Hi Gang,
I’m working on a new shop building, 25×21 ft main space, with adjacent 25×11 auto bay that will be heated occasionally. Walls are 6-inch structural insulated panel (SIP), about R-21 and we will be putting in good ceiling insulation too. Initial research suggests that 20,000 BTU would be more than plenty. Does that sound reasonable based on y’all’s experience? We’re in Ann Arbor Mich., so we get a real winter (most years).
Are there any particular brands or manufacturers to look for (or avoid)? Thanks!
Ted
Replies
Ted: There are calculations for heat loss based on insulation value, square feet, outside design temperature. Might be better then a guess, though 20k sounds about right. What about windows and doors? They get plugged into the calculation somewhere. As far as equipment goes I like Graingers Dayton brand. They stand behind it and are great in terms of locating units and/or parts.
Gee, wish I was building a new shop building. View Image
I has no foundation, just sits on the dirt. Kinda like me :~) Duke
"... Buy the best and only cry once.........
Tedly,
I just finished a 600 sq ft shop in AR, had air conditioning with some heavy filtration put in, but did not bother about any heating. We drop down to 15 F on occasion, but will normally be above 20F so it's not as bad as where you are.
My rationale is that I don't live in the shop and when I'm in there I normally do physical work, so a sweater and 50F is quite comfortable.
For a reasonably insulated shop, you can work on around 1000 Watts per 100 sq ft. if you want the ability to heat up to 80F with outside temperatures around 10F. In a newly built home, using latest insulation materials, you can work on around 600 Watts per 100 sq ft.
Everyone here at home thought I was joking when I purchased two 1500 Watt heaters at Lowes for just over $6 a piece. With an outside temp at 21F yesterday, these two heaters kept me above 53F and in the afternoon at 40F outside I went up to 76F inside.
So in conclusion, with two heaters, each putting out less than a hair dryer, I keep my shop comfortable.
Edited 1/29/2007 11:57 am ET by Willie
Wille: No problems with moisture? My shop is only heated when I'm in it so I've had some problems. I keep cast iron waxed and have a heater under the tool cabinet where the planes, router bits, hand saws, measuring items etc. are. I mostly use propane and occasionally a 3kw electric heater. My power costs are very high with electric going for $0.12 kwh for the first so many and going up rapidly from there.
Duke"... Buy the best and only cry once.........
Duke,
Those $6 heaters from Lowes are actually electrical, with an element and a fan, so no moisture problems.
I can uderstand the pain with electricity costs, we don't have that here fortunately, it's actually cheaper than gas, most homes use electrical clothes dryers.
With all the wood scraps we produce, a wood burning stove sounds appealing in your situation.
Check out the Reznor UDAS series of gas/propane unit heaters. They are "direct vent" using outside combustion air which is a real plus if you are sanding or finishing. I recently installed one in my new shop and it's proving efficient and economical to operate.
Rick
Is the advantage of the Reznor direct vent that they don't draw in fine dust or finish fumes to use for combustion air? The direct vent is around 50 percent more $ than an equivalent size Reznor model so it would have to have some significant advantage to justify it I think.Thanks to all for the advice, this is helpful.Ted
Ted,
Correct.....the advantage is that all of the combustion air comes from outside thus no chance of drawing any combustibles into the combustion chamber. Many (likely most) building codes now require this type so I had no choice when building a new shop....but I likely would have used this anyway as I believe in self preservation. In my mind that's definitely worth the extra bucks. A company named Empire also makes direct vent wall heaters which are, I believe, a bit less expensive. But in my situation I didn't want to dedicate any wall space to a heater so opted for the ceiling mounted Reznor unit.
Rick
Direct vent units do not use air from the room for combustion, but that does not mean that they are totally benign when dust or fumes are in the shop air.
The surfaces of the heat exchangers get very hot, probably around 400 degrees fahrenheit, maybe more, when they are on. Dust carried in through the unit's air vents while the unit is on will toast and give a definite smokey smell to the air. If the heater has been off for awhile, dust will settle on the heating surfaces and burn up the next time the heat comes on.
Paint fumes that get drawn over the heat exchanger will "crack" creating a really nasty smog in the shop, enough so that the shop will need to be ventilated just to be habitable.
I really like these heaters, I use them in both my home and my shop, but they are not without their problems.
John White, Shop Manager, Fine Woodworking Magazine
Ted
I, too, live in Ann Arbor. I have a gas fired, radiant heater that is the cat's pajamas. In fact, the cat wouldn't need pajamas with this kind of heat and no dust blowing around. If you would like to see my shop let me know.
Frosty
P.S. It does require some ceiling clearance though.
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