BTu sizing for pole barn

[jim7]

I am getting crazy different answers from online and installers on what I need for a hanging unit heater.. here is what I have

30 x 64 pole barn
10 foot ceilings
R19 with vapor barrier in walls
R39 with report barrier in the ceiling
Interior is all covered in metal same as the outside
Center Ridge vent on roof
4 winows on the left side windows and 3x4 feet
Standard service door in the front
18 foot garage door also in the front
I will not be going in and out or opening the garage door that much in the winter most access will be from the service door


Zip 60449 Chicagoland area

Might want to keep it at 40 when not used but 70 when used
I would like a decent recover time but don't want to over size and short cycle
I have gotten estimates from 45000 to 300000 btu to do the job.. only the distributors have access to the software to figure this out and they are the extreme answers... one say 45000 and other events says 300000
Please help
Jim

 

[D45]

Jim

I assume you will use natural gas to heat it?

100,000 sounds good

 

[Done That]

You can use HVAC-Calc for $49 to do your own load calculation if you really wanted to go that route.

Not sure your budget, might want to consider a 2-stage unit. The Modine ones are 50%/100% firing rate. Get a little flexibility that way.

 

[zmotorsports]

I recently completed my 50x60x16 but only 40x50 is heated (all of it insulated though) so almost the same square footage as yours @ 2000 ft2 but my ceiling height is quite a bit higher @ 16'. Insulation values are very similar to what you stated, R19 walls, R39 ceiling but only two 4-0 windows a man door and two 12' wide by 10' tall insulated doors. When my GC and I calculated it out playing with a few variables I was just over 100k btu, if memory serves in the 105k-115k range. There was a bit of a price jump between the 100k btu heater and a 125k btu heater but very slight bump in price to go the next step up to 150k btu. I too was worrying about short cycling but was told it was not enough of a jump to affect that, had I gone more like 200k plus it would have been more of a concern with my size cubic feet.

I also wanted a fairly quite recovery time as I do open my shop doors to pull vehicles in and out so I knew my door(s) would be open for short periods during the working time in the shop. I think you will be fine around the 100k range but there are some on-line calculators to assist you with your figures.

I ended up going with the Reznor UDAT 150 and it is a surprisingly small package, not much larger physically than my 75k btu Hot Dawg in my last 1150 square foot shop.

 

[engineer2]

A very rough estimate is about 10,000 BTU per 10x20 car space. That would put you at about 96,000 BTU. This is for upper midwest winters and good insulation.

Another way to look at it: many homes that are 2000 sq ft have a furnace that is around 100,000 BTU.

You might consider 2 heaters in opposite corners for more even heat distribution and redundancy. Ceiling fans help too.

I'm sure there are online guides. Maybe the pole barn manufacturer has some info too.