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The indoor air conditions in single-family houses with heavyweight wall structures in Finland are being studied in a research project “Air tightness, indoor air conditions and energy efficiency of residential buildings”. The research project started in March 2005 and it will end in March 2008. Altogether 70 detached houses and 60 apartments in block of flats were measured. This paper deals with the results of moisture excess and moisture product studied in these single-family houses and apartments. Indoor air temperature and relative humidity have been measured during a period of one year with data loggers measuring at one-hour interval. The data of outdoor air conditions was provided from the Finnish Meteorological Institute. Moisture excess and moisture product distributions in different house types have been analysed. The calculations take into account the number of occupants and the ventilation rate. Moisture excess is also represented as a function of outdoor air temperature. The moisture excess values were averaged over the cold period (Tout ≤5°C) and over the remaining time (Tout >5°C). Comparison to the test results of 101 timber-framed houses studied in previous study is made as well.

Development of an improved model for mould growth: Laboratory and field experiments Kimmo Lähdesmäki(1, Juha Vinha(1, Kati Salminen(1, Tomi Strander(1 Hannu Viitanen(2, Leena Paajanen(2, Hanna Iitti(2, Tuomo Ojanen(2, Ruut Peuhkuri(2 1 Tampere University of Technology (TUT), Department of Civil Engineering, Finland 2 Technical Research Centre of Finland (VTT), Finland ABSTRACT Mould growth in eight construction materials (edge glued spruce board, polyurethane (paper coated and grounded), glass wool, expanded polystyrene, polyester wool, concrete, autoclaved cellular concrete and expanded light aggregate concrete) have been studied in Finland in a study by Tampere University of Technology and Technical Research Centre of Finland. The experiments consist of the tests for the materials and for the exterior wall assemblies in laboratory and in field conditions. A mathematical model of mould growth on pine and spruce sapwood materials has been created in 1990's in Finland by Ph.D. Hannu Viitanen. One of the objectives of this research is to extend the range and reliability of the recent mathematical model. This is achieved by extending the measurement data necessary for the model development by applying several materials, different types of material surfaces and different kinds of fluctuating temperature and humidity conditions. New experimental results from the mould growth on different material surfaces and in exterior wall assemblies are presented in this paper. Experiments and calculation results of mould growth have also been compared. The comparison shows that there are some limitations and unpunctuality in the recent model. The different surface types of wooden materials and also other construction materials need correction coefficients. A more detailed analysis of this comparison and the improvement the recent mathematical model is presented in another paper to this conference.

A large experimental study on 8 different building materials is going on in collaboration with VTT and TTY, Finland. These materials are tested as pure materials and as a part of building envelope constructions both in laboratory and outdoors. The laboratory tests are made partly under constant, but different conditions, and partly under varying conditions to simulate the effect of fluctuated wet, dry and frost periods. In the field exposures outdoors, the materials and constructions are tested under real conditions. The main aim of this experimental programme is to use the measured results in developing of an improved model to predict mould growth. This improved model is based on an existing mathematical model developed on wood at VTT during 1990's. The focus in this new model is to extend the use for other materials, too, and also for a greater variety of conditions. This paper presents how the existing model is improved and also discusses the whole problem of modelling such a phenomenon. A sensitivity analysis of modelled mould growth and comparison with measured mould growth are also presented. The experimental set-ups and the results since 2005 from these extensive measurements on many different materials are presented more detailed in another paper to this conference.

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Calculation of relative humidity and temperature in an early stage of the design process is important to avoid moisture damages in wooden walls. Previous studies show that a sufficient air flow in the air gap behind the façade panel is important to ensure a moisture safe construction. This study investigates if blind WUFI 5.0 calculations with a varied air flow in the air gap behind the façade give a better correlation to measured values compared to calculations with a constant air flow. Calculations for two cases are compared to measured values in single family house. The results show that calculations with a wind dependent air flow does not necessary give better correlation to measured values compared to calculations with a constant air flow. However, the calculated values are confirmed with measured values during the warm period and there are deviations in the outer part of the wall during the cold period. Variations in measured values at the same depth in different places in the studied wall are larger compared to differences between calculated values with or without a wind dependent air flow in the façade air gap.

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As governments continue to impose more and higher energetic requirements for buildings, they also need better assessment-tools to take into account as many parameters as possible. This results in continuous developments of new calculation methods and softwares, where a balance has to be found between practicality and accuracy. To answer this problem, specifically with regard to the thermal bridges, the three Belgian regions developed a new and common pragmatic approach for assessing thermal bridges, confronting them either to simple basic rules of thumb or to maximal heat transmission coefficients, depending on the type of junction. While thermal bridges that don’t meet the requirements are sanctioned, thermal bridges that perform better can be taken into account to lower the calculated heat-losses. For this project, several very common thermal bridges were selected. Sensitivity analyse are carried out for the different parameters, such as dimensions and thermal conductivity of the components. The calculated heat transfer coefficients are confronted with the boundary-(‘limit-’)values and the default-values of the new methodology. Nevertheless, these analyses weren’t meant as a test for the methodology. They aim at allowing designers to quickly assess their common building details to the new regulation, without having to do preliminary numerical simulations of each individual thermal bridge. They also help them to better understand the correlations between the parameters of the building detail and the resulting heat transmission coefficients. The challenge that rose, was to summarize the results in pragmatic, straight-forward formats.

Calculation of relative humidity and temperature in an early stage of the design process is important to avoid moisture damages in wooden walls. Previous studies show that a sufficient air flow in the air gap behind the façade panel is important to ensure a moisture safe construction. This study investigates if blind WUFI 5.0 calculations with a varied air flow in the air gap behind the façade give a better correlation to measured values compared to calculations with a constant air flow. Calculations for two cases are compared to measured values in single family house. The results show that calculations with a wind dependent air flow does not necessary give better correlation to measured values compared to calculations with a constant air flow. However, the calculated values are confirmed with measured values during the warm period and there are deviations in the outer part of the wall during the cold period. Variations in measured values at the same depth in different places in the studied wall are larger compared to differences between calculated values with or without a wind dependent air flow in the façade air gap.

publishedVersion