Measurements in some dwellings show differences of the absolute humidity as a function of the kind of ventilation (only natural or mechanical exhaust air or balanced ventilation) and the position of the single rooms, especially of the bedrooms. Therefore is investigated into the expected moisture transport in two different ground plans. The main humidity production is in the kitchen and bathroom. If kitchen and bathroom are on the outer side, the dwelling is loaded with this moisture through the main wind direction.
Long term measurements of attic wood moisture content have shown that at least fifty kilograms of water may be stored in roof sheathing members over the course of the winter, to be released in the spring. Overlaid on this seasonal cycle there is a daily variation driven by temperature changes in the attic. A dynamic model is required to predict the resulting attic air humidity ratio. Hourly moisture flows in a typical attic - from ventilation and from the wood - are examined, and a simple first-principles dynamic mathematical model to relate them is developed.
The paper describes the main results from a research project performed by "The Mobile Laboratory of Indoor Climate Measurements" one of the five mobile laboratories of the Institute. The aim of the project was to investigate if undesirable consequences occurred in the indoor climate when using an energy saving method consisting of reducing the mechanical exhaust from the "wet rooms" to app. 40 per cent of the normal performance during 12 hours of day and night.
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