Summary
• Imperial College carried out research on the service life of Wood Window Alliance windows.
• It concluded that WWA windows could achieve a service life of 60 years.
• JELD-WEN worked with Osmose on preservative treatment of window components.
• The paint formulation was developed by Sherwin Williams, with the Becker Acroma and Sayerlack brands.

Timber windows are renowned for their longevity compared with other materials. You only have to look at some of England’s historic cities to see the longevity of timber windows, with many surviving for centuries without ever needing replacing.

Aware of timber’s natural properties, JELD-WEN set out to investigate ways to lengthen guarantees and service life predictions for our 21st century timber windows.

Local authorities and housing associations are ever more conscious of specifying windows that offer the very best lifetime values and are looking for products that have the same predicted service life as the new homes being constructed. New homes within this sector are typically expected to have a useful service life of 60 years before major refurbishment or replacement, so our objective was to use the latest research and technology to replicate this six-decade span in terms of a guarantee which really will deliver.

Independent research

Imperial College, London, recently carried out independent research into the service life of certified windows produced by Wood Window Alliance (WWA) members. The study was undertaken in accordance with BS ISO 15686-8 (2006) and examined the influence of modern substrate, design and coating systems on the service life and whole life costings of fully finished timber windows. Its conclusions were that timber windows manufactured to the design, materials, quality and processes required by the WWA will achieve a minimum estimated service life of 60 years. This study provided the trigger for us to build on this research and develop a guarantee that would provide added reassurance to housing associations, local authorities and homeowners that when they bought our fully-finished timber windows, they would be investing in a product that would save them significantly on replacement windows over the lifetime of the building.

The first area of development was to look at the preservative treatment that we applied to our timber components. For this, we worked with wood preservation technology provider Osmose. Prior to assembly our timber window components were treated with Osmose’s Protim enhanced wood preservative system, which is designed to provide effective protection for external joinery, as defined in BS EN 8417.

Preservative and coatings

The preservative system is applied to every engineered softwood timber component under JELD-WEN’s 60-year guarantee option, before it is finished with a newly specified coating system that provides extra defence against cracking, flaking and blistering. Our wood preservation process is independently audited by Osmose and further reassurance is provided as this is underpinned by periodic laboratory analysis of treated samples to check compliance with Osmose penetration and loading requirements.

Following the preservative treatment, the timber components undergo a specialist factory finishing process. The paint formulation has been developed by Sherwin Williams with the Becker Acroma and Sayerlack brands to provide detailed protection on the windows, specified as part of JELD-WEN’s Lifespan Guarantee, leading to our offering a 15-year paint finish guarantee as part of that.

When combined, these two processes provide the 60-year service life, which is unique in the industry.

Developing a specification which meant that replacement windows and those for new builds could deliver this long extended service life is a major breakthrough in the market for timber windows. It reinforces how timber does offer better whole life costings than other materials. And, when you consider that carbon will be stored within the timber for its lifetime, then it is clear to see that buildings with these windows have a further reduced carbon footprint.

Benefits

Although these windows are charged as a premium product, due to the very specific production processes, many specifiers in the social housing sector are recognising the benefits in terms of improved whole life costings, especially in the savings on maintenance and replacement costs.

This breakthrough has huge implications for both the new build and refurbishment sector, particularly in social housing, and elevates timber windows to a whole new level in terms of guaranteed long life and reliability.

It is guarantees like this that are helping timber to rise above its competitors in the window market.