The suburban carbon slashers

In an ordinary south London terrace something strange is afoot. The house in the midst of a suburban estate looks just like all its neighbours, but inside is an experiment in saving the planet.

The house, owned by housing association Hyde Group, has just been upgraded with the goal of cutting its carbon dioxide emissions by 80%.

Government pressure for green homes is almost all directed at newly built property, but there’s increasing demand from corners of the industry to pay more attention to homes already standing. Since only 20% of houses are likely to be replaced by 2050, existing homes will pump out the bulk of domestic carbon emissions. Campaigners from the Existing Homes Alliance, which is lobbying for the current stock to be made greener, also want emissions from homes cut by 80% by 2050 rather than the government’s 60% target.

Fine words indeed. But can those goals be achieved in reality? Hyde, along with architect ECD, contractor Mears and a host of suppliers and advisers, decided to find out. They aimed to find efficient ways to cut emissions from the house by at least 80% which could be replicated elsewhere. The results of their labours were unveiled this week and tenants will move in next month to test it out.

State of the house

When the house was built it did not even have a bathroom. Upgrades over the years included a gas boiler, an extension with a rear bedroom and bathroom, a shower room, double glazing - albeit of poor quality - and some basic insulation.

The house’s SAP rating was a surprising 60, well above the national average of 48, making an 80% reduction difficult to achieve. Its airtightness was also above current building regulation requirements but the windows, holes for incoming services and the loft hatch were the main sources of leaks.

Insulation

The biggest predicted reduction in carbon emissions – 27% - will come from upgrading the insulation of the house. Phenolic foam will be used in the suspended floors and external walls, insulation backed plasterboard dry lining panels will be used in the main body of the house with wall board with a silicone render used in the rear extension. In the roof of the extension 220mm polyurethane boards will be used with glasswool in the eaves. The loft will be home to much of the monitoring and plant equipment so the insultation needed to allow access and headroom. It also had to be airtight when recessed light fittings were installed in the ceiling below. Ease of installation and performance were favoured rather than embodied energy of the materials.

Windows

Replacing the old, poor quality double glazed windows with triple glazing with insulated frames is likely to cut a further 5 per cent from the house’s carbon emissions. The front and back doors will also be replaced b insulated equivalents.

Ventilation

A mechanical ventilation unit will extract air from the kitchen and bathroom and reclaim about 90% of the heat from it to warm incoming fresh air which is sent to the living room and bedrooms. In summer, the unit sends the extracted air outdoors. The system will help to reduce carbon emissions from heat lost through ventilation by around 15%. The combination of the new windows, insulation ventilation unit should cut the property’s heating requirements by over 86% to 2410 kWh per year.

Heating

With ground source heat pumps and biomass boilers the flavour of the month, it’s seems surprising that Hyde and ECD dismissed them in favour of a gas condensing boiler. But solid concrete floors in the kitchen made ground source heat pumps unattractive as they work best with underfloor heating. Underfloor insulation levels would also have to be reduced if the pumps were installed. The team decided heat pumps would struggle to produce carbon reductions on a par with an efficient gas condensing boiler because electricity is very carbon intensive in the UK in comparison with gas. They also thought the ground source heat pump systems were relatively expensive and needed extra space. Biomass was dismissed because the team felt tenants would find it onerous to source wood pellets to fuel the system.

Solar panels

Two solar thermal collectors on the roof should provide between half and 60% of the heat needed for hot water.

The biggest predicted reduction in carbon emissions – 27 per cent - will come from upgrading the insulation of the house.

Lighting

Instead of standard compact fluorescent low energy lights, the house will have LED lamps because they contain no contaminants so can be safely recycled. They are much more expensive but offer 50,000 hours of use compared to 10,000 for compact flourescents and so should last 20 years. The lighting changes cut carbon out put by 1%.

Even with all these changes, the house was still a few per cent short of its 80% reduction goal, largely because it had a relatively good SAP rating before the improvements were made. The team decided microgeneration would ensure the house hit its target. They will install eight photovolataic panels on the roof of the extension which should cut carbon emission by 7%, cutting emissions by more than 80%.

Water and more

The project is mainly about carbon reduction but the team took the opportunity to cut back on water too. Dual flush toilets, aerated taps and shower head and a low volume bath. A water harvesting tank fed from an external downpipe requires no electricity and will supply almost all the water required to flush the toilet. The development was also topped off with various environmentally friendly extras such as longer lasting and lower emission paints, natural floor finishes, composting bins and recycling bin storage.

Fuel bills

Once tenants are shown how to make the most of the energy savings devices, fuel consumption in the house is expected to drop by 85% with residents expected to save around £600 per year on fuel bills.

Energy use for everything apart from lighting and appliances was 414 kwh per m² per year with carbon dioxide emissions 100 kg per m² per year and space heating demand 223 kwh per m² per year before the upgrade.

After the refurbishment those figures should drop to 67 kWh per m² per year, carbon dioxide emissions to 17 kg per m² per year and space heating demand to 32 kWh per m² per year.

Hyde hopes the project can make a major contribution to tackling fuel poverty.

Monitoring

Water, gas and electricity consumption will be recorded by a metre. A series of thermocouples will record temperatures across the wall and roof fittings to check for heat loss. A heat metre linked to the boiler will record space heating and hot water. The residents will also be questioned on what the house is like to live in and their answers will be compared with those of another family living in a similar house nearby which has not been upgraded.

The house will be monitored for two years but the findings will start to be disseminated from April next year and incorporated into Hyde’s stock investment plans after a year.

Cost

The project has an £80,000 budget for the improvements including VAT and fees, paid for by Hyde, but many of the firms involved are donating time or materials so the real cost would be higher. Part of the project is to work out the real cost and put together a cost benefit analysis of the upgrade.

Partners

ECD Architects

The Hyde Group - landlord

Keegans – cost consultants and CDM coordinators

The team decided heat pumps would struggle to produce carbon reductions on a par with an efficient gas condensing boiler

Parity Projects - data monitoring

PPCR Associates - post occupancy evaluation

Mears - contractor

Travis Perkins and Kingspan - supply chain, technical advice and materials

Web Dynamics – materials and installation

Wetherby Building Systems – materials and installation

Valliant – boiler and ventilation system

Solar Technologies – supply and installation of photovoltaic panels

NorDan – windows and doors

GreenLED - lighting

Dulux – paint

Chamois – kitchen