Building Ventilation The State of The Art by Mat Santamouris and Peter Wouters.
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Building Ventilation The State of The Art by Mat Santamouris and Peter Wouters.

The invention of boilers and chillers made total indoor climate control technologically possible regardless of outdoor conditions, building architecture and use. Buildings became, as Le Corbusier portended during the 1930s, of the same type: hermetically closed and controlled at a constant temperature in all climates (Mahdavi and Kumar, 1996). This energy-intensive solution is supported by the belief that maintaining constant conditions ensures comfort and satisfaction.

By applying this approach, however, the building industry failed in many cases to satisfy the comfort needs of occupants. Different studies claim that as many as 43 per cent of occupants are dissatisfied with heating, ventilating and air conditioning (HVAC), and 56 to 89 per cent of government workers regard HVAC as a problem in Europe and the US (Lomonaco and Miller, 1996; DiLouie, 2002).

The tendency for the HVAC industry is, then, to keep indoor temperature at a constant value that will dissatisfy the least number of people without affecting productivity since the cost of salaries is 8 to 13 times the cost of building operation. The trend towards a greater control of the indoor environment is accentuated by the development of building management systems (BMS).

BMS control the indoor temperature within narrow limits in the hope that occupants’ complaints will be reduced. To test this hypothesis, let us assume that a female wearing a skirt because of the corporate dress code or current fashion sits at her desk with bare legs. She shares the same thermal comfort zone with a male colleague in a business suit. A comfort evaluation with a predicted mean vote (PMV) index will show that there is no temperature that will satisfy both people and that the offset between preferred temperatures will be 3° Celsius (C).

In the absence of individual temperature control, the compromise is to control the building at a constant value based on average clothing (clo) and metabolic rate (met). If clo = 0.7 (average winter/summer) and met = 1.2 (office activity), the temperature should be 24.1° C in order to obtain a PMV index of 0. This temperature will dissatisfy both the woman and the man from the previous example (Fountain et al, 1996).

Keeping the indoor temperature at a constant value has a high investment cost and is energy intensive, with implications for resource consumption and environmental impact. Important energy savings can be obtained if the building has a larger range in which it can run freely. This saving can be augmented if ventilation is used for cooling. In fact, field studies show that people accept a larger range of temperature variation in naturally ventilated buildings than in air-conditioned ones (de Dear et al, 1997; Brager and de Dear 1998, 2000).

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