MODERN METHODS OF CONSTRUCTION 77


Scots take the Passivhaus road with new standard


The planned introduction of the ‘Scottish Passivhaus’ standard brings opportunities to minimise energy demand and eliminate the performance gap. Jonathan Ducke of Kingspan Insulation discusses the likely contents of the new standard


T


his Summer, the Scottish Government is due to consult on the “Scottish equivalent to the


Passivhaus standard,” as a compulsory requirement for all new homes. This represents a significant shift, with modelling from the Passivhaus Trust suggesting that heating demand from homes completed to the Passivhaus standard could be 79% lower than an equivalent home built to the current requirements in Scotland. The Passivhaus standard requires properties to be highly insulated, with thermal bridges eliminated and air leakage reduced to very low levels. Delivering this at scale will require the entire industry to look carefully at its practices and the construction approaches being adopted. In particular, offsite solutions such as structural insulated panels (SIPs) offer a number of advantages which make them highly suited to these requirements.


Understanding Passivhaus requirements


While the exact format of the Scottish equivalent is yet to be confirmed, the Passivhaus standard itself provides an indication of what we may expect. Passivhaus was developed to close the performance gap and provides an approach that is quality assured throughout the build process, ensuring that certified buildings really deliver reduced energy use, good indoor air quality and comfortable temperatures throughout the year. It sets out a range of ambitious energy performance requirements which certified properties must meet: • Airtightness n50: ≤ 0.6 ACH @ 50 Pa • Space heating/cooling demand: ≤ 15 kWh/m².a


• Primary Energy Renewable (PER): ≤ 60 kWh/m².a


ADF MAY 2024


• Surface temperature: ≥ 17°C • Overheating: Max 10% > 25°C


The space heating/cooling demand is far lower than for an average existing UK home – estimated to be around 130 kWh/m².a. The PER metric, meanwhile, is designed to encourage the use of onsite renewables, applying fuel factors to different sources of energy. These factors are typically set lower for low carbon technologies and onsite renewables, essentially making it simpler to achieve compliance with these approaches. The air leakage rate is calculated using an n50 measurement. This differs from the measurement used in Part L and Section 6 of the Building Regulations


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