When we are building our log homes, we use a 75000 btu propane fueled salamander type heater, It has a blower, so it rquires a 120 Volt plug outlet. You can buy these at Tractor Supply, Lowes, Home Depot, Menards. Buy a 100# cylinder and your good to go...as you use it more you may want to upgrade to a house type furnace or ceiling mounted "Unit Heater" . I have a Reznor Unit Heater, ceiling mounted, 75000 btu, 87% efficient , I heat a 30x48 10' ceiling insulated and drywalled work shop. I have a 250 gal tank and here in Michigan it cost me with todays fuel $500 a year to heat my shop. I leave it set at 45 degrees, unless I am in it then its 70, thermostat controlled. I built it to use year round and I do...virtually every day. A whole LOT better than fuel oil or Kerosene type heaters.

I have used a old house furnace before in my garage, just put a Top Hat on the furnace and blow the heat out the top with a few 90 degree elbows. Old take out house furnaces can be bought cheap. You can find a 80 percent efficient take out for usually $100-200. These are either, propane or Natural gas fueled. Call any heating and cooling company and see if they have any take out units that someone upgraded to a 90 percent efficient unit. 90 plus eff. units will work too but they generate a lot of condensate...not airborn type. These furnaces usually have a gravity drain or a pump. I personally....would stay away from these, if you dont keep it heated all the time the unit has water in plastic areas that will freeze and crack. Unit heater in a shop is the way to go, 87% efficiencies , blower, clean...but new 50000btu units are $800 google... Dayton, Reznor, unit heaters.

Probably more than you wanted to know about heaters, but at least your now well informed.

 

alot of opinions here any heat source will draw moisture, any.Air circulation and ventilation are important for proper burn and for your own safety when using fuels.whatever you get hook it up properly and follow specifications.Propane leaks are MIGHTY dangerous when your tank is in an enclosed area.Just be careful of afixiation and burning your house down sh*t happens.

 

I walled off just enough to work in, then I use one of those pot heaters talked about before. If its not getting worked on, it stays in cold storage. Not worming up and cooling down every other day. I dont like to keep them cold, buts it better than hot/cold/hot/cold IMHO....

 

I have to admit, my 3 bay garage is insulated and has radiant heat in the floor.....Only problem is it takes several hours to get the heat up into the 60's since I keep it set on 54 while I'm not working in there...

 

I got an older moble home propane furnace out of the classifieds for $50. Ran the exhaust vent up through the roof and hooked up to a 100# tank. Blower was on the bottom and it works great for me.

 

I put in a 230 volt outlet purchased a comercial plug in electric heater. Set it on about 60 degrees and It keeps the garages warm. Takes a while to get going, but works great. If it is real cold (10-15 degrees out) I also have an infrared propane heater I use along with the electric heater to get going, then shut off the propane heat to avoid condensation. The propane tank infrared heaters really work great, they will heat a drafty airplane hanger when it is freezing outside. Almost no smell, burns clean.

 

If you plan on staying in your house for a while I would highly recommend installing a vented furnace in your garage. I put in a unit two years ago that hangs from the ceiling and vents out the wall after years of using a propane unit that fed off a 20lb bottle. It is by far the best thing I've ever put in my garage. I now spend most of my winter on projects in the garage.

You can look into insulating later down the road.
You'll need a gas line and electricity run to the unit and a vent through your outside wall.

 

I use a salamander and a stand up kerosine.
Run both.
Turn off the salamander when it gets toasty.
The Stand up unit can then keep it nice.

 

My garage is reinforced concrete below the house so it stays pretty warm all the time without a heater. But when I was a kid we used a wood stove and it heated up the garage great even during cold New England winters.

 

I use these situated hanging over my work area. Heat is immediate & clean.

http://www.grainger.com/Grainger/items/3WA99