Wind towers (scoops situated on the roofs of buildings to catch the wind) have been in use for centuries in the Middle east and Pakistan, to provide ventilation and cooling with minimal mechanical plant. In Europe, the problem of cooling buildings has generally not been significant, but in recent years there has been a trend towards substantial increases in internal heat gains from IT equipment etc., and overheating in summer has become one of our major concerns.
Electric utilities in the Pacific Northwest have spent over $100 million to support energy efficiency improvements in the HUD-code manufactured housing industry in the Pacific Northwest over the past several years. Over 65,000 manufactured housing units have been built since 1991 that exceed the new HUD standards for both thermal performance and mechanical ventilation that became effective in October, 1994. All of these units included mechanical ventilation systems that were designed to meet or exceed the requirements of ASHRAE Standard 62-1989.
Many dwellings with natural or gravity ventilation systems suffer from poor airchange rates. In Sweden, especially houses built in the 1960-ies and 1970-ies heated with electric resistance heating and thus without chimneys, are at risk. Improving the airchange rate in these houses is to some extent performed to decrease Radon gas concentrations where appropriate. For comfort, most homeowners learn to live with low airchange rates, accepting e.g. odours or window condensation and trying to compensate this with increased airing.
The suitability of night ventilation for cooling for the UK is first assessed by presenting plots of summer weather data on the bioclimatic chart for three locations within the country. These indicate that most of the external weather conditions lie within the thermal mass and ventilation effectiveness areas of the charts. To confirm this, thermal simulations of a typical office module under a variety of internal conditions and summer weather data were performed.
Since 1985 more than 170 very low energy houses, all of the same type and structure, were built in the Flemish Region, Belgium. Because conduction losses are very low, mean Urn-value 0.30-0.35 W/(m².K), ventilation losses become very important, up to 45% of the heat losses if no heat recovery is utilised. Three of the houses were monitored in detail for energy consumption, energy and ventilation efficiency. All houses are equipped with the same ventilation system: balanced mechanical ventilation with heat recovery.
While the use of heat energy has decreased since the middle of the 1970's the use of electricity in the Swedish stock of commercial buildings has increased dramatically. In the average Swedish office building, roughly 30 % of all electricity is used for heating, ventilation and air-conditioning WAC). Another 30 % is used for lighting, 20 % for office machines, and about 20 % for other loads. In order to study the use of electricity in Swedish office buildings in detail, the Swedish Council for Building Research initiated four monitoring and bddiing simulation projects in 1989.
The acceptance and appreciation of ventilation systems is mainly determined by the perceived indoor air quality, thermal comfort and noise. Noise in relation to ventilation systems can be divided into three categories: outdoor noise (entering the dwelling through ventilation openings, cracks, mechanical supply and exhaust openings etc.); noise generated by components of the ventilation system; the impact of ventilation systems on sound reduction of partitions (between dwellings, rooms etc.). Depending on the type of ventilation system, one or more of these aspects are of concern.
The comparison of the performances of ventilation systems must take into account different issues. For indoor air quality, different kinds of pollutant sources have to be defined. To make an evaluation of the results, the best approach is to consider the people exposure. Four generic pollutants are taken into account : rooms components or furniture, human metabolism, cooking activities, passive smoking. As the definition of the unit for each pollutant is free, it is useful for their comparison to press them on a common "normalised" basis.
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