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
typical R-values for different types of doors.
R-Values Of Common Door Types
| Single Pane Glass |
0.9 |
| Double Pane Glass |
2.0 |
| Hollow Wood |
2.0 |
| Solid Wood |
3.0 |
| Hollow Metal |
2.0 |
| Insulated Metal |
4.0-8.0 |
Infiltration 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 a magnetic type
of weather-stripping, 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 weather-stripping,
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.
