J4D3 Thermal construction — general

What is J4D3 - Thermal Construction?

J4D3 - Thermal Construction — General provides guidelines for the installation and calculation of thermal insulation in buildings to ensure energy efficiency. It sets out requirements for the proper installation of both bulk and reflective insulation, ensuring they contribute to an effective thermal barrier. Key provisions include:

1. Insulation Compliance: Insulation must comply with AS/NZS 4859.1 and be installed to form a continuous barrier, abutting or overlapping adjoining insulation (except at supporting members) and without obstructing services or fittings.

2. Reflective Insulation: Reflective insulation must be installed with sufficient airspace to achieve the required R-Value. It should fit closely around penetrations, doors, and windows, be supported by framing, and adjoining sheets must be overlapped by at least 50 mm or taped together.

3. Bulk Insulation: Bulk insulation should maintain its position and thickness, except when compressed between building components like cladding or pipes. In ceilings, it must overlap the walls by at least 50 mm if no insulation is present in the walls beneath.

4. Thermal Properties: Materials used for roofs, ceilings, walls, and floors must meet the thermal properties specified in Specification 36 or specific values provide by suppliers.

5. Total R-Value and U-Value: The required thermal performance (Total R-Value and Total System U-Value) must be calculated or determined according to relevant standards, including AS/NZS 4859.2 for roofs and floors, Specification 37 for walls and glazing, or Specification 39 and CIBSE Guide A for sub-floor spaces.

These provisions ensure that thermal insulation is effectively installed, minimizing energy loss and contributing to a building’s overall energy efficiency.

J4D3 - Thermal Construction Modelling on Speckel

The majority of the clauses within J4D3 are qualitative commitments to constriction quality, with the exception of clause 5, where the required thermal performance (Total R-Value and Total System U-Value) must be calculated or determined according to relevant standards, including AS/NZS 4859.2 for roofs and floors, Specification 37 for walls and glazing, or Specification 39 and CIBSE Guide A for sub-floor spaces.

Speckel provides specific calculations for AS/NZS 4859.2, Specification 37 for walls and glazing or Specification 39 and CIBSE Guide A within our applications. When used as part of a Part J4 Building Fabric assessment, Clause 5 is automatically met.