This is the third item in a series on methods for predicting condensation risks within structures. It answers criticisms made of the method described in NO 1729, on the basis that the method does not give the same answers, nor does it take account of the effect of the occurrence of condensation on the vapour pressure gradient within the structure, as does the graphical method described in NO 1728.
Describes in detail a computer-based technique for predicting the risk of condensation occurring in building structures. The technique not only indicates the position at which condensation is likely to occur, but also puts a figure on the risk of decay in timber within the structure. In the case of ventilated roofs or walls it gives the minimum sizes for ventilation openings.
Retrofitting of older buildings brings about a noticeable drop in air supply. Fireplaces in buildings need sufficient combustion air. Tight windows may cause insufficient air supply. Therefore an adequate combustion air flow for the fireplace may not be attained and poor combustion will take place. In this study data on length, tightness, etc of windows, doors and other openings in buildings of the last 30 years have been collected.
From a hygienic viewpoint, optimum indoor air quality can be characterized as the complete absence of pollutants. The most important sources of such pollutants are reviewed, including those entering a room from outside, those generated by human activity and those emanating from various materials. Thebasic requirement is for all emissions to be as low as possible. For CO2 and formaldehyde the existing standards are reasonable. For most of the other substances it is not recommended to define tolerable limit values since such definition may decrease the efforts to attain a zero level.
The theoretical and experimental study of heat losses and energy consumption and its influence on the air quality in buildings has been undertaken by the Silesian Technical University since 1980. The heat consumption of buildings isinfluenced by the thermal insulation of buildings components, airtightness of these components and the types of ventilation systems. Simultaneously, the thermal comfort and also air quality is influenced by the modern building material and different types of buildings.
The total energy consumption for five detached houses with air change rates of around 3 per hour right after construction, was measured and compared with estimated values, over a three-year period. Air change in the bedrooms was also measured. It was found that the recommended value was only obtained in very tight houses. If two windows are open, the ventilation system is partly short-circuited. A modified exhaust air ventilation system was designed to provide a sufficient air change in the bedroom with a reduced total air changein the house as a whole.
Ventilation requirements for the reduction of humidity. Required air change rates for hygiene and moisture removal for various rooms are given. Air flow rates are calculated for natural ventilation with closed windows, hopper windows and controlled ventilation. Ventilation by window opening is discussed. Gives examples of the transfer of moisture within a building, and the main reasons for ventilation, with particular emphasis on moisture removal. Lists danger of condensation on various building elements, causes and remedies. Advises on ventilation measures.
It is necessary to design the ventilation system to avoid excess humidity in the apartments. Discusses the sources of moisture release in rooms, properties of air temperatures in relation to moisture absorption, condensation in bedrooms in particular, and moisture damage to building fabric. Advises on ventilation measures to control humidity.
The simple steady state model which is frequently used to relate radon concentration (C), source strength (S) and ventilation rate (l/tau) is expressed in the equation C=S tau. The assumptions of this model are given and their validity explor
To propose guidelines for minimum ventilation rates which are sufficiently large to meet the demand for fresh air without unnecessarily wasting energy, in IX "Minimum ventilation rates" within the IEA Programme "Energy conservation in buildings and community systems" nine countries are co-operating. The participants have in a first step summarised existing knowledge, national standards and current and required research. The work that was required covers a wide range of disciplines, from hygiene and medicine on one hand to engineering and building science on the other.
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