New Build Passivhaus Scheme, York

Project Overview

Background

The architectural practice Mikhail Riches led a multidisciplinary design team in the development of an innovative new-build residential scheme in York. It focused on a brownfield site in the Duncombe Barracks neighbourhood to the north of the city centre.

It set out to create 34 new homes – ranging from one- and two-bedroom flats to four-bedroom family houses – together with public spaces and secure shared gardens.

The project was commissioned by the City of York Council and sought to create homes that would not only comply with Passivhaus standards, but also achieve operational Net Zero carbon. The scheme would help to meet an immediate need for residential homes but, importantly, it would also serve as a blueprint for future sustainable housing developments.

Mikhail Riches notes that the scheme went through “three pre-applications before being submitted in October 2020.” It was approved in 2021.

Brief

Passivhaus principles would be applied throughout the scheme. This included the use of terraces, and orientating properties to the south to make optimal use of sunlight and warmth. By incorporating microgeneration technologies and sustainable energy systems (such as solar PV and air source heat pumps), the design also sought to ensure that the developments would generate as much energy as their householders consumed.

Meeting Passivhaus standards would also call for high levels of airtightness and energy efficiency. Part of the design brief therefore called for the installation of external wall insulation systems on various elevations.

Design and Specification:

The chosen EWI comprised:

  • Permarock Mineral Fibre External Wall Insulation (EWI) System: On north-facing elevations, the EWI system incorporated 140 mm insulation, adhesively bonded and mechanically fixed to the substrate. On south-facing and end elevations, the system was used with 40 mm insulation to create recessed feature bands at the heads and jambs of window and door openings, and rendered panels below some windows in the otherwise brick facades.
  • Permarock SiliconeUltra K Finish (textured render). This was used throughout. On the north-facing elevations, dummy windows were created using a masking technique along with Permarock SiliconeUltra Façade Coating in the same colour as the textured render.

As a combined system, Permarock Mineral Fibre and Permarock SiliconeUltra K-Finish have an A2-s1,d0 reaction to fire classification (EN 13501-1) and can be used on buildings of any height. They also permit extremely airtight façades to be achieved.

Performance: Sustainability and U-Values

Permarock Mineral Fibre External Wall Insulation systems have low embodied energy and are BIM Level 2 compliant. The insulation has a thermal conductivity of 0.036 W/mK, and is available in a wide range of thicknesses enabling very low U-values to be achieved. The system has an Ecopoints score of 0.10 (m2) – an ‘excellent’ rating.

Mineral Fibre insulation is manufactured to EN 13162, it is non-combustible, and CFC- and HCFC-free. It has zero Ozone Depletion Potential and zero Global Warming Potential.

Result:

In 2022 and 2023, the project won a number of awards including:

  • Royal Town Planning Institute Yorkshire Award (2022)
  • (Project) Planning Award (2022)
  • Housing Design Award (2023)

The scheme has also been the subject of an energy efficiency study, the full results of which were still being gathered at the time of writing. Amongst other considerations, these have examined the effects of using timber frames and organic, cellulose-based insulation internally. Indicative ‘embodied carbon’ results have been gathered from Blocks A, B and C at Duncombe Barracks. Passivhaus Plus magazine reported that “Blocks B and C meet the RIBA 2030 target of 625 kg CO2e/m2 GIA, with scores of 595 and 587 respectively, while Block A scores 642.”

Working from a sample property, project partners have estimated the following results:

  • Average space heating demand (PHPP): 15 kWh/m2
  • Heat load (PHPP): 10 W/m2
  • Airtightness (at 50 Pascals): 6 air changes per hour
  • Projected energy consumption: 35 kWh/m2/year

In July 2024, a Housing Development Manager for York City Council wrote that the rear elevations at Duncombe Square featured “140mm rockwool slabs with PermaRock render. The additional insulation here gives a ridiculously low U-value of 0.09W/m2K!”

Shape Homes York (a brand owned by the City of York Council) estimates that residents’ energy bills will be 70% lower than those faced by occupants living in more conventional homes.

More details, including the architect’s own commentary, can be seen here:

 

Note:

This scheme is one of several notable projects involving collaboration between Permarock Products and Mikhail Riches. Other projects have included Park Hill Flats (Phases 2 and 4) in Sheffield, Goldsmith Street in Norwich, and another new-build Passivhaus scheme at Burnholme Green, also for City of York Council.

Project
New Build / Residential
Client
City of York Council
Specifier
Mikhail Riches
Substrate
Timber Frame
System
Permarock Mineral Fibre External Wall Insulation Systems
Finish
Permarock SiliconeUltra K Finish