If you must keep him confined to a crate while you are working you might try to place the crate in direct light from a window, and open the blinds so he at least has some direct/indirect light.

I agree with Jack, but SGC raises an excellent point. Your pup most likely hasn't developed the coat to help him deal with those temps while being kept inside.

And -15 is no joke, so stick with what you know, just try to get him as much sun as you can.