modelling

For the transient analysis of the thermal and moisture conditions in multilayer constructions a numerical algorithm and a computer program based on the Crank-Nicholson method and quasi linearisation are formulated. Temperature and moisture content are used as transport potentials. In energy balance equations and conditions, convention and accumulation of moisture, the diffusion flow of water vapour, the capillary and surface diffusion flow of liquid water and the viscous flow of humid air and water are considered. The boundary layer and interfacial balance equations are derived.

Individual mathematical models for formaldehyde concentrations in each of 3 normal rooms in a single family house is used to estimate ventilation rates needed to maintain formaldehyde concentration below the recommended Danish indoor standard (0.15 mg/m3). In an initial period after the house was finished a ventilation rate more than 10x the recommended Scandinavian maximum value (0.5 ach) was needed to keep the concentration below the indoor standard.

After a brief treatment of the ideas and aspects that play a role in ventilation, gives a general outline of chosen investigation methods, with a concise review of apparatus and calculation models used. Presents a review of the ventilation investigations carried out by IMG-TNO during the last 10 years in factories, labs, hospitals, auction halls etc.

Describes research work in Finland concerning air infiltration and ventilation in buildings from 1979. Types of ventilation system in finnish houses, flats and other buildings are discussed. Reports on a model developed to predict the correlation between various factors and air infiltration. Gives a summary of pressure test measurements carried out in a few hundred small houses, and presents proposals for recommended airtightness levels in new buildings. Describes warm air heating systems, heat recovery systems in flats, and maintenance problems with ventilation systems.

Describes trials undertaken by BRE and ECRC at Inverclyde to test small domestic electric dehumidifiers in council houses. Assesses 3 types of machine, selected to give a range of extraction rates from 1-4 kg per day. These were supplied free of charge and the running costs reimbursed. Shows that the equipment did lower the moisture levels in the houses satisfactorily. Preliminary analysis of results show that the early BRE model predicting moisture and ventilation interactions work well.

Energy is consumed in heating the air infiltrating into houses maintained at temperatures above ambient. By using climatic data tapes and a daily profile for indoor temperature of a house, it is possible to calculate factors, which in conjunction with a relationship between air change rate and wind speed enable the energy consumption due to infiltration to be calculated on amonthly basis. This has been done for Melbourne, Australia and the factors tabulated on a monthly, annual and heating season (April Nov) basis.

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

Describes a model that predicts air infiltration from both wind and temperature influence to within 20%. Compares the predicted value and measured infiltration from a full-scale test structure, revealing an average discrepancy of less than 10 m3/hr (out of an average of approx 150 m3/hr). Presents direct measurements of the wind velocity and pressure coefficients induced by the wind on the full-scale test structure.

Develops a model apartment building based upon existing surveys of such buildings and computer simulations carried out to determine the independent effects of climate and size on its energy consumption. The Meriwether Energy System Analysis program used has previously been calibrated by simulating four existing buildings of known energy consumption. From these results, develops data which enables a norm to be derived from the energy consumption of any high rise apartment building at any location in Canada.

Evaluates results from constant concentration tracer gas measurements and fan pressurization measurements in three houses and predicts ventilation rates for longer time periods using the LBL model. Test results show that the best way of both supplying adequate ventilation and conserving energy is to make sure that the building envelope is sufficiently tight and then install a mechanical ventilation system. Shows that it is possible to correlate fan pressurization measurements and infiltration rates.