English

Describes a system which measures the rate of air infiltration in buildings using sulphur hexafluoride as a tracer gas. Discusses two methods for evaluating the infiltration rate,the decay method and the constant concentration method. The system automatically operates a portable electron capture detector /chromatograph and samples air on a one-minute cycle. In the decay method the slope of concentration vs time on a semilogarithmic plot can be used to compute infiltration rate.

Reviews use of tracer compounds to demonstrate the transfer of pollutants from one local area or city to another. A study of gaseous compounds resulted in the selection of three suitable materials:sulphur hexafluoride, bromotrifluoromethan andOctafluorocyclobutane. These materials are all non-toxic, rare in the atmosphere and can be readily dispersed from tanks.Describes two systems developed to detect tracer gases. Sensitivity of 10-5 p.p.m. was achieved for sulphur hexafluoride without concentration of the sample. Gives method for collectingair samples and analysing them.

Describes apparatus and test method used for measuring air leakage through metal windows in the laboratory. Gives results for different types of windows and summarises air tightness standards in Japan and other countries.

Describes operation of thermal imaging cameras with a display monitor detecting infra-red radiation. Since temperature differentials of 0.20C are significant for insulation of buildings, camera must be used to limits of its sensitivity and monitoring procedure must be carefully chosen. Treats measurement limitations in field of building. Uses details of thermographic surveys to illustrate some difficulties of measurement and analysis. Emphasises importance of correct inspection procedures for particular situation.

Wind tunnel test conducted on a scale model of a classroom show that, provided the test air speed is kept in excess of about 3mph, it is feasible to use models for predicting, with good accuracy, the air-flow conditions in and around full-scale buildings. In the case of low-pitch roofs the height of the stagnant zone set up as a result of flow separation occurring at the windward eaves of a building is influenced by wall height rather than by roof pitch.

Developes a simple procedure for calculating exterior wall pressure differences and air infiltration rates for various wind velocites and direction by applying the pressure data obtained from a wind tunnel model study to a computer model building. Gives separate expressions for air infiltration caused by stack action and by wind and an expression for the combined effect. Gives example of infiltration calculations compared with computer results and finds good agreement.

Awareness has developed in the United States in the last five years that traces of radioactive radon gas and its daughter products are present in varying amounts in the indoor air. Reviews the existing literature in the subject giving a table showing reported radon concentration. Notes wide variation in results. mentions standards developed to protect uranium mines. Recommends research to quantify radon concentration data.

Describes investigation of air infiltration in a house using chlorothene as a tracer gas. Gives table of the data collected. Reports the unexpected result that infiltration rates could bereduced by increasing inside relative humidity. Suggests this is due to changes in hygroscopic building materials, especially wood. Concludes that increasing relative humidity from 20 to 40%could save from 5 to 15% on fuel costs. This analysis does not take into account the energy used to evaporate humidification water.

Discusses the need for shelterbelts over farmland and gives expression for drag force exerted by a barrier in terms of air density, wind speed, barrier height and ratio of wind speed in the shelter to that in the open. Describes field study to determine the effect of a shelterbelt on vertical wind profiles. Presents two-dimensional wind reduction patterns in the lea of the shelterbelt. Calculates drag coefficients for the shelterbelt. Concludes that a shelterbelt can be very effectivein a very short period after planting.

Describes a simple pressure method for measuring the air tightness of small buildings. It measures the leakage rate from all apertures in the external envelope simultaneously, from which total leakage area of openings could be inferred. Site measurements have shown that obvious sources of leakage like doors and windows account for only the minor part of total leakage area in the average dwelling. Results from 25 dwellings show no trend of leakage area per unit of gross floor area.