humidity

The Heat Protection Ordinance (Warmeschutzverordnung EnEG) issued in 1977 aimed to reduce heating energy consumption and has become part of the building ordinances. Beside the heat transmission resistance (k-value-a measure for the size of the heat transmission losses), also the crack flow exponent (a-value) has been controlled to reduce ventilating heat losses. Practical experience has shown that, without mechanical ventilation, hygienic, physiological and building physical disadvantages will turn up.

A mathematical model, CLIM, is used to compare constant air flow ventilation with adjustable ventilation controlled by indoor relative humidity. Exhaust air flow varies in a ratio of 1 to 4 between 40 and 75% of relative humidity and the mean annual air flow is divided by 2 in comparison with a classical mechanical ventilation system.

Discusses methods of preventing condensation: dehumidification, ventilation, controlling vapour flow; insulation and heating. Particular attention is paid to interstitial condensation and condensation in roofs

Summarises risk by building type and the various physical processes involved in moisture transfer and condensation.

Pollutants in a substantial number of buildings have now been investigated by public and private agencies. The archive of data on indoor pollutant levels observed in office buildings under conditions of normal operation and occupancy are reviewed using a computer based Building Performance Database. Representative values of 153 pollutants as well as detailed frequency distributions of commonly measured pollutants and of temperature and humidity are presented.

Describes automatic equipment for measuring thermal comfort based on resultant surface temperature, convective heat flux density, air temperature and relative humidity. Results obtained in an environmental chamber are presented and evaluated.

The effect of reduced air infiltration rate caused by energy-saving measures has been studied by comparing the indoor climate in 25 sealed apartments with the conditions in 25 unsealed apartments in Denmark in four seasonal periods. 

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.

As airtight houses become more popular across Canada, reduced ventilation rates may lead to poor air quality and high humidity problems in these dwellings. This paper reviews the needs for ventilation, ventilation methods and systems, and current codes and standards, particularly with respect to airtight and energy efficient houses. Current research in Canada is reviewed and considerations for a new ventilation standard are discussed.

Contains articles on rain penetration and moisture damage in residential construction, moisture sources in houses, control of surface and concealed condensation, and ventilation of houses. Illustrates the various types of condensation problems that may occur, explains the active processes involved in some of these problems and discusses in detail the principal factors surrounding these phenomena i.e. sources of moisture, choice of construction detail, and current ventilation practice.