Jonathan Ducker of Kingspan Insulation GB, discusses the shortcomings of the Future Homes Standard, and why a more ambitious approach is needed for the building fabric in particular to create ‘net zero ready’ homes.

At the end of 2023, the Government published its consultation on the Future Homes Standard (FHS) in England. This standard was intended to ensure all new homes in England are “net zero ready.” However, the consultation recommendations have been criticised as lacking in ambition – particularly in relation to fabric performance. This is largely unchanged from the existing requirements, which already lag behind those in Scotland and Wales. If applied, this may mean new homes fall short of “net zero ready” performance, could be more expensive to heat and could place additional strain on the National Grid. It could also require the properties to be retrofitted in the future at considerable extra cost. 

All of these issues could result in reputational damage for housebuilders, despite new homes being fully compliant with the FHS. It should therefore be a priority for everyone within construction to ensure the FHS is fit for purpose and delivers on its promise.

FHS Proposals

Perhaps the most notable changes proposed within the FHS consultation are to the Notional Dwelling specification in SAP. This is applied to a theoretical building of the same dimensions as the proposed home within the energy modelling software to generate the performance targets (for carbon emissions, Primary Energy and the Fabric Energy Efficiency Standard (FEES)).

The latter considers only the U-values, thermal bridging values, thermal mass, internal and solar gains and the airtightness of the property.

The consultation provides two options for the Notional Dwelling, both requiring the use of low carbon heating. Option one retains the current fabric specification (shown in the second column of the table below) but requires air-leakage to be reduced with a mechanical ventilation heat recovery system used to provide ventilation. It also includes use of wastewater heat recovery and photovoltaic (PV) panels covering the equivalent of 40% of the ground floor area. Option two is virtually unchanged from the existing requirements aside from the addition of low carbon heating.

As with the existing system, developers would be free to differ from the Notional Dwelling specification on the actual building providing they meet the mandatory performance targets and that no areas of the specification are worse than set limiting values and compulsory requirements (such as the use of low carbon heating). 

The decision to leave the fabric specification unchanged from the existing version of Part L was unexpected. In the consultation for the 2021 Part L change, the Future Homes Standard in 2025 was suggested as introducing ‘world leading standards of energy efficiency’ and included a more ambitious indicative specification (shown in the third column of the table on following page). Similarly, the Climate Change Committee had recommended that heating demand in new homes should be limited to 15-20 kwh/m²/year – similar to the requirement for Passivhaus properties. 

Limiting heating demand for new homes is important, not only to lower heating costs for homebuyers, but also to avoid placing unnecessary strain on the National Grid as we switch to electric-based low carbon heating systems, such as heat pumps. This is key, as estimates suggest that the electrification of heat, transport, and industry means demand for electricity is expected to grow fourfold by 2050. If the fabric targets for new homes are not tightened, this may mean they have to be retrofitted in the future at considerable cost. 

A better approach would be to use the fabric requirements which were outlined in the 2021 consultation. This approach is laid out in the third column of the table. As you can see, while the requirements are a step-up from existing requirements in England, they are still less demanding than those already being delivered in Wales. As such, they should be practical to achieve. 

While these lower U-values may have an impact on the thickness of insulation required, this can often be minimised by using products with lower thermal conductivities (lambda values). The lower the thermal conductivity of a material, the better it is at preventing heat loss. This can reduce the thickness of insulation needed to achieve a desired U-value.

In addition, many manufacturers now provide thermal detailing guides for products. These will typically be designed to achieve better psi-values than the default values or global values within the energy modelling software. This can support compliance, particularly with the FEES requirement.

Monitoring

Aside from these changes, the consultation also looks to address the performance gap between the designed and actual energy performance of buildings by introducing a Voluntary Post Occupancy Performance testing requirement for new homes.  

While this is a welcome inclusion, a compulsory requirement for all new homes would seem to make more sense. This would allow the causes of underperformance to be more easily identified across our housing developments, and lessons learnt to prevent this. The simplest way to do this would be to replace the current Primary Energy Metric (which considers not only the energy use in a home but also in upstream activities such as refining of the energy source) with a simpler Delivered Energy Metric which looks solely at end use in the home. This would allow easy comparison of the designed and actual energy performance. 

Lasting solution

The FHS is a key step in the country’s journey to net zero emissions. By targeting a fabric specification that is more ambitious than the current proposals but still reasonable and practical to achieve, we can help to ensure that new homes do not place unnecessary strain on the national grid, that they are affordable to heat and
that they do not need fabric retrofits in the future. This should ultimately help to minimise future regulatory upheaval on energy performance for housebuilders, supporting specification and long-term planning.

Jonathan Ducker is head of regulatory affairs at Kingspan Insulation GB