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What to look for in new doors

Doors, too, offer a wide range of choices for materials, finishes, and insulation.  As with windows, the ENERGY STAR® designation and the  NFRC label will tell you the energy efficiency of a particular door. U-factor  is the most important consideration for doors; a rating of 0.30 or  less is recommended. Keep in mind that the more glass area in a door,  the lower the thermal performance.

Door Features

Several features contribute to the ENERGY STAR® and NFRC ratings, including:

  • Insulated steel. Commonly made with a steel face and filled with polyurethane insulating foam—with a U-factor as low as 0.17—these doors can exceed the energy performance of a wood panel door considerably. They usually come prefinished and prehung in a weather-stripped frame.
  • Wood. Although the traditional wood panel door has the benefits of less expansion and contraction than steel doors, it also has a relatively poor thermal performance (U-factor of about 0.50) and has higher maintenance requirements.
  • Insulated fiberglass. With the thermal advantages of an insulated steel door, fiberglass products usually have a wood-like appearance and are paintable and stainable. In addition, they have less expansion and contraction than steel doors.

Pay attention to the bottoms of doors

The bottoms of doors, unlike jambs, are subject to wear and therefore the weather-stripping must be more durable. There are two ways to strip this area: by using a threshold or by attaching a door bottom or sweep. Some thresholds will adjust to accommodate different clearances, but others will not.

Door sweeps require no clearance, because they attach to the side of the door. Thresholds are generally installed to replace existing worn out ones. Often only the vinyl or rubber weatherstripping is defective, not the entire assembly. Check to see if new inserts can be purchased separately. If the whole threshold must be replaced, select one with replaceable gaskets.

Door bottoms or sweeps are usually installed on doors with no existing bottom weatherstripping. They are installed flush with the floor or threshold of the existing sill to provide a positive seal against air movement. Select a sweep that can be adjusted to compensate for wear or movement due to dimensional changes from temperature fluctuations.