Since the cost of energy is increasing sharply a trend to conserve energy in the indoor environment and in addition to improvements in thermal insulation, two possible solutions are adopted. The first one is to provide reduced air gaps and opening for newly constructed buildings to minimise the infiltration of outdoor air. The second one is to reduce the ventilation rate or the fresh air supplied in air conditioned buildings. These two solutions are the reason for some serious problems of indoor air quality.

A basic condition for low energy houses is a demand controlled ventilation combined with an air-tight building envelope. Within the scope of different research projects financed by public grants and measurements effected by private order mainly in the south of Germany, the airtightness in low energy and minimum energy houses has been checked according to the DC pressurization method and the places of leakage have been determined. Considering the results with respect to the recommendations of the SIA 180 (standard of Switzerland), 40% of approx.

One of the important advantages of ordinary double glazing in comparison with single glazing is the avoidance of condensation at the inner surface during normal household activities. The reason being the higher internal surface temperature when using double glazing. However, highly insulating glazings will have lower external surface temperatures due to the good thermal insulation. During periods of clear sky during the night the outside surface temperature may drop below the external air temperature.

Domestic heating systems with a heat exchanger are generally assessed for efficiency by the ratio of primary energy input delivered energy output. In practice, performance depends on all the components in the heat delivery system and on their matching. In the air heating system addressed here, the components include: the gas burning air heater, supply ducts, return ducts, heat recovery system, controls, fans, filters and pumps. This paper describes experiments conducted on a test house in Bath during the years 1991 to 1993.

As part of a project financed by the National Foundation for Energy Research (NEFF), the Building Services Section at the EMPA examined the thermal behaviour of one building, with zero energy demands, located in a low energy housing estate in Waedenswil on the border of the lake of Zuerich. The estate was initiated by Dr. R. Kriesi who also made the energy concept. The architect was R. Fraefel and the estate was financed also by the government of Zuerich. The measures taken in order to reach a minimal heating demand in the chosen zero energy test house were as following:

The aim of the study was to design and build a small house with 50% lower heating energy consumption than in typical existing Finnish small houses. Energy saving is based on three technologies: super insulation, airtight construction and ventilation heat recovery. The first monitoring results show the heating energy consumption of the house to be less than half of the measured consumption of typical small houses located in the same area. Also, the results show the air quality to be good.