RT 2012 - The use of RC (resistor-capacitor) scheme in thermal behavior study of a group

Successive French thermal regulations, from RT 88 to the current RT 2012, have seen a steady increase in the energy consumption requirements for new buildings. This increase in requirements is naturally accompanied by an increase in the complexity of the calculations needed to assess them.

The sheer scale of the calculations, and the resulting multiplication of parameters and input data, make it difficult to take an intuitive, or even physical, approach to improving energy efficiency in the regulatory sense. This is why a good understanding of the intricacies of the calculations carried out can pave the way for further optimization of the regulatory study.

The general RT 2012 calculation process (see article [C 8 110] ) is based on a dynamic simulation of the thermal behavior of premises. This behavior is modeled by a method known as "RC" for resistance-capacity, by analogy with electrical calculations.

The aim of this article is to explain this modeling method, detail the calculations involved and propose a mathematical solution.