Warm-up/cool-down cycles provide a secondary
advantage in times of extreme weather. Should the heating
and cooling equipment be unable to maintain the setpoint
temperature due to a lack of capacity to condition
the ventilation air because of its extreme temperature, the
warm-up/cool-down cycle could close the outside-air
damper and reduce the volume of outdoor air until interior
conditions were restored to near the setpoint. Since
the system would run continuously in either case, this
procedure technically doesn’t save energy but it does
maintain thermal comfort without expending additional
energy.