Energy Efficient Timber Windows
Can modern timber windows really contribute to reducing energy bills? You bet they can!
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 as formers to build the external walls around. The windows suffered and the subsequent paint covering served to temporarily conceal the damage caused mainly by ingress of moisture and leading the way for plastic PVC replacements
We now face the changing climate, cost and replacement of fossil fuels and the need to conserve energy. Insulate our homes, reduce our energy bills, prepare for the future, recognise the legislative changes and codes of practice - the mainstay of this guidance being reduction in our carbon footprint.
 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. Any energy consumed in the process and the ongoing running of the property must be offset by carbon gains and renewable energy resources.
Most manufacturers of building products have been working on new products and building systems to meet these objectives. Leading quality brands in the timber window market are no exception and companies such as Mumford & Wood and Clearwood UK, both members of The Performance Window Group (PWG), set a benchmark in the design and manufacture of timber windows.
Timber, as a natural raw material, is of course light years ahead in its environmental integrity. Where certificated, wood is the most renewable, sustainable material on this planet.
Today’s windows can be assessed by the British Fenestration Energy Rating Council (BFRC) to achieve an energy rated label. The ratings are classified from A as best down to G. Double glazed and factory finished timber windows can meet a variety of ratings in both casements and sliding sash models. It’s important to note that ratings are based on a standard window size but here size does matter due to the value of solar gain relative to the surface area of the glass in a larger window. 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. A rated windows reduce energy loss to zero.
Improved building procedures 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 - but this is in the hands of the individual builder.
At the same time the Building Research Establishment (BRE), has produced the Green Guide which rates products on an eco rating points system. These cumulative points 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. The more points gained, the closer the dwelling gets to a zero carbon rating. In the Green Guide timber windows made by the PWG companies are rated A+, a rating which gains maximum eco credits in the CSH, equal to Level 6 Zero Carbon, the ultimate goal.
Installing quality timber windows will help to meet the 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, reducing the need for artificial light to reduce emissions and energy consumption – as well as contributing to sound reduction and security performance - will help meet the requirements in a fourth category of Health and Wellbeing for extra credits.
In today’s market we are only just raising the standards of house building to meet the CSH and probably most new houses are reaching a Level 3 standard – the performance that must be achieved by 2010 – or below, so there is a long way to go and much depends on the affordability factor.
One thing for certain is that 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.
Can modern timber windows really contribute to reducing energy bills? You bet they can!
By choosing good quality timber windows, developers and Local Authorities will be helping homeowners and residents to reduce energy costs and consumption - as well as encouraging the planting of more farmed trees and adding to the value of the property, aesthetically and in performance values.
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