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Radian / Social housing retrofits give big carbon savings

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Many people are living in social housing that is draughty and expensive to heat. But it doesn’t have to be that way.

Housing association Radian has become a leading authority on energy efficient retrofits and new builds.  Nearly 44,000 people are living in more energy efficient homes as a result, and reaping the benefits every day in lower fuel bills and a better quality of life. And by improving efficiency, Radian has achieved cuts of 34 per cent in CO2 emissions across its housing stock.

 Over 11,600 cavity walls and 12,100 lofts insulated

435 kWp of solar PV installed

 43,750 residents are benefitting from reduced fuel bills and improved comfort

"The training is about attitude, paying attention to detail on insulation, etc. It’s been good to get involved with Radian and Parity Projects, and we’ve got more business through it."

Roger Chung, Business Manager, Drew Smith Group (contractor for Radian)


Reducing energy use and CO2 emissions from homes is a key challenge for the UK in the coming decade – in 2008, about 30% of all UK energy use was in the domestic sector. Of the UK’s 27 million homes, over eight million were built before 1945, and over four million before 1919; unless they have been retrofitted, these homes have very low levels of energy efficiency. Although new build homes are much more energy efficient than the average for the UK housing stock, they are still some way off from being ‘zero carbon’.

Of the UK’s total housing stock, over 4.8 million are in the social housing sector, with just over half being managed by housing associations and the rest by local authorities. All social housing has to meet the Decent Homes standard, but this can be achieved while still having relatively poor energy efficiency. The majority of homes owned by social landlords were not built recently, and require significant retrofitting to bring them up to a good standard of energy efficiency. Radian is leading the way in demonstrating how this retrofitting can be achieved within the budget of housing associations and other social housing providers, even though rents are set nationally.

Retrofitting these homes with a range of measures, including external wall insulation and high efficiency heating and glazing, has cut CO2 emissions by 80%

The organisation

Radian is a housing association operating in Southeast England. It was formed in 2006, from the merger of similarly sized Swaythling Housing, Parkside Housing and Drum Housing as equal partners. Radian owns around 16,000 homes, providing accommodation for over 43,000 residents, and has some responsibility for the upkeep of a further 1,500 leasehold flats within blocks that it owns. It has 650 staff and in 2010 had an income of £105 million.

Radian’s primary focus is to provide its residents with good homes and service, and it sees sustainability as a core feature of this. Improving the sustainability of its housing stock can improve the quality of life for residents by reducing fuel bills, improving thermal comfort and enabling them to choose more environmentally friendly lifestyles.

The programme

The constituent housing associations that joined to form Radian had been working to improve energy efficiency since 1996, but the pace has increased in recent years with the pressure of rising fuel prices and concern over climate change. By efficiently managing its housing stock and operations, Radian is able to allocate sufficient resources to continually upgrade the energy efficiency of its older housing, and ensure that new housing is built to high environmental standards.

I used to have to pull a jumper on before I got out of bed, but now the house keeps the heat in really well.

Mrs Hill, Radian resident in retrofitted home

Radian uses contractors to construct new homes, but carries out most of the retrofit and maintenance work using its own direct labour organisation, Radian Services, and brings in contractors where necessary. Two different methods of retrofitting to improve energy efficiency are used by Radian. The first is to include the retrofit within the planned maintenance programme, replacing windows, boilers, etc. with more efficient versions as they reach the end of their lives. The second method is to carry out an intensive ‘whole house’ retrofit, where all the work needed to bring a home up to a high standard of energy efficiency is done over the course of a couple of months.

The latter approach clearly requires a larger one-off expenditure, and the residents must also be relocated while the work is carried out, but the advantage is that the home will then need no further work for many years. Radian selects which approach to use according to the current state of the housing, available finances and the wishes of the residents.

The technology

How does it work?

For older homes that need retrofitting, Radian plans projects to use the most cost-effective measures, progressively adding the less cost-effective ones until the desired energy efficiency is achieved. Homes with solid walls are classed as ‘hard-to-treat’, and these are surveyed with a thermal imaging camera before and after retrofitting, to ensure the best measures are not just selected but also correctly installed. Radian also undertakes pre- and post-retrofit air tightness testing and in certain cases intermediate stage air and smoke pressure testing.

External wall insulation is being installed on the house next door to the retrofitted show home

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%.

It’s very satisfying to be involved with a major project like this; we’re usually just involved with kitchens and bathrooms.

Ken West, Retrofit Site Manager, Radian

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.

For each technology, Radian has carried out detailed reviews of their performance and made the results freely available on their website and via extensive programmes of dissemination ranging from local schools to the European Parliament.

How much does it cost and how do users pay?

The rent paid by social housing tenants is controlled by central government, so they do not pay any more when their home is retrofitted or if they move to a new build home of a similar size. All retrofitting is paid for out of Radian’s capital budget.

Retrofit in progress Petersfield, Hampshire

Radian spends around £25 million a year on maintenance and repairs to existing homes, including that spent on retrofitting energy efficiency measures. A key to its retrofit policy is “don’t lock the carbon in”, by saving money in the short term rather than going for a more energy-saving option. A good example is external wall insulation, where Radian fits panels that are 100 mm thick, rather than ‘locking in carbon’ with 40 mm panels – the minimum thickness required to meet current efficiency requirements.

Ashden Award for Reducing Fuel Poverty


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Radian has found that retrofit typically costs 10-20% more than is often predicted from the cost of the measures installed, due to work such as redecoration, moving window sills and drainpipes after external wall insulation, relocating tenants during the work, the pursuit of grants and project management. Even so, it can be very cost effective, as Radian found at a site where some of the very poor quality homes were retrofitted and others were demolished to make way for new build. Here the new build cost around £120k per property, while the retrofit cost only £60k per property, of which £45k was related to energy efficiency. (On this particular site, the new build was at higher density, so Radian could recoup the higher cost of rebuild from greater rental income).

In general, Radian has found that it is possible to build homes to Code 5 standards for about £1,450 per square metre and Code 6 for around £1,600 per square metre, compared to £1,200 for the minimum Code 3 that they are required to meet.

On all our sites there’s a good level of eco-awareness and energy efficiency, not just in new build but in retrofit as well.

Angela Sleet, Radian Resident Liaison Officer

Radian has an excellent track record of securing external funding to help support the organisation’s sustainability work. In 2009 they became the first housing association in the UK to secure European Regional Development Funding (ERDF) for research in the field of retrofitting social housing.

Recognising the changing financial and economic environment, Radian is working with a range of partners including Global Environmental Social Business to set up a Revolving Retrofit Guarantee Fund. This is designed to encourage banks to lend at a low cost to households and landlords through the fund, enabling them to collectively retrofit many more properties to improve energy efficiency.


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.

The refit can be quite a stressful time for residents, but once they’re back in their homes they find that they are much cosier. Some have made huge savings on energy bills – up to £200 per quarter.

Angela Sleet, Radian Resident Liaison Officer

It is important to note that the majority of the energy savings and CO2 emission reductions for hard-to-treat homes are achieved through measures such as insulation and new boilers, and the extra savings due to using microgeneration equipment are relatively small compared to their cost, though they are essential to reach the high standards that Radian aims for. The table below shows how the CO2 emissions are estimated to fall as each retrofit measure is added, along with the costs of the measures.

Social benefits

Residents are benefitting from significantly reduced fuel bills and warmer homes with draughts and damp eliminated, with resulting health benefits. All social landlords are required to consider their tenants’ views, and Radian consults with residents over retrofit and new build projects. In some cases, it has offered current residents the choice of either having their homes retrofitted or having them demolished and new ones built, and going with the majority on different roads.

Paul Ciniglio, Sustainability Manager at Radian, with resident

Economic and employment benefits

Radian recognised that they would need more skilled tradespeople to carry out the scale of retrofit projects that they wanted to. They have addressed this need by providing relevant training for their staff in Radian Services, and have also part-funded ‘business assistance’ training on retrofit technology for contractors. The contractors have since paid for more training, having seen the benefits, and this is helping the training delivery businesses to increase their capacity as well. Several new jobs have been created within Radian and contractors as a result of the retrofit work, and some of Radian’s own tenants are working on the projects.

Potential for growth and replication

Radian is planning to continue retrofitting to increase the energy efficiency of its housing stock, and new build housing will be Code Level 4 or higher whenever affordable, but always at least Code Level 3. It has also started a £4.25 million programme to install 1.75 kWp solar PV systems on 720 homes, benefitting residents with lower electricity bills and bringing an income for Radian from the Feed In Tariff. Radian is continuing with its monitoring work, feeding the results on costs and effectiveness into their retrofit and new build programmes. Across the UK there are over 2.53 million homes owned by housing associations and over 2.35 million owned by local authorities, most of which are far below current new build standards for energy efficiency. There is significant scope for social landlords across the UK to follow Radian’s lead and reduce CO2 emissions from their housing stock and lower fuel bills for their tenants at the same time.

Radian is not just publishing the results of its technology trials in retrofit and new build, it has also run a highly successful annual conference on a sustainability theme every year since its formation. Other social landlords, builders and contractors attend these events, giving Radian the opportunity to pass on the lessons it has learned through its sustainability programme, inspiring others to do the same.

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