The Building Research Establishment is currently investigating the impact of various radon remedies at a radon affected test house. Tests aim to assess how different ventilation strategies affect indoor radon levels and the building environment. Those examined include natural underfloor ventilation, mechanical underfloor ventilation (supply and extract), and whole house pressurisation. The test house has a suspended timber floor with an inaccessible underfloor space and is typical of much of the UK housing stock except for indoor radon levels regularly in excess of 1000Bqm^-3.

Almost 60% of French residential buildings were built before the seventies, and an important part of those is to be retrofitted for complying with new needs with regard to acoustic insulation and energy saving. Retrofitting modifies the airtightness of the building envelope and can lead to an insufficient air change rate in passive stack ventilated buildings ; the existing ventilation system has therefore to be redesigned in order to insure adequate indoor air quality.

Airtightness and infiltration rate measurements in office and other commercial buildings have shown that these buildings can experience significant levels of air leakage [1,2]. The energy impact of air leakage in U.S. office buildings was estimated based on the analysis of a set of 25 buildings used in previous studies of energy consumption [3,4]. Each of these buildings represents a portion of the U.S. office building stock as of 1995.

Air flow measurements and simulations were made on a 13-story apartment building to characterize the ventilation rates for the individual apartments. Parametric runs were performed for specific conditions, e.g., height, orientation, outside temperature and wind speed. Our analysis of the air flow simulations suggest that the ventilation to the individual units varies considerably.

The material presented in this paper highlights some aspects of""two research projects, The control of natural ventilation , and Night cooling strategies . The research has led to the development of generic control strategies. These have evolved from consideration of the control strategies used in naturally ventilated buildings utilising Building Management Systems (BMS) control together with experience obtained from monitoring three naturally ventilated buildings. The site monitoring has also led to recommendations being provided for commissioning and fine tuning procedures.

With effect from January 1st, 1995 the amended Heat Transfer Barrier Act (,,Warmeschutzverordnung ) was introduced in the Federal Republic of Germany, replacing the 1982 version. This decree is binding on all houses to be built so that they reach the low energy standard. Former decrees envisaged mainly the reduction of the transmission heat loss while the amended version takes into account all other relevant aspects such as internal and solar heat gains as well as ventilation heat losses, and includes them into an energy balance procedure.

Especially in modern buildings with small capacity of humidity storage it is necessary to reduce the humidity in the supply air. Normally a refrigeration system containing CFC s is used. There are some alternative fluids available, but mostly they show a high global warming potential. These systems all need electrical energy to be driven and therefore it is necessary to consider other possibilities with alternative systems. The most promising systems are sorptive systems which are used in open cycles.

A breakthrough in ventilation research was made once it was realized that ventilation principles based on mixed flow patterns are not optimal and that further energy savings can be achieved if an alternative technique could be developed. Several researchers, particularly in the Nordic countries, have shown by theoretical studies that replacing mixed ventilation flow by displacement flow increases ventilation efficiency. This also results in decreased air supply volumes and thus decreased energy requirements. In addition, lower air velocities may reduce problems of comfort and noise.

Nowadays it is rather common with demand controlled ventilation in public buildings and offices. The purpose of demand controlled ventilation is to adapt the ventilation to the varying needs of the occupations. In dwellings it is rather unusual with demand controlled system. The main reason for that is the high investment cost for the system. The outdoor air used for ventilation in dwellings is therefore not effectively used. For example in a mechanical exhaust ventilation system 50 % of outdoor air is leaving the house without being used of the people.

The installation of packaged heat recovery ventilation (HRV) systems has recently become common practise in new homes in Canada. Despite improvements in product quality and reliability, HRV systems are only capable of providing safe, continuous, efficient and effective ventilation if homeholders have a understanding of the basic operation and maintenance procedures and the system's interaction with other house systems. Furthermore, homeholders must be able to perceive the value of HRV systems if they are expected to operate them.