Sliding sash windows from Mumford & Wood

With the marketing skills of uPVC window manufacturers, consumers can be forgiven for any confusion that has been created in the debate on environmental advantages of one material over another, but according to a recent report entitled Window of Opportunity, there is sufficient evidence to “justify the long-held position by WWF and other major environmental organisations that PVC is unsustainable and hazardous”, (Source WWF-UK, July 05, Christian Thompson). In fact, responsible timber window manufacturers have bonded together under a recognised scheme created by the British Woodworking Federation (TWAS – Timber Window Accreditation Scheme) in order to collectively overcome misinterpretation. In this Scheme members are independently audited for their manufacturing processes and work towards gaining the BS Kite Mark badge after qualification. Consumers should not only look out for this seal of approval but also that of the new energy ratings standards, under the British Fenestration Rating Council (BFRC), which is dedicated to an accurate and credible system of measuring thermal efficiency.

By assessing the performance of a window, both from the point of conserving energy by not allowing it to escape and also from trying to obtain as much free energy as possible from the sun using the solar gain properties of the window, the ratings, from A to G, much the same as the ratings on domestic white goods – A being top – give a measurement of the combined performance of these two elements. Consumers should select window products from reputable window manufacturers.

Carbon Footprint With the government’s urgent drive to reduce CO2 emissions and achieve carbon zero rated homes, it is not only the visual appearance that timber windows contribute to the environment but the part they play in the fight against climate change. In the search for more sustainable ways of building, the European timber industry is able to offer a positive contribution to the challenge of sustainable development and the reduction of greenhouse gas emissions and many new, environmentally friendly solutions are being put into practice.

By choosing wood, homeowners are making their own positive contribution to reducing impact on climate change in the conscious rejection of alternative, less environmentally-friendly materials. The carbon footprint of a product or material and its impact on the environment is a measure of the CO2 it emits in every aspect of its life cycle – from harvesting, manufacture, delivery, use and eventual disposal.

In this Life Cycle Assessment, timber has the advantage that trees absorb CO2 during their growth cycle and beyond the life of the material through recycling.

Recovery of this stored energy by burning provides a substitute for fossil fuels and still further, the regeneration of forests as timber use encourages replanting, in turn establishes the cycle of CO2 absorption from the atmosphere.

Whole Life Costing is another technique used to enable comparative cost assessments for a product, taking into account all relevant economic factors – initial capital costs, future operational and maintenance costs – providing the total cost of a product during its life. In recent studies*, high performance timber windows had a substantial 14% lower Whole Life Cost than uPVC when comparing identical specifications. The WWF-UK report, Window of Opportunity, identifies that “it takes eight times more energy to manufacture a PVC window than an equivalent timber frame”.

Sustainable timber Sustainability is more than a current buzz word. In the timber industry 0an environmentally conscious manufacturer will go to great lengths to ensure that the timber he uses comes from sustainable sources. Manufacturers should be working towards Chain of Custody certification – this is proof of the unbroken path which products take from the forest to the consumer including all stages of manufacture, transportation and distribution.

It provides the evidence that the product originates from well managed forests and verifies that these products are not mixed with products from uncertified forests at any point in the supply chain. Certification offers independent verification of the truth of product labelling and reassures purchasers that a forest product bearing a label conforms to the claims being made on the label.

Modern paint and/or stain finishes provide extended service life and because the substrate material of timber is easily worked and repaired, long term maintenance costs are much reduced over other materials. Most manufacturers give long warranties for service life of the window product and given that the window is maintained over its life in accordance with the manufacturer’s installation and maintenance guidelines, homeowners can expect it to last their life time and beyond. The longevity of timber is illustrated in the existence of many hundreds of thousands of timber windows which still exist in historic properties.

* Whole Life Costing was carried out by The London Borough of Camden in 2003 on timber and uPVC window products.

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