when the minisplit won't work, which shouldn't be that many. Or, if you don't have water in the shop, just don't work on those super cold days.

As has been mentioned, the minisplit has a major advantage in that it dehumidifies. I can't wait to get one in my shop for this reason alone. It not only limits rust on machines, but keeps lumber more stable, and helps with finishing, too.

The only advantage I can see for propane is the quick heating. However, the minsplit should do pretty well in a well-insulated space. I bet MA has some incentives for insulation and minisplits.

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Originally Posted by Brian W Evans

John,

I live very near you. Last year I installed 6 minisplits in my house and I am still overwhelmed with how well they work. I plan to add one to my shop in the future when finances allow. I currently have a 220v electric heater which keeps the shop above freezing and will get it up to the 50s on most winter days. You could get one of these for very cold days when the minisplit won't work, which shouldn't be that many. Or, if you don't have water in the shop, just don't work on those super cold days.

As has been mentioned, the minisplit has a major advantage in that it dehumidifies. I can't wait to get one in my shop for this reason alone. It not only limits rust on machines, but keeps lumber more stable, and helps with finishing, too.

The only advantage I can see for propane is the quick heating. However, the minsplit should do pretty well in a well-insulated space. I bet MA has some incentives for insulation and minisplits.

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WOW, 6 mini's! Must be a large home.

Lot of folks advocating mini's

John, based on my experience with the unit in my shop, if/when we downsize, if the HVAC system in whatever home that is is old or inefficient...I'd replace with minisplit without hesitation. They are heat pumps but for cooling they are much, much more efficient than regular "whole house" type heat pumps. Brian may have had to use 6 units rather than a couple multi-handler units due to logistics for the piping between interior and exterior units for his particular home setup/design.

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Originally Posted by Jim Becker

John, based on my experience with the unit in my shop, if/when we downsize, if the HVAC system in whatever home that is is old or inefficient...I'd replace with minisplit without hesitation. They are heat pumps but for cooling they are much, much more efficient than regular "whole house" type heat pumps. Brian may have had to use 6 units rather than a couple multi-handler units due to logistics for the piping between interior and exterior units for his particular home setup/design.

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Happy to hear such overwhelming endorsement of the mini's but any way you cut 6 units is a lot of house. I am happy for him but I don't I have 6 rooms.

BTW we have discussed a few things over the past few months and I think my "garage" power situation should be improved in a major way soon. Hoping to have 50amp 240v soon. Right now I can't run my jobsite saw and a shop-vac at the same time on a single 120V 15amp circuit shared with my internet router and modem.

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Originally Posted by John McKissick

WOW, 6 mini's! Must be a large home.

Lot of folks advocating mini's

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Sorry for the confusion - I installed 2 outside units and 6 "heads" - one in each of four bedrooms and two in common areas.

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Originally Posted by Brian W Evans

Sorry for the confusion - I installed 2 outside units and 6 "heads" - one in each of four bedrooms and two in common areas.

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Ah, that makes more sense. Thought I had really rich neighbors..lol

Appreciate the experience with mini-splits and advice

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Originally Posted by John McKissick

Happy to hear such overwhelming endorsement of the mini's but any way you cut 6 units is a lot of house. I am happy for him but I don't I have 6 rooms.

BTW we have discussed a few things over the past few months and I think my "garage" power situation should be improved in a major way soon. Hoping to have 50amp 240v soon. Right now I can't run my jobsite saw and a shop-vac at the same time on a single 120V 15amp circuit shared with my internet router and modem.

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If you only have 50 amp service going to the shop, putting in a MiniSplit or any form of electric powered heat is going to be tough, honestly. You may need to do a properly vented gas heater in that case.

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Originally Posted by Jim Becker

If you only have 50 amp service going to the shop, putting in a MiniSplit or any form of electric powered heat is going to be tough, honestly. You may need to do a properly vented gas heater in that case.

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Power feed hasn't been run yet, I have some options

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Originally Posted by John McKissick

Power feed hasn't been run yet, I have some options

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"More" is better when it comes to your shop subpanel. You don't have to fully use it, but that's a lot better than not having enough when you decide to buy a shiny new machine or run a dust collector, power tool and HVAC system while the compressor decides to kick on while you're doing that, not to mention lighting, etc., all at the same time. That's actually a real world example of my shop, leaving out the CNC machine that's sometimes doing its thing at the same time, too. :) Seriously, the largest part of the cost of installing heavier service to the shop is the cost of the wire. There's not a lot of difference in cost with the terminations including the panel and breakers. This is one of those things where investing up front can pay, even if you have to wait a little longer to fund something else that can be handled after the fact more easily because it's hard/expensive to change out that wire in the ground or however it's run.