Providing people with a quality indoor environment means full air conditioning with an energy use tag that we would rather not mention in the debate about environmental impact and sustainability. But is this really the case? Is it not possible to design mechanical systems so they use less energy than their naturally ventilated counterparts? The law of conservation of energy means we can use the same energy repeatedly. As long as we are aware of how energy is degraded in quality and temperature terms, we can design systems that repeatedly recover and reuse energy.
Mechanical ventilation systems, designed to meet ASHRAE's Standard 62-1989 and to modify building pressures, were installed in two New Mexico elementary schools to reduce elevated levels of indoor radon, carbon dioxide, and airborne particles. Although the systems did not meet design conditions for outdoor air delivery, ventilation rates were increased by factors of 2 to 4 over pre-existing natural ventilation rates, and levels of indoor air pollutants were significantly reduced.
A new mechanical ventilation system which continuously controlled the indoor-outdoor pressure difference was installed in six houses, where the long-term radon levels ranged from 670 to 3 080 Bq/m3. When the new system had operated for several months, the indoor radon levels decreased to levels from 120 to 600 Bq/m3 , the effective dose reductions being from 40 % to 88 %.
Fungal spore content in dust accumulated in air ducts was investigated in 24 mechanically ventilated single-family houses of which 15 had also a central air heating system. Dust was collected from the ducts simultaneously with cleaning of the ventilation systems. Besides spore concentrations and flora of culturable fungi, total fungal spore concentrations were determined in dust samples by the aqueous two phase technique and spore counting with epifluorescence microscopy.