Sustainability Report

A full whole-life carbon assessment was not undertaken as part of the original scope. Material selections were guided by low-energy and durability considerations, including the use of masonry construction, high-performance insulation, and standardised components to support build efficiency.

Operational emissions overview

• The project was not initially designed to meet the Passivhaus standard; this requirement was introduced during the design process. The scheme was subsequently developed iteratively through 3D modelling to align with Passivhaus principles. This included refining and simplifying the building form, optimising glazing ratios, and upgrading the building envelope through increased insulation, reduced thermal bridging, and a continuous airtightness layer.
• The external walls are constructed as cavity masonry walls designed to achieve a U-value of 0.12 W/m²K. The outer leaf consists of brickwork, while the inner leaf is formed from 140-millimetre concrete blockwork. The cavity incorporates 260 millimetres of Isover mineral wool insulation, while airtightness is achieved through a continuous parge coat applied to the inner masonry leaf, forming the primary air barrier.
• The target U-value for the windows was below 1.00 W/m²K. This was achieved using Idealcombi Futura+ triple-glazed windows, which deliver a U-value of 0.74 W/m²K. As a result, Passivhaus-certified windows were not required, avoiding significantly higher costs while maintaining comparable performance.
• Operational energy performance was modelled during the Passivhaus design development process using PHPP (Passive House Planning Package) to assess and optimise building performance. The modelling indicated that the dwellings will meet very low operational energy demand targets, with reduced space heating requirements resulting from the enhanced fabric performance and airtightness strategy.
• The services strategy was adapted to accommodate Mechanical Ventilation with Heat Recovery (MVHR) and air-source heat pumps in response to the project’s reduced heating demand. These changes formed part of a coordinated fabric-first approach developed to achieve low-energy, Passivhaus-aligned performance.
• Predicted space heating demand ranges from 15–23 kWh/m²/yr across the different blocks, while predicted total primary energy consumption is ≤135 kWh/m²/yr.
• The project also incorporates Velux Solar Passive House roof windows, a Bauder Bio Solar Extensive green roof system, and Vaillant aroTHERM plus air-source heat pumps.