028 GGP 1213

GGP December 2013

Energy Efficiency Alan Fielder, director of sales and marketing for IG systems specialist Edgetech, asks whether there’s an opportunity for the industry to sell more highly insulated windows. 28 December 2013 WERS and DERS do exactly what they say on the tin TThe basis of the almost defunct Green Deal relied heavily on calculations for savings to offset future fuel bills from the energy savings measures. SAP ratings also rely on manufacturers’ ‘as-built’ predictions to calculate the level of efficiency within buildings. But the reality, as shown in the Joseph Rowntree Energy Efficient Refurbished Homes Report (www.jrf.org.uk), is often very different. Using a 1930s semi-detached property in York, typical of the housing stock in the UK, the trust installed and tested building fabric improvements, from draught proofing to wholesale renovation, in order to evaluate their effectiveness and potential payback. The ‘as-built' measurements revealed that overall, the improvements achieved only 71 per cent of the predicted reduction in heat loss. Only two measures did what they said they would. Floor insulation and triple glazed windows. The on-site measurements of the new triple glazed windows showed that the predicted ‘U’ value was achieved and there was a vast improvement in airtightness. We believe that the accuracy of the predictions for windows was so high because, unlike most other energy savings measures, these are engineered products. All components for windows and doors are put together in a factory. Obviously, windows need to be correctly installed, but any issues are easy to find. Contrast this to other energy savings measures that are often hidden and impossible to check if they’re fitted correctly. The Joseph Rowntree Trust’s report showed cavity wall insulation may not have entirely filled the void. The results showed the cavity wall insulation was predicted to reduce the ‘U’ value of the external walls from 1.68 to 0.45 W/m²K, yet heat flux sensors measured ‘U’ values that varied from a highest value of 1.93 W/m²K to a lowest value of 0.70 W/m²K. The reasoning behind WERs and DSERs was to have a clear and easy to understand measurement for the energy performance of products. There’s good evidence to suggest these schemes are popular with homeowners and we’re seeing high numbers of ‘A’ energy rated windows sold. However, we often hear that independent energy surveyors overlook windows and doors as a measure to decrease energy bills. Home and commercial building owners looking for retrofit energy saving measures are advised to fit other products first like roof and wall insulation. However, because windows and doors do what they say on the tin to increase energy performance, perhaps there’s an argument to bring these higher up the list. With more highly insulated units and the introduction of the higher A+ and A* WERs, should the industry question whether there’s an opportunity to gain more market share against other energy savings measures? “we often hear that independent energy surveyors overlook windwos and doors as a measure to decrease energy bills”


GGP December 2013
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