Roof space ventilation is important in warm weather to dry out moisture that may have accumulated in the roof space. It is important to reduce the movement of moisture from the living areas to the roof space and to ventilate the latter by means of vents distributed between the upper and lower parts of theroof to take advantage of both wind action and stack action.
Describes the principal causes of condensation in dwellings in the UK. Monitoring the existing environmental conditions within a building, plus a structural and tenant survey, is required to determine the correct cure. Theinstrumentation and techniques are listed, and some solutions are suggested.
Outlines some of the principles behind air driven aspects of moisture in buildings and illustrates how calculation methods and mathematical modelling techniques may be used to both predict and remedy associated problems. Primary remedies include a reduction in the generation of moisture, ensuring thermal integrity of the building and providing adequate ventilation. The use of dehumidification may also have a role to play. Mathematical models offer an inexpensive method for assessing design ideas at an early stage of development.
This paper reviews the work carried out in the Netherlands on moisture problems. In current air flow simulation models for buildings, moisture transfer and diffusion in and between rooms are not taken into account. The aim of the research project is the development of an integral hygrothermal model in which the above mentioned aspects are incorporated.
Over the last few years frequent cases of mould growth in dwellings have occurred. The problem is essentially due to an excessive moisture content of the building elements, which can result from hygroscopic adsorption or from frequent surface condensation.
A series of laboratory tests for moisture problems were conducted on an air infiltration barrier. One series involved the condition where warm and moist indoor air circulates through wall cavities.
Notes that the trend to airtight window constructions has upset the balance in buildings between moisture generation and its removal. Treats the factors which combine to determine whether a building will have moisture problems. Presents a procedure for the straightforward determination of the specific minimum air flow required in a particular building to prevent condensation on the inner surface of corners formed by two dimensional external walls. Determines the base air flow and the supplementary air flow for four models of representative apartments.
A major cooperative study of the effect of ventilation of timber flat (cold) roofs on combatting condensation and moisture accumulation has been undertaken in Denmark. Field measurements of moisture content in a number of test roofs over long periods and under different conditions are evaluated and conclusions drawn. They include the advice that, where moisture accumulation is a problem, it can be aggravated if roof vents are installed.
Concentrations of airborne radon ranging from 0.05 to 135 pCi/L were found in houses in Maine. Track-etch cups were placed in five positions for 100 houses to determine integrated average radon concentrations over the period October 1980 - May
Discusses strategy for dealing with indoor air pollution in office and similar buildings, including verification of the mechanical ventilation system, measurement of building pressure, problems due to stack effect, presence of moisture. Suggests that the causes and cures of indoor pollution are diverse and surprisingly simple. Mechanical ventilation systems should be less complex, have dynamic stability and correct uncontrolled excessive moisture.
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