Q I have a remote thermometer in the attic. What should the attic temperature be, relative to the outside and house temperatures, assuming a new, supposedly well insulated house?
A Check the temperature an hour before sunrise.
In an ideal world, the attic temperature would be the same as the outside temperature. In reality, however, variables get in the way. For example:
Snow acts as an insulator. As snow accumulates, it alters the temperature profile of an attic and roof surface.
Snowpack on a roof, covering vents of any type, alters the airflow from ventilation, thus altering the insulating value of attic air and the temperature of attic air.
The roof assembly: shingles, roofing papers, framing and deck have thermal resistance and possess thermal mass.
The roof is a solar collector. Evidence is the sun melting snow on very cold winter days.
All of these -- roof structure, snow and air -- have "thermal mass," the specific heat capacity of the materials, the amount of energy absorbed or released, per pound, per degree of temperature rise or fall of the material. This thermal energy flow through the materials acts as a flywheel, slowing the rise and fall of temperatures.
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