Envelope Heat Capacity: Heat Capacity is the ratio of the heat added to an object to impact the resulting interior temperature. Consider the range to begin at thin no-to-low insulated walls, and increase as the wall assembly's thermal mass improves. Read more about thermal mass here.
a) Very Light: 80,000 e.g. Pavilion Wall with no insulation
b) Light: 110,000 e.g. Wood Framed
c) Medium: 165,000 e.g. Steel Framed, Curtain Wall
d) Heavy: 260,000 e.g. Concrete Wall, CMU
e) Very Heavy: 370,000 e.g. Industrial Concrete Wall, Trombe Wall
The factor units are J/K and it is multiplied by the floor area to quantify the envelope heat capacity based on ISO Standard 13790 (Table 12). To convert the factors into IP units divide the J/K value by 1899.1 to get the Btu/F value.