controlled ventilation

Discusses how air flow in a building is affected by the position of the ventilation openings in the outside wall. Treats factors determining selection of controlled ventilation system and provides examples of systems available: small air vents, mechanical ventilation with acoustic and thermal insulation, ventilation with heat recovery, etc. Discusses an optimal solution with air quality control.

Long-term monitoring of radon, aerosol and carbon dioxide concentrations was carried out in two Finnish public buildings. In each case, a distinct periodic behaviour of pollutant concentrations was observed. CO2 and aerosol showed maxima during the working hours, but the fluctuations of the aerosol concentration were faster and more irregular. The radon concentration peaked at night and on weekends, dropping off rapidly in the working day mornings when ventilation was turned on.

A microprocessor system is being developed for occupancy related ventilation control of mechanical ventilation in Brunel University Library. The objective is to reduce space heating costs by decreasing the input of (cold) fresh air to the building below existing (heating season) levels, when the number of occupants in the building is sufficiently small to allow this. The occupancy levels can be measured in terms of CO2 level in the exhaust duct. The microprocessor control system is operational when linked to a CO2 monitor.

In Finland there are not yet any regulations or standards concerning the airtightness of buildings. Drafts have caused discussion about whether controlled airtightness would increase the building costs too much, and improved airtightness worsen the indoor air quality. In modern Finnish buildings a good or satisfactory airtightness can be achieved with normal careful workmanship. To secure good indoor air quality, a functioning ventilation system is also necessary. There seems to be no return to traditional 'breathing' structures and natural ventilation.

This paper compares the conventional exhaust system with a supply-exhaust system with regard to the possible degree of control of the air exchange in the individual rooms. Ventilation efficiency and air exchange efficiency are defined and some examples show the local concentration, mean ventilation efficiency and mean air exchange efficiency for some simple ventilation schemes. Exhaust systems require a very tight building with small make up air openings. The ability of the different systems to avoid leakage out from the building of indoor air is also compared.

Describes the CO2-controlled ventilation system of the energy efficient EKONO II office building in Helsinki. An air sample is taken from a main return air duct, pumped to a CO2 analyzer which gives the message of the concentration tothe computer. The computer regulates the opening of the recirculation air and outdoor air dampers to keep the CO2 concentration in return air below a certain level. Shows fluctuation of outdoor air rate and CO2 concentration during one day.

Within the last ten years, energy shortages, economic pressures, and changes in indoor environmental requirements have resulted in buildings that are more energy efficient but less forgiving, environmentally. These results indicate that energ

Examines CO2-controlled ventilation for a variety of buildings. A theoretical study shows that the modification of the ventilation rate which can be obtained by the control of a 2 speed fan or by variation chimney cross-section enables the ventilation rate to be independent of external conditions (wind, temperature) and to produce annual energy savings of the order of 1500-2000 KWhr for a 100m2 house.

Describes an energy efficient hypermarket built in South Wales. Describes energy conserving features, including CO2-controlled ventilation using an infra-red analyser. Briefly discusses problems of installing and calibrating the system.

DEscribes the ventilation system which supplies outdoor air into the living room and extracts air in the kitchen and bathroom as a function of measured air humidity. Explains how air pollution by carbon dioxide and odours from occupants is associated with the production of water vapour. The only pollutants not so associated are in the kitchen and WC, which can have supplementary air evacuation.