Window frame spares tropical forest

No tropical forests felled for this window frame: with wood and help from WUR, a “polder-frame” is now available.
Photo: WEBO

The project’s official name is ‘Circular Frame’. But, ‘Polder-frame’ has a nice ring to it, says associate professor Forest Ecology and Management Ute Sass-Klaassen. And it is an apt description, as the wood originates from the Flevopolder. The window frame is the tangible result of a successful EU project to produce a sustainable alternative to tropical hardwood.


‘Circular Frame is a real chain-project’, Sass Klaassen explains. ‘The entire chain, from tree to window frame, is included. We selected the most suitable type of wood and mapped its availability.’ The wood selected is the maple, a fast-growing species that can be made more sustainable through treatment with heat or acetic acid.

If the outer layer is eroded, you simply remove and replace it

Ute Sass-Klaassen, researcher Forest Ecology & Forest Management

The treatment with acetic acid protects against mould and ensures the wood retains its shape. This method was developed by chain partner SHR Wood Research. The wood is produced at Accsys in Arnhem. The frame itself is made by  WEBO  (links to Dutch content) woodworkers in Rijssen. 


The modular construction of the frame is a novelty. Only the exterior, which must be weather-proof, is made of treated maple. The inner part is made of spruce. The two parts can simply be clicked together. ‘If the exterior is eroded after say 30 years, you simply remove it and click on a new part. The window frame can thus be used indefinitely.’

Sass-Klaassen is delighted with the result, despite trees being felled for the product. ‘I’m a fan of logging. Wood is a wonderful, renewable material that stores CO2 for long periods of time. If the wood is harvested from sustainably managed forests, it is a CO2 neutral building material. Wood is invaluable to the bio-economy.’

Wood production

There is, however, one problem: There is insufficient maple wood in the Netherlands to meet the demand. ‘We have not yet reached that stage, but we could. I am not calling for wood production in all of the Netherlands’ forests, but we can contribute. We could formulate a vision, for example concerning the planned expansion with 37,000 hectares of forest.’

The new circular window frames have already been used on campus in the new education building Aurora. ‘Sadly, not with the treated maple. The architect and WUR did not want it and chose an aluminium exterior instead. A missed opportunity.’

You may also like:

Leave a Reply

You must be logged in to write a comment.