As part of a collaborative trial on the effects of ventilation on house dust mites and asthma, 20 mechanical ventilation units were installed in houses in the Southampton area in southern England. The hypothesis is that continuous ventilation over winter months can maintain humidity below a mixing ratio of 7 g/kg, with a consequent reduction in house dust mite numbers. The systems served upstairs only, extracting from bathroom and landing and supplying fresh air to bedrooms.
Three ventilation systems were installed in the EA Technology Ventilation Test House: passive stack ventilation (PSV), mechanical ventilation with heat recovery (MVHR) and extract fans. Humidifiers were used to simulate occupancy and the performance of the systems monitored over the winter of 1993/94. The aim was to assess the effectiveness of different ventilation systems in controlling indoor humidity at a level that will inhibit the growth of house dust mites.
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