For outsiders, a national energy performance (EP) requirement level is quite a black box. Within the EU Asiepi project (www.asiepi.eu) we are developing a methodology to make a comparison of EP requirement levels possible among member states of the EU.An unexpected finding has been that far from all EU countries consider all energy uses in their EP method required by the EPBD (Energy Performance of Buildings Directive). The energy use for fans, domestic hot water and cooling are among the energy uses which are not taken into account by various countries.

The indoor air quality is a very important issue and it generally depends on the airtightness of theshell, the ventilation rates, the deposition and the resuspension rates of the particles and the internalsources as well.The whole experimental procedure took place in a PASSYS test cell, which is located at the University Campus of Athens.

Renovation of existing buildings, in order to reduce energy consumption, represents a big market inEurope. As the first efforts often concentrate in improving insulation and airtightness of the buildingenvelope, important insufficiencies of ventilation can appear, generating health risks for the occupants and a degradation of the frame. Taking into account the difficulties to insert ductworks in existing buildings, it can be easier to use distributed ventilation systems for room-by-room ventilation instead of centralised systems.

In 2005 the first Energy Efficiency Plan for South Africa was developed by the Department of Mineralsand Energy. This plan sets the target for energy efficiency improvements of 12% until 2015. Onepoint of the strategy is to improve the energy performance of public buildings like schools. Manyschool buildings in South Africa are inadequate to provide a suitable learning and teachingenvironment for students.

Since 1991 has Sweden regulations on compulsory inspection of ventilation systems (OVK). Thereasons to issue these regulations were many studies on poor indoor climate and health problems for building occupants. The studies have shown also that poor upkeep and maintenance have led to a decline in the performance of existing ventilation systems. If, in the future, we do not look after ourventilation systems properly and adapt operation and maintenance to current user habits, then evenmore buildings will become problem buildings.

Ventilation is essential for the health and comfort of building occupants. It is particularly required todilute and/or remove pollutants emitted by occupants' metabolism and activities. The concentration of metabolic CO2 is well correlated to metabolic odour intensity. Therefore CO2 concentration can beefficiently chosen as an indoor air quality index when occupants are the main source of pollution inside the buildings.

Even when providing the same nominal rate of outdoor air (OA), different ventilation systems distribute air in different ways, affecting the occupants differently depending on the dwelling, on source disposition and strength, on occupants behavior, and on the cooling or heating system.

In Central and Northern Europe several thousands homes conform to the Passivhaus standard havebeen built. The applicability of this Standard has not yet been sufficiently tested in warmer climates,where reducing cooling needs under growing summer comfort requirements poses a challenge.The IEE Passive-on project has drafted a proposal to adapt the Standard to the conditions thatcharacterize Southern Europe.

In schools the temperature of the indoor air is one of the most important factors in terms of the indoorclimate. The resulting indoor air temperature is depending on many factors; the temperature of thesupply air being one of the more significant one. One fan-assisted natural ventilation system includesa supply air system where the outdoor air should be passively heated respectively cooled when passing components in the ground before it is supplied to the classrooms. The objective is to examine the ability of the supply system to transfer heat to/from the outdoor air.

The Center for Building Performances and Diagnostics of Carnegie Mellon University is experimenting with Hybrid Ventilation in Pittsburgh, Pennsylvania, USA, to evaluate the potential energy savings of this technique in a region where there are many variations in climate throughout any given year. Sharing the results of this experiment aims to increase awareness of this technique in the US and develop its implementation in the future.