Achieving zero carbon homes

This is a guest post by Sarah Birt, Senior Development Manager at Greater London Authority and FoL Alumni Rep.

For the first alumni event of 2021 and in a new series – Leading the way for cities – the focus was rightly on how cities will deliver on their climate emergency declarations through zero carbon developments. New housing developments, in particular, are under pressure to balance ‘net zero’ with affordability and project viability, which is easier said than done.

To help, this event built on FoL’s Achieving Net Zero project, and dived into the anatomy of a high-profile net-zero project to explore what made it successful and how this can be applied to other places.

Alumni Rep Mandar Puranik, Programme Manager at LB Sutton, chaired the alumni roundtable discussion, joined by David Mikhail of Mikhail Riches architects to hear his insights, experience and reflections on delivering the 2019 RIBA Sterling prize winning scheme at Goldsmith Street with Norwich City Council.

Find out more about Goldsmith Street in this short Mikhail Riches video

Climate emergencies declared – but what do we need to do?

Many local authorities have now declared climate emergencies, and the Mayor of London has set 2030 as a net zero target for London, ahead of the UK Government at 2050. However, do local authorities know how best to respond or to implement plans to move towards these targets? With an increase in local authority house-building, and the significant embodied and operational carbon generated by these schemes (and from existing local authority housing stock), councils need to make sure their housing is delivering on zero carbon.

As noted by David, local authorities should be ambitious when writing development briefs and project objectives, and ensure they get the right team on board and senior-level support for the project.

From the architect’s point of view “the client [local authority] is critical in setting these standards and setting the vision for the zero carbon development.” This is exactly what happened at Goldsmith Street. Norwich City Council pushed for the scheme to be Passivhaus.

Density is also important and delivering 100 homes per hectare is the optimal scale for delivering zero carbon housing. At this size, Passivhaus, air source heat pumps and photovoltaics (PV) can be affordably deployed. It is possible to deliver zero carbon at higher densities, although this may need to include carbon off-setting.

Recognising the value of zero-carbon homes

A well-versed challenge is that zero carbon development costs more to construct than traditional forms, which tend to be worse for the environment. However, local authorities are increasingly seeing the value of zero carbon development through the experiences of their residents.

Council officers and politicians hear real-life stories from residents living in affordable zero-carbon homes. Positive examples include the eradication of fuel poverty and improvements made to health, wellbeing and quality of life. Local authorities can consider the lifecycle costs of new affordable housing, including reduced energy bills and take a long-term view on their assets. Long-term efficiency savings and enhanced resident wellbeing offset higher short-term construction costs.

Price of land often too high to make zero carbon development viable – correction required from Government?

Another significant challenge to achieving zero carbon developments is the price of land. To be competitive on the open market, developers and housebuilders apply their standard assumptions using a short-term private sale revenue model. They do not have to factor in any additional costs from building zero carbon homes, which are over and above planning policy.

There is a role for the UK Government to update planning policy though, so that all developers and housebuilders bidding for land on the open market have to include the cost of delivering to net zero carbon. This change would help the public sector and level the playing field on the price of land.

Where land is already publicly owned, the public sector can take a longer-term stake and take on higher short-term costs that will be offset through efficiency savings later. Furthermore, land value could be secondary to ensure delivery against other policy priorities, such as community-led housing.

Delivering affordable housing and zero carbon – can we have both, and what needs to be prioritised?

With the prohibitive prices of land, it may not be viable to deliver on all fronts: zero carbon with policy-compliant levels of affordable housing. Therefore we may have to prioritise – sustainability at the cost of affordability. Or vice versa.

Other alumni viewpoints on this issue:

  • Cash in-lieu payments could be used to reach net-zero for denser schemes in cities where we can’t get to zero through Passivhaus, heat pumps or PVs.
  • On the other end of the scale, there are different challenges in bringing forward 100% affordable small sites/infill schemes. It is difficult to achieve net zero and remain viable on smaller schemes.
  • The GLA housing team have considered the equality impact of investing in sustainability standards, which has been key in incentivising investment. Fuel poverty is one benefit, but the benefits are much broader, including promoting thermal insultation/energy efficiency and improving air quality which benefits resident health and wellbeing and can be of particular benefit to groups with protected characteristics.
  • Top design tip: get energy demand down through orientation and good building fabric design – insulation, air tightness and reducing thermal bridging.

Leading the way for cities

This event was part of Leading the way for cities – an alumni-led series of events, podcasts and posts that will engage with city-makers on their aspirations for the future of our cities, drawing on their collective experience, ideas, resilience and leadership as we emerge from the pandemic.

The series reappraises the status quo, brings fresh thinking to tricky issues, and helps us challenge ourselves on ways to be more ambitious for our cities.

We will share practical insight across topics such as strategic visioning for cities, green recovery, health and well-being and delivering quality.  Themes of leadership and ‘thinking big’ weave throughout, to help the next wave of leaders in the alumni network respond to these new opportunities and challenges. Watch out for more content on the Alumni Network webpage.

Mikhail Riches event

Join Mikhail Riches, the City of York Council and Norwich County Council to hear more about the story of Goldsmith Street, the first 100% social housing project in history to win the Stirling and – what happened next.

11 May, 11 am to 12.30 pm
Mikhail Riches event: How we built world class sustainable housing at scale. Affordably.
Register here

Featured image courtesy of Mikhail Riches