Social housing can harness Passivhaus principles

There’s no escaping the fact that homes for the poorest in society sometimes fall short in their purpose of providing shelter from bad weather or harm, highlighted most recently by the death of two-yearold Awaab Ishak from a respiratory condition resulting from exposure to mould in his home. The Better Social Housing Review, commissioned by industry bodies the National Housing Federation and Chartered Institute of Housing, recognised the poor quality of social housing in its findings last year, while the government’s Housing Ombudsman continues to report failings. 

After Ishak’s death the government announced improvement measures, including guidance on damp and mould, but rising fuel poverty has prompted fears that mould problems – often dismissed by landlords as ‘lifestyle issues’ – could become more prevalent.

It doesn’t have to be this way, as the Better Social Housing Review panel found at Mikhail Riches’ new Passivhaus homes in Goldsmith Street, Norwich. ‘It was striking that people were so happy with the fact their homes were warm and comfortable,’ says panel member and architect Sumita Singha. It’s rare.

Newbuild reality
Numerous studies, including the five year-long Building for 2050 research project, funded by the Department for Energy Security & Net Zero (formerly BEIS), have highlighted challenges in delivering healthier, more energy efficient homes. These range from complex designs with innovative technologies, which resulted in poor installations, a  performance gap and hard-to-manage homes, to common misconceptions. Among the latter is that, ‘Clients often think low carbon equates to low energy bills and that’s not the case,’ says Tom Dollard, partner – sustainability and innovation at Pollard Thomas Edwards, who worked alongside project lead Aecom on Building for 2050.

The study’s in-depth look at four new low-carbon housing schemes found energy bills weren’t as low as expected at design stage, with some significantly exceeding expectations. The 2022 update of Part L of the building regulations may not help either. ‘You’ll get a significant energy bill on a new house whose builder made minimum fabric improvements, such as insulation and airtightness, and just put in heat pumps,’ says Dollard.

Extensive research on ventilation in new homes also makes unhappy reading, and is largely unnoticed by policymakers because, he says, ‘until recently, there hasn’t been enough lobbying for good air quality, and it’s been led by researchers, who don’t have a powerful voice.’ 

Dollard has been involved in two studies demonstrating the scale of the problem with ventilation. In 2016, one by Zero Carbon Hub found consistently compromised air quality, including condensation and mould, in a sample of 33 new homes on six sites, ‘with potentially serious consequences for occupants’ health. A government study in 2019 demonstrated ventilation failures in 80 newbuild homes across seven sites. In all, 55 of these homes used ‘system one’ ventilation (intermittent extract fan in the bathroom and trickle vents in windows); only two met ventilation rates required by building regulations.  

The core issue is a lack of controlled mechanical ventilation, combined with an increasingly airtight fabric. ‘On a still day in a relatively airtight home built to the new regulations (without centralised mechanical ventilation), levels of air change rate will be very, very low, so any sort of moisture build-up from – and this is where resident use comes in – drying clothes or even boiling a kettle will start to result in mould,’ explains Dollard. 

Doing better
The government’s forthcoming Future Homes Standard is likely to phase out System 1, which calls for intermittent extract fan in the bathroom and trickle vents in windows, instead requiring continuous mechanical extract ventilation (MEV) or mechanical ventilation with heat recovery (MVHR). When reconciling low carbon, low energy and air quality, Dollard cites the mantra of sustainability consultant Peter Rickaby: ‘No insulation without ventilation’.

These are two of the five ‘pillars of Passivhaus’, as detailed in Dollard’s book, Designed to Perform. In it he describes Passivhaus as ‘the optimum fabric-first solution’, one of the factors attracting clients like Cambridge Investment Partnership (CIP), an alliance of Cambridge City Council and Hill Investment Partnerships. CIP is developing Passivhaus schemes for social rent and market sale in the city, with Pollard Thomas Edwards’ projects ranging from six houses to 70 apartments.

The practice also wrote the council’s Sustainable Housing Design Guide, which mandates Passivhaus certification. But setting that requirement in the Future Homes Standard would be a step too far for the housebuilding industry and its supply chain, says Dollard.

Growing understanding
Councils and community groups have been in the vanguard of low-carbon housing provision as they respond to climate change and local housing need. Hari Phillips, director with Bell Phillips, which works largely with local authorities, says, ‘Passivhaus comes into conversations a lot more. I think clients do want that badge.’ Local authority clients are placing increased emphasis on building performance, he explains: ‘Because councils are concerned about tenants and are there for the long game, more are looking at post-occupancy evaluation to go back and monitor energy consumption and see how buildings are performing against expectations.’

The practice has hosted seminars for councils on designing low-cost, low energy principles, addressing some of the myths surrounding Passivhaus as well as common concerns, particularly the demands and cost of certification. ‘Full Passivhaus is a learning process and some councils are discovering it’s not as easy as they thought,’ says Phillips. ‘The principle must be followed through carefully from outset to completion, and it’s more technically challenging for contractors so they price in that risk.’

Given constrained council budgets, it’s not surprising to find some opting for Passivhaus principles but stopping short of certification, like Watford Borough Council with its terrace of five family houses at Riverside Road. This council pilot in tackling climate change achieved a four-star ranking in BRE’s Home Quality Mark, which considers running costs and impacts on health, wellbeing and the environment. Bell Phillips’ design incorporates brises soleil to minimise overheating, high insulation and airtightness levels, MVHR, photovoltaics, good form factor, air source heat pumps and carefully considered  windows. All are designed to improve on Part L requirements by 70% – matching schemes targeting certification.

‘The big criticism of the approach of saying we’re going to have Passivhaus principles is that it works in theory, but you’re never required to prove it,’ admits Phillips, but he argues it’s better to aim at Passivhaus principles than Part L. And like clients, contractors are still learning: ‘As they get more familiar with Passivhaus, hopefully it will get easier and prices will drop correspondingly.’ 

Scaling up
Among schemes helping to establish Passivhaus in the UK is Agar Grove’s estate regeneration, the UK’s largest Passivhaus project and part of Camden Council’s programme to develop larger, energy efficient homes to give families the space they need while limiting energy costs and carbon emissions.

Of the scheme’s 507 homes, 359 will meet the standard, with around half of all homes being affordable. With every phase of the development, Hawkins\ Brown and Mae are creating diverse architecture and house types that refute the idea its principles produce monotony.

While the project’s budget included a premium for increased insulation and the workmanship for good airtightness, cost savings were made, notably by linking to a district heating system rather than combined heat and power. Triple glazing was needed anyway for elevations close to a railway. ‘The additional cost routinely associated with Passivhaus is not always clear cut,’ stresses Alex Ely, principal at Mae. ‘You can often find savings elsewhere and in Camden there’s a clear value uplift because it’s reducing costs longer term.’

Such projects show value in building healthier, cheaper-to-run homes, but Passivhaus remains the preserve of enlightened clients. ‘We were appointed to work on Agar Grove in 2012 so it’s already a 10-year-old project in its design concept,’ says Ely. ‘Even among councils, it’s still far from standard. I wish Passivhaus – or at least this level of performance – was the norm now.’

Learn more about Passivhaus with the RIBA Academy course