Supplying products that will improve the energy efficiency of a new home is important not only for compliance with Building Regulations, but to meet the growing demand for measures that will reduce the consumption of energy. It must also be remembered that windows play an incredibly important role when it comes to the overall thermal performance of a home.
Recent developments in product design and manufacturing processes have closed the thermal performance gap between man-made materials and timber, and as such, the many merits that timber offers, especially over alternatives such as uPVC, are starting to come to the fore. Self-builders should be aware of the various benefits of timber windows and why they should be considered, not only for aesthetical appeal, but when energy efficiency and savings need to be achieved.
Whilst Building Regulations will indicate the performance that’s required as a minimum for both new build and refurbishment projects, both U-values and energy ratings provide specific guidance on the level of efficiency that can be expected. These specifications can be met through the design, as well as the use of a variety of high tech coatings on the inside of the glass, special gas within the units themselves, plus widely available options of double or triple glazing.
The general consensus has traditionally been that uPVC has the advantage in terms of energy efficiency, especially when combined with considerations around perceived low maintenance and capital cost. However, leading manufacturers now offer high performance timber windows with high A+ energy ratings in compliance with the BFRC Window Energy Rating scheme, such as JELD-WEN’s Stormsure Energy+ Casement range.
To demonstrate the true efficiency and thermal performance of modern timber windows, there’s no better example than the partnership between JELD-WEN and the United Kingdom Antarctic Heritage Trust (UKAHT).
UKAHT manages historic buildings in the British Antarctic Territory on the Antarctic Peninsula. Two buildings at Port Lockroy on Goudier Island, Bransfield House and a restored Nissen hut, had their original timber windows (also supplied by JELD-WEN over 60 years ago) replaced with triple-glazed casement windows. They have proven to be more than capable of withstanding the extreme environment, providing enough protection and added insulation that only minimal heating is required during the summer months. This is extremely important for reducing the cost of energy consumption and for the comfort of staff that now use the Nissen hut for accommodation.
Given that Port Lockroy is designated as a Historic Site and Monument No 61 under the Antarctic Treaty, conserving the look and feel of the original buildings, as well as the environmental credentials of all materials used, was crucial. Timber is much easier and more efficient to recycle as well as having natural non-polluting characteristics, which aids compliance with regular environmental audits.
Although very different to a typical property in the UK, the restoration work completed by the UKAHT, beautifully demonstrates why timber windows shouldn’t be underestimated in terms of longevity and energy efficiency.
Finally, the life-time performance of a window must also be considered when calculating the energy savings it will deliver until the point of replacement.
Studies, such as the one by Heriot Watt University, are spreading the word that timber frames made to Wood Window Alliance (WWA) standards are likely to last up to 60 years with normal maintenance, compared to just 35 years for uPVC. The growing trend for factory finished timber products means that the latest designs come pre-painted, pre-glazed and are protected against rot and fungal decay during the manufacturing process, meaning they will stay in a good condition and continue to perform as needed for both comfort and thermal efficiency.
Ultimately, timber windows offer many benefits both practically in terms of energy efficiency and aesthetically by creating an aspirational place to live. As the debate of timber versus uPVC becomes defunct, there is a clear argument to take a closer look at the thermal performance that timber windows can deliver to the benefit of all types of self-build project.
For more information about JELD-WEN’s timber window range and to find a retailer, visit the company’s website.