The heat loss due to thermal expansion and contraction of air will be quite minimal.
Thermal density (specific heat) of air is going to be ~1000x less than that of solid objects.
The specific heat of gypsum (the primary constituent of drywall) is 1.09 kJ/kg.K
For dry air it's 1.0 kJ/kg.K
Air's density is 1.225 kg/m3.
A 6m x 9m x 2.3m (20' x 30' x 7.5') room has a volume of about 130m^3, so a 10% exchange would be 13m^3, or 16kg.
That's about 15 kJ of heat energy per degree C, or roughly 0.0004 liter (0.0001 gallon) of heating oil equivalent.
The drywall would be (in feet) 20x7.5x2 + 30x7.5x2 + 20x30 ft^2 (I'll assume the floor is some perfect insulator for now, and that the room has no doorways), and 1/2 inch thick, or 1.6 m^3. That's about 3600 kg of gypsum, which has a heat capacity of about 4000 kJ per degree C, or about 0.1 liter (0.027 gallons) of heating oil equivalent.
Thermal density (specific heat) of air is going to be ~1000x less than that of solid objects.
The specific heat of gypsum (the primary constituent of drywall) is 1.09 kJ/kg.K
For dry air it's 1.0 kJ/kg.K
Air's density is 1.225 kg/m3.
A 6m x 9m x 2.3m (20' x 30' x 7.5') room has a volume of about 130m^3, so a 10% exchange would be 13m^3, or 16kg.
That's about 15 kJ of heat energy per degree C, or roughly 0.0004 liter (0.0001 gallon) of heating oil equivalent.
The drywall would be (in feet) 20x7.5x2 + 30x7.5x2 + 20x30 ft^2 (I'll assume the floor is some perfect insulator for now, and that the room has no doorways), and 1/2 inch thick, or 1.6 m^3. That's about 3600 kg of gypsum, which has a heat capacity of about 4000 kJ per degree C, or about 0.1 liter (0.027 gallons) of heating oil equivalent.
If I'm doing my maths right.
Sources:
Specific heat of gypsum: http://www.engineeringtoolbox.com/specific-heat-solids-d_154...
Specific heat of dry air: http://www.engineeringtoolbox.com/air-specific-heat-capacity...
Density of gypsum: https://en.wikipedia.org/wiki/Gypsum