modelling

In the calculation of natural ventilation systems there is a lot of data which is not dependent on the ambient weather conditions. Data calculated by project engineers include geometrical size of the building; effective vertical distance between inlets and outlets; indoor loads/heat, moisture, fouling gases; interior climate requirements, relative humidity, density of air etc.Some of these factors are not changeable after the completion of the building, but there are some which could or need to be changed.

Identifies alternative methods available to control indoor air pollutant exposures. Describes the performance characteristics of ventilation systems and of air cleaning devices used in mixed modes for ventilation of occupied spaces. Reviews models for predicting effectiveness of several alternative modes, with field trial validation results cited where available. Briefly reviews previous confined-space studies as points of departure for consideration of necessary air quality, ventilation and air cleaning.

Shows the usefulness of a model for extrapolating environmental chamber results on pollutant emissions from combustion appliances to determine indoor pollutant concentrations in actual residences. Investigates the effects of infiltration, whole-house ventilation, and spot ventilation on pollutant levels. Results show that a range hood is the most effective means of removing pollutants emitted from a gas-fired range; removal rates vary from 60%-87%.

Describes a computer program, Harmon, developed for the simulation of the thermal response of buildings (based on BRE's "admittance procedure") which can be used on mini-computers and utilized at the sketch design stage for the comparative evaluation of alternative designs. Gives an account of the validation exercises completed and outlines further intended refinements.

Discusses the evaluation of building surface pressures resulting from the action of external wind, the modelling of individual components through which air flows, the determination of their characteristics under the action of pressure and temperature differences, and the solution of large airflow networks consisting of several such dissimilar components. Describes the integration of airflow calculations with heat transfer calculations in an attempt to produce a balanced approach to the determination of energy requirements for buildings.

A knowledge of the pressure fluctuations on buildings exposed to strong winds is important for wind loading calculations. Presents the statistical quantities of such fluctuations in terms of rms values and power spectra for models resembling the Aylesbury experimental building of BRE, and compares this with full-scale results. Suggests that, provided the properties of the longitudinal velocity component are suitably simulated, then agreement between full-scale and model results in terms of rms values and power spectra can be achieved.

Illustrates the building, comprising 24 flats in four storeys constructed in 1957 and heated by an oil fired boiler. Notes the intensive monitoring of the thermal characteristics of the building since 1980, with readings from 600 sensors.

Provides the first results of a comparison of computer predictions of building energy demands with measurements in actual buildings - the Maugwil single family house and the "La Chaumiere" block of flats. Describes the buildings and summarises the measurement results and predicted values in graphs. Concludes the results indicate that the DOE-2 program can predict the thermal behaviour of buildings with an accuracy to within 5-10% on condition that it uses precise hourly meteorological and air change rate data. Stresses the important influence of the program user.

Describes a scale model test technique designed to estimate building ventilation flow rates due to wind as a function of its primary variables. Use of this method is illustrated by its application to the determination of wind-induced ventilation flow rates in earth-bermed, above-ground fallout shelters. Shelter models with 3 different sets of wall openings are tested over a range of relative wind angles varying from 0 to 90 degrees and wind speeds from 2.25 m/s to 6.75 m/s. Helium filled soap bubbles released in the approach wind boundary layer trace the flow through the buildings.