Hi,   Many of us have integral garages. My architect just assumed that we would use a fire rated internal door between the house and the garage.   The door has to achieve three things though - fire resistance, security and insulation.   Insulation - The garage and garage door are insulated and in my current house that tends to keep the garage temperature above 10C even when 0C outside. Thus the temperature differential between the two sides of the door will be low s