Indicative investment: about €400/m² (triple glazing, installed)
Eko sklad subsidy: up to 40 % of eligible costs, capped at €300/m²
Effect: 10-15 % lower total heating costs
Look at Uw, not Ug
Manufacturers often quote the transmittance of the glazing (Ug), which is more favourable than that of the whole window (Uw). Only Uw, which includes the frame and the spacer, is meaningful for assessment. Quality frames in timber, PVC or thermally broken aluminium contribute significantly to the overall value. For Slovenian conditions we recommend windows with a Uw of 1.1 W/m²K or lower, in line with the requirements of the PURES regulation.
Installation determines real performance
Even the best window will disappoint if it is badly installed. We recommend installation to the RAL system with three sealing levels: a vapour-tight tape on the inside, thermal insulation in the installation joint, and a vapour-permeable tape on the outside. This prevents moisture migrating into the joint and mould forming around the reveals.
Do not forget ventilation
Replacing windows sharply reduces unintended air infiltration. That is good in energy terms, but it means ventilation has to become deliberate - or a heat recovery system has to be installed. After a window replacement it is therefore worth adopting short, intensive airing several times a day.