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TECHNOLOGY 37
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affect properties such as thickness swelling. However, this process tends to degrade the raw material,
The thermal performance of a window is greatly affected by which negatively impacts its strength properties.
the material used for its frame. With the growing emphasis on It is important to note that, depending on atmospheric
sustainable design, window frame materials must demonstrate conditions, and the colour and quality of the coating, any

superior environmental performance to be considered truly varnish that is not removed during recycling can negatively
sustainable. impact the strength properties of the manufactured wood
Consequently, a comprehensive performance metric is materials.
needed to evaluate window frame materials effectively. This However, it has also been demonstrated that a suitable
study analysed three identical aluminium, polyvinyl chloride coating can help maintain the highest wood quality.
(PVC) frames and wood. Reclaimed wood from demolition can be successfully
Their thermal performance was initially assessed and repurposed for structural use, with promising applications in
compared using a heat transfer model. Subsequently, the carbon creating engineered wood products (EWPs) like cross-laminated
footprint of each material was calculated for a one-square- timber (CLT) and glulam.

meter window area with comparable thermal performance. This approach minimises waste and contributes to the
The results revealed that wood window frames excelled sustainability of wood construction by incorporating recycled
over aluminium and PVC in thermal and environmental materials into advanced building components. Recent projects
performance. However, aluminium frames had a significant have faced challenges, with unsatisfactory outcomes primarily
environmental impact and lower thermal performance. This due to wood species’ diversity and difficulties in sorting materials.
study thoroughly analyses window frames, considering their Wood sourced from furniture, window frames, and
environmental and thermal performance. mouldings presented significant obstacles to maximising the

Window frames are classified as bulky waste, complicating use of recycled materials.
their collection and recycling compared to routine waste As a result, subsequent efforts have concentrated on
materials. The collection process for window frames is less developing more effective methods for sorting raw materials
efficient than everyday waste. These frames serve as structural for recycling.
support, providing form and stability to each window. A notable advantage of window frames is their relatively
As lifestyle changes and economic conditions drive the large dimensions, which makes them ideal for shredding and
demand for inexpensive, quickly replaceable products, bulky repurposing in applications such as particleboard production.
waste, including window frames, has become a relatively Recycling wooden window frames supports a closed-
small but steadily increasing waste stream in many countries.

Recycled wood can be used as a raw material in producing John Loo
wood-based composites, such as particleboard, fibreboard,
and structural panels, resulting in high-value products.
Unfortunately, the literature offers limited examples of
recycling window frames, but there are instances of recycling
other wood–plastic composites that could inspire further
research. One notable example is the hydrothermal processing

of particleboard, where the recovered wood material is reused
to manufacture new particleboard.