City of York Council: Zero Carbon Homes Programme

A new build housing programme with all homes built to Passivhaus certification, ensuring high thermal efficiency. In addition, all schemes are low parking developments with a focus on cycling and walking with car free streets.


The challenge

One of the major challenges the Council faced is delivering Passivhaus homes on a large scale when there is little experience in the sector. In addition, additional skills in the design, commissioning and maintenance of air source heat pumps is also needed.

Build costs are also a challenge with the measures to achieve zero carbon adding a significant cost uplift to the properties. This is combined with little market data showing sales value increases for eco homes, although initial indications are that people will pay a premium.

The solution

To ensure the Council had the expertise to deliver the project they ran an extensive procurement for a 5+ year multi-disciplinary design team. By setting ambitious goals, reducing insurance levels, and embedding design principles at the heart of the procurement they were able to attract more specialist consultants. This has provided them with the expertise to deliver the programme, led by architects Mikhail Riches.

They have also designed using an off-site manufactured timber frame system which provides comfort to the main contractor working on Passivhaus which they will not have done at scale before, with the supplier guaranteeing the first air tightness test.

The Council have accessed additional grant to provide training locally on the installation and maintenance of heat pumps in preparation for construction.

The impact

The energy usage of homes will be significantly lower than a standard new build property. Over the course of a year each home will generate at least the same amount of energy as it uses, and many properties will actually create a surplus. Due to this, total energy bills are calculated to be more than 50 per cent lower than a building regs new build property. 40 per cent of the homes on each site will be affordable, so this saving will greatly help tackle fuel poverty for those residents and increase their disposable income.

The Council have also considered embodied carbon in the design process and used that data to drive decisions. This approach has been used to save a forecast 120,000Kg of Co2e just by changing the foundation design on one of the schemes.

Lessons learned

There is still significant cost involved in the design and build of environmental housing. The cost of solar PV has reduced, but air source heat pumps are still a relatively expensive item.

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