Assessment of thermal bridges effect on energy performance and condensation risk in buildings using DoE and RSM methods

Abstract

Energy performance of buildings, assessed along design stage or rehabilitation phases during service life, is directly influenced by the manner thermal bridges are approached, being that their unavoidable presence in structures affects the risk of surface condensation and the level of thermal comfort. A realistic evaluation of these responses depends on the accuracy of estimate for thermal bridges share in heat loss. The assessment method recommended by European regulations and implemented through national regulations in Romania, uses linear and point thermal transmittances and temperature factors. The broad variety of building details leads to a large typology of thermal bridges, with unattainable coverage through catalogues with precalculated values. This paper contributes to the efforts of expressing mathematical relations for calculation of linear thermal transmittances and temperature factors, for the main types of thermal bridges. For this purpose, a method applied previously to similar problems has been adapted in order to formulate the relationships between the aforementioned parameters and their influencing factors over their variance range. Values of response parameters are determined with polynomial equations, coefficients of which are obtained through statistical data processing with DoE and RSM method. The method validation has been analysed by comparing the results with other sets of values obtained through numerical simulation. For the mathematical models investigated and the variability of factors, there have been made remarks over the attained precision and its adequacy to the submitted aim.

Keywords:

• heat transfer
• thermal bridge
• numerical simulation
• statistical analysis
• response surface methodology

Acknowledgements

The authors thank the Executive Agency for Higher Education, Research, Development and Innovation Funding, Bucharest and the Government of Romania for funding the studies under New eco-concrete to increase energy efficiency in agro-zootehnical buildings.

Additional information

Funding

This work was supported by the Executive Agency for Higher Education, Research, Development and Innovation Funding, Bucharest and New eco-concrete to increase energy efficiency.