The major objective of the IEA task XIII project is to design and construct low energy dwellings which should be technically and economically realistic in the period 2000-2010. The design criteria for the Belgian dwelling are the following: - low energy demand for heating purposes; - good thermal comfort conditions, as well in winter as in summer with attention to the problem of overheating; - very good airtightness (n50 <= 1 h^-1); - good indoor air quality conditions; - attractive design for majority of potential clients; - only use of realistic technical solutions.

This paper shows the extensive influence of humidity on comfort, cooling load and refrigeration capacity. Modern computer programs allow an effective consideration of humidity in systems.

The BRE method of predicting water vapour conditions in houses is based on two generalised moisture admittance parameters a and p. Previous laboratory experiments suggested that it is possible to determine these coefficients for an unfurnished room with wooden panels, using measurement periods of six hours under dynamic equilibrium conditions. The present study explores the possibility of using such conditions to determine a and P in-situ for the living-room and bedroom of a furnished flat of conventional construction.

The air distribution in a room is investigated using computational fluid dynamics. Four common methods of supplying air to a room are compared. The effect of air change rate on the ventilation effectiveness for contamination is small, however the effect of room heating or cooling load can be very significant. It was found that air turbulence has a major influence on the air movement, air velocity and dispersion of contaminants in the room.
 

In urban non-residential buildings air-conditioning systems are generally required to achieve acceptable air quality. To reduce the energy demand of HVAC-plants free cooling is proposed. The present study deals with free cooling by outdoor air (untreated or additionally cooled by evaporation) during the night. Therefore a sufficient building mass (about 600 to 800 kg/m²) is necessary which stores the heat produced in daytime and which is cooled down at night. In most conventional non-residential buildings, however, the building mass is at about 400 to 600 kg/m².

This paper presents the results of monitoring the ventilation in Netley Infants School in Hampshire. The study was carried out on behalf of the Department of Trade and Industry as part of the Energy Performance Assessment Project, as managed by the Energy Technology Support Unit. The school was designed so that during the summer the solar heating of a south facing conservatory would enhance the stack effect and induce ventilation in the adjacent classrooms. It was expected that ventilation rates would be adequate to maintain comfort conditions and air quality.

For several years the technology of chilled ceilings has been a favourite issue among HVAC technicians and underwent a boom in the past few years. According to the survey of a German technical journal, on March the first 1993, a total of 308,490 m² of chilled ceilings had been installed in German buildings, out of which 69 per cent had been installed in new buildings and 31 per cent in modernized projects. Cooling ceiling systems are the ideal.application where high demands are placed on comfort requirements and where the energy loads are very high compared to material loads.

Mechanical ventilation with heat recovery (MVHR) and passive stack ventilation (PSV) systems are both proposed as methods of ensuring satisfactory ventilation rates in UK housing. MVHR provides controlled ventilation in all rooms together with heat recovery, while the cheaper PSV system offers lower running costs, but without heat recovery and without a controlled air supply to all rooms. The relative energy consumption of the two systems depends on a number of factors that are difficult to predict.

For thermal comfort and energy conservation reasons, displacement ventilation and radiative cooling systems are increasingly used. Simulation programs are generally not able to correctly simulate such systems because of their one node approach for the air temperature. A procedure for creating DOE-2 inputs to simulate both system types each alone or in combination - without program code change - was developed, based on a more detailed new TRNSYS-Type, and validated against existing experimental data sets.

The continual reduction of the transmission heat losses of residential buildings causes an increasing importance of the ventilation heat losses. Energy saving can be achieved by using a mechanical ventilation system with heat recovery. A great improvement is the combination of heating and ventilation in one system. In this project such a combined system was developed to reduce the energy consumption of the fans, the operating expenses and also the investment costs in comparison to existing systems. In future a high market acceptance is expected for combined heating and ventilation systems.