Performance indicators

Night-time ventilation is a natural cooling technology, in which cold ambient air is used to cool indoor spaces. This literature review analyses how recent studies have defined the effectiveness or efficiency of night-time ventilation. Most studies used the similar indicators related to heat removal, energy saving, cooling demand reduction, and thermal comfort. However, there were significant differences between the definitions of performance of night-time ventilation, both in terms of criteria of judgement and methods of analysis.

The lack of indicators assessing ventilative cooling effectiveness in a way to compare it with active cooling technics, makes its acceptance more difficult. Practitioners, norms, standards and guidelines are used to design and evaluate cooling systems in terms of Cooling Power (CP) or Seasonal Energy Efficiency Ratio (SEER). What could be the CP of a passive technique based on a day to night offset of the cooling process? What could be the SEER of mechanical night ventilation for summer cooling?

Residential ventilation standards, especially in Europe are slowly but substantially moving away from their usual prescriptive approach towards performance based specifications. While academics and policy makers argue about the relevant IAQ indicators, housing developers and end users need to make a choice between the different ventilation system options they are faced with in the market. Although several IAQ rating systems have emerged, a comprehensive assessment method to rate the inherent qualities of the ventilation system itself is not available [6].