The environmental assessment of buildings is a potentially powerful means of reducing environmental impacts including those arising from energy consumption, writes Josephine Prior, Alan Yates and Paul Bartlett, Building Research Establishment
One of the important advantages of ordinary double glazing in comparison with single glazing is the avoidance of condensation at the inner surface during normal household activities. The reason being the higher internal surface temperature when using double glazing. However, highly insulating glazings will have lower external surface temperatures due to the good thermal insulation. During periods of clear sky during the night the outside surface temperature may drop below the external air temperature.
Domestic heating systems with a heat exchanger are generally assessed for efficiency by the ratio of primary energy input delivered energy output. In practice, performance depends on all the components in the heat delivery system and on their matching. In the air heating system addressed here, the components include: the gas burning air heater, supply ducts, return ducts, heat recovery system, controls, fans, filters and pumps. This paper describes experiments conducted on a test house in Bath during the years 1991 to 1993.
The work was concerned with measuring natural convection through a large horizontal opening between two rooms in a building. Airflow rates between the two rooms were measured using a tracer-gas decay technique. Room 1 was heated to various temperatures in the range l8°C to 33°C using thermostatically-controlled heaters. Room 2 was unheated. A multi-point sampling unit was used to collect tracer-gas samples from each room. The concentration of SF6 tracer was measured using an infra-red gas analyser.
The effect of airflow through an opening (or a crack) on the natural convection in a stairwell model is presented. The flow is driven by energy input from an electric panel heater located in the lower floor of the stairwell. The work concentrates on the effect of the size of inlet opening by varying it while keeping the area of the outlet constant. New data are presented for the measured temperatures and velocities at various cross-sections of the stairwell.
In modem livestock buildings air distribution and air quality are important parameters to animal welfare and to the health of full-time employees in animal production. Traditional methods for calculating air distribution in farm buildings are mainly based on formulas for air jets which do not include the effect of room geometry, obstacles or heat sources. This paper describes the use of Computational Fluid Dynamics to predict air flow patterns and temperature distribution in a ventilated space.
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