What Size Heater for Garage

[1960Corvette]

I found this site and I was impressed with the knowledge base. I'm probably going to give too much information about my project, but it appears more is better than less from the threads I've read here.

I'm trying to determine the correct size heater to put in my garage. It's roughly 34 X 24 with a 10' ceiling and it has a side room that's about 120 additional square feet. I calculated the cubic feet to be around 9300. All walls are 2X6 construction and well insulated. The ceiling has 12" of blown insulation. The two doors are high-end with an R Value of about 13. There is one insulated outside access door and one double glazed window. The garage is attached to my home along two walls and most of the winter maintains at least 40 degrees. On cold days (like now, -15 to 0 degrees), it will come close to freezing and my guess is that the floor close to the doors is below freezing.

I'm going to install a natural gas heater that will usually be used only when I'm in the garage working - a couple times a week for few hours at a time, occasionally more. When it's really cold, I will likely use a thermostat to keep the temp at least 45-50 degrees.

Most sites I've seen that give advice on BTU requirements reference outside air temp and the desired degree rise in temperature. Since the garage maintains a decent temperature I'm assuming that the outside air temp isn't the primary factor but rather the minimum temperature that the garage maintains. That said, I could be completely wrong.

Given the (likely overkill) information I provide, what size heater would you all recommend? Also, are there any preferences on brands? Modine was one that was recommended, but I know people who have Mr. Heater Big Maxx heaters, too, and I'm sure there are a variety of others out there.

Thanks in advance for your input.

 

[stratoguzzi]

I see your in Minneapolis.Around 100,000 btus at least.A good hang from the ceiling Modine type heater is in order.Should heat quickly and maintain temp even on really cold days.

 

[Shop Specialties]

You should be more than good with 45,000-60,000 BTU.

 

[CNGsaves]

Sounds like your insulation and protection from weather helps keep your attached garage reasonable temperature.

Big 4 brands of hanging garage heaters are: Reznor UDAP (or UDAS for seperate combustion), Sterling Garage Guy, Modine Hot Dawg, Mr Heater Big Maxx. You'll need to determine whether you'll install with horizontal or vertical flue - - - thus, plan your install location accordingly.

Hopefully you have natural gas supply accessible just after meter that you could T off and run properly sized NG supply line over to garage.

I'd think that 60K to 75K Btu would be more suitable to your occasional needs, and maintaining normal temperature of 50 or 55 degrees.

 

[rodm1]

I think a 45 to 75,000 would be ok. I think the 45 will work hard to get to temp fast and warm up completely. This calculator bellow is a good estimate it has worked well for me. I would think you wouldn't won't to weight long for it to worm up.

Beacon/Morris is another excellent brand.

http://www.ultimategarageheater.com/natural-gas-garage-heater/search.php

 

[dave67fd]

I am using a 75k BTU Big Maxx (the newer model is the 80k) in my Insulated detached 28 x 38 x 10.5 in New England with great results. Good cost and great customer service.

All the Heaters "CNGsaves" mentioned are all good heaters. The Big Maxx is probably one of the more cost effective heaters of the bunch and can be had at Northern Tool for a good price.

As mentioned, research the location of the heater (typically you want it blowing toward your service doors or area of coldest air entry) and then determine the best location and type (vertical or Horizontal) of venting. Vertical venting is preffered and horizontal only if the vertical is not possible or practical.

Consider all your venting and gas piping costs as well as your code requirements in your town. Don't bypass your codes as it can be a matter of insurance issues regardless if you do a good installation. Many hang the heater and wire (elec and thermostat) and have a licensed contractor install the vent and/or gas.

Good luck.

 

[mygarageone]

Doesn't anyone believe. In doing a heat loss anymore . You can get heat loss calc's on the net now days , why not use them , rather then guess.

 

[jvitez]

Try this one:

http://www.dimplex.com/en/customer_support/heat_loss_calculator

 

[1960Corvette]

Thanks for all the input.

 

[blaperle]

As others have indicated have a heat loss caculation preformed. It sounds like a vary well insulated garage I would expect the load to be more in the 20 to 30k btu size. Load calcs are typically done with the location mean temperature rather than the extreme so its not grossly oversized for all other times.

Brian

 

[JPrato]

I'm just finishing a 32x45 shop with 16' ceilings in upstate NY. About 23k cubic feet. R21 in the walls, R38 in the ceiling, two 10x10 overhead doors (r-12), no windows and three insulated steel man doors. I installed a SunStar 50k BTU radiant tube heater down the middle. It will heat the shop but it's recover time is a couple hours to raise the inside temp from 35 to 50 when 10 degrees outside. 50 in the shop is not bad while active and you do have that "mini-sun" up on the ceiling giving warmth. That aspect also helps keep you comfortable while air temp comes up too. 60 would be nicer but with propane approaching $4/gal 50 is just fine, thank you. I would think a forced hot air heater would bring the temp up faster but with my high ceilings thought the radiant would be better overall. My plan was like you, to heat it only when I'm there. When really cold outside, I've been using my 135k BTU torpedo heater for 5-10mins when I come in as it will raise the air temp to 65 fast. It puts some moisture into the air and stinks a little but seems to take care of the need to quickly bring the temp up.

Maybe a 75k BTU heater would have been better? My 50k unit can be upgraded to 75k with a jet and restrictor plate change. I'll think I'll wait until the shop is all finished and I've used it for a while before I make any changes.