Heater sizing question - I'm close and need some advice

[TheGunCollector]

Trying to get my NG line plumbed in so I can finish my shop.

Live in Western Colorado.

I have a 37 x 28.5 garage with 11' ceilings. R16 walls. R30 Ceiling. 3 overhead doors - 1 10 x 12 , (2) 8 x 9. One entry door from an unheated garage above.

Ran my heat loss calculation and came up with 50,522 btuh needed.

I'm in the garage 3-5 evenings a week for 1-3 hours and sometimes on the weekend. I'd like to keep the garage heated to 40ish(constant and bringing it up to 60-70 when I plan on being in there working) in the winter to be able to keep certain paints & chemicals from damage. The garage doors are facing west, and IIRC have a R value of R11 ( I plan to add an addition 1.5" of EPS foam to the door panels to increase that)

* There is a *slight* possibility that once I have heat in the lower garage, I might want to open the entry door to the upper garage to bring heat up there. I'm assuming that the heat would follow it's natural path upwards and heat the upper garage pretty well?

Should I be even considering a 45,000/50,000btu heater, or should I be looking at a 60,000 or just go for the 75,000 and be done?

Thanks!

 

[dairdvl]

first off, what type of heater are you looking at? a ducted or suspended like a Reznor? not that it matters im just curious . i would recommend the 75,000 btu. i have a Reznor 100,000 btu input 88,000 output and love it. my garage is pretty close to what you have. and i keep it at 40 when im not working in it
don't forget you have to heat everything in the garage not just the space

 

[TheGunCollector]

first off, what type of heater are you looking at? a ducted or suspended like a Reznor? not that it matters im just curious . i would recommend the 75,000 btu. i have a Reznor 100,000 btu input 88,000 output and love it. my garage is pretty close to what you have. and i keep it at 40 when im not working in it
don't forget you have to heat everything in the garage not just the space

Thanks.

Suspended. Either the Hot Dawg or Big Maxx due to ease of getting parts locally.

 

[jvitez]

If your heat loss calc is 50,000 btu/hr, a hanging forced air NG heater is 80% efficient, so you'll need 50/.80= 62,500 btu/hr input to equal 50K ouput. So I'd look for a 60K heater, especially if you want to bump it up at times.