Examination of the change of the overall heat transfer coefficients of building structures in function of water content

Abstract

Nowadays, the most applied insulation material in the building sector is the expanded polystyrene. Different types of expanded polystyrene are used but more widely used is the graphite added type. Our research focuses on the analysis of heat conductivity and sorption properties of expanded polystyrene as these two are the most important physical properties from energy saving point of view. In this paper, the variation of heat transfer coefficient of an insulated wall is analysed in function of humidity content of insulation material. Brick and concrete walls with 0.4 m thickness were chosen for substrate and 0.1 m expanded polystyrene (30, 100, 150, 200 and the so-called grey expanded polystyrene) materials were applied as insulating layers. The investigations of sorption behaviour of the materials are important from the point of view of fundamental research and building technology as well. Sorption data taken from our previous measurements results were used for predicting the change of the overall heat transfer coefficients of different wall structures constituted this way.

Practical application: The present technical note is based on our previous measurement results. Water can cause undesirable changes in the building structures and introduced in this article. During the fixing procedure of the additional insulating of a given building bad weather conditions (high relative humidity and/or low external temperature) can dominate. These phenomena can be imagined for building new houses. By the ‘in-building’ of the moisture into the wall structure, numerous and measurable change can happen in the U-value of the building envelope. The presented changes are estimations only, but can be used and can also help for planning and executing the insulating process.