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Published on 12 December 2018 10:15

Cradle to Grave: The Comparison of Window Life Cycles

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Key Learning outcomes
  • Understanding different materials from which a window can be made.
  • Understanding the energy consumption and environmental effects of manufacturing each material.
  • Understanding the lifecycle of each material.
  • Understanding the maintenance requirements of each material.
Windows play a significant role in buildings and are available in a wide range of designs and frame materials.

Throughout this article we will aim to understand the frame materials available within the window industry; uPVC, aluminium, timber and composite aluminium/timber.

We will review their impact on the environment, the energy consumption during the manufacturing processes and the overall lifecycle of each material from cradle to grave.

We will also consider the expected durability and maintenance requirements of each material along with the economic benefits.

1.0 Window materials and environmental impact

uPVC
Polyvinyl chloride (PVC) is a common, strong lightweight plastic material used in construction, made up of repeating units of vinyl chloride. This is typically used in building materials (not inclusive of windows - such as drainpipes, light fittings etc), as it has been plasticized to make it softer and more flexible. uPVC is an unplasticized version of PVC which allows it to be more rigid for the process of becoming a window.

The production of uPVC requires the use of fossil fuels and chlorine gas. uPVC decomposes very slowly and as a waste product it contains environmentally dangerous substances such as cadmium and lead based stabilisers. Whilst the recycling of PVC is a complex procedure due to the presence of the associated polymers and reinforcement materials, it has been shown that uPVC can withstand repeated recycling and can still be used for window profiles.

Aluminium
Aluminium is the most abundant metal in the Earth’s crust and it is obtained mainly from bauxite. Properties such as strength, lightness and resistance to corrosion have led to aluminium being a preferred choice of material within the construction industry.

Production generates large amounts of environmentally dangerous pollutants; however, a benefit of aluminium is that it can be recycled repeatedly with little deterioration in quality, whilst using about 7% of the energy needed for its primary production.

Timber
Timber is wood prepared for use as a building material.

Timber is categorised as either softwood or hardwood, softwood is commonly used for timber structures due to its relatively low cost and ease of workmanship. Hardwoods are typically used for exposed structures where durability is key.

Timber can be defined as a renewable material. Environmental concerns have led to the introduction of sustainable forest management. This ensures that for every tree that is felled, at least another two are planted. PEFC/FSC ratings should be sought when using timber products.

Alu-Timber composite
Composite windows are made from a combination of aluminium and timber.

The theory behind a composite product is that it combines two materials to provide a product which performs better than a singular material.

Whilst the energy process for creating the external aluminium sash is extensive, this is somewhat compensated by the low energy manufacturing process of the internal timber mainframe. Studies have shown that up to 93% of composite window systems can be reused.
The image shows a Green Guide rating for a composite window.  We would recommend you speak to your preferred window supplier to obtain the Green Guide ratings for their products.
The image shows a Green Guide rating for a composite window. We would recommend you speak to your preferred window supplier to obtain the Green Guide ratings for their products.
 
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