PR1995

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.

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.

A preliminary study of the potential for using central forced-air heating and cooling system modifications to control indoor air quality (IAQ) in residential buildings was performed. The main objective was to provide insight into the potential of three IAQ control options to mitigate residential IAQ problems, the pollutant sources the controls are most likely to impact, and the potential limitations of the controls. Another important objective was to identify key issues related to the use of multizone models to study residential IAQ and to identify areas for follow-up work.

To achieve acceptable indoor air quality (IAQ), ASHRAE Standard 62-1989 recommends the use of the alternative IAQ procedure. The IAQ procedure can treat both constant-volume and variable-air-volume (VAV) with constant or proportional outside airflow rates. The relationships in Appendix E of the standard must be used in conjunction with the IAQ procedure to directly calculate indoor air contaminant concentrations in an occupied space.

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.

Two factors - CO2 emissions fiom heating and cooling systems and restrictions on the use of CFC refrigerants - have accelerated the development and introduction of new and more environmentally friendly cooling systems. These new cooling systems also include the so-called "Desiccant Cooling Systems (DCS)" [1]. The desiccant cooling systems consist of a rotating dehumidifier, a rotating heat exchanger and evaporative coolers. For design, control and operation of desiccant cooling systems new criteria have to be considered because of the specific properties of these new technologies.

For the planning of "silent cooling" systems built by free convective coolers, it is necessary to support characteristic data for the cooling performance and the effect of different installation and operating parameters on the cooling performance. At the "Institut für Angewandte Thermodynamik und Klimatechnik" at the University of Essen measurements of the cooling performance of free convective coolers were carried out by using a testing chamber as well an enlarged and modified testing room with dimensions near to practise.

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.

In line maintenance hangars, air planes stay about 2 hours, usually at night-time. The coolingdown of the inside air during the opening time of the hangar gates (up to 5 times per night, lasting 15 to 30 minutes each) has a considerable impact on the comfort conditions for the workers, and on the energy required for reheating. The time-dependent air flow rates and associated heat loss rates during the door opening and closing cycles is assessed by simple transient thermal models and CFD (Computational Fluid Dynamics) calculations.

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.