Scotland is leading the way with the introduction of Passivhaus (PH) equivalent legislation, announced in Jan 2023. Described as ‘radical, ambitious, practical and forward-thinking’ if successful, could “future proof” homes, preventing retrofits. Moreover this should upskill the construction sector and make Scotland’s new homes significantly more energy efficient. But what are the implications to such a move, and how can it be achieved?
Alex Rowley, the Labour MSP for Mid Scotland and Fife drafted the Domestic Building Environmental Standards (Scotland) Bill in response to the Scottish Climate Assembly Recommendations for Action, in which 97% of the Assembly voted in favour of the Scottish PH equivalent for new build projects. Scotland’s minister for zero carbon buildings, Patrick Harvie confirmed that the Scottish government would implement the standards within two years through secondary legislation – seeking the laying of amending regulations in mid-December 2024.
PH standards, which have been around for 30yrs, include accurate design modelling using the Passive House Planning Package (PHPP), high levels of insulation, extremely high performance windows with insulated frames, airtight building fabric, ‘thermal bridge free’ construction and a mechanical ventilation system with highly efficient heat recovery. The aim of the measures are certainly “of our time” – admirable, both in the context of the current cost of living crisis and the wider climate emergency.
The ongoing savings from PH energy efficiency and the lack of conventional heating will very quickly recoup upfront costs. A new-build PH is designed to operate with a space heating need of 15 kWh per square metre per year. By contrast, the space heating demand of the average UK home is currently about 145 kWh/sq m/year and a new-build home to the new Scottish requirements has been modelled to be about 28 kWh/sq m/year. Amid rising inflation, more than one in three people in Scotland find energy bills unaffordable. Of these, 80% say rising energy costs are a factor and 24% say their home is hard to heat. PH standards represent a positive and welcome measure.
In 2019 the PH Trust published a report into PH Construction Costs, confirming that there has been a consistent trend in PH costs reducing in the last 10 years. As of 2018, best practice costs were only 8% higher when set against comparable homes built to minimum Building Regulation standards. Indeed the report concludes that at scale, such costs could be reduced to a 4% premium.
Housebuilders operate in a continually shifting landscape – the list is endless; NPF4; cladding standards; ban on gas boilers etc. In an industry already suffering from spiralling costs and supply chain pressures, less than 2 years doesn’t seem long for the industry to formulate new standards and implement necessary changes to comply. However, there is no doubt that there is a movement towards this energy standard becoming more mainstream; West of Scotland HA, Kingdom HA, Hanover HA and Midlothian Council all have PH developments in their programmes. Scottish local authorities have embraced PH for their newbuild school programmes. This has been massively spurred on by a simple but impactful change to the funding criteria established two years ago for the Scottish Government`s Learning Estate Investment Programme (LEIP).
It is critical that the new Scottish PH equivalent standard is drafted in consultation with housebuilders of all sizes to ensure that disruption to the supply and costs of new build housing is kept to a minimum, to enable PH standards having the best chance of being the building performance ‘super power’ we need for new homes.
