By Nuno Correia

Earlier this year, the UK government launched a consultation on the Future Building Standard, including changes to Part L and Part F of the building regulations in England and Wales, due to come into effect in 2021. This is a follow up from the Future Homes Consultation and will lead to an update of the approved documents, which are overdue a refresh. As for 2025, the strategy is still high level and will be subject to further consultation.

What’s on the cards for 2021?

One of the key outcomes of the previous consultation was that local authorities will retain their ability to set planning targets that go beyond Part L. The Greater London Authority (GLA) has been leading the way with ever more stringent requirements in each version of the London Plan. Now more than 400 UK councils have declared a climate emergency and may also be looking to go beyond minimum targets. It is questionable whether Part L should be used at all to set targets for buildings as it was never designed to predict energy consumption and currently underestimates actual consumption by a large margin.

The 2021 standard for homes proposes a 31% carbon reduction saving over Part L. Additionally, it retains the Fabric Energy Efficiency Standard (FEES), which is the key enabler for a fabric first approach and has been the subject of substantial debate.

For non‑domestic buildings the current options are for 22% and 27% reduction. The new notional building will include a relatively small improvement in fabric efficiency and an increased weighting to thermal bridges – a welcome addition. Moreover, minimum building services efficiencies have also been increased. When combining these changes with a decarbonised electricity grid, the likely result is a significant number of buildings complying with Part L targets despite having a relatively inefficient building fabric. Overall, thermal performance and airtightness requirements should go further to avoid the risks of locking tenants to higher fuel bills and landlords to costly fabric retrofit works in the future.

The National Calculation Methodology (NCM) gets a bad reputation for not accurately predicting energy use, however, this was never its objective as it was designed to demonstrate compliance with Building Regulations. Its 2021 non-domestic version brings in a few updates but still fails to address one of its flaws – understating space heating demand. This is both hard coded in the way that ventilation is treated, and a function of excessive internal gains in an outdated activity database, reminiscent of an era of inefficient lighting and equipment. Addressing this issue would perhaps contribute to prioritising fabric efficiency.

Part L 2021 will introduce a requirement for non-domestic buildings over 1,000m2 to have design stage energy forecasts using CIBSE TM54. This will facilitate a level of capacity building in the industry, and ties well with the recently announced plans to introduce a performance-based policy framework (BEIS).

In this context, the proposal to include a primary energy metric, with variable fuel factors (much like carbon), seems slightly out of place. Over the past year, an increasing number of commercial developers have been getting ahead of the curve by signing up to the UKGBC Net Zero Carbon buildings commitment and in some cases pursuing Design for Performance and NABERS UK. In doing so, our industry is understanding the value of using energy use intensity (EUI, in kWh/m2) to drive down energy demand.

The update to Part F brings numerous changes, including a requirement to provide the means to increase the ventilation rate by 50% in reaction to the pandemic. We see this as excessive considering the lower occupant densities we’ve seen. The conflict with Part L energy targets will lead to much larger ventilation equipment with associated loss of space, operating at lower efficiency during most of the time.

Finally, overheating is now the subject of an approved document. The draft includes further details on using CIBSE TM59, and the simplified method. The latter is indeed too simple in not fully considering orientation and daylight; and complicated in its building groupings, percentages glazing and openings based on floor areas. A good idea but not fit for purpose in its current form and needing further evidence to support it.  

What about 2025? And 2050?

Future homes will need to target a 75-80% reduction by 2025, which will require a step change in the way buildings are designed. There isn’t yet a clear target for non-domestic buildings but they are likely to follow a similar trajectory to domestic buildings; these will need to be “capable of becoming carbon neutral over time as the electricity grid and heat networks decarbonise”. Fine in principle, depending on the definition of carbon neutral (?) and on legislation to ensure the decarbonisation of heat networks occurs. As it stands, the current proposals do not go far enough in pushing for low carbon networks. The goal should be to encourage 5G networks and a clear trajectory should be set to allow existing district networks to adapt.

The consultation introduces the concept of non-domestic energy demand types, classifying buildings based in their suitability for heat pumps and savings achievable. There are a few ways in which this could go wrong and lead to the specification of inefficient systems. It is suggested that further evidence is required to develop targets that incentivise demand reduction and are technology agnostic.

Between now and 2050, existing buildings will become the main challenge. These will require more stringent targets than the relatively light touch approach proposed for the 2021 Part L update. Upfront embodied carbon and whole life carbon calculations and targets will need to become common practice to enable net zero.

In summary, there are a few steps in the right direction, but is this the level of regulatory incentive the industry needs to accelerate the net zero carbon transition? The consultation is open until April 13th – have your say! If you wish to discuss in more detail, please get in touch.

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Nuno Correia, Sustainability


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