"Ed Hayes" wrote in message

This winter I would like to build them a place where they can stay
which will keep them relatively warm.
I can easily build them a small house and put a blanket in it but I
would like to insulate it and maybe add heat.

Proper sized door and some insulation and they will be plenty warm. Look up
the thread about heated dog houses here a while back, maybe 2 to 4 weeks
ago.