CASE STUDY
and in certain cases intermediate stage air and smoke pressure testing.
Loft and wall insulation are always used when possible, as these deal with the most significant heat losses from any home. Double-glazed windows are also installed whenever possible, dealing with draughts and external noise as well as reducing heat loss. Any remaining draughts are then sealed, and mechanical ventilation with heat recovery is routinely added to kitchens and bathrooms. Radian has typically achieved a doubling in the improvement of air tightness post-retrofit. Having installed passive measures, installing a condensing boiler and low energy lighting throughout the house bring further savings, and by this point a hard-to-treat property has been brought up from a SAP energy rating of mid 40s to low 80s, or just below Code for Sustainable Homes Level 3. Adding solar water heating and solar PV can then bring the home up to high 80s, or even into the 90s in some cases – these are equivalent to Code Level 4. The typical CO2 emission reduction for a hard-to-treat retrofitted home including a solar PV installation is 80%.
For new build homes, meeting at least Code Level 3 of the Code for Sustainable Homes is compulsory for housing associations receiving funding from the Homes and Communities Agency (HCA), but a proportion of Radian’s new build goes beyond this, meeting levels 4 to 6. The technology Radian uses for new build is similar to that for retrofit, except that the walls are often built using various types of prefabricated (modern methods of construction) systems such as sustainably sourced closed panel timber frame. The mechanical ventilation with heat recovery used in new build is usually a whole-house system, rather than individual units in the bathroom and kitchen. Solar water heating and solar PV technology is also required to achieve the higher code levels.
In both retrofit and new build homes, Radian has trialled a range of innovative technologies, often in partnership with other organisations, such as the Building Research Establishment (BRE), The Energy Saving Trust (EST), The Environment Agency (EA) and the Technology Strategy Board (TSB). The technologies trialled include: – Aerogel to insulate floors using very thin layers, avoiding expensive work to stairs and doors that would have been required with thicker insulation. – Rainwater harvesting, using buried storage tanks and pumps, and also using small-scale systems with tanks in lofts, along with metering to measure the impact.
– Ground source heat pumps and hybrid systems combining a solar thermal collector and an air source heat pump to provide space and water heating.
– Waste water heat recovery systems. |172| ENVIRONMENT INDUSTRY MAGAZINE
Benefits
Of the 16,000 homes Radian owns, about 1,600 have been built since 2008, all of which meet or exceed Code for Sustainable Homes Level 3 (the minimum legally required). About 85, or 5.3%, of these homes met Code Level 4, 5 or 6. For the older housing stock a range of measures have been used, according to the age and design of the house. Since 1996, the numbers of measures installed are: – 11,624 cavity walls insulated – 12,172 lofts insulated or topped up – 198 solid wall homes fitted with external wall insulation – 11,800 homes given replacement double glazing – 12,000 efficient boilers installed or upgraded – 435 kWp of solar photovoltaics installed – 115 solar water heating systems installed – 232 air or ground source heat pumps installed
Environmental benefits Between 1996 and March 2011, the annual CO2 emissions of Radian’s properties have fallen by an estimated 34%, or 34,000 tonnes/year, or from 6.3 to 4.1 tonnes/year per property. In addition to this, there have been reductions in the amount of water used by households due to the installation of efficient taps and appliances, and rainwater harvesting. Radian also takes great care of the environment during new build projects, enhancing biodiversity and ecological features wherever possible, for example installing bird and bat boxes, planting trees and improving streams. Whenever protected species are present on a site, the development is planned to ensure their safety, or they are relocated by qualified personnel.
Future plans Radian is aiming to ensure that new build homes meet or exceed Code for Sustainable Homes Level 4 whenever affordable, and is also continuing with its monitoring programme, feeding the results into decisions on new build and retrofit projects. It also continues to publish its findings and hold annual conferences on sustainability issues.
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