Heater BTU question

[Rmeav8er]

I'm looking to add heat to my barn/garage and have researched till I'm cross-eyed and would like some help.

I bought the property last year and the barn is a 30x60 with a 13x22 extension off the side. It looks like a big L. With a square footage of roughly 2100 and 10 foot ceilings, what size BTU heater do I need? I was initially looking at infrared tube heaters but I don't think I can maintain the clearance required around the heater for the stuff in the barn.

In floor heat isn't an option since it has an existing slab and I'm not tearing it up. I don't have natural gas so it's either propane or electric. I'm pretty sure electric won't be cost efficient so I think I've narrowed it down to a propane forced air heater. I already have a 220 outlet in the top corner so running electric won't be an issue.

The barn does have a large sliding door on one end that is roughly 8 feet tall and 14 feet wide. It's not insulated but I have done what I can to seal the gaps. The walls are 2x6 and insulated but I don't know the R value. I assume the ceiling is insulated but it's finished and the loft above is as well. The loft stays cold with no noticeable heat coming up from above. There are 10 total decent sized windows on the walls.

The temps at night here in upstate NY have been about 0 degrees and the barn hasn't dropped below 35. Last winter when it was down to -35 outside, the barn never got below 20. I can run a small portable torpedo 55,000 BTU heater and get the temps up to 50 in about an hour to an hour and a half.

I would like to keep it at about 45 all winter and then be able to turn it up to 55-60ish when I want to work in there. How do I calculate the BTUs I really need? I was originally thinking 100,000 to 125,000 but after reading others posts, I think 65-80 might make more sense since I don't want to short cycle it.

 

[6768rogues]

I am near Rochester, NY and I have two buildings, one is 1800 square feet and one is 2400 square feet, with 14 foot ceilings and moderate levels of insulation. Each has a Reznor 100K BTU hanging natural gas heater and they heat easily. To maintain 45 degrees they run occasionally and the cost is not much. If I want it warmer, either building will be noticeably warmer within 15 minutes of turning up the thermostat. That makes the heaters run often, because everything in the building including the floor has to warm up. Before I retired, I would come home from work and turn up the thermostat. Then I would go in the house and change my clothes and look at the mail, and return to the barn to find it warm.
You said upstate, I am upstate but there are places that are further upstate than I and a lot colder.

 

[Rmeav8er]

Thanks for the info. That’s what I was originally leaning towards and I think that may be the size for me. I try to work out there several evenings and the quick temp increase may be worth the little extra price.

I’m slightly more upstate than you are. I’m in the Watertown area, right in the lake effect snow belt


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[TractorJeff]

My guess is in NYS it would NOT be cost effective to use electric heat!
Your post indicates you want to heat it all the time.
A suggestion would be on that big door if it is limited access is to put a false wall insulated of course in front of it.
A big quilted moving blanket would act as a barrier to the cold.
If you heat the building, then go outside and shoot that door with an IR Camera you would see it glowing from the heat loss!

 

[ForceFed70]

It's hard to say without more info, but I'd be looking at 100k or even 125K units. That's a large building. You might want to look at installing 2 smaller heaters to get better heat distribution. Otherwise, definitely plan on investing in some ceiling fans or another way to help circulate that air.

 

[Rmeav8er]

No, electric isn’t cheap. I do have a large solar panel array that was installed a couple months ago but I’m still using more electric than I’m producing.

I thought of trying to build a false wall but that door is how I get my tractor and vehicles in and out to work on them. The doors are sliding so I can’t build them up. I’m thinking of putting one inch foam board insulation in between the 2x4s to try to help with the heat loss.

I think I may start out with a 100k unit and add a smaller unit in the smaller portion if it’s not enough heat.


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