I'm in the process of designing a (approx) 40x60 pole barn that will be off the power grid. Our plan is to have a slab with radiant to heat it to about 45-50 degrees for 3-4 months in the winter. It will be used to store and maintain 2 large snowmobile trail grooming tractors. We may ad in a second zone for a future office/meeting room in one corner but the barn design is just under way. My part is to design (or conceptualize) the power and heat.

We will be running a propane generator to charge up batteries and then invert to our building for power. It will be remote on for the most part unattended. I may add some renwable energy sources but power is not important to this post other than what ever heating we instal must be very electrical thrifty.

I hope to be able to afford spray foam to seal up the envelope but we may have to go fiberglass. Maybe even SIP's for the walls if it's cost justifable. There will be at least 2 large garage doors (that will have to be opened to vent the CO from the deisel groomers while they warm up) and one entry door. Possibly a few skylights for passive solar heating (would it be worth it for the heat loss at night?)

We were originally thinking of going with a water heater (takagi or rinnai type) to keep costs down but maybe if we can get a mod con for 2-3k it will be worth it. There will be no water in the barn, and we will use anti-freeze since the heat will be shut off when the snow melts (but we can still freeze).

Any suggestions on where to start for components, especially electrically efficient designs?

Thanks
Steve

This message has been edited. Last edited by: SteveA,

skylights are a huge loss, not a net gain. passive solar design requires optimal window placement and mass to receive the heat.

heat source depends on heat load. If it's low enough, a pilot light and tank water heater might be your best bet. With an ECM pump you could potentially run the whole system on as little as 8 watts. If a heat source upgrade matters because your load is higher, then a mod/con would be a step up and as I just posted in another thread it's not too bad in power usage but killing the standby situation would be good. 30 watts standby.

Since you're off grid the cost of power is extremely high and heat high. That means the payback to you of containing heat is much more than someone who is on grid so I'd say the place to start isn't with your heating system but with your building design. A good envelope going to have a better payback than almost anything else you can do. Since infiltration is a substantial percentage of energy use I'd look seriously at how to reduce that to a minimum. SIP's would be worth investigating, but so would conventional construction but with very careful attention to sealing every last opening. There are books available on this exact topic from Building Sciences Corp.

Of course sealing a building that has overhead doors is going to be tricky and frankly I'm not sure exactly how to do it but I'd give it a try. Maybe a system where you button up a tarp or something to seal against leakage. Give it some serious thought.

My other observation is that you are only looking to maintain a relatively modest temperature. In fact it isn't much more than ground temperature. Do you have the possibility of building underground or into a hillside? Earth is a great insulator, very low infiltration and cheap.

As for passive solar gain, that is something that depends entirely on your local conditions. As you know glass is a terrible insulator (and expensive) so you need to have lots of sunny days to make it worthwhile. Even then if you don't need the sunlight (because it isn't living space) it is likely better to go without.

So bottom line is focus on minimizing the losses from the building. See how far you can push these down and then start thinking about kind of heat you're going to need.

Money spent on reducing losses will have much better payback than anything else given you are off grid.