ventilative cooling

This report summarises the outcome of the work of the initial working phase of IEA ECB Annex 62 Ventilative Cooling and is based on the findings in the participating countries.

For zero and low energy buildings, high-energy efficiency ventilation is very often confused with a complex mechanical ventilation system with heat recovery. In school gymnasiums, where large volumes have to be ventilated, and where intermittent occupation is very usual, demand controlled natural ventilation has several advantages, making this technique very attractive. High stack height makes natural ventilation very efficient, limiting the necessary number and dimensions of windows.

New buildings have to satisfy ever-tightening standards regarding energy efficiency and consumption. This results in higher insulation levels and lower air leakages that reduce heating demands. However, even at moderate outdoor temperatures these buildings are easily warmed up to such a degree that in order to ensure acceptable indoor environment quality, removal of excess heat becomes unavoidable. Use of electric energy related to mechanical cooling is considered incompatible with achieving zero energy buildings (ZEB).

An advanced heat and electricity saving strategy for the regulation of hybrid ventilation systems with automatic night cooling (ventilative cooling), mechanical compressor cooling, natural ventilation and exterior solar shading by the inclusion of MPC (Model Predictive Control) has been developed in this project. The focus is on the optimization of the total energy cost (cost function) as compared to indoor climate requirements and variations in the outdoor climate. During the test period, the test persons could override the automatic control of the natural ventilation and solar shading.

Ventilative cooling (VC) is a way to cool or to prevent overheating in a building by means of ventilation rates higher than hygienic ventilation rates. To this end, natural (such as windows, vents, louvers) as well mechanical (extract or supply fans) ventilation devices can be used.

Higher insulation and air tightness levels of buildings, increase the risk on overheating. Ventilative cooling as passive technique can limit overheating and decrease cooling energy consumption. The national energy performance regulations (EPBD) determine whether, how and under which requirements ventilative cooling can assist to reduce cooling demand and overheating. Therefore, those regulations are a key factor in the market uptake of ventilative cooling. Without a realistic and achievable approach, ventilative cooling will marginally be applied in buildings.