Guidance and tools for night and evaporative cooling in office buildings.

In France, mechanical cooling is increasingly used in office buildings. This situation isrelated to a demand for a better comfort, the increase of the thermal insulation and internalgains, and the changes in the building design.Nevertheless, in many cases, it is possible to achieve a thermally comfortable environmentby passive means - as thermal inertia, and solar protection of the external envelope - and useof low energy techniques as night or evaporative cooling. When mechanical cooling is yetrequired, the same approach can be used to reduce the peak demand and the energy needs.These parameters have to be taken into account at the early stages of building design.Therefore, there is a need for simple tools enabling to give first guidance to the designer. Onanother hand, these tools must be produced by a more precise one in order to improve thedesign in further stages, or to take into account specific situations.In addition, the development of efficient strategies in this field requires to take into accountthe fact that the maximum cooling power is generally available at night, and the coolingpeak demand occurs in the middle of the day. This leads to two consequences :1. The tools must take into account in a quite accurate way the non steady state thermalbehaviour of the rooms,2. The control strategies must compensate the lack of maximum cooling power byprecooling the building at night, while keeping the indoor climate comfortable duringoccupancy.The works conducted at CSTB aims to fulfil the above requirements. Developed within theframework of IEA annex 28 "low energy cooling", they are based on two kinds of tools :detailed tools, and guidance ones.