In September, City of York Council confirmed that its programme to deliver 600 sustainable low-energy homes in the next five years will be led by award-winning architect practice Mikhail Riches. It will be supported by a team including our Yorkshire-based building services and design consultancy cooperative Leda.
The first two proposed sites are about to go to public consultation, with York developing a design manual of five key principles including an emphasis on healthy homes and neighbourhoods, placing making, and energy use.
York is committed to making at least 40% of the homes affordable and retain 20% for social renting. All new homes must be built to the certified Passivhaus standard.
City of York Council declared a ‘climate emergency’, and made a commitment to be carbon neutral by 2030, joining many other councils in targeting carbon reduction as a priority. This ambitious housing delivery programme is a key component in demonstrating its commitment to achieving these aims. York wants to see the project achieve the highest environmental standards, and views Norwich City Council’s multi-award winning Goldsmith Street Passivhaus scheme, designed by Mikhail Riches, as a great example.
Why Passivhaus is important
For us at Leda, the compelling reason for adopting the Passivhaus approach is simple: the methodology is robust and able to deliver buildings that perform as anticipated.
From our experience of one-off houses, the rigour it places on the architects, structural engineers and contractors is very welcome in a world where site quality standards are usually seen as a robust finish.
As building service engineers, we are all aware that how a building performs is very much about what goes on under the building’s skin. This is where the hidden problems with continuity of insulation and air tightness are hidden from view.
Certification, among other things, is a quality-assurance system for thermal performance. It considers the design, modelling, construction, commissioning and documentation with a rigour that Building Regulations or other standards don’t come close to matching.
We’ve worked with the architects to come up with a scheme for creating zero-carbon housing that fits well with the carbon-neutral commitment made by York. To deliver net zero carbon in use – including an allowance for unregulated energy – we see the Passivhaus methodology as the way to achieve the lowest-possible heating energy demands in a predicable way, allowing us to calculate reliably the renewables needed to offset these demands.
Passivhaus is agnostic about the heating system and hot water, giving us the freedom to design the most appropriate system
Initially, we see this as being accomplished with only a heat pump for hot water and photovoltaics (PV) for electricity, although the details of such solutions need to be thoroughly examined and the right balance of end-user simplicity, maintenance and energy use achieved.
However, if a big chunk of heating demand has been eliminated by the design, then the solution becomes simpler, and it is primarily the hot water load we need to meet in the most efficient and appropriate way. Passivhaus is mostly agnostic about the heating system and hot water, giving us the freedom to design the most appropriate system to meet the project needs.
We want to demonstrate that York’s aims of being carbon neutral can be achieved on any site, while ensuring good architecture and landscape design, too. It’s also exciting and inspiring to be working with architects who push for the best in design and outputs for the clients.
With Exeter City Council, Norwich City Council and City of York Council committing to build Passivhaus-certified housing, it feels like there are changes afoot with new-build social housing.
We have worked with Leeds-based sustainable housing developer Citu and seen it go from strength to strength. However, more builders need to take on this ethos of building better homes, with energy and place making at the top of the agenda.
- Leda’s Little Kelham housing project won CIBSE Yorkshire Commercial and Industrial Project of the Year in 2017 (Mat Finish, CIBSE Journal, April 2018). The CIBSE Yorkshire Awards 2019 will take place on 15 November at the Royal Armouries, Leeds. Read about Exeter City Council’s Passivhaus swimming pool on page 6 of this month’s Hotel and Leisure Special
- Jim Wild MCIBSE is director and senior engineer at Leda