Similar to windows, exterior doors experience slight heat loss by heat transfer
through the door structure itself; however the majority of the losses occur due
to infiltration (air movement) through the door seals and the opening and closing
of the door. The exterior doors installed in this house met the Energy Star
guidelines at the time of construction, ensuring that the heat losses will be
kept to a minimum. The doors for this home were special ordered with a wider
door jamb to accommodate the 9 inch thick walls.
To reduce the heat losses even further, an air-lock door system, utilizing
two doors in series that do not open simultaneously, could have been installed.
However, since the home itself was so airtight, the minimal infiltration through
the exterior doorways was deemed acceptable and beneficial to the number of
overall air changes per hour when compared to the additional cost of the air-
lock door system.
FIGURE 1: The locks are installed on the front exterior door.
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