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.
A supply of fresh air is necessary in any dwelling to ensure a comfortable, safe and hygienic environment, but the heat loss to this air, during the heating season, may represent a substantial proportion of the total heat loss. This points to the need forgreater control of domestic ventilation, either by using a mechanical system or by better design for natural ventilation. This paper touches upon both of these possibilities. Gives simple method for assessing approximately the possible reduction in heat loss achieved by the use of a mechanical ventilation system.
Describes detailed study of infiltration rates measured with a tracer gas and air leakage rates obtained from fan pressurization in small, 3 - bedroom California house as part of a larger study. Finds surface pressure measurements are an essential step in process of finding a correlation between natural air infiltration and air leakage by pressurization. Measurements also show significant duct leakage and air flow between attic, living space and crawl space.
With improved thermal protection of buildings proportion of ventilation heat loss has grown until it now accounts for 50% and more of total building heat losses. Since ventilation cannot be reduced below certain limits for comfort and hygenic reasons, selection of appropriate type of ventilation system is increasingly important to control heat losses. Describes characteristics and consequences for heat energy consumption and hygiene of constant ventilation and abruptly increased ventilation such as window opening etc.
Treats development of generalised model of hourly air infiltration in residences. Describes its testing. Uses tracer gas measurements of infiltration in 9 research residences inColumbus, Ohio, under widely varying weather conditions. Estimates various linear and physical models against 7000 measurements. Measures and correlates weather parameters. Correlation coefficients ranged around 0.9 with an error between 0.1 to 0.36 air changes. presents Fortran algorithm.
Known principles for the prevention of rain penetration and air leakage are not being applied in practice. States that rain penetration requires the simultaneous presence of water, openings and a force ; the two-stage weathertightening or "open rain screen" separates the control of these factors and allows the production of a weathertight joint under practical conditions. Outlines the causes of air infiltration and gives brief case histories to illustrate the serious problems that can arise from air leakage.
States that current methods of estimating heat demand of buildings are very inaccurate, and so large safety margins are used which usually result in overestimating the necessary heating plant capacity. Describes computer program developed to improve the accuracy of heat demand calculations. Gives formulae used in the program for calculating heat demand, pressure conditions and air flow within the building. Gives example of the use of the program to calculate the effect of wind on an eight-storey residential building.
Derives equations for the calculation of air-change-rate in a room where carbon dioxide is being produced at a known rate using the measured initial and final concentrations of CO2. Also derives expression for the calculation of air-change-rate with no source of CO2 but a high initial concentration
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