- Q.Some hvac contractors in
this area of Virginia size cooling systems using an
indoor design temperature of 78ºF. I’m
under the impression that a system should be designed
for an indoor temperature of 75ºF. Is there a
standard interior design temperature for cooling
systems?
A.Martin Weiland, manager
of technical services at ASHRAE, responds:
Both the ASHRAE residential load calculation method
described in the 1997 ASHRAE Fundamentals
Handbook and the ACCA Manual J are
based on an indoor temperature of 75ºF. I
am not aware of a system-sizing method that uses a
78ºF indoor design temperature.