A multi-cell calculation model was developed for calculation of the interconnections between airtightness, air change rates, pressure conditions and energy consumption. The flow equation used in the model is quadratic, which can be used as well for a single leakage path as for a whole building envelope. For energy calculation the area of wind directions is divided into12 sectors (each 30 degrees) plus one sector for calm wind conditions. The mean values of wind speed and outside temperature applied to each wind sector are calculated from weather data of several years period.
In these instructions for measuring the airtightness and air change rates in buildings, the principles of measurement methodics, the need for measurements and choosing the correct method for different purposes, are presented. Details of measuring are described for the most common methods: the pressure test, the collector chamber method for measuring local leakages, and the tracer gas methods. In addition, other methods and auxiliary measurements are presented.
The share of ventilation in the energy demand in Finnish building stock is about 50 per cent. An essential part of the ventilation heat losses is uncontrolled due to air infiltration, which only partly serves the demand of ventilation. The aim of improving the airtightness of windows and other leakpoints is to prevent the infiltration. But then, if the supply air intake is not mechanical, certain risks of insufficient ventilation occur. In thereport, the interconnection between the building envelope and ventilation system is studied.
The technical chapters in the draft proposal for the Ventilation Code differ from the existing one. The technical means for achieving acceptable indoor climate will be described in a new way. In order to secure acceptable quality also in practise (not only in design), new requirements are suggested for design and especially the documentation of design, for commissioning and for maintenance planning. The suggested minimum ventilation rate is 4 l/s per person in rooms where smoking is not allowed and 10 l/s per person if smoking is allowed.
The new proposal for ventilation requirements in the National Building Code of Finland is on public review. The structure of the proposal is different from the existing ventilation code. Minimum requirements for acceptable indoor climate will be given to a wider extent than before, eg new requirements for indoor air temperature and purity are proposed. Also the quality of outdoor air should be taken into account in design of ventilation. Health aspects are also considered, based on today's international knowledge of indoor air quality and human health.
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