# Paper Conference

#### Proceedings of BSA Conference 2013: 1st Conference of IBPSA-Italy

**The air energy balance equation paradox**

Livio Mazzarella**Abstract:** In building physics applications, mainly related to the building energy performance simulations, the master equation is the inner air energy balance equation. Historically the followed approach in writing down such master equation was to adopt the simplifying hypothesis of incompressible fluid for the air assumed dry. This hypothesis, among others, reduces the general integral energy balance equation to the usual formulation which is reported in textbooks and manuals and has been used in available energy simulation programs, such as Energy Plus, Esp-r, TRNSYS, etc. Later the moist air problem, the indoor air humidity control, has been faced just by adding a new integral balance equation: the water vapour mass balance equation. In this work it is pointed out how this "layered" historical approach leads to a building physics textbooks do not give any detailed information on such basic equations, like [Hagentofl, 2001], [Hens, 2010], and just a few lines are normally present in buildings **Pages:** 15 - 28 **Paper:**

bsa2013_02