What amount of BTU do I need?

[83trekker]

I have a 23x26 garage, 10ft walls, 13 ft ceiling because of scissor trusses I had installed. R12 walls(2x4) r40 in the roof, insulated 16x9 door, good windows, insulated man door. I was just wondering what the lowest BTU over head furnace I would need for an area like mine? I might have a line on a Lennox, just waiting to here back what kind of BTU it has, but it’s not a very large one. I would like to keep the garage around 3 degrees Celsius all the time to keep my paint and other liquids from freezing. Then turn it up when I’m out there to work. Just to keep in mind I also have in floor heating too, but that won’t be running this winter. So next winter ill have both going.Thanks

 

[Junkman]

You need to have a heat loss calculation done on the building to know exactly what you will need. R12 in the walls isn't much at all for your area. I would have used 2 x 6 construction and R19 in the walls where you live, but that is academic at this point, since you have already built. If you haven't finished the inside walls, then I would consider building another wall inside, and increase the insulation factor. It will be more expensive, but you will save the cost in heating expenses for years to come. Have a heating contractor give you a "bid" on a furnace and let them do the calculations. Buying a heater that is a good buy doesn't make any sense, unless it is large enough to do what you need. Anything less is just wasting money. Do it right once, and you will never have to do it again.

 

[83trekker]

Here is a quote in a post below, “75k btu will heat a 1000 sq. garage easily”. I’m not looking for a an exact science for what I need, just a general kind of guestimate. Just because I’m in Canada doesn’t mean it’s that cold here. Yesterday was 40 Fahrenheit. That’s not too bad above freezing for 2 weeks before Jan. We get Chinooks here all the time, our winter is not that bad. We get 2 to 2/12 weeks out of the year that’s is absolutely freezing then it goes back to semi mild again for the majority of winter. We are easily a lot warmer than a lot of the states that get winter. You hardly see 2x6 wall constructed Garages in Calgary, even my house is 2x4.

 

[MXtras]

Here:

http://www.hearth.com/calc/btucalc.html
(this one does only 8' ceiling)

Or try this one:
http://www.heatershop.com/btu_calculator.htm

Or this one:
http://67.114.233.34/cgi-bin/lansaweb?procfun+CW@MISC+BTUCALC+PRD+ENG

Or maybe this one:
http://herman-nelson.com/btu_calculator.cfm

Or even this one:
http://www.woodstove.com/pages/btu.html

Scott

 

[83trekker]

Thanks GUY!

 

[chrenan]

Trekker,

I'm in Edmonton, I have a 22x28 detached garage no windows, 2x4 8' walls, 2x6 ceiling joists, walls and ceilings are insulated and drywalled. R12 in the walls, R19 in the ceiling, double layer of R19 along the outer lengths of the roof space where I don't have a flooring to store anything.

I have a 45,000 BTU Superior gas radiant heater, I keep the garage at 5 C when I'm not there, and just crank it up when I am working. 45K BTU is plenty for me, heats up quickly. I'm not sure if it would be the same situation if you used forced air, and of course your higher ceilings would require a bit more BTU.

Chrenan

 

[Vincent Vega]

I have a 24x24. I have a 18k vent free propane heater. R12 walls R19 ceiling. I can get it up to 55. Plenty warm for me. I don't spend too much time out there when it is this cold. It's just nice to get the chill out and my tools warm enough to handle.

 

[hammlm]

I'll chime in. I'm in PA, not too cold here.

It's been in the high 20s and low 30s lately.

I have a 1220sf garage with living space above. I have R-30 in the ceiling, R-19 in the walls. Insulated garage doors, but I've come to think that's a bunch of hooey. Several windows, a couple of regular doors.

I run a Mr-Heater (good sale at Northern) 75K BTU hanging in one corner.

I keep it about 57. It runs once or twice a night, for about 5 minutes. When I go out there, I crank it up to 62 or 63 if I'm working. It runs several times in the first couple of hours to get up to temp, and then settles down. The slab is about 56 degrees, I think that helps a lot.

When it runs, it gets wicked hot, wicked quick. I think even with a moderately insulated garage with normal height ceilings, at your size, 75K would be too much. I think I would have been fine with the 45.

Matt

 

[Kevin54]

I have a 28' x 36' garage with 2x4" walls / R13 and R30 in the attic with 8 1/2' ceilings. I put in the furnace out of our house which is a 75,000 btu. I keep it turned down to 50F unless I am out there. When I am I kick it up to 75 and it heats up in just a few minutes. I could have probably gotten by with a 45,000 but this was a freebie due to putting a new furnace in the house. Besides that, I would rather heat up fast and shut off, than overwork a smaller furnace. I think something along the lines of a 45,000 would be working harder and then you have the risk of cracking the heat exchanger or shortening the lifespane of the unit.

Kevin

 

[scottr]

I have a 23x26 garage, 10ft walls, 13 ft ceiling because of scissor trusses I had installed. R12 walls(2x4) r40 in the roof, insulated 16x9 door, good windows, insulated man door. I was just wondering what the lowest BTU over head furnace I would need for an area like mine? I might have a line on a Lennox, just waiting to here back what kind of BTU it has, but it’s not a very large one. I would like to keep the garage around 3 degrees Celsius all the time to keep my paint and other liquids from freezing. Then turn it up when I’m out there to work. Just to keep in mind I also have in floor heating too, but that won’t be running this winter. So next winter ill have both going.Thanks

I have a slightly larger footprint (34 x 20), with essentially the same insulation ratings in walls/ceilings. Also have the R14 garage doors. You do have a higher ceiling however.

I have an ADP CAYENNE rated at 45,000 BTU and it works like a charm. I keep the garage at a constant 50 deg., and it only takes 5 minutes to warm it up to 70 deg. when I am working out there. Takes about the same amount of time to recover from opening the garage door. Cycles seem o.k. (doesn't come on too often).

I personally can't image a significant benefit of the 60,000 or 75,000 BTU unit although lot's of guys have obviously gone this route. My 2 cents worth....