ESSENTIAL THINGS YOU NEED TO KNOW ABOUT U-VALUE
Buildings have a significant contribution in the overall energy consumption in the EuropeanUnion (“EU”) by about 40%. For this reason, the EU has issued specific directives to member states related to the Energy Performance of Buildings and the use of renewable energy in buildings. Cyprus has embedded into national law the aforementioned directives, by taking various measures, such as issuing relevant decrees (Federation of European Heating, Ventilation and Air Conditioning Association).
U-value or thermal transmittance (reciprocal of R-value) is the rate of transfer of heat through a structure (which can be a single material or a composite), divided by the difference in temperature across that structure. The units of measurement are W/m²K.
Well-insulated parts of a building have a low thermal transmittance whereas poorly-insulated parts of a building have a high thermal transmittance. Losses due to thermal radiation, thermal convection, and thermal conduction are taken into account in the U-value. Although it has the same units as the heat transfer coefficient, thermal transmittance is different in that the heat transfer coefficient is used to solely describe heat transfer in fluids while thermal transmittance is used to simplify an equation that has several different forms of thermal resistances.
Minimum requirements of 2016 (Κ.Δ.Π. 119/2016 και Κ.Δ.Π. 379/2016) In effect from 1.1.2017
Walls maximum U - value: 0.4 W/m2 K Walls can be up to 0,6 W/m2K if windows up to 2,5 W/m2K
Roof and floor in contact with external environment maximum U - value: 0.4 W/m2 K
Floor above closed unheated spaces maximum U - value: 2.0 W/m2 K
Window maximum U - value: 2.9 W/m2 K
More information available in the attachment!