This paper discusses design issues for underfloor air distribution systems : design objectives, air distribution issues, occupants comfort issues, control of interior and perimeter zones.
Studies on buildings have shown that airtightness and insulation increased in family buildings and detached houses too, due to new thermal regulations. In the same time, studies concerning health and indoor air quality have shown that the need of fresh air will increase too.
The performance of various kinds of ventilation systems (mechanical supply, mechanical exhaust, mechanical supply and exhaust, crawl space supply and hybrid exhaust) was evaluated in a full-scale test house during heating period. The concentration method (SF6 tracer gas) was used to measure the ventilation air flow rates to each roomntilation. Results of experiments are presented, showing the air distribution between floors and rooms.
This paper deals with the steady state simulations carried out with the CFD software Flovent along with dynamic building energy simulations using the ESP-r programme applied to three buildings (located in Ireland, Poland and Denmark) intended to be equipped with supply air windows coupled with passive stack ventilation systems. Supply air windows consist of two layers of glazing separated by a ventilated layer. Air enters the cavity at the bottom from outsides and enters the building at the top. Systems design from simulation results is discussed.
Overnight free cooling in buildings brings potential benefits that have been known for some time. This study investigates those benefits when used in conjunction with an under floor air delivery system (UFAD). A detailed study using CFD was undertaken for a building in an airport in the UK with under floor air conditioning system and mechanical ventilation providing fresh air. Results show the energy consumption and peak cooling loads reductions when using night time cooling with outside air during the cooling season.
Advantages of floor supply and floor return systems (UFAD: under floor air distribution systems) are described. They are presented by the author as being capable of better performance (thermal comfort, indoor air quality) than floor supply and ceiling return system. They also offer flexibility and ability to allow individual control.
The concentration of fungal spores is higher in the crawl space than inside houses. Domestic mechanical exhaust ventilation systems may create air flow between crawl space and base floor through leaks. This study used data from eight buildings to develop a model providing relation between indoor and crawl space fungal spores concentrations. Results show that the correlation between the fungal spores in the crawl spaces and indoors depends on the size range of microbe species.
A simple conceptual approach to room surface convective heat transfer is presented, defining a global room heat transfer coefficient. It is applied to two room ventilation systems : mixing and cross-ventilation.
Two new blocks of flats have been built for people with respiratory diseases. A number of points were taken into particular account during the design and construction of the buildings. For example, the project designers and builders were given training in prevention of problems with indoor air, only building materials that had been tested and found to have low emissions were used, and a supply/exhaust ventilation system and a central vacuum-cleaning system were installed.
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