English

A method for environmental evaluation of buildings that is general, open ended and based on scientific foundations. Such a method is demanded increasingly, both in Sweden and abroad. This is why the Swedish Council for Building Research is financing both national and international projects in this field.

This Update is the first of two that discuss mechanical ventilation systems in houses. It explains why houses need to be mechanically ventilated, and examines the main characteristics of an ideal system from the standpoint of design and installation.

The effect of external pollution levels on indoor air quality is a subject of growing interest, especially with the increasing application of natural ventilation in urban areas. The analysis described in this paper allows the effects of varying external pollution levels to be estimated for any configuration of ventilation system, natural or mechanical. The analysis takes into account filter efficiency and position, internal pollutant sources, degree of re-circulation and varying fresh air rates.

Results of an investigation of the effects of window position on the airflow characteristics for a typical bedroom setting in Taiwan are presented. Four different window positions were examined in the experiment which used a full-scale laboratory bedroom model with a single bed. A three-dimensional ultrasonic anemometer was used to measure airflow distribution and the results of flow measurements at two height levels are presented. Computer simulation of the airflow distribution was performed using the standard k-e turbulence model.

Current approach for design and installation of mechanical ventilation systems in houses is described in the framework of Canadian building codes and standards, which contain requirements about air change rates, air distribution, sound level, interference with other systems or building envelope.

Gravimetric determination and continuous monitoring of respirable dust in air has revealed that there are high levels of dust at some roadside and indoor locations in urban areas. Furthermore, where high dust levels are measured in roadside samples, high concentrations are also measured in adjacent buildings. The dust levels measured inside a building have been shown to be very closely correlated to ambient levels, and traffic emissions, particularly from diesel vehicles, are the principal source of respirable particulates.