Another heater sizing question

[eyes11]

Here is the info:
1st garage is detached, 24x28, 672 square ft, 8ft ceiling, r13 walls and r 36 ceiling.
one insulated 16x7 door
central wisconsin winters
want to maintain around 40 degrees all winter with the ability to crank it up to 60-70
natural gas reznor

2nd garage is attached to home, 36x24, 864 square ft, 9ft ceiling r13 walls, r45 ceiling
One 16x7 insulated door one 7x9 insulated door
same heating expectations
natural gas reznor

From what ive been reading i think i can go with a 45k in the first garage and a 60k in the 2nd. My only worry would be these sized heaters in each garage cycling too much at 40 degrees.

One calc i did for each garage said i could get away with a 30k and 45k which i think i probably can for maintaining the lower temp but i worry about them being able to get it up to that 60 to 70 degrees on a very cold day.

Thanks for any input in advance

 

[Steevo]

I think you are spot-on with your estimate of a 45k for the 672 sq. ft. space and a 60k for the 864 sq. ft. space. More than minimum required, but not overkill.

 

[ForceFed70]

Agreed, I also think you've got it sized correctly.

 

[eyes11]

Thanks for the info

 

[toyotadriver]

Agree. Sounds about right.

 

[Electric]

My garage is more or less identical to your first garage, and our climates are probably quite similar. I wrestled with the 30 vs 45 decision and went the same way you did - I bought a 45 kBTU (input) 80% efficient Hot Dawg.

Maybe we will both have slightly oversized heaters together, but I don't think 45 is far off.