air change rate

Shows need for intermittent high ventilation in dwellings to remove water vapour and odours. Suggests openable windows as the simplest and most common method of ventilation control. Gives air-change-rates in two british houses using carbon dioxide andnitrous oxide as tracer gases, showing the effect of opening windows. Shows that increase in ventilation rate caused by opening windows can be tenfold and is not confined to the room with the open window. Closing of internal doors has a significant effect. Describes investigation of air flow within rooms using smoke.

Considers the likely impact of alternative conservation measures on the incidence of surface and interstitial condensation on or within the elements of the building fabric. Considers specifically domestic buildings in temperate climates such as in the U.K. and Ireland. Outlines the mechanisms whereby condensation occurs and considers broadly the effect of reducing heating levels, reducing ventilation and increasing insulation.

Briefly outlines the approach used and the results obtained by computer modelling in estimating the magnitude of natural ventilation in irish housing. Concludes that in general air-change-rates in irish housing are excessive.

Reports measurements in seven groups of town house in Gavle, Sweden of concentrations of radon and daughter products. Gives results with the type of building materials, the ventilation systems and air-change rates measured using nitrous oxide as a tracer gas. Gives formula for the permitted limits of radionucleides in building materials. Discussed results and concludes that the concentration of radon does not differ significantly from single family to multi-family houses.

Reports measurements of air change rates made in the tower of an eleven-storey building using sulphur hexafluoride as a tracer gas. Inside to outside pressure differences were also monitored as a function of temperature and wind speed. Gives expression for autumn and winter air change rate as a function of windspeed. Reports finding that wind direction and stack effect had little effect on the air change rate. In this building toilet exhausts and other weather independent mechanisms were more important than natural infiltration.

Reports two-year programme to evaluate the effect of air infiltration on the heating needs of 29 electrically heated homes. Air-change rates before and after retrofitting tominimize infiltration were measured by a pressure method and heat energy consumption and occupancy effects were monitored. Thirty similar homes were also tested for infiltration and retained as controls.< Describes the retrofit methods, their effect upon the induced air infiltration, the other data which are being collected, and the data analyses which are expected at the completion of the programme.

Discusses the mechanisms which govern natural ventilation. These are wind speed, flow, characteristics of openings in buildings and pressures generated at building surfaces by wind and temperature difference. Gives formulae for simple cases. Outlines ways of determining natural ventilation rates. Gives brief account of the effect of turbulence and openings in one wall only.

Describes adaptation of photo-electrical optical technique to measure ventilation rates in wind tunnel models. Illustrates probe photographically and diagrammatically. It comprises essentially a light-emitting diode and a hybrid photodiode-amplifier detector. Compares technique with conventional tracer gas technique using helium and a katharometer and finds good agreement. Considers optical probe has considerable potential for measurements in small and multi-celled models where conventional techniques are not feasible.

Presents method for collecting air infiltration data in a large sample of dwellings. The method consists of a tracer gas dilution technique using sulphur hexafluoride and employing air sample bags which are analyzed in a central laboratory. Themethod is easy to perform and inexpensive and will be used in approximately 300 dwellings on 16 sites to give air exchange rates under typical heating season conditions. Presents preliminary data on air infiltration rates in low-income housing in Portland, Maine.

Summarizes measurements made on a flat. These include inside to outside temperature and pressure differences, infiltration rates using helium as a tracer gas, duration of opening windows and doors and weather conditions. Also describes wind tunnel measurements made on a model of the building with and without obstacles and terrain roughness.