Sol-air temperature (Tsol-air) is a variable used to calculate cooling load of a building and determine the total heat gain through exterior surfaces.
It is an improvement over: Where: The above equation only takes into account the temperature differences and ignores two important parameters, being 1) solar radiative flux; and 2) infrared exchanges from the sky.
The concept of Tsol-air was thus introduced to enable these parameters to be included within an improved calculation.
The following formula results:
{\displaystyle T_{\mathrm {sol-air} }=T_{o}+{\frac {(a\cdot I-\Delta Q_{ir})}{h_{o}}}}
just found can now be used to calculate the amount of heat transfer per unit area, as below:
An equivalent, and more useful equation for the net heat loss across the whole construction is:
Where: By expanding the above equation through substituting
the following heat loss equation is derived:
{\displaystyle {\frac {q}{A}}=U_{c}(T_{i}-T_{o})-{\frac {U_{c}}{h_{o}}}{[a\cdot I-F_{r}\cdot h_{r}\cdot \Delta T_{o-sky}]}}
The above equation is used for opaque facades in,[1] and renders intermediate calculation of
unnecessary.
The main advantage of this latter approach is that it avoids the need for a different outdoor temperature node for each facade.
Thus, the solution scheme is kept simple, and the solar and sky radiation terms from all facades can be aggregated and distributed to internal temperature nodes as gains/losses.