Somewhere over the
rainbow
Justin Davies, general manager for The Window Store explains the jargon behind window and door energy ratings and asks whether triple glazing should be a genuine consideration when looking at glazing options
Know your ratings! August saw the number of signed Green Deal plans rise to 132, up from 36 the previous month. Energy minister, Greg Barker said that the figures showed “genuine consumer interest” in the scheme. So with energy bills creeping ever higher with no end in sight, and a hint towards higher council tax and stamp duty for those living in inefficient and leaky homes, there’s no escaping the pressure to make our homes more energy efficient. Glass and glazing plays a vital role in the effi-
ciency of a property – from windows and doors to conservatories and glass extensions. Many
With energy bills creeping ever higher with no end in sight, and a hint towards higher council tax and stamp duty for those living in inefficient and leaky homes, there’s no escaping the pressure to make our homes more energy efficient
people will be au fait with the sliding ‘rainbow’ scale more commonly associated with house- hold appliances. Stating the energy efficiency rating of a product, with the dark green coloured band being A (the best rating) down to dark red, G (the lowest rating and therefore the least energy efficient), what many people don’t realise is that this rating is also applicable to both windows and doors. There are a number of factors to look out for
when establishing the environmental perform- ance of a door or window – the energy index and the u-value; these combine with air leakage and in some instances, solar factor, to give
either a window energy rating (WER) or a doorset energy rating (DSER). Remember these ratings relate to the whole unit not just one indi- vidual component.
U-values To understand DSERs and WERs, people must first get to grips with U-values. A U-value is an independently verified measure of heat transfer through a building element, in this instance a door or a window. The lower the U-value the better the material/product performs as a heat insulator, less energy is lost, and the more effi- cient and economical the unit.
Energy index The Energy Index (kWh/m2
/year) is one of the
most important values, as it sets out the amount of energy lost or gained by a window. The value is displayed in terms of kilowatt-hours per square metre of glazing per year. Energy lost is displayed as a negative figure, and energy gained by a positive number. So the higher the number, the greater the energy conserved – and the more money saved on energy bills.
Improved rating with Low E Significant proportions of glazing can have a dramatic impact on the energy and thermal effi- ciencies of a property; even something as sim- ple as an entrance door with between 5 per cent and 20 per cent glass. One solution is to install Low E glass instead of standard glazing. Low Emissivity glass, Low E for short, is a more energy efficient glazing alternative. It dramati- cally reduces heat transfer and reflects interior heat back into a room. Low E glass is also rec- ommended for properties that are north or east facing as a greater proportion of heat loss would be expected.
Continued overleaf...
selfbuilder & homemaker
www.sbhonline.eu
45
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68