prediction

Gives a series of short articles on air quality, air infiltration, and the ventilation needs of low energy buildings. These are -< 1. Sandberg M. Quantifying the pollution. Defines the quality of ventilation< 2. Warren P. Predicting infiltration rates. Explains BRE's method of predicting air infiltration in houses< 3. Getting close to zero. Describes the low energy EKONO office complex< 4. Sherman M. Grimsrud D. Which ventilation system? Shows that the choice of the economically optimum ventilation system depends on the tightness of the building.

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.

States that the calculation of building energy flow is very complex, and so validation is a vital element in the development of any model. Describes an IEA R and D project to compare 23 computer programs (from 8 different countries) both in terms of consistency between programs, and in thei relative accuracy in modelling the behaviour of a real building (the Avonbank office block in Bristol). Summarizes the major conclusions developing out of the project and discusses the most important aspects which need to be considered in the development of a reliable computer program.

Describes the computerized instrumented residential audit (CIRA), a collection of building energy analysis programs designed for a wide variety of microcomputers. Covers methods and type of input, and types of output produced.

Gives a brief overview of:< 1. Measurement of air change rate using tracer gas.< 2. Measurement of air leakage using steady state and alternating pressure.< 3. Calculation methods (by hand and by computer) for predicting air exchange in a building.< Indicates where relevant research in these areas is being carried out, and outlines the role of the Air Infiltration Centre.

Describes a predictive model for air infiltration in residential structures. Uses wind speed and outdoor temperature data, along with selected building and site parameters to predict average infiltration. Presents long-term field validation results obtained in a portable test structure, together with long-term data from 3 unoccupied test houses at the Owens-Corning Technical Centre. Finds that the ratio between predicted and measured infiltration peaks near one in all comparisons. The estimated standard deviation of the ratios decreases with longer averaging times.

Describes an investigation to see what energy saving can be achieved by the regulation of mechanical ventilation systems in high rise buildings. Measures air leakage in a block of flats, and uses a calculation model to predict the amount of energy lost due to ventilation in various situations. Concludes that the reduction of ventilation has no disadvantageous consequences for the operation of the system, and that the extracted air flow is affected more by incorrect adjustment of extractor vents then by opening windows, regardless of the setting of the ventilator.

Uses a similitude approach to develop predictive graphs for the ventilation rate due to the stack or chimney effect. Uses a half scale model of an open side wall structure with a continuous and restricted open ridge, and finds that:< 1. Ventilation rate is approximately proportional to ridge outlet width< 2. Outlet Reynolds number response ie ventilation rate to changes in Grashof number is a function of the ratio between building height and ridge width.

Looks at the requirements for computer model validation, especially in regard to predicting energy usage in buildings. Discusses the IEA project for comparing and validating several computer programs in this context. Describes the Glasgow commercial building monitoring project, which includes detailed measurement of temperature and air flow rates to provide data for model validation. States what type of data is needed for validation.

Proposes a simple equation derived using a more complex theoretical model for use in the prediction of the infiltration performances of houses over a range of meteorological conditions. Initial comparisons have been made with the results from field measurements in a range of typical modern UK house types.