Good day:
On a current job we are designing we have 8140 CFM supply air. We also have 900 CFM outdoor air coming in. Upon doing our calculation for the mixed air temperature coming into the air handling unit, we arrived at 64ºF (heating side). This unit serves a field of variable air volume...
The builders that built your home, and those of your neighbors, may also be using the attic space as a way to vent the combustion air from the furnace or the water heater.
In the ASHRAE book of Fundamentals (1997), on page 9.14 it discusses the thermal environment and what is considered to be "comfortable" for the typical person. In the second column, first paragraph, it mentions "For a resting person wearing trousers and a long-sleeved shirt...