Changes to the Code for Sustainable Homes are afoot. A new standard is being introduced which will require the energy efficiency of new homes to be improved through their fabric. This means ensuring windows, walls and roofs are properly insulated. Marisa Maitland, low carbon buildings associate, at carbon reduction company Sustain, looks at why it's important to get the basics right and shows how lessons can be learned from a project they have worked on with Aspire Housing.
The pressure on housing associations to meet increasingly stringent environmental targets is causing many to look more closely at how they can best achieve energy efficient homes. Renewable technologies, such as heat pumps and solar panels are clearly a crucial part of the solution but getting the basics right first, mainly ensuring the house is properly sealed and insulated, is the most important first step.
At Ingestre Square in Blurton, Stoke-on-Trent, we helped Aspire Housing achieve Code Level 3 without using any renewable measures - an unusual approach but one that focuses on insulating the homes first to ensure their basic structure is as energy efficient as they possibly can be.
The project is a redevelopment of houses that have now been demolished and are being replaced with a mix of 41 houses and flats as well as a community building. Aspire Housing is working in partnership with Stoke-on-Trent City Council to develop this new estate district centre. The project is being built in two phases, the first of which was started in January 2010 and is expected to be completed before the end of this year. The second phase is due to be finished by the end of 2011.
In order to obtain funding from the Homes and Communities Agency, Aspire Housing had to achieve at least Code Level 3 on the domestic buildings. In the first instance, we were appointed to complete some modelling work, looking at how Code Level 3 could be achieved using a variety of different measures. This would inform the design and build contract which was put out to tender and won by Kier Partnership Homes.
Working with Axis Design Architects, we modelled a range of scenarios to see how different designs would translate into carbon emissions savings. Using SAP 2005, the standard modelling procedure in the UK for measuring energy in buildings, we were able to calculate the energy use of each home when applying different measures, such as a certain type of heating system or window specification. This enabled us to see how much energy is needed to heat the water, for instance, and from where energy is being lost. We could then use this data to recommend the most feasible solutions with the best carbon emissions savings.
One of the challenges was to work out how to achieve Code Level 3 in the apartments without using renewable energy measures. Aspire Housing was keen to keep maintenance to a minimum so concentrating on the fabric of the building was the preferred option.
Apartments by their very nature benefit from less heat loss than houses because there are not as many exterior walls and surfaces. This means that there is limited scope for energy saving measures when heating systems and air tightness are the only options. Our solution was to focus instead on ensuring the design of the windows could meet tough energy saving requirements.
The final designs resulted in some impressive energy saving statistics. The u-values - a measurement of heat loss - were extremely low at 0.13 W/m²K for the floor and walls compared to a typical value of 0.2 W/m²K. The roofs achieved a u-value of 0.1 W/m²K, the windows achieved u-values of 1.4 for the houses and 1.9 for the doors compared to typical values of 0.15, 2.2 and 2.2 respectively. The windows of the flats were particularly low at 0.7 W/m²K. Excellent insulation across the houses and apartments was supplemented with an A rated gas boiler to heat the properties and their water.
The designs also achieved a high level of air tightness - 3 m3/hm² compared with the much lower level of 10 m3/hm² as stipulated by building regulations. As a result, the properties needed a robust ventilation system so we recommended a mechanical heat recovery ventilation system.
When the next round of HCA funding is announced, it is likely that all housing associations will be required to meet Code Level 4. To achieve Code Level 3, a home needs to be 25 per cent more energy efficient compared to Part L 2006. To achieve Code Level 4, this increases to 44 per cent.
At Ingestre Square, it would have been difficult to achieve Code Level 4 without applying renewable technologies. In fact, while it is possible to achieve Level 4 in theory using just insulation and air tightness, it is unusual and requires a departure from traditional building methods. Level 4 could have been reached at Ingestre Square with the addition of a Combined Heat and Power system - a particularly appropriate solution for a community of this scale. For smaller scale projects, where the focus is on driving down carbon emissions of individual houses, solar photovoltaic panels work well with a ground source heat pump.
As legislation continues to drive the green agenda, it's more important than ever that housing associations get the basics right first so that there is a solid platform to work from onto which renewable technologies can be applied.
