The advantages and disadvantages of various ventilation systems have been assessed in Germany over the past four years. The programme covered research in unoccupied test rooms as well as in occupied buildings. Results are presented, and the possibilities and limits for energy saving while meeting comfort requirements are discussed.

The use of heating and ventilation was measured in several flats to find the relationship between the two. Measurements were taken in 9 flats in a 6-storey block in Berlin, with various types of ventilation system. Two flats remained uninhabited to serve as a comparison. The duration of the opening of windows of the individual rooms lastd on average up to 15 hours per day during the whole heating period. The tenants' own evaluation of the duration of airing differed immensely from this result.

In order to determine ventilation performances in hot arid regions a transient program was simulated for a single room with glass windows. The calculations were done on climatic data of a typical city close to the central desert of Iran. Results indicate that the incident solar radiation to the room has a high influence on the room air temperature.

Evaluates results of the 'Ventilation in Residential Buildings' research programme of the German Federal Ministry for Research and Technology. It was found that conventional ventilation methods based on infiltration and window opening cannot secure proper air quality and at the same time provide energy conservation and user comfort, nor can intelligent ventilation habits be expected of the average user, for subjective and objective reasons. All ventilation systems evaluated had shortcomings.

In new buildings, the requirements for indoor air quality and energy efficiency cannot be met with natural ventilation. In renovations of existing buildings it is, however, often difficult or uneconomic to install a mechanical system. What is often forgotten is that the conditions for natural ventilation will have changed, even if no alterations are made to the ventilation system.

Describes a new ventilation strategy for retrofitted buildings. The system consists of two units including heat recovery, fan, filter, etc, which are installed in the window openings. They are operated in opposite directions which are periodically reversed. When desired, the unit is stopped and used as an airing panel. In laboratory tests the specified values were achieved. The heat recovery proved so efficient that no air heating was needed even at the lowest temperatures. Some noise and freezing problems were reported.

Some of the problems for designing ventilation systems for retrofitted buildings are presented. Measurements were taken in two public buildings in Helsinki with three ventilation systems of different types. In these two buildings only a balanced mechanical ventilation system seemed to fulfill therequirements for a satisfactory and healthy indoor environment.

Displacement flow has been found to be the best flow principle for ventilation, with ventilating air being supplied to the occupied zone. The design procedure should, amongst other things, contain an analysis of contaminant source in order to design the ventilating system to create the most favourable flow pattern for the contaminants. This paper deals with design principles and problems related to displacement ventilating systems.

A short description of a second generation low-energy house built at Hjortekaer in 1984, with a calculated annual heat demand of 3500 kWh (excluding domestic hot water), is given. The house is superinsulated and very airtight. The roof and walls are insulated with 400 and 300 mm of high quality mineral wool respectively, with infinitesimal thermal bridges, and the floor is a slab-on-grade construction insulated with 200 mm polystyrene. Most of the windows are south facing and fitted with a new type of lightweight external insulating shutter.

A single family residence in St. Paul, Minnesota, constructed in 1957, was retrofitted in 1983. This resulted in approximately 50% reduction in annual heating consumption compared to the average consumption over the previous three years. However, the occupants complained of poor air quality. Measurements indicated that total particulates, CO, CO2, relative humidity, and temperature were at levels of some concern; NO2, radon and formaldehyde concentrations were not significant.