There are a number of concerns that a cold climate creates relative to air baths. All of these concerns are resolved by making certain the ambient temperature of the air your blower is drawing from is room temperature or higher all year round.
Many people fail to think about the placement of their bath relative to exterior walls, pipe chases and other air spaces that can get very cold during late fall, winter and early spring in cold weather climates. If these concerns are not thought through before installation they may end up with a bath that has been placed in a setting where the air underneath the bath is frigid during these seasons. This will result in the actual bath fixture being cold when not in use making it difficult to get warm and keep warm. It will also result in the blower motor heating element becoming nearly ineffective and blowing cold air into the bath. In worst case scenarios it can result in pipes freezing.
The first solution is to properly insulate all exterior walls and pipe chases with a non-friable insulation before closing in your bath. A properly insulated air space will result in the air beneath your bath being far warmer than it otherwise would be. Your bath will be easier to heat and keep warm and the blower motor heating element will work as designed. The second solution is to relocate the blower motor to a closet where the air temperature is room temperature. Blower motors can be as far as twelve feet away from the bath. The advantage here is two fold. First, the blower will draw warm air and heat it as designed before delivery to the bath. The second advantage is quick and direct access to the blower motor should it ever need service.
Please discuss these concerns with your installer before beginning the project and again before the bath is enclosed.