The classification of outdoor (ambient) air as fresh for the purposes of ventilation is not always appropriate, particularly in urban areas. In many cities of the world, urban air frequently violates health-based air quality standards due to high ozone concentrations. The degree of protection from exposure to ozone offered by the indoor environment depends on the relationship between indoor and outdoor ozone levels. Existing concentration data indicates that indoor/outdoor ozone ratios range between 10 and 80%.
Modern one-family houses in Scandinavia built before 1980 are often naturally ventilated and heated by electric baseboard heaters. The overall supply of fresh air is often inadequate during the heating season in many of these houses. Long periods of time individual rooms might get too little fresh air. The performance of a natural ventilation system is very much dependant upon the overall airtightness and the distribution of the airtightness of the building and the weather.
During the last decade several surveys in Sweden have indicated that the indoor climate in existing schools is unsatisfactory, therefore a thorough project was carried out in Växjö). The indoor climate was investigated in three schools during 1989. Detailed measurements were made of ventilation (e.g. rates, air exchange efficiency), indoor air quality (e.g. CO2) and thermal comfort (e.g. air velocity). The main results were: high indoor temperatures, low air velocities and high concentration of CO2. Improvements were made in all three schools during 1990.
Radon is the largest source of risk to human health caused by an indoor pollutant, at least in the industrial countries. Subslab Ventilation (SSV) is one of the most effective and common methods of reducing indoor Rn concentrations in houses with a basement. In this paper, we first quantify the impact of this technique on the air exchange rate, through numerical modeling of a prototype house with basement for a range of permeabilities of soil and subslab aggregate and various sizes of the cracks in the basement floor.
In well insulated buildings the ventilation heat is sometimes higher than the heat losses by transmission. For a air change rate of 0,8 per hour the specific heat flux must be calculated with 25 w/m², so heat recovery can save some energy. In all considerations the saving in the heating system must be compared with the additional energy for the fans, because this energy is of a higher quality. To optimize the heat recovery system, the different designs of the heat exchanger, the annual running hours and the annual hours for heat recovery must be taken into account.
The NORWEB Headquarters in Manchester, UK, is an air conditioned energy efficient office building of unusual design, completed in 1988. It has three stories with overhanging canopies providing solar shading and 21 % solar control glazing. The open plan interior is ventilated by a displacement system with three twist outlets in the floor to each desk position. A detailed questionnaire survey showed this to be one of the 'healthiest' buildings tested so far, with a very low 'building sickness symptom score'.
The present paper reports on tracer gas measurements performed in five large buildings during normal operating conditions. In all buildings air was supplied through ceiling diffusers and returned through a ceiling plenum. The measurements were taken during summer with the systems in cooling mode, i.e. the supply temperature was lower than the room temperature. The global air change effectiveness and the occupied zone average air change effectiveness were calculated based on the age-of-air concept.
Experiments were carried out in four naturally ventilated offices to measure the indoor environmental parameters such as air velocity, turbulence intensity and air temperature at three vertical levels, Air change rates for various indoor and outdoor climates were detetmined. The concentration of carbon dioxide in the room was monitored. Subjective assessment was made to evaluate the thermal comfort and indoor air quality in the offices. The effect of opening windows and doors on the indoor comfort conditions was also investigated.
The greenhouse effect is one of those topics in environmental politics which are currently worldwide at stake. There are several national concepts aiming at the diminution of CO2-emission in order to lessen the greenhouse effect. One of these concepts is the CO2-reduction programme of the Federal Republic of Germany. With this resolution, passed on November 7th, 1990, Germany's Federal Government aims high: national carbondioxide emission is to be cut back by 25 per cent by the year 2005.
For more than 20 years, energy recovery systems have been operated successfully in European countries in comfort and industrial ventilation systems in order to reduce the heating and cooling capacity as well as to reduce the annual energy consumption for the treatment of supply air. By 1991 the total heating capacity of all installed energy recovery systems in Europe was about 60.000 MW and the equivalent of the annual energy savings was about 10 million tons of oil.
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