how many BTUs - new member

[whholder]

Hi folks,
I realize this newbie question probably has been answered, but I can't find it. Not very good at forum board navigation.

I am having my garage remodeled. Body past of the point of being able to do it my self.

Going to install a gas heater on the ceiling or wall, but have no clue on where to start regarding BTUs, etc. Garage is 21x22 and 10 foot ceiling.

Garage is on the back side of the kitchen, so I am assuming that the gas heater can tee of the line to gas stove. I have a gas heater in the house, gas water heater, and gas stove as far as other appliances that will draw on the supply.

I want to have a thermostat that keeps the garage around 38 degrees during the winter. Looking at gas since I believe it will be cheaper to operate.

And that is the end of my knowledge related to garage heaters.
Have read some of the posts, sounds like there is wealth of information that I hope I can tap into.

Thank you in advance!!

 

[allinon72]

Using those calculations and assuming average insulation, you'll need just over 20k BTUs to maintain 38 degrees. However, it's likely you'll want to maintain a higher temp than that. Most gas heaters start at 45-50k and don't get smaller. You don't want to risk short cycling the heater. So you'll be looking at a combination of a higher temp and possibly downsizing the heater by plugging burners.

 

[The Cobbler]

first question is, how well insulated , how tight, is the door insulated? what about window(s)

 

[Shiftless]

first question is, how well insulated , how tight, is the door insulated? what about window(s)

Absolutely.
You can’t calculate the heat needed without all the info. Location is an obvious variable. My uninsulated and unheated attached garage never gets below 55. That’s because I live on the east side of the SF Bay only about mile from the water. And the common wall has heated space on the other side.

Even in a cold climate, if it’s well sealed and super insulated on the outer walls and ceiling, I bet that heat leaking through the common wall would keep it above 38 with very little extra added heat on the very coldest days.

 

[toyotadriver]

General location or which weather zone you live in is also needed to give a better idea.

 

[danski0224]

You are looking for the Goldilocks Number.

Not too many, not too few.

Just right.

There are plenty of online calculators for the information you are looking for.

 

[whholder]

Thank you everyone for your answers. As expected, more to this than I know. As part of my remodel, the garage will be insulated. I have weather stripping around the rollup up door. The man door to the backyard is pretty tight. Living in Utah. The average temperature in the winter is in the lower 30s in the day, in the teens at night.

 

[whholder]

and there are no windows.

 

[toyotadriver]

You will need to add together all the BTU draws of everything to see if you will exceed your available capacity. You may not be able to tap off the stove line if the line isn’t big enough for the draw of both the stove and the heater together.

I suspect a 30k BTU gas furnace would be plenty. That’s a SWAG but probably pretty close to what you need.

https://www.amazon.com/dp/B0153WVUM6/?tag=atomicindus08-20

You might also be a good candidate for a mini split heat pump given your area. I don’t like vent free heat but heat pumps typically have a hard time keeping up when the temps really drop so you could supplement with a small radiant propane heater when needed. A mini split assumes you have decent electric rates.