About this time every year, the same question starts popping up in every woodworking group I'm in: "How do I keep my shop warm this winter?" Everybody has a different answer. So here's mine, from about four years of freezing my butt off (and baking it in the summer) in my own shops.
I'm not a heating and cooling expert. But I've bought just about every solution under the sun, and I can tell you what has worked for me and what hasn't.
Why It Matters
A cold shop isn't just uncomfortable. Glues, paints, and finishes care about temperature, and most list a minimum application temperature right on the label. Check yours before you glue up or spray in a cold shop. If you're spraying finishes this winter, my post on HVLP spraying for beginners covers the rest. It's built around the TCP Global HVLP spray gun kit I recommend for beginners.
Convection vs. Radiant
There are two ways to heat a shop.
- Convection heats the air.
- Radiant (infrared) heats things. And you are a thing.
Which one is right for you depends on one question: is your shop sealed?
Sealed or Insulated Shop: Convection Works
If you're in an attached garage, or an insulated shed or building with weather stripping on the doors and no open roof vents, convection can be the way to go. Your options include:
- Small electric space heaters. The 1,500-watt kind, usually with 750, 1,250, and 1,500 settings. Even if the box says "radiant," these are convection heaters.
- Oil-filled radiators. Despite the name, they don't radiate much. They warm the air between the fins, and that warm air rises and circulates. That's convection.
- Gas forced-air heaters that run on LP or natural gas.
- A mini split with a heat pump. In an earlier shop, which was sealed and insulated, a 3-ton mini split worked fantastic, and it doubles as your AC.
In a sealed shop, the electric options are probably your best bet and the cheapest to run.
What About a Diesel Heater?
In my old shop, I used a dual-fuel forced-air heater that runs on diesel or kerosene. Where I am, at the time I made my video, kerosene was almost $6 a gallon and diesel was around $3.29 to $3.50. Both have about 140,000 BTUs per gallon, so I ran diesel.
It burns about a gallon an hour, so roughly $3.50 an hour. A 10-hour day is about $35. In a sealed shop it heats up fast. But it puts off fumes, and even in that leaky old shop they got to me after about 30 minutes. So I only ran it for about half an hour on 25 to 30 degree mornings to get the temperature up quickly.
Unsealed Shop: Infrared, Period
My old shop was about 2,500 square feet. It had two roof vents, open gables, and not one sealed door. There was always a breeze. A 5-ton unit blowing in from my office wouldn't touch it. Heat the air in a shop like that, and it rises and leaks right out.
If your shop isn't sealed, go infrared. Period. Don't waste your money on convection.
Here's why infrared works:
- It's windproof. It warms you and your surfaces, not the air. That's why patio heaters, which are infrared, work outdoors even in the wind.
- It keeps working after you turn it off. Your bench, your floor, and your tools soak up that heat energy and give it back for a while, so the temperature doesn't drop the moment the heater shuts off.
What I Ran in My Old Shop
Here's what I ran in that unsealed shop:
- Three 1,500-watt quartz infrared heaters, about 5,000 BTUs each, all aimed at my main workbench. That's 4,500 watts and about 15,000 BTUs pointed right at me. The shop was 41 degrees when I filmed, and I was toasty at the bench. They stayed on all day. If you want to try quartz heaters, here's an infrared quartz heater 2-pack.
- A Mr. Heater tank-top propane heater. Each burner goes up to 15,000 BTUs, with 5,000, 10,000, and 15,000 settings. It's perfect if you mostly work in one area. Single-burner versions sit right on a 20-pound tank, and there's a smaller "little red box" style that runs on small canisters and sits on your bench.
- A Mr. Heater 30,000 BTU wall unit. I ran it about two hours in the morning to warm the shop up, then turned it off. This Mr. Heater 30,000 BTU vent-free radiant wall heater runs on propane or natural gas.
- Two parabolic infrared heaters, the kind that look like fans. They work really well, and I could set one beside the bench and point it right at me.
The trade-off is that the heat is localized. When I walked over to the table saw, I got cold, so I'd make my cut and get back to the warm spot.
Insulation
In my new shop, I sprayed Bondure closed-cell spray foam on the ceiling, which is wood with a metal roof on top.
I took temperature readings in early summer:
- Bare ceiling: about 104 to 105 degrees
- About ½ inch of foam: 99 degrees
- About 1½ inches: 96 degrees
- About 2½ inches: 92 degrees
That's about a 12-degree difference. It doesn't spray perfectly evenly, but you can do multiple coats. I bought the 240-square-foot kit, which came with the gun and protective gear. The link above is the 240-square-foot kit, with 12 cans of foam, the foam gun, gun cleaner, gloves, goggles, and a coverall. And do wear the PPE. It gets everywhere.
My test was about keeping summer heat out, but insulation slows heat moving in either direction. It also helps seal the leaks that make convection so pointless in a drafty shop.
Safety
- Fuel-burning heaters (propane, natural gas, diesel, kerosene) produce fumes and carbon monoxide. Ventilate, follow the manufacturer's indoor-use instructions, and put a carbon monoxide detector in your shop. If a heater connects to a gas line, have it installed properly.
- Never bypass a tip-over sensor. They can go bad. When one does, replace it.
- Watch what a radiant heater can "see." It warms everything in its line of sight, including that can of stain on your bench. Keep finishes, solvents, and other flammables out of the beam, and respect the heater's clearance distances.
- Keep heaters clear of sawdust, and plug electric heaters into an outlet rated for the load.
Quick Recommendations
- Sealed or insulated shop: convection. A mini split, an oil-filled radiator, or an electric fan heater.
- Unsealed shop: infrared, period. Quartz heaters aimed at your main work area, plus a propane radiant heater if you need more.
- Need a fast morning warm-up: a forced-air heater for about 30 minutes or a wall unit for a couple of hours, then let the infrared carry you.
- Own your building? Insulate and seal it, and convection becomes a real option.
Stay warm out there, and if you have questions, leave them on the video. I'm happy to help.
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