Evaluation of Material Compositions of Sloping Roofs from Environmental and Energy Perspectives

Five variants of material compositions of sloping roofs were analyzed from environmental perspectives. They were designed to fulfil the requirement from thermal transmittance (U = 0.10 W/m K) for nearly zero-energy buildings. The environmental impacts were expressed by indicators such as embodied energy (EE) from non-renewable resources, CO2eq. emissions (GWP, global warming potential) and SO2eq. emissions (AP, acidification potential) as well as environmental indicator ΔOI3. They represented the equivalent emissions within the LCA boundary - cradle to gate and input data were extracted from the LCA database - IBO. The final values were compared by using methods of multi-criteria decision analysis. The lowest value of embodied energy of 745.52 MJ/m2 achieved variant with lower thickness of mineral wool thermal insulation. Highest values of embodied energy of 1408.455 MJ/m2 achieved variant with additional thickness of mineral wool thermal insulation. The best alternative from CO2 emissions (−106.1 kgCO2eq./m2) was the variant defined as green roof but concurrently it achieved the highest value of SO2 emissions (0.617 kgSO2eq./m2). The worst variant from regarding CO2 emissions (57.75 kgCO2eq./m2) consisted of mineral wool thermal insulation.