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
This equation only takes into account the temperature differences thus, ignoring solar radiative flux and infrared exchanges from the sky. The Tsol-air was then introduced to accommodate these two parameters.
where
and is to be used in
An equivalent, and more useful equation for the net heat loss across the whole construction is:
where
Expanding the above equation by substituting gives the following heat loss equation:
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.