BTU calculation questions

[PushnFords]

I bought a house a few months ago with a 25' by 25' garage with 8' ceilings. According to the BTU calculators I've used online I'd need approx 28,500 BTU's to increase temps 50 degrees. Here in KS we get some weather around 0-10 degrees & quite a bit of wind. Normally I'd keep the garage between 45-50 degrees when I'm working...but occasionally I'll need to go warmer for painting. Also the ceiling is not solid...every other rafter has a ceiling board and the others are open for access to storage in the rafters.

With the added space of the rafters and a double wide garage door would I be better off getting a 45K BTU heater? I've been looking at the hanging forced air units.

 

[dave67fd]

We may be better able to offer some suggestions/opinions once we know "if" or "how well" your space is insulated. Gas heaters listed BTU is rated input. A 45,000 btu listed FHA heater will "output"~36,000 btu's.

If you do alot of painting, consider a heater with a seperate combustion chamber.

Regards

 

[PushnFords]

The walls & ceiling have R19 fiberglass insulation. The walls are getting OSB put up instead of Sheetrock. One small north window & one newer steel door both in good shape. South side has an uninsulated 10' garage door that I will either insulate & seal or replace.

 

[ishiboo]

That's a lot of insulation in the walls, good work!

Unfortunately it seems the ceiling needs some added.

 

[dave67fd]

That's a lot of insulation in the walls, good work!

Really? Pretty much standard for a 2 x 6 wall as far as im aware.

The walls & ceiling have R19 fiberglass insulation.

R value in your ceiling seems a bit under par for your location but the 45K unit should be more than enough.

 

[PushnFords]

Really? Pretty much standard for a 2 x 6 wall as far as im aware.



R value in your ceiling seems a bit under par for your location but the 45K unit should be more than enough.

He said that because I mistyped & said I had R29 when it is actually R19.

Guess I'm not sure how I could do much better on the walls. It is 2x4 framing so only have that much space to fill. I guess I could do a layer of sheathing but that isn't a huge difference. Where my rafters are open to the room I can't put in blown insulation but I may look into adding something more or getting spray foam.

Is 45k too much or would I be better off going with 30k?

 

[Danno63]

I used a 10K BTU kerosene heater in a 588 square foot garage with R19 in ceilings, R13 in walls, and an insulated 16' garage door (21X28 feet garage). I heated nicely, it was just slow. That heater would lift the temp about 40 degrees when there was no wind. I think a 30K heater would probably do it for you. I am just now installing a 17K BTU (5000 Watt) heater in there since kerosene is harder to find and expensive. I want to go with a higher BTU to warm the garage quicker. The 5KW heater will cost $0.50 an hour to run, so I will use it judiciously. My garage refridgerator is freezing the veggies so I want to keep the garage above freezing. This is the first year in a while the garage has actually gotten below freezing. It has gotten close several times, but now it is time to add some more permanent and convenient heating. Good luck.

 

[dave67fd]

Have you made a choice or looked into either gas or electric regarding costs in your area? A 45k FHA heater maybe a bit borderline but should be ok. You don't want to be too oversized to avoid excessive cycling. If you have 240V with the available current a 6-10k watt heater may suffice.

Best to avoid a non vented heater to avoid excessive CO and moisture.

Northern Tool is a good popular source for heaters.

http://www.northerntool.com/shop/tools/category_heaters-stoves-fireplaces

 

[PushnFords]

Have you made a choice or looked into either gas or electric regarding costs in your area? A 45k FHA heater maybe a bit borderline but should be ok. You don't want to be too oversized to avoid excessive cycling. If you have 240V with the available current a 6-10k watt heater may suffice.

Best to avoid a non vented heater to avoid excessive CO and moisture.

Northern Tool is a good popular source for heaters.

http://www.northerntool.com/shop/tools/category_heaters-stoves-fireplaces

No I haven't made a choice yet. Mainly looking at the forced air gas heaters because there is an old one there already so the mount & gas line is in place. Our electric is pretty high...and I'm trying to keep from maxing out my electrical service to the garage. I'll also have an air compressor & powder coat oven running.

I'm still working on the walls too. The R19 fiberglass insulation fills the walls so I'm not sure how I could increase that unless I put a layer of the rigid foam insulation under the OSB. I know it would be nice to have better insulation in my roof but I think to do that I'd need to enclose the attic area and put a layer of loose fiberglass up there. But...I really need to keep that storage space available. So....

 

[dave67fd]

The R19 in your walls is fine, it's the ceiling that will benifit from the increase. Is the old heater operational? If so have it properly cleaned and serviced and have your service guy evaluate it. If it runs well and is sized properly you may not gain much if any in efficiency with a new one. If it's NG it's a no brainer. Propane is most likely a benifit over elec in your area as well.