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First homes built to Future Homes Standard set for March handover

Words:
Stephen Cousins

Twelve houses on Eco Drive in Birmingham will cut carbon emissions by 80% – and already have lessons for the next tranche of homes under the scheme

The 12 homes on Eco Drive were modelled in Beta SAP 10 software to achieve an 80% cut in carbon emissions
The 12 homes on Eco Drive were modelled in Beta SAP 10 software to achieve an 80% cut in carbon emissions Credit: Tony Hopkin

The first houses modelled to meet the Future Homes Standard – which will cut greenhouse gas emissions by 80% – are due for handover in the West Midlands next month, with lessons learnt on specification and buildability already affecting plans for 2025.

The 12 homes on Eco Drive, in Handsworth, are being constructed by Tricas Construction for Midland Heart Housing Association as part of the Project 80 research and development programme.

Led by Birmingham City University (BCU) and various industry partners, the programme will see more than 50 homes of different typologies built to meet the Future Homes Standard before 2025. Pre- and post-occupancy monitoring data will be used to shape the government’s consultation on the new standard.

Performance and design criteria for the 12 masonry homes on Eco Drive were developed based on a new baseline for predicted FHS requirements. Properties were initially modelled to meet current Building Regulations, then remodelled in Standard Assessment Procedure 10 (SAP 10) software, currently in Beta format, to reduce CO2 emissions by 80%.

Most of the specification is consistent, but specific plots had different block density, airtightness levels and ventilation strategies, as well as different approaches to low carbon heating and hot water.

The four-bedroom, three-storey houses on plots 1 and 2 were designed to achieve a high airtightness in conjunction with mechanical ventilation with heat recovery. Other variations include aircrete blocks and Baxi air source heat pumps and hot water cylinders.

On plots 3-4, the two-bedroom two-storey houses incorporate GlenDimplex panel heaters and hot water heat pumps and windows with a higher g value to address potential overheating.

The three-bedroom, 2.5-storey houses on plots 5 to 12 were designed to achieve lower airtightness in conjunction with ‘natural ventilation’. These plots incorporate Vaillant air source heat pumps and hot water cylinders.

Tony Hopkin, head of construction, quality and innovation at Midland Heart, said: ‘Part of our logic was to explore two different ways of ventilating the properties because historically we've had residents who hear the fan noise of an MVHR and think it’s costing them a large amount of money, so they sometime turn them off or tape over the vents to try and reduce costs.’

As an example of upgrades to fabric performance, U-values in the house on plot 5 were reduced from 0.13W/m²K (current Building Regs SAP 2012) to 0.11W/m²K (SAP 10) for floors; from 0.18W/m²K to 0.13W/m²K for external walls; from 0.14W/m²K to 0.1W/m²K for the roof; and from 1.4W/m²K to 1.2W/m²K for windows and doors. Air permeability was cut from 5.12N/m² to 5.0N/m² in the naturally ventilated home.

‘Installing 150mm of PIR cavity insulation provided a significant improvement compared to current levels. Roofs were generally an easy fix achieved using 450mm of mineral wool,’ said Hopkin.

  • All homes built to the Future Homes Standard must utilise a low-carbon form of heating and hot water, with a ban on gas boilers in new-build homes
    All homes built to the Future Homes Standard must utilise a low-carbon form of heating and hot water, with a ban on gas boilers in new-build homes Credit: Tony Hopkin
  • The research project has identified certain challenges around buildability and specification
    The research project has identified certain challenges around buildability and specification Credit: Tony Hopkin
  • Homes are designed to provide superior insulation and incorporate low and zero carbon technologies including solar panels
    Homes are designed to provide superior insulation and incorporate low and zero carbon technologies including solar panels Credit: Grosvenor PV
  • Air source heat pumps and hot water cylinders from different manufacturers are being installed to explore the performance of different products
    Air source heat pumps and hot water cylinders from different manufacturers are being installed to explore the performance of different products Credit: Tony Hopkin
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Contractor tenders for the scheme came in, on average, 13% higher than the equivalent scheme built to current standards, a percentage that Hopkin believes will reduce to between 8% and 10% when FHS hits its stride.

Lessons learnt so far on site include challenges around the use of ‘full-fill’ PIR insulation, which bricklayers found difficult to work with, with even small deviations in cavity width having a ‘massive impact’ with situations where insulation can push brickwork out. The use of a partial-fill 100mm PIR board is now being explored as an alternative alongside modifications to heating and ventilation.

Architects may need to think carefully about layouts and storage space, said Hopkin: ‘Moving away from a combi boiler, you need space for a hot water storage tank and an expansion vessel etc. to make these technologies accessible for maintenance and servicing.’

Building orientation, thermal efficiency and window size are other challenges. Overheating analysis by Project 80 identified a risk of overheating in some homes, so the team had to specify glazing with lower g-values. ‘The architect needs to think about the size and amount of glazing and the orientation of the building. The same goes for the PV on the roof – it’s about trying to extract the maximum benefit of PV so you can scale down the overall size of the system,’ he explained.

According to Hopkin one of the biggest obstacles to meeting FHS requirements was sourcing appropriate windows and doors. An initial plan to specify Passivhaus glazing was abandoned in the absence of a local supplier, instead superior double glazed units were installed alongside improvements to insulation and waste heat recovery etc.

The supply chain for installers of technologies including heat pumps and solar PVs will need to scale up significantly over the next three years if FHS is to be rolled out successfully, he added.

All properties on Eco Drive will be monitored over the coming year to assess performance, even down to the level of individual circuits. Initial results are expected at the end of this summer before a full dataset arrives in March 2023.

The findings will feed into a comprehensive Project 80 report, developed jointly with Birmingham City University and key product manufacturers, industry bodies and contractors, which will assess different ways of delivering the FHS using different technologies and build methods and in a range of building types.

The FHS is due to enter into Building Regulations from 2025 and require all new homes to meet more stringent building fabric requirements; utilise a low-carbon form of heating and hot water and emit 75-80% less carbon than homes built under current regulations.

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