I have been using a diesel heater in my work space. And I have an unheated room for cutting wood and anything else that
makes dust. I will be using the same heater to heat an oven that is built around the mold to bring the temp. up to 55C.
Also I have a small electric heated in a foam box to keep the epoxy resin at about 20C.
A note about my weather conditions, it very rarely goes below, -5C where I live.