As an alternative to our usual field trips, on 14 July Future of London ran its first Video visit + discussion on the theme of Net Zero Housing. A small group of attendees ‘visited’ (via video) New Garden Quarter in LB Newham. We then discussed the scheme and the wider issue of building zero carbon homes with Pollard Thomas Edwards architects Tom Dollard and Justin Laskin, and Victoria Thorns from London Legacy Development Corporation.
Above: Attendees watched this video about New Garden Quarter before attending the discussion with our speakers. We recommend you watch it before reading the write-up. Video courtesy of Pollard Thomas Edwards. Below: You can get a sense of the site by exploring our interactive map.
As Justin Laskin, Associate Partner and Pollard Thomas Edwards’ project lead on the scheme, explains in the video, New Garden Quarter is sustainable city-making in the truest sense. It was a derelict brownfield site that has been turned into beautiful new homes and a square, that are very close to amenities and good public transport links.
It has an excellent sustainable draining system (SuDS) strategy, that deals with rainwater in a way that’s both sustainable and beautiful. The landscape architect, Churchman Thornhill Finch, designed the SuDS in such an integrated way – with blue roofs, a rain garden and a water feature – that it feels like a natural part of the landscape.
And the local ecology has been significantly enhanced from the mature trees and native species that have been introduced. In the discussion, Justin pointed out that London Legacy Development Corporation (LLDC) should take much of the credit for this because the trees were a condition specified by them in the planning application process, right down to the trunk diameters of each tree species.
Although Pollard Thomas Edwards (PTE) haven’t done a formal post-occupancy evaluation on this project yet, the feedback they’ve had from residents has been overwhelmingly positive. People like the light and generous space standards, and parents appreciate being able to open their doors and let their kids play outside thanks to the clear delineation between public and private space.
But is it net zero? And what does that mean? To answer those questions, Tom Dollard, Associate Partner and Head of Sustainable Design at PTE, explained that you have to look at how the zero carbon standard in London has changed since 2006, when future PM Gordon Brown announced that every new home would be a zero carbon home by 2016.
Defining ‘net zero’
In response to Brown’s call for zero carbon homes, the Zero Carbon Hub was set up. One of the Hub’s tasks was to define zero carbon, but this definition was slowly watered down and in 2015 the national policy of delivering net zero homes by 2016 was scrapped. (The Hub itself closed in 2016.)
Designs for New Garden Quarter began in 2010 and the scheme met the 2011 London Plan definition of net zero. This stipulated that new buildings achieve a 35% carbon reduction on site, but didn’t require any carbon offsetting payments.
The Intend to Publish London Plan, published in December 2019, now calls for 35% carbon reduction on site but specifies that for residential buildings 10% should be achieved through energy efficiency measures. The remaining 65% can be paid for in offset payments or an offset mechanism, with the GLA recommending the price of carbon is set at £95 a tonne.
So although New Garden Quarter doesn’t meet London’s current definition of net zero housing, it was considered best practice at the time. “This highlights one of the key challenges of large, complex projects like this: they take a really long time to deliver,” said Justin. “PTE first started working on this site in 2011 and in that kind of time, both policy and technology inevitably move on. Balancing sustainable design and best practice with the fact that projects may take a decade to complete is challenging.”
“Today, and looking forward to 2025 and beyond, net zero carbon encompasses everything: embodied carbon, operational carbon, and whole-life carbon over the whole lifecycle of a project (typically 60 years),” explained Tom. “This definition still allows for offsetting payments but the onus is on reducing carbon as much as possible on site.”
New Garden Quarter’s energy strategy
Justin explained that the scheme’s energy strategy followed the GLA’s energy hierarchy (which is still in use today):
- Be lean: use less energy
- Be clean: supply energy efficiently
- Be green: use renewable energy.
New Garden Quarter is lean because of its good fabric efficiencies, with U-values of 0.13 to 0.16. Although PTE is now delivering buildings with higher fabric efficiencies, at the time these U-values were considered good practice.
It’s green because most of the roofs are covered with solar electricity panels, also known as photovoltaics (PV).
And it’s clean because it has a combined heat and power (CHP) on-site plant that provides electricity and hot water to the entire development. Although they did consider connecting into an existing local heat network, the inherent inefficiencies in that heat network meant that plugging into it would significantly increase the scheme’s carbon emissions. So clients Notting Hill Genesis and Telford Homes decided to build their own CHP plant.
It was through the combination of fabric efficiencies, energy delivery and PV that they achieved the 35% carbon reduction target.
Heating and ventilation challenges
Several audience members had interesting questions and comments regarding heating and ventilation. Alexia Laird, Sustainable Design Executive, Landsec, pointed out that the GLA’s preferred approach today is for large-scale developments like this to join existing heat networks – but this is somewhat contradictory if connecting to an existing heat network creates more carbon emissions.
Victoria Thorns, Community and Sustainability Manager, LLDC, agreed that joining an existing district heat network is complicated. LLDC inherited a gas-based district heating network that had been built as part of the infrastructure for the 2012 Games infrastructure.
It serves buildings in the Queen Elizabeth Olympic Park and venues like Westfield. But as the grid has begun to decarbonise and improved fabric efficiency has reduced demand, developers aren’t always keen to join the existing heat network. So LLDC is currently working with the heat network on these various challenges on a project-by-project basis.
Juliette Bartlett, Project Director, Swan Housing Group said that as a long-term asset holder, Swan Housing is interested in installing ground source heat pumps but there are very few large-scale projects in the UK that are using them and have data to show they’re working well. Tom pointed out that Building for 2050 is currently reviewing a Galliard Home scheme in Leyton, LB Waltham Forest, that has done a communal, air-source heat pump low-temp system at scale.
And in response to a question from Susan May, Head of Housing Design, Urban Design London, about dual aspect and ventilation, Justin acknowledged that maximising dual aspect is always challenging because, from a cost point of view, developers want the maximum number of flats per floor. But 70% of the homes in New Garden Quarter are dual aspect, including all the family homes.
“Once you’ve maximised dual aspect, then it becomes a technical challenge with the need for as much ventilation as possible,” added Tom. This can be achieved by having windows that open (including in common areas that often overheat) and a tried-and-tested Decentralised Mechanical Ventilation With Heat Recovery (MDHR) system that works.
Lessons learned: Improving New Garden Quarter
One of the most useful and refreshing aspects of this event was Justin’s and Tom’s willingness to speak frankly about how one of their practice’s schemes could be improved upon. Without this level of honesty and transparency about past projects, it’s difficult to set new benchmarks for best practice and continue to improve.
“We wouldn’t have to change the design much to meet the Intend to Publish London Plan standards,” said Justin. “We could use a slightly better fabric, install triple-glazed windows throughout, and rely on a communal heat pump system rather than a CHP system.”
In response to a question from Matt Lally, Associate Director, Arup, Tom explained that although it would be cheaper to do these things on a new build, it is possible to retrofit certain features like heat pumps, ventilation systems and glazing. (Although the real retrofit challenge lies with buildings built before 2000.)
They would also have to commit to a post-occupancy evaluation that looks at in-use data on energy performance and is led by an independent third party, such as a consultant or a university.
“But the real challenge would be to deliver 100% net zero,” said Tom. “That would require a pretty radical redesign, especially in terms of the specifications at the construction stage.” His suggestions included:
- using timber instead of concrete for the frame, as long as this met fire regulations
- using as much recycled material as possible and re-using the existing materials on the site
- adding more PV, although he acknowledged that in a six-storey block of flats the roof area per unit is quite small. (Houses have much larger roof areas, which makes it easier for them to become net exporters and thus pay off embodied carbon that way.)
“How to achieve net zero on high density housing projects is a key question,” added Tom. “So should we be aiming for net zero on these kinds of project when it’s clearly quite hard to achieve?”
LLDC’s sustainability strategy – moving towards net zero
Created in 2012, LLDC is a regeneration body that’s answerable to the Mayor of London. It was set up to drive the growth and innovation in east London that was kickstarted by the London 2012 Games and the creation of Queen Elizabeth Olympic Park.
Community and Sustainability Manager Victoria Thorns outlined LLDC’s sustainability strategy, which was first developed back in 2012. She acknowledged that LLDC’s approach has evolved as definitions of net zero have changed. Initially, LLDC called for new buildings to deliver a 65% reduction in carbon, with the remaining 35% offset by paying into local schemes.
Today, they’re working with LETI and Riba’s 2030 Climate Challenge to commit to much more absolute targets and whole life carbon assessments. Like Tom, Victoria emphasised the importance of defining what we mean by zero carbon: “As a sector and an industry, it’s important to be really clear about what we mean by net zero and what our specific targets are.”
Places for people
Victoria also stressed the importance of working with, and ‘educating’, residents. LLDC operational carbon targets don’t just focus on energy efficiency measures and devices; they also aim to reduce operational carbon by 15% through an engagement programme with residents. “People live in buildings in different ways and some people will leave the lights on, so we have to encourage behaviour change,” she added.
For LLDC, sustainability is about more than carbon and energy – creating a sustainable place is also about responding to the needs of the people living there. “Now that we’re all spending so much more time at home, the need to create well-designed places for people – both sustainable homes and sustainable neighbourhoods – is even more pressing,” said Victoria.
To achieve this, it’s important to make the case for the wider social benefits of zero carbon housing. “The Passivhaus standard, which is the premium standard across world, is aligned with numerous other health and wellbeing benefits such as improved indoor air quality, better acoustics and reduced fuel poverty,” added Tom.
Pushing the Net Zero housing agenda further
During the Q&A, both speakers and attendees reflected on how we might see more net zero housing schemes in London. Victoria, Tom and Justin all agreed that post-occupancy evaluations at New Garden Quarter and other LLDC housing developments would be key in assessing the extent to which energy efficiency and net zero measures are important to residents.
And we need to see more clients and developers committing to best practice when it comes to net zero standards in housing. Tom agreed with Lorraine Ford, Area Manager – Housing & Land, GLA, that until now it has mostly been the public sector, third sector and institutional landlords (like universities) leading large-scale net zero projects.
Asked what would push other clients and developers to commit to building more net zero homes, Tom said that’s where policy was needed – to legislate for higher standards. “But investors and shareholders are also starting to ask organisations what they’re doing to work towards net zero,” added Victoria.
Watch all of the video visit + discussion here. Video visit of New Garden Quarter courtesy of PTE.