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Highlights • Thermal response of roof/wall was analysed by altering U value and solar properties. • Solar absorptivity has significant effect on total energy use, especially at U > 0.3. • Optimal total energy use in Hamburg and Granada was always achieved by cool coating. • Coating's solar properties affect indoor thermal comfort in summer and winter. Abstract In recent decades, high level of urbanization, air pollution and climate change have caused a frequent occurrence of urban heat islands, resulting in thermal discomfort and increased energy use of buildings. As a response, a lot of attention has been paid to building envelope characteristics, with an increasing number of studies investigating building envelope solar properties as one of the important factors affecting thermal performance. However, different climate characteristics are the reason why solar properties may have different efficiency at various locations, also because in cold or temperate climates building envelope has to be more thermally insulated, namely having lower thermal transmittance. Therefore, within this study, building energy use and indoor thermal conditions were analysed for an office cell using different types of solar absorptivity (e.g. white, dark grey, collector or cool coating) and thermal transmittance, on either external wall or roof. The analysis was conducted for hot-arid and temperate climate locations. The results showed that solar absorptivity can have a significant effect on total energy use, especially in cases with higher envelope thermal transmittance. It also showed that the application of cool coatings is more reasonable if the external building envelope is not intensively thermally insulated (e.g. in hot-arid climate). In general, the optimal total energy use in both analysed climates was always achieved by implementing cool coatings. Furthermore, the results showed that white and cool coatings have comparable external (20–30 K above T air in summer) and internal surface temperature responses, while dark grey coatings cause the surface to heat up significantly (external surface 60 K above T air in summer). [ABSTRACT FROM AUTHOR]

In recent years the use of wood based products in building industry has expanded. Although lightweight timber constructions essentially decrease environmental impact of a building, their consequential low thermal mass can lead to overheating during summer. Therefore, the purpose of this paper was to investigate various examples of enhanced lightweight constructions from the thermal response point of view. Several improvements were investigated (e.g. clay boards, wood wool thermal insulation, Phase Change Materials, etc.) and compared with the performance of a conventional thermally insulated high mass wall. Finite element model was created and dynamic thermal performance of enhanced lightweight external walls was analysed in three different European locations: Helsinki (Finland), Vienna (Austria) and Madrid (Spain). Certain enhancements resulted in lower internal surface temperature of constructions up to 1 °C, depending on location. In addition, it was shown that in order to further improve thermal performance, application of high intensity ventilation is necessary, which additionally lowered the internal surface temperature up to 8 °C. It was shown that enhanced and naturally cooled lightweight constructions are more suitable for locations with milder summer temperatures (Northern, Central Europe), rather than for hot climates (Mediterranean). It was concluded that the application of lightweight constructions should be thoughtful in order to achieve adequate thermal response of buildings. However, in lightweight buildings the integration of materials characterised by high thermal mass, high thermal effusivity and low environmental impact should be encouraged. [ABSTRACT FROM AUTHOR]