Your Front Door Could Be The Hidden Cause of Constant Chills in Your Home

A metal door often functions as a radiator. Steel conducts heat roughly 300 times faster than wood, rapidly transferring internal energy from the living space to the hallway or the outdoors. Thermal imaging data shows that up to 40% of heat loss occurs through door assemblies and their adjacent wall sections. While the metal leaf is a conductor, the primary leakage point is typically the threshold and the gap beneath it. The heat loss mechanism at the bottom of the door is driven by a direct air channel. Unlike the top or sides of the frame, the threshold faces constant mechanical stress from foot traffic and furniture movement. This wear accelerates the breakdown of the sealing contour. Hinge sag compounds the problem. When the door leaf shifts, the bottom gap widens, creating a thermal bridge—a high-conductivity zone that allows heat to escape the apartment unchecked.