The Project

Project Video

Windows are responsible for about 30-50 % of the heat loss through typical building envelopes, depending on the size and distribution in each building. Even though today’s windows are considerably efficient, the heat loss per area through windows is still much greater than through building walls and roofs. A measure of the thermal insulation and performance is given by the U-value. Lower U-values mean lower heat loss and better insulation.

A window unit is composed of two main elements: glazing (glass) and frame. Recent developments for improving thermal performance of windows have been targeted towards the glazing area. However, frames represent the weakest point of the window in terms of thermal insulation (up to 30% thermal loss) and therefore reduce performance of the whole structure. The material used to produce the window frame plays a prominent role. Wood and polyvinylchloride (PVC) provide the best thermal insulation. However, wood is sensitive to weather conditions and requires high maintenance. Thus, PVC is the preferred material of choice (with 56% of the European market) but it still lacks the desired low U-value below 0.7 W/(m2K). Some solutions involve incorporation of polyurethane (PU) foams inside hollow PVC profiles after extrusion of the profiles, i.e. out of the production line and requiring more time and machinery. This results in higher cost of production and more expensive products (by 20%).

THINFRAME will develop PVC plastic profiles filled with newly formulated thermal insulating foam manufactured in a single step during the extrusion process. This PVC profile will serve to produce highly insulating window frames. THINFRAME is aimed to comply with the most stringent national regulations on thermal insulating properties as required by national building codes in Europe.

The final results of the project will be:


  • A novel foam formulation that will be prepared from a mixture of polystyrene (PS) and polyethylene (PE) filled with a Phase Change Material (PCM) in order to increase the energy efficiency of the frame.
  • An in-line processing method for production of foam filled PVC profiles by co-extrusion of the internal foam core (PS/PE/PCM) and the external PVC layer.
  • A profile and window structure with improved thermal insulation optimised for the European market.



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