Why Composite Doors Let in Cold Air—And How to Fix It Fast Composite doors are praised for their energy efficiency, strength, and style. However, if yours is letting in cold air, it can be disappointing—especially after investing in a high-quality door. Cold draughts are more common than many expect, even in well-fitted composite or patio doors. Often, the issue lies in poor installation, worn seals, or frame misalignment. Identifying problem...