VOICES | JULIE GODEFROY What regs revisions mean for zero carbon New Approved Documents on energy use, ventilation and overheating are intended to be stepping stones towards zero carbon buildings. Julie Godefroy highlights their impact and where regulatory improvements can still be made S hortly before Christmas, the government published a Building Regulations package, including the new Approved Documents L and F for new and existing buildings, and a new Approved Document O on overheating for new homes and other residential buildings. The changes will come into force in June, and are meant to be stepping stones towards the 2025 Future Homes/Buildings Standard (FHS/FBS), when new buildings will not need future retrofit to become zero carbon with grid decarbonisation. Carbon reduction The government expects this revision to deliver carbon savings of 31% for new homes and 27% for new nondomestic buildings. What it will actually deliver is uncertain, as the calculation methodologies (SAP and the NCM) do not relate well to actual performance, and cover regulated uses only. Metrics The notional dwelling has a gas boiler; a heat pump would have given a clearer message A major change is the introduction of a primary energy metric, alongside carbon dioxide, to encourage efficient use of energy resources at the system level. While no metric is perfect, 80% of consultation respondents, including CIBSE, raised concerns about this change because: It means little to consumers, so doesnt facilitate a closer link between performance and occupants Primary energy and carbon emissions rely on conversion factors that change over time, so it doesnt help with tracking progress Primary energy could favour gas over electricity, which will send confusing messages on heat decarbonisation. An energy-use metric, together with carbon emissions, would better address the key goals of energy efficiency, carbon reduction and consumer engagement. Low carbon heat DR JULIE GODEFROY is technical manager at CIBSE For new homes, the 2021 notional dwelling the one that sets targets for the actual dwelling has a gas boiler; a heat pump would have given a clearer message and more incentive for low carbon heat. For non-domestic buildings, the heating fuel in the notional building follows that of the actual building, except for coal and other high-carbon fuels, which are compared with gas. A statement in the consultation response is a telling illustration of the perverse effects of these shifting targets: We will be revising the specification of the heat pump notional building. This reduces the assumed efficiency of the heating system in the target building, providing additional incentive to install heat pumps.1 Instead of setting an ambitious target that buildings would have to meet regardless of their heating system, promoting energy efficiency and low carbon heat in a technology agnostic way, low carbon heat is encouraged by allowing poorer installations, at the cost of performance and impacts on consumers. There are important changes in how heat networks are treated: For existing networks, the notional building is connected to a network of the same performance so, there is no incentive for existing networks to improve. Instead, existing networks should be required to produce a decarbonisation plan, and their performance should be assessed on a much similar basis to other solutions. For new networks, homes are compared with an onsite gas boiler, and non-domestic buildings with a network with 15% distribution losses supplied, for the majority, by a CHP, with some heat pump contribution, giving a carbon content of heat similar to that of an onsite boiler (0.23kgCO2/kWh). This should provide more incentive for efficient and lower carbon new networks. Gas connections to new buildings are still allowed, but will be banned from 2025 for homes and possibly some non-domestic buildings. The consultations included clear statements about heat decarbonisation, anticipating a mix of technologies in future, with a key role for heat pumps. New home Significant changes are introduced to air permeability testing: all homes need to be tested, with sample testing no longer allowed. The low-pressure pulse (pulse) technique, which provides results at 4Pa, is approved as an alternative to the fan pressurisation (blower door) technique. Testing should be done according to CIBSE TM23 (2022). 14 February 2022 www.cibsejournal.com CIBSE Feb22 pp14-15 Julie Godefroy.indd 14 28/01/2022 16:04