PR1995

The ventilation of an attic is critical in estimating heating and cooling loads for buildings because the air temperature in the attic is highly sensitive to ventilation rate. In addition, attic ventilation is an important parameter for determining moisture accumulation in attic spaces that can lead to structural damage and reduced insulation effectiveness. Historically, attic venting has been a common method for controlling attic temperature and moisture, but there have been no calculation techniques available to determine attic ventilation rates.

A demand controlled ventilation system with humidity as the control parameter was tested in an experimental demonstration project in 16 apartments. In the same housing complex 16 identical apartments with a constant exhaust airflow rate were included in the test as a reference group. The purpose of the study was to investigate whether satisfactory physical health conditions could be reached in the humidity-controlled in apartments, while at the same time reducing the use of energy for heating.

A laboratory, designed to form the basis for research aiming at increasing the knowledge concerning the interactions between indoor pollution sources and the indoor environment, has been taken into operation. One long term purpose of the activities in the laboratory is to develop theoretical models, based on experimental data, for the prediction of the air quality in real buildings. At present, the experiments focus on the relationship between the emission of pollutants from building materials and the environmental parameters, i.e.

The workplaces located in southern (18 places) and central Finland. The total amount of workrooms measured was 87. The mean concentration of radon was 254 Bq/m3 (range from 12 to 1647 Bq/m3) during working hours. The calculated radon entry rates varied from 2 to 4780 kBq/h. The measured air exchange rates varied from 0.1 to 13.3 l/h and calculated ventilation flow rates varied from 30 to 55200 m3/h. Radon concentration was found to depend on the type of foundation, whereas types of ventilation or the ventilation flow rates did not correlate significantly with the concentrations of radon.

A recent investigation into the thermal environment of tropical housing required a low cost method for the measurement of high ventilation rates. As a result a simple measurement system, using the detection of the decay of smoke density, was developed. The sensor, based on an infrared LED emitter and a silicon diode receiver, was easily portable, highly robust and could be constructed for less than 50. It was found to be suitable for the measurement of decay rates in excess of 20 air changes per hour.

As part of a collaborative trial on the effects of ventilation on house dust mites and asthma, 20 mechanical ventilation units were installed in houses in the Southampton area in southern England. The hypothesis is that continuous ventilation over winter months can maintain humidity below a mixing ratio of 7 g/kg, with a consequent reduction in house dust mite numbers. The systems served upstairs only, extracting from bathroom and landing and supplying fresh air to bedrooms.

Describes the main tasks of air conditioning, heat load from human bodies, humidity and comfort, influence of the humidity on refrigeration capacity and refrigeration systems for A/C. It concludes that A/C technology is changing, especially in the comfort part by considering the influence of the humidity. One of the main developments in energy savings is the separation of dehumidification and transport of sensible heat gains.

Office workers continue to complain about air quality problems, and a significant industry has developed to measure pollutants and environmental conditions such as temperatures and humidity. The effectiveness of the ventilation system is often ignored because it is a difficult measurement to carry out and interpret. The results contained in this paper make a start towards understanding the performance of mechanical ventilation in New Zealand office buildings.

Depending on the demands regarding the size and location of the occupation zone and the need for outdoor air flow rates, different ventilation systems and air supply devices have to be used in different kinds of buildings. The occupation zone in a residential building can be dficult to define, as many different activities can take place. Furthermore the hrnishings of the room can change with time. The highest air velocities and the lowest air temperatures in the occupation zone will often occur close to inlet air devices.

A study of the reliability of systems by considering the ability of different systems to maintain a required air flow rate over time is included in a subtask of IEA Annex 27 "Evaluation and Demonstration of Domestic Ventilation Systems". Measurements were performed to determine the variation in ventilation rates due to variation in climate and variation in performance of the ventilation system. The monitoring was carried out in one-family houses and apartment buildings, which are representative of the Swedish housing stock.