While exterior doors typically cover less area than walls, roofs, or windows, gaps around doors can allow significant air leakage. These drafts allow conditioned air to escape and outdoor air to enter, increasing heating and cooling costs.

Energy-efficient doors

When replacing an exterior door, choosing an energy-efficient model can improve insulation and reduce air leakage. Modern energy-efficient doors often include insulated cores made from materials such as polyurethane or polystyrene foam, which provide better thermal performance than older hollow doors.

When selecting a new door, look for products that have been tested or certified for energy performance in your region. Climate-specific ratings can help ensure the door is designed to perform well in the local weather conditions.

Air sealing and weatherstripping

Many door leaks occur around the edges of the door or underneath the bottom of the door. These gaps can often be identified by feeling for drafts, seeing visible gaps, or noticing outdoor light around the closed door.

To reduce air leakage:

• Inspect weatherstripping around the top and sides of the door. Replace weatherstripping that is cracked, compressed, damaged, or no longer creates a tight seal.
• Install or replace a door sweep along the bottom of the door to seal the gap between the door and the threshold.
• Apply caulk or sealant around the exterior door frame if there are visible cracks or gaps between the frame and the wall.

These improvements are generally inexpensive and can significantly improve comfort by reducing drafts and preventing conditioned air from escaping.

Glass doors

Sliding glass doors and patio doors can be a common source of heat transfer and air leakage because they contain large areas of glass and moving parts that can develop gaps over time.

To improve performance:

• Clean door tracks regularly to ensure the door closes completely.
• Inspect and replace worn seals or weatherstripping.
• Use insulated curtains, blinds, or shades to reduce heat gain during hot weather and heat loss during cold weather.

For many homes, improving the seal around existing doors can provide noticeable comfort improvements without the cost of a full door replacement.