Storm or Thermal Doors

In addition to their obvious function of providing entry and egress to or from the home, doors also function as part of the thermal envelope or shell of the home. Like other components of the shell, doors are subject to several types of heat loss: conduction, infiltration, and radiant losses.

Conduction losses can be minimized in several ways, depending on the existing door type and the home's aesthetics. A wooden door can be made more energy efficient by adding a storm door. Like a storm window, a storm door works by creating an insulating air space between the storm and primary doors. A tight-fitting storm door can also help reduce air leakage or infiltration. If the primary door is fiberglass or metal with vinyl coating or trim, a glass storm door may not be the best option. Heat from the sun can be trapped by the glass and damage the plastic or vinyl. If a storm door is unacceptable for aesthetic or other reasons, installing an insulated metal door is the best option. Insulated metal doors have a core filled with either fiberglass or rigid foam insulation. They are more durable than wood and provide better security. The table below lists the R-values for different type doors.

R-Values Of Common Door Types

Filtration losses can also be reduced with an insulated or thermal door. Insulated metal doors do not warp, shrink, or swell with temperature or humidity changes. This means that they can be installed to a much tighter fit without interfering with their operation. They often incorporate magnetic-type weatherstripping, similar to the seal on a refrigerator door. Both of these factors combine to cut air leakage substantially. If a wooden door is preferred, a tight-fitting storm door, combined with good weatherstripping, will help.

Radiant losses occur primarily through glass. When possible, the use of glass in doors should be minimized or avoided. If glass is used, double-paned or double-paned Low-E glass should be considered.