Social housing supplement Heating case study

private domestic arena too. ‘From next year, people can claim RHI on solar thermal and the heat pump. They could recover the money over the course of the RHI and end up in profi t. It’s really a 10 per cent return on your money. If you invested that in a bank you wouldn’t get 10 per cent.’ Cottsway’s ambitious goal is to fund its retrofi tting programme through the RHI by year fi ve of its 10-year programme of air source heat pump installation. By this time, the programme will generate about £400,000 a year from the RHI. This year, Cottsway is spending £300,000 installing nearly 100 air source heat pumps in homes not connected to the gas grid. Air source heat pumps also have a higher life expectancy, lasting 20 years compared with a gas system’s average of seven or eight – which, says Salter, means the air source heat pump will pay for itself within a decade (based on today’s energy prices) and will generate an income for the next decade, plus generate a huge saving on maintenance. The unvented cylinder in the air pump does require an

annual maintenance check, but, enthuses Salter, there is no need for a landlord’s safety certifi cate and the Ecodan unit requires little more than a visual check-up and annual clean. This costs just £50 compared to the usual £85-£90 for a landlord’s certifi cate, and is organised and paid for by Cottsway.

Running costs

The home is now one of 100 undergoing post- occupancy evaluation (POE) as part of the Energy Saving Trust’s EST100 monitoring programme, which involves recording the running costs of the air source heat pump and how well it works. For this to take place, Cottsway has developed its own

fl exible control system that allows the tenants to put the system into ‘holiday mode’ when the home is empty, and control whatever systems are introduced. The system also shows homeowners their energy consumption and coeffi cient of performance (COP). A photovoltaic (PV) system is now being installed by Cottsway at this property and, by September, it intends to have 20 systems installed on other homes. Salter explains: ‘We’ve got a bigger target to hit for

2050, and heat pumps and PV go together very well because of the amount of energy you can generate. If you had a 2.48kW system on your roof, this would probably provide more than 50 per cent of your energy for your heat pump.’ Salter says the government’s new Feed-in-Tariff (FiT)

also makes fi nancial sense, possibly generating £840 a year and could knock £200 off each tenant’s annual electricity bill.

Cottsway aims to introduce 1,100 heat pumps in the

next 10 years for any properties without gas connection. Each property is being fi tted with a twin-coil cylinder, which adds about £100 to each project, but, says Salter, it could save the association £2,000 in each case should further retrofi tting with solar thermal be required in the future. ●

www.cibsejournal.com June 2010 CIBSE Journal

11

Enstone house

• Three bedroom mid-terrace house • Two adults, two children • 1960 traditional brick built • Solid concrete fl oor slab uninsulated. • 50mm cavity wall that has been fi lled with rock • Wall insulation • 300mm loft insulation • Double glazed windows and front and rear doors • Storage heaters in all rooms • Storage convector in lounge • Solid fuel open fi re in lounge

Before:

• Total electrical consumption – 15,563 kwh a year • Total bags of coal used – 24 x 50 kg bags • 3,466 kwh at peak rate – £372 • 1,2097 kwh at Economy 7 rate – £525 • Cost of 24 bags of coal – £240 • Total cost for the year – £1,137 • Electrical consumption – 6.56 tonnes of CO2 per year • Solid fuel coal – 2.89 tonnes of CO2 per year • The property’s total carbon footprint – nine tonnes of CO2 per year

After:

• Electricity used to supply all the heating and hot water using the heat pump – 4,156kwh

• Cost of running the heat pump – £384 • The total cost of electricity for the whole house – £810 • Cost of heating and hot water reduced by 50% • Carbon footprint of the property reduced by 65%

Photovoltaics can generate up to 50 per cent of the energy required to operate an air source heat pump.

“It takes two to three weeks to set the heat pump up to get the tenant comfortable”

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