makeup air *

[donhossinc.com]

A friend of mine has a home on an acre lot which has an out building that is 20X30 feet; cement floor, shaped like a quonset hut but only 8 foot ceiling, and completely insulated and vapor barriered (tight construction). His son is going to run a wood working shop out there and I’m wondering how to heat the place with so much dust around. This is in Southern Ontario Canada where a gas appliance would be used for heating. Cooling the building likely would not be required although the option would be nice. Due to the dust, is a heating unit that that conditions 100% outside air, and not recirculated air, a good * Could the heating unit sit on the ground * If I set aside 4 square feet inside for an indoor heating appliance, would that make more *

[juster]

I would think that 100% OAT is a nice to have but not required. If you did have a 100% make up unit, it would cost a fortune to heat the space. A gas or electric forced air furnace with proper duct filtration would be fine. Will need to check the filters often depending on the amount of dust and how often the heating unit operates. Having a fresh intake duct with a damper, would allow a % of fresh air in the space. Of course if you are using a gas furnace or appliance you will need a fresh air duct close to the unit for combustion reasons.
Supply and return ducting along the floor on different sides of the room. You may want to duct the supply along the length of the building for a more even heating distribution. You may also want to install two ceiling fans with speed controls to keep the over all space temp even.

[donhossinc.com]

What filter is recommended for fine wood * You know, to keep the heat exchange surfaces from building up wood dust. I don't know if this makes any difference to your recommendation, but here in Canada, as of December 31, 2009, the minimum efficiency for natural gas burning furnaces is 90 percent AFUE. We can't get mid efficiency furnaces anymore, unless we go cross boarder shopping into the USA. Lets say I put in a condensing furnace in that wood shop, considering all the fine wood dust, it wouldn't be a good idea to go with the cheap fiber mesh filters right.