Part J4 Building fabric
Last updated
Last updated
J4 Building Fabric addresses the building envelope requirements for energy efficiency. Its intent is to provide Deemed-to-Satisfy Provisions for roofs, ceilings, roof lights, walls, glazing, and floors.
These provisions ensure compliance with Part J1P1 by offering clear guidelines for the thermal performance of the building envelope. J4 is designed as an alternative to Performance-based Solutions, offering prescriptive measures to meet energy efficiency requirements without the need for detailed modelling, ensuring streamlined compliance for construction projects.
Our J4 Building Fabric compliance approach is unique, with the building fabric elements (including roofs, walls, glazing, and floors) being automated for streamlined Deemed-to-Satisfy assessments. This method significantly reduces the time and effort required, allowing the focus to shift towards optimizing thermal performance. A typical building’s compliance can be assessed within hours, including all necessary simulations and results.
Compliance with J4 Building Fabric is provided by the Performance Requirements - J1P1 Energy Use.
J1P1 Energy Use sets out performance requirements for energy efficiency in buildings, excluding sole-occupancy units of Class 2 and Class 4 buildings. It ensures that buildings, including their services, incorporate energy-efficient features appropriate to the building's function and use, while also ensuring comfort levels are maintained.
Key considerations include:
Utilisation of solar radiation: for heating and controlled to reduce cooling energy.
Energy source: optimizing the energy used by building services.
Building sealing: to minimize air leakage, enhancing energy efficiency.
For conditioned spaces, it sets maximum regulated energy consumption limits based on building classification:
Class 6 buildings: 80 kJ/m².hr.
Class 5, 7b, 8, or 9a (non-ward areas) and Class 9b schools: 43 kJ/m².hr.
Other classifications: 15 kJ/m².hr.
These criteria aim to ensure that energy use is optimised while considering both the building's intended function and the need for human comfort.
Note, while J1P1 references kJ/m².hr values, these are unlikely to be met via modelling as they represent very high performance buildings. They are 'demmed' to be met only and serve no functional purpose.
