NG garage heater sizing

[Electric]

I put a logging thermometer in the garage for a month. On the coldest night, the difference between what I want the temperature to be (15 Celsius), and the measured interior temperature, is 25 Celsius.

The garage is 20x18x10 ft with one wall shared with the house. Garage doors are insulated, side walls and ceiling are not but they are drywalled. Exterior walls are brick.

I am leaning towards the smallest Modine heater, which is 30 000 BTU. Does that sound reasonable?

 

[The Cobbler]

I have a 17x23 well insulated.r20 walls & 2 50 ceiling . MY hvac guy told me to get a 30k heater. It's not installed yet but other threads on here indicate it will do the job

 

[CNGsaves]

OP . . . . to get best GJ advice, need to know WHERE you are located.

Update GJ Profile with a Location.

You may get by with the 30K Btu heater, but if you don't plan on insulating and you're in cold climate year-round, I'd say go with 45K or 50K Btu heater instead.

 

[Electric]

...need to know WHERE you are located.

Eastern Ontario, on Lake Ontario.

My main problem is that the calculators I can find, refer to a rise from the exterior temperature to the desired inside temperature, and they use a factor based on material (insulation) properties.

But I know exactly the interior rise I need because I have measured it. I also know the exterior temperature that night (it was -29.9), but it seems more direct to calculate using the interior rise.

I am certainly able to tear down the existing drywall and insulate. Also, to blow in cellulose in the ceiling. But I would have to convince myself that I would break even on the capital cost within 5 years, and I'm not yet convinced that's the case.

 

[Showkey]

There many calculators to figure the insulation pay back........but.........it's a no brainer. Insulation is critical just based on fuel cost, comfort, ice dams etc etc

 

[bczygan]

Do a heat loss calculation.

And please put your location in your profile.

Here:
http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm

You ARE going to insulate.....Right?

Bill

 

[Adk Mike]

Modine Hot Dawg HD45 is what I would get . I have one in my shop 20 By 25 With a 10 ft ceiling. Insulated. The unit is just right. We have a simlar climate.

 

[bczygan]

I put a logging thermometer in the garage for a month. On the coldest night, the difference between what I want the temperature to be (15 Celsius), and the measured interior temperature, is 25 Celsius.

The garage is 20x18x10 ft with one wall shared with the house. Garage doors are insulated, side walls and ceiling are not but they are drywalled. Exterior walls are brick.

I am leaning towards the smallest Modine heater, which is 30 000 BTU. Does that sound reasonable?

Rough idea figuring my location is 40,000BTUH output
So a 50,000BTUH input at 80% effic,

Bill

 

[bczygan]

The advantage of the calculator linked to above, is you can change the parameters and see the savings from the change in the yearly cost at the bottom.

It is based on a 70 degree F interior temp.


Bill

 

[Electric]

Do a heat loss calculation.

Here:

Again, I am not looking for calculators that use crude insulation and air leakage factors, for the reason I posted above.

You ARE going to insulate.....Right?

Likely not. The heater will only be on from about 01h00 to 07h00, for 4 months per year. Like I said, I would need to get the capital cost of insulating back through gas savings within five years and I don't think it's reasonable to expect that. The cost of the 45k BTU heater seems to be the same as the cost of the 30k BTU heater.

Modine Hot Dawg HD45 is what I would get . I have one in my shop 20 By 25 With a 10 ft ceiling. Insulated. The unit is just right. We have a simlar climate.

That is great input, thanks.

The advantage of the calculator linked to above, is you can change the parameters and see the savings from the change in the yearly cost at the bottom.

It is based on a 70 degree F interior temp.

Again, uses crude parameters and my setpoint is 15 degC (actually there is margin there, I am planning to use 8 degC or so). But thanks for your posts.