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Can modern timber windows contribute to reducing a householders annual energy bills? You bet they can!

9 Oct 2008
Byword: Roy Wakeman, CEO, The Performance Window Group

Many people have a poor perception of timber windows based on a bad reputation gained from the 60’s and 70’s building booms. Then, softwood window frames were used in a primed state by house builders as formers for the bricklayer to build the external walls around. As a result, the windows suffered and the subsequent paint applied served to temporarily conceal the damage already caused, mainly by ingress of moisture, from the building process. This lead to the timber frames rotting and hence the bad reputation which has taken decades to address.

What followed, and possibly understandably, was a growing demand for improvements and these came mainly in plastic PVC replacements.

Today the world has moved on and we now have to face up to the changing climate, cost and replacement of fossil fuels and the need to conserve energy. We are being told daily how to insulate our houses, reduce our energy bills and prepare for the future by recognising the changes being made in the current Building Regulations and various codes of practice.

The mainstay of the guidance surrounds reduction in our carbon footprint and almost everyone must by now be aware of their responsibilities and the required actions although one suspects many are still lacking in the knowledge as to how this will impact within their lifetime and beyond.

For housing the goal has been set by the Government under the Code for Sustainable Homes (CSH), in which by 2016 all new housing will be Zero Carbon rated. This means that any energy consumed in the process and the ongoing running of the house must be offset by carbon gains and renewable energy resources. Whether this will be achieved is now doubtful given the current difficulties the housing market is facing, but for the average person the benefit of knowing how to achieve some of the energy reducing initiatives must be desirable.

Most manufacturers of building products have been working on new products and building systems designed to achieve the ultimate levels of energy efficiency in preparation to tap into this growing and essential demand from government, developers and homeowners alike. It is not surprising therefore that the leading quality brands in the timber window market, which both belong to The Performance Window Group (PWG) – Essex-based Mumford & Wood and Devon-based Clearwood UK - have been at the forefront of this development and have set a benchmark for timber window design and manufacture. Timber, as a natural raw material, is of course light years ahead in its environmental integrity in comparison with man-made materials. Where certificated, wood is the most renewable, sustainable material on this planet.

Today’s timber engineering techniques leave all the wood that is not used in the conversion process in the country of origin where it is recycled at source.

Today’s windows can be tested and assessed by the British Fenestration Energy Rating Council (BFRC), and can have an energy rated label just like a fridge does. The ratings are classified from A as best down the alphabet to a G rating. Double glazed and factory finished timber windows made by the PWG can meet a variety of ratings, in both casements and sliding sash models. It’s important to explain that the ratings are based on a standard window size but here size really does matter due to the value of solar gain relative to the surface area of the glass in a larger window. For example, a C rated standard size window can actually increase to the equivalent of an A rating for a window of greater size. The higher the proportion of glass the better the solar gain, the greater the energy rating achievable. As a greater proportion of the windows made by the PWG companies are larger than a standard unit, there is more capacity to achieve the comfort of an equivalent A rated window which reduces energy loss to zero.

House building methods have also improved greatly and factory finished windows are installed into prepared openings and not left open to the elements whilst the building process is carried out. Importantly, improved building procedures also take into account that a window fitted behind a reveal rather than forward in the opening will make considerable impact on the performance of a window and account for an improvement of as much as one rating point. This is of course in the hands of the individual builder but it is as well to be wise.

At the same time the Building Research Establishment (BRE), has produced the long awaited and much heralded Green Guide. This is widely recognised and rates products on an eco rating points system. These points accumulate and are used against the Code for Sustainable Homes (CSH) scoring criteria in order to meet the controls for reducing carbon footprint.

The aim of the CSH is to present points in nine different categories based on the design specification of the house. The more points gained, the closer the dwelling gets to a zero carbon rating - the target the Government has set the construction industry to reach by 2016. In the BRE Green Guide timber windows made by the PWG are rated A+, a rating which gains maximum eco credits in the CSH, equal to Level 6 Zero Carbon which is the ultimate goal. Installing timber windows manufactured by Mumford & Wood and Clearwood UK will help to meet the stringent criteria of the CSH in the three main areas of reduced energy and CO2 emissions, materials and their processes and management at all levels of the harvesting, manufacturing, distribution and waste systems.

In addition, good natural day lighting through windows, helping to reduce the need for artificial light and so reduce emissions and energy consumption, will help meet some of the requirements in a fourth category of Health and Wellbeing. Here also, the sound reduction qualities of these modern high performance windows contribute still further in this important category. These windows are also tested for the very latest security performance standards and will gain extra credits.

In today’s market we are only just raising the standards of house building to meet the CSH and at a guess most new houses are what we would describe as Level 3 – the performance that must be achieved by 2010 - or below. Zero carbon is Level 6, so there is a long way to go and much depends on the affordability factor.

One thing is for certain and that is we can make modern timber windows now that are built to the future energy and eco standards well before the due deadlines of 2010 and 2016.

Replacing windows of course is not a frequent occurrence so the opportunity to install high performance, double glazed and factory finished windows may not occur for a number of years in many properties. But when the occasion arises, advises The Energy Saving Trust, homeowners are advised to prioritise the introduction of materials and products that will make most impact on energy savings in the home. By choosing good quality timber windows homeowners will be helping to reduce energy costs and consumption as well as encouraging the planting of more farmed trees and adding considerably to the value of the property, both aesthetically and in performance values.