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The house was recently featured in September edition of the RIBA Journal.Parity Projects recently completed its second demonstration retrofit on a newly purchased Victorian semi-detached property in South London. Parity’s first demonstration house focussed on installing and testing a wide range of different and innovative measures, with a view to understanding their practicality and performance. In contrast, the more recent property was intended to be a more realistic retrofit, using measures that could be easily applied in homes up and down the UK. Since the house was also in need of a wider refurbishment and extensions were planned, the project also presented an opportunity to see how the “marginal cost” of improving its energy performance could be minimised through taking a genuinely integrated and thoughtfully sequenced renovation.


As always, the project was started with a detailed analysis of the property using Parity Projects’ Home Energy Masterplan assessment tool. Masterplans, unlike many similar products in the market, are designed to account not only for the physical details of the property, but also the lifestyle of its owners and their household. Taking this approach, Parity was able to identify in advance the most cost effective measures for reducing both the energy bills and the environment impacts associated with the property, and avoid the potential to waste money on inappropriate measures. We wanted to show that significant energy savings were possible without the usual eco-renovation price tag. In that vein a significant amount of the work was carried out DIY


Aside from standard upgrade measures, all the walls were brought up to around 40% better than current building regulations through a combination of internal and external insulation. A tricky side wall was actually dealt with by enclosing it and it is planned to keep it as an unheated buffer area in the winter.


A whole range of heating options were evaluated from heat pumps to biomass. Due to the very low predicted heat load, by far and away the most cost effective solution was a gas boiler central heating system with radiators.  This has been optimised by zoning the house into four individually programmable and thermostatically independent zones.


Taking out the cost that would have been incurred in a standard renovation, the overall marginal element of the fabric and heating system eco measures is estimated at around £10,000.In addition, photovoltaic and solar thermal systems have been added at a marginal additional cost of £12,500. The renovation is also expected to see an 83% reduction in the carbon dioxide emissions from the house, and a £2,250 reduction in the running costs – £1,000 of which is from Feed In Tariffs. Proving that energy-led renovations are not just about saving money, a recent survey of the property has estimated that the renovation has also increased the value by over 40%.