Wood Heat for a Shop

Wood stoves in a shop introduce concerns about safety and about excessively dry shop air. January 20, 2010

I want to install a wood burning stove in my shop. Am I going to have issues with my lumber getting to dry, or problems with completed jobs (cabinet doors) swelling up six months from now? If I do burn wood, I want to use my plywood scraps too. I plan to make a large box around the stove out of cement board for safety, and a fan above.

Forum Responses
(Cabinetmaking Forum)
From contributor Q:
Yes your shop will become too dry. Also, did you talk about this with your insurance company? I don't think they will agree.

From contributor G:
Why would your shop be any drier with wood heat than other types of heat?

From the original questioner:
I am not sure why it might. I guess whether it is propane or wood, the heat still comes from metal (radiant) weather it is the stove itself, or a metal heat exchanger in a furnace. The dried up (or burnt) air still goes out a flue either way. Can anyone explain if I am wrong?

From contributor M:
I'm with contributor Q. My insurance company said absolutely not.

From contributor J:
You're absolutely right. Any air that touches a flame goes right up the flue. What makes it dry in the winter is the cold dry air outside that is drawn in to replace the loss up the flue. That outside air is dry to start with and then heated, which expands it a lot, so the same moisture content is in a lot larger volume. Hence really dry air.

From contributor M:
1. If you are worried about drying out the shop, put a pot of water on top of the stove to add moisture. On residential HVAC equipment they have humidifiers on them.

2. Talk it over with you insurance company, I heat my shop with a wood stove and have no issues with my insurance company. That's how my 1800's building has always been heated. If you follow the building codes concerning installation there should not be an issue. Provided you aren't spraying any flammable vapors or generating large concentrated volumes of dust.

3. Keep a good fire extinguisher handy, but then you should already have one of these in your shop anyway. Mine just happens to be a 1977 fire truck parked out back.

From contributor S:
I heat with an outside stove. My insurance company made me put it 100 feet from the building. If I was hoping to burn the shop down I would have it in the shop. Otherwise itís not worth the fire danger. Dust is like a drop of water, it can get in anywhere.

From Gene Wengert, forum technical advisor:
The stove suggested and also a dust system that exhausts to the outside will both dry out a shop in the heating season. For a stove, consider using outside air for the air and then use a plenum system to capture the heat (like a gas or oil furnace in a house does). In other words, the air for burning is separate from the shop air. Of course, finishing in the shop with flammable or explosive vapors is not a good idea.

From contributor K:
I have a Ben Franklin wood burning stove in my shop. They are safe enough for a home, so I am ok with one being in the shop. It has been serving me well for over ten years, so I don't think the sky is falling yet. If I burn anything other than solid wood, I keep the doors closed on the heater.

I have had one fire in the shop. The bit on my CNC got too hot and lit up a piece of plywood on the machine. I was close by and put it out quickly. Nothing to do with the heater, but you still need extinguishers and some common sense. The pot of water on the stove helps with the dry air. Anything that makes heat will remove moisture.

From the original questioner:
I wondered about an add-on wood furnace, enclosed in a metal shed, with duct work going to and from the shop.

From Gene Wengert, forum technical advisor:
Foggy air at around 40 F that is brought into a shop and heated to 68 F will be at around 35% RH and 7% EMC.

From contributor J:
That's exactly right, it has nothing to do with what type heat source you have, it's the air expansion from heating it. Air expands a lot when heating it. The humidity doesn't leave, it just gets displaced into a lot larger volume of air which makes the "percentage" go down.