Perhaps the most remarkable thing about Eco Drive in Handsworth, Birmingham, is that it isn’t remarkable at all. The brownfield development of 12 houses, for Midland Heart Housing Association, has been designed to deliver an 80% reduction in operational carbon emissions from the 2013 version of Part L, in line with the 2025 Future Homes Standard. But it looks just like many other small social housing projects up and down the country.
And that’s exactly the point. Midland Heart wanted to explore how high-specification, low-carbon homes could be delivered without reinventing the construction industry, allowing the approach to be replicated more widely. Rather than starting out with an entirely blank canvas, Midland Heart adopted a site for which a traditional contextual design of standard layouts, by Oakley Architects, already existed. These would be adapted to tough low-energy specifications, by increasing insulation and airtightness, and installing heat pumps and photovoltaic (PV) systems.
However, they would all still be built using brick and block masonry – the most common form of residential construction in the UK – using established supply chains where possible. Designers, contractors, subcontractors and suppliers would learn together, confronting any challenges to traditional workflows. Rigorous testing and post-occupancy monitoring, in partnership with Birmingham City University, will also help to inform future developments.
The existing plan was for a mix of two-, three- and four-bedroom houses. As three house types were available, the decision was taken to trial three different approaches to meeting the standard: Type 1 was the four-bed unit, Type 2 the two-bed, and Type 3 the three-bed.
All three were given external masonry walls with an outer leaf of facing brick and a fully filled cavity. One of the key fabric changes to the 2025 regulations is the requirement for thicker walls to accommodate extra insulation. Given Eco Drive’s existing arrangement of plots, there was little room for expanding the building envelopes without increasing site density or reducing internal space. The chosen solution was a 352mm wall fully filled with 150mm of high- performance rigid PIR insulation.
Behind this, Types 1 and 2 both employed an inner leaf of aircrete blocks, coated in an experimental polymer spray, with the aim of reducing air permeability to 1.5m3/h/m2. Type 3’s inner leaf was formed with lightweight aggregate hollow blocks and had a less strict 5m3/h/m2 target. The design U-values for the walls of each house type was 0.13W/m2K, exceeding the Passivhaus standard, although windows and doors, which were double rather than triple glazed, performed slightly worse.
The more airtight Types 1 and 2 required mechanical ventilation with heat recovery (MVHR). Type 1 had a 7kW air-source heat pump for space and water heating, while the smaller Type 2 included a water-only heat pump and electric panel radiators. Type 3 was naturally ventilated, and included a 5kW air-source heat pump for space and water heating. All 12 homes have 2.2kW of PV roof panels.
The design performance led to an estimated reduction of 85% in operational carbon emissions for Type 1, 80% for Type 2, and 90% for Type 3. Airtightness tests found the air permeability of Type 1 and 2 houses was 2.46 2.98m3/h/m2, meeting the Future Homes Standard but not the project’s stricter target. This was due to air leakages around windows and doors, highlighted by thermal imaging. All Type 3 houses met their less onerous air permeability target. Thermal cameras also showed a reduction in thermal bridging at junctions between walls and corners in all house types.
Post-occupancy monitoring indicates that the Eco Drive households are achieving up to a 70% monthly carbon reduction, which will rise as the grid decarbonises, as well as savings on energy bills. The overall cost of the project was about 15% higher than an alternative built to 2013 Part L. The additional costs are mainly due to the better insulation for walls and roof, the higher-specification windows, alternative services costs for heating and ventilation, and the provision of PV panels.
