The heat loss per area through windows (U-value) is still much greater (around 1.0 W/m2K) than through the building’s walls and roofs. Reduction of window heat loss is essential to reduce the energy use of buildings and their environmental impact as required by the recast Energy Performance of Buildings Directive (EPBD), Directive 2010/31/EU.While substantial effort has been made to improve glazing’s performance, frame’s properties need improvement as 30% of heat loss takes places through the frame. U-values below 0.7 W/m2K are required for best energy efficiency in nowadays buildings. Poly vinyl chloride (PVC) frames represent the highest market share (56%) in Europe due to better weather resistance than wood and lower maintenance required and over aluminium due to better insulating properties.Our solution includes the development of an insulating foam material made of polystyrene (PS) and polyethylene (PE) filled with a Phase Change Material (PCM). It will be processed in-line with the PVC profiles made by extrusion and will provide ease of adaptation to current production methods of the industries involved, lower heat loss of the windows installed (U-value of the frame lower than 0.7 W/m2K ), improved energy efficiency of buildings (savings of energy and CO2 emissions at European level) and cost-effective solution (below 200 €/unit) able to compete with PVC systems (as low as 170 €/unit) of lower insulation properties.THINFRAME’s SME proposers will achieve a leading position compared to their competitors due to the direct profits derived from their project participation since the market will continue to grow in the next years driven by the renovation works, the EU legislation on thermal efficiency as well as a continued annual net growth of the housing stock with around 0.5 million new buildings annually. Based on current market data and the expected market growth we can forecast profits of around 17 M€ in 5 years of commercial exploitation.