This spring I'm starting a garage renovation and need to get some heat in there for winter projects. The garage is 13x24 and used mostly for motorcycle work. Currently the walls are insulated with R13 batt insulation As you are likely aware, this is somewhat less than ideal. I am guessing that it would be difficult to easily improve this.and part of the project will be to install a ceiling with R30 above R-30 would be adequate. I'll also be installing a man door in a side wall and a window Windows are one of the main sources of heat loss. Consider the size of the window and get a good performing version.in the rear wall since the only way in now is the overhead door. I need some advice on which way to go on a heater. Natural gas is not available in my 'hood so that's out of the question. Propane makes me a little nervous because of the ignition source and threat of fire. I think you are overstating the potential danger of propane. Tanks can generally be rented if you do not wish to purchase. I would also need a propane tank installed. I don't think I need a lot of btu's since the space is small and will be fairly well insulated. I live in PA with pretty cold winters and plan on keeping the garage around 45 degrees during the winter and bumping it up when I go out to work.
I do have 100 amp service to the garage as a subfeed from my 200 amp main panel. How much amperage is actually available from your shared 200A total capacity?
Any advice would be greatly appreciated.
For a continuously conditioned space, I would not consider any solid fueled devices, or kerosene units. Given your circumstances, I would limit myself to either electric or propane. Within that range however, are several alternatives.
Jackfre (above) suggests a direct-vented propane wall heater. A quick look at the cut sheets for that unit suggest an easy install, modulating output (which is not typical by the way), an "off hours" setback temperature of 38 degrees F which would meet your requirements, etc. The only questionable spec was for the "convection fan" (actually this appears to be just a squirrel cage fan - convection occurs due temperature gradients) which doesn't indicate much 'throw' for the unit, as well as relatively high leaving temperatures when the unit is on high fire. If placed on the short wall of your space, you will likely encounter some temperature difference at the far end of your shop.
This is just one propane choice. Many others are out there to consider.
As for electric, basic resistance heat is going to be an expensive proposition, especially with your current insulation, overhead door, etc. For discussion's sake, lets look at a 5KW heater for your application.
Using a common electric rate, $0.11/kwh, you are spending $0.55 for each hour operation of the heater. If we consider only the four coldest heating months (November thru February), and if we figure that the heater on average only operates 30% of the time ( a conservative number - likely to be higher), you will have spent about $480 in electricity, or $120 per month to heat the space. In my mind, this is excessive. [Disclaimer: This is a not a substitute for an actual energy analysis. The example given is merely for an illustration to prompt discussion]
As an alternative I would propose a thru-wall heat pump, particularly one that will function well at low outdoor temperatures. My shoot-from-the-hip guess is that the electric consumption would be less than half of the resistance heater, plus you would have the summertime advantage of cooling and de-humidification that you would not have with the other choices.
There are of course other considerations - how long you intend to utilize the space, utility costs for your particular area, energy rebates, your particular design conditions, requirements for air filtration, operations to be performed in the garage, etc.
Just something for you to consider.
Good luck with your project.
As always, offered only as opinion
