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York Passivhaus programme gathering pace

Three housing projects are underway, with more in the pipeline, as part of the City of York’s commitment to delivering 600 Passivhaus certified homes. The City of York Council is working with an interciplinary team, including PHT member Mikhail Riches architects and Passivhaus consultant PHT Patron WARM, to deliver the city-wide Passivhaus housing programme, which is part of the City’s pledge to meet net-zero carbon targets by 2030.

Projects underway

There are seven Passivhaus housing projects currently in the pipeline as part of this delivery programme, with three projects more advanced.

Ordnance Lane

No. of homes: 98

Project stage: Planning permission

Build start date (predicted): 2024

Completion (predicted): End 2026

Ordnance Lane York/Ordnance Lane Passivhaus development. Image credit Mikhail Riches

Duncombe Barracks

No. of homes:34 & 1 commecial unit

Project stage: On site

Build start date: 2022

Completion (predicted): Summer 2024

Duncombe Barracks Passivhaus development Image credit: Mikhail Riches/ Darc Studio

Burnholme

No. of homes: 78

Project stage: On site

Build start date: 2022

Completion (predicted): December 2024

Burnholme Passivhaus residential development, York City Council. Image credit Mikhail Riches/ DarcStudio

Other project sites include:

Boroughbridge Road (former Manor School)
Rawcliffe Drive (former Primary school)
Woolnough House, Woolnough Avenue
Askam Bar site, Moor Lane

Design principles

All homes within the housing delivery programme are aiming to be certified Passivhaus. Heating is provided by air source heat pumps and an array of solar PV panels on the roof will ensure the homes are effectively net zero carbon in terms of energy usage. The embodied energy of the construction materials (the energy consumed in their extraction, production and transport) will also be closely monitored, as well as the homes’ energy consumption. Other features of the design include reduced car parking provision and car free play streets.

Off-site timber frame construction is the chosen construction method, with brick and roughcast render and complementary timber cladding. The use of pre-fabricated timber frames has helped to make the project lower risk for contractors;

Passivhaus is like base camp when you’re trying to climb the Everest of zero carbon. We’re planning to go above and beyond, taking into account much more than just the efficient fabric of the houses.

David Mikhail, Architect, Mikhail Riches

High density terraces

Burnholme Passivhaus development, York - birds eye view. Image credit Mikhail Riches

Duncombe Barracks Passivhaus development, York - birds eye view. Image credit Mikhail Riches

Ordnance Lane York/Ordnance Lane Passivhaus development - a birds eye view. Image credit Mikhail Riches

The schemes are being designed in low-rise high density terraces, of approximately 50 homes/hectare, to take advantage of the good form factor provided by terraced housing. By building the terraces close together the design team aims to maximise use of the land available as well as creating a close-knit feeling of community. Careful modelling is needed to ensure that the minimal separation between the houses will allow just enough solar gain with the low winter sun to be acceptable for the Passivhaus standard while maximising the number of homes in the plot.

Funding model

The City of York Council is working with Homes England who are keen to support their zero carbon approach. This has helped the council unlock extra Affordable Homes Programme grant funding. The scheme is funded through a mix of Right to Buy receipts, Homes England funding and market sales.

A minimum of 40% of the programme's homes will be available either for social rent or shared ownership, significantly above what local planning guidelines currently require. The rest will be up for market sale, with market sales used to subsidise the cost of the social rent and shared ownership affordable homes,

Delivery team

Council officers carefully recruited a multi-disciplinary design team that would work on the scheme for at least five years. PHT members Mikhail Riches, architects of the award-winning Norwich Goldsmith Street project. are leading the project,

The programme is supported by RICS-accredited project managers driving on-site quality. A RICS-accredited clerk of works will play a key role in championing quality across the sites and RICS-accredited valuers are being utilised to provide confidence in sales projections to support the business case development.

Burnholme Passivhaus residential development, York City Council. Image credit Mikhail Riches/ DarcStudio

Upskilling of local workforce

York has been proactive in addressing the fact that most contractors are not experienced in delivering Passivhaus projects at scale.The Council is also aiming to give more local people the skills to work in sustainable building and is using grant funding to work with a local college to develop Passivhaus training. York's procurement process incorporated skills development for contractors, with the council setting out minimum requirements for supporting skills and apprenticeships. The council has established a stakeholder group with local colleges focussed on sustainable building, which involves both the council’s housing and skills team.

Caddick Construction, which has been chosen as the main contractor for the Burnolme and Duncombe Barracks projects, has committed to creating 30 jobs, 22 work placements and a programme of training and development for 14- to 19-year-olds. As well as aiming to source 70% of their subcontractors and suppliers within 30 miles of the site, they will offer training on site through apprenticeships, traineeships, and higher qualifications for new and existing staff. Working with York College, York Apprenticeship Hub and Job Centre Plus, Caddick has committed to support the development of ‘Green Skills’ in the supply chain. This will be achieved by taking part in local construction industry skills forums, engaging with local trades and construction firms, and contributing to construction training content with local further education and higher education providers.

Challenges

The main challenge the delivery team is experiencing is achieving a net zero standard that’s affordable and can be scaled up for big developments of houses.

The project has been vulnerable to risk pricing (contractors increasing their prices due to uncertainty) and there was potential for quality issues on site. Higher building costs make it difficult to compete for new land that comes up on the open market, as other developers with lower build costs can offer higher prices.

Lessons learned

The team has found that focusing on Passivhaus design principles is important for helping to keep costs down. The council originally added three storey dormers to some properties, for design purposes. but this altered the buildings’ thermal envelope and meant significantly more insulation was required. Sticking to simpler building forms has reduced the need for insulation and kept costs down.
As heat demand is very low, due to building to the Passivhaus standard, sourcing air source heat pumps that are sufficiently small has been challenging on the project. It may be that communal air source heat pumps might be more effective for future projects.