Underground building climate

Methods for calculating and evaluating the thermal properties of the ground are presented. The temperature of the ground at any depth at any time of year is calculated as a function of the mean annual temperature, the annual temperature amplitude at the surface, the time of year, the phase constant, and the thermal diffusivity of the soil. The density, specific heat, thermal conductivity, and thermal diffusivity of rock, soils and concrete are reviewed. Lag times exist in the temperature wave at different depths and average 1 week/ft depth in a soil with average thermal diffusivity. Amplitude damping for various soil thermal diffusivities is calculated. The subsurface degree days for a soil profile can also be determined from a sinusoidal function incorporating the upper limits of the comfort zone, the mean daily temperature, and a 65/sup 0/F temperature index line. The calculations are used for evaluating the thermal parameters affecting underground structures.