This programme is the first of its kind in the UK, and will see social housing units across the country retrofitted with innovative technologies that demonstrate whole house solutions for refurbishment that cut carbon emissions and energy use. Low carbon consultants Encraft, together with Warwick District Council, won the competition to run this pilot scheme against 400 other bids, with the SmartSash window contributing not just thermal efficiency, but also affordability.
“The SmartSash window not only provides excellent U-values but is also good value when compared to similar products. This was an important issue as the scheme has to show solutions that are cost-effective and that can be rolled out throughout the country,” said Encraft project manager Helen Brown.
The properties are three-bedroom semi-detached houses built in the 1930s and were chosen as typical of rural properties found across Warwickshire and the rest of the UK, being poorly insulated and entirely reliant on electricity for heating, being off the gas network. This leads to massive fuel bills: one tenant, using an electric boiler for heating, was £6000 in arrears with their electricity supplier.
The project’s targets were a 78% reduction in primary energy requirement, a 95% reduction in carbon dioxide emissions and improve the whole house U-value to 0.9w/m2k. The project also had to demonstrate that retrofit measures can take place while tenants remain in the dwelling so there is minimal disruption to tenants and no associated temporary re-housing costs.
This ruled out invasive insulation measures such as floor insulation, so Encraft had to achieve PassivHaus or near PassivHaus standards to compensate. The triple-glazed version of SmartSash, with a U-value of just 0.7w/m2k was ideal, particularly when paired with Bowater Doors’s Eco Series Composite Doors, achieving the target u-value of 1.2 W/m2K.
Encraft opted for the highest performing version of SmartSash, but the ‘modularity’ of the system enables PVC-U doors and windows to be fitted now to comply with the Code for Sustainable Homes (CSH) Levels 3, 4 or 5 as required – and then be simply, easily and inexpensively upgraded to Level 6 standard at a later date. It also allows for much larger sash sizes, while maintaining thermal performance. This is achieved through glazing elements, which can be changed and enhanced as budgets provide.
Government policy, articulated in the CSH, says that by 2016 – 2013 for the social sector – all new homes will have to be zero carbon rated (Code level 6), meaning that all windows must have a U-value of 0.7 W/m2K or less, while all doors achieve a U-value of 0.8 W/m2K or less.
Essentially, specifiers and building owners have four opportunities to fit now and upgrade doors and windows over time and as resources allow. In the first instance, the door or window can be installed in an ‘entry level’ configuration – featuring a standard 28mm double glazed unit, with thermal insert, which offers a U-value of 1.2 W/m2K.
Second, a unique parting bead arrangement allows for performance enhancement with the subsequent insertion of a third, single pane to effectively create a triple-glazed installation. If the third pane is 4mm float glass, then a U-value of 1.0 W/m2K will be achieved and CSH Levels 3 and 4 will be met. However, and thirdly, by then substituting a 4mm hard coat glass with an emissivity of ε0.10 for the float pane, it will achieve a U-value of 0.8 W/m2K and meet CSH Level 5.
Ultimately, the entire glazing arrangement – as in Warwick – can be fitted with 44mm argon triple-glazed units to achieve a U-value of 0.7 W/m2K. There is also a glazing arrangement that gives a sound reduction up to 50 dB, whilst still achieving a U-value of 1.2 W/m2K. This level of performance does depend on the initial installation of an outerframe incorporating foam-filled inserts at the outset.
The Eco Series of double rebated doors in the public sector from sister company Bowater Doors is capable of achieving a u-value as low as 0.8W/m2K, equivalent to the Code for Sustainable Homes Level 6.
