A special window system dedicated to passive constructions. Incorporation of treble glazed units with Ug=0,5 allows this system to fulfill passive standards. During the process in which the timber profiles are laminated (pine is normally used due to its beneficial thermal properties) layers of Purenit are included in the middle layers. This special material has been developed by Puren GmbH. Purenit does not absorb moisture and improves the stability of the laminated timber profiles. Purenit is free from any preservatives and is 100% recyclable, maintaining the Eco-friendly benefits of a timber window. Of course this system maintains all the benefits of Bertrand’s Strongline system.