Underfloor air distribution (UFAD) strategy is gaining popularity during the last years, howeverresearches about the performance of such systems still need to be deepened.One of the appreciated features of this technology is the use of an underfloor plenum below a raised floor. This plenum is used to distribute the conditioned air in the rooms and makes possible to avoid large air ducts to be installed.
There are several factors that affect the hygiene in the surgical operating theatres. The HVACairside system plays an important role to maintain the adequate hygiene level in the operatingtheatres. The present paper displays comparisons between different HVAC airside designs toassess their impact on the surgery staff and patient health and comfort. The present workutilizes a numerical modelling technique to predict local flow field characteristics, heattransfer and air distribution profiles.
Continuous measurements have been operated on 28 identical low energy houses near Leipzig (Germany) during two years.The houses face due south, have two levels and one occupied attic, with a total aera of 147 m2. Heating period is from September to May. All houses except 2 were equipped with different mechanical ventilation systems, providing about 180 m3/hr of fresh air : central balanced flue systems with heat recovery, air heating system with heat recovery, central exhaust ventilation with heat recovery by heat pump, room mechanical ventilation systems.
The Norwegian Building Research Institute (NBI) has completed a study of the performance of balanced residential ventilation systems with heat recovery (HRVs) in Norway. The study involved both a national questionnaire survey and thorough laboratory tests of 10 HRVs on the market. The overall conclusion is that balanced ventilation with heat recovery provides very good air quality, and has a payback time of 4~6 years for the most profitable systems despite Norways cheap hydropower (0.09 /kWh in 2002).
Describes the California Healthy Building Study, which attempted to assess the relationship between ventilation system type and employee symptoms. Three naturally ventilated, three mechanically ventilated and six air conditioned buildings were studied. Higher adjusted prevalences of most symptom outcomes were linked with both mechanical and air conditioned ventilation.
The acoustics and ventilation method allows the designer to explore natural ventilation and acoustics issues at an early design stage. Few input parameters are necessary, like the number of people the space must accommodate and the volume of air per person appropriate to the acoustic function. While allowing the comfort temperature to rise during occupation by some 10 to 15%, the natural ventilation and acoustics can be discussed via the volume of the space.
Buildings located in noisy areas require a high degree of sound insulation. This will usually involve making the building envelope virtually airtight, and as a result losing the possibility of utilising natural ventilation. The solution is to employ a mechanical ventilation system, but such systems can themselves constitute a source of intrusive noise. Discontinuities in ducts result in the generation of flow noise and a loss of static pressure. The greater the discontinuity, the greater is the loss in static pressure and the greater is the sound power generated.
The author maintains that the testing methodology of ASHRAE 62-1989R, mired in a swamp of controversy and "continuous maintenance," may need some fresh air.
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