New evidence must drive change in practice

The record heat in the UK last week inspired lots of discussion about its impact on our health – with particular focus on how our built environment – homes, workplaces, schools, hospitals and transport infrastructure  - are ill-suited to extreme heat and harming our health.

This has led to animated discussion on the need for air conditioning in our buildings, with heated (!) exchanges over why we don’t have air conditioning in UK homes and, inevitably, to our overly regulated planning and energy policies.

A particularly interesting and evidence led take on this is here.

The Mayor of London responded with a Heat Plan, which outlines interventions across the capital to mitigate the impacts of extreme heat on health These included increased provision of blue spaces, drinking water and trees in public areas and a commitment to introducing cooling to homes, hospitals and public transport. He obviously took heed of my recommendations!

If this is an affirmation amongst our politicians, media and general public that the buildings and places that we inhabit, work in, visit and transit affect our health and wellbeing and that we must address this in our planning and energy policies – then that is progress in itself. But what has also happened over the last few weeks is the emergence of some hard evidence linking our built environment to our health, and specifically to demands on the NHS. This data doesn’t lie – and it gives us all a resource and an opportunity improve planning practice and to genuinely build for health.

The first body of evidence was put out by the Royal College of Occupational Therapists and demonstrates that poor housing costs the NHS £1.5billion each year to treat individuals who suffer from illnesses and injuries directly linked to poor living conditions.

In its Building Health into Homes report, the RCOT calls for housing to be treated as a core part of health and care.

The report’s author stated

“Everyone lives somewhere, but housing is too often treated as an afterthought in health and care, meaning people are reaching the point of crisis before they get support …our report

shows how the home can be used as a health intervention, not just something to react to later”.

The second body of evidence was presented through research that demonstrated how the introduction and expansion of London’s Ultra Light Emission Zone (ULEZ)  has saved lives and NHS money through reductions in hospital emergency admissions.

The study found that since their introduction, the London schemes were linked to 8.1 % reductions in yearly trends for cardiovascular disease, 6.2% for respiratory disease and 3.1% for all cause related hospital admissions in the intervention area. 

The report’s author said

“Our results highlight that the central London ULEZ and toxicity charge are broadly linked to positive impacts on health – with a reduction in emergency hospital admissions for cardiovascular disease and all-causes.” 

The Mayor of London said the evidence was "now overwhelming and unarguable"

Over the weekend I was talking with a senior leader for NHS Emergency Medicine in London who told me that he could see a reduction in respiratory admissions and commented on the ULEZ report and its impact. So it’s cutting through to the front line – not just the policy geeks.

So what does this mean for designers, planners and developers of the built environment?  Three things come to mind.

First, it’s time to revisit the methods, content and purpose of the Health Impact Assessment (HIA),  something I’ve been challenging since the pandemic, and whose fitness for purpose is questioned  by public health expert Michael Chang in a recent article for the Planner:

“Evidence linking our built environment to health is growing by the year, and Health Impact Assessments (HIAs) help planners, health officials, local authorities and community groups to use this evidence to measure these links. But increasingly the HIA is seen as less of a vital public health safeguard and more as a bureaucratic hurdle, raising an urgent question – are we using HIAs to shape better places, or merely to satisfy process?” 

A team led by Silviu Pirvu of Optimal Cities recently examined the HIA in the age of AI and showed that not only is there an abundance of data on the spatial distribution of health outcomes, but there are now powerful tools to use it for measuring health impact at the local level and to construct multiple scenarios and interventions. They argue

“Just as effective healthcare relies on fresh, trusted data and a multi-layered diagnostic process, robust Health Impact Assessment (HIA) depends on timely, validated information. In healthcare, doctors, clinicians and other health professionals gather data from various sources – vital signs, laboratory results, imaging – and then use these insights to establish a diagnosis and propose a treatment plan. When Artificial Intelligence (AI) – which refers to the ability of machines to replicate human-like cognitive functions – integrates real data detected from satellites, ground-based sensors and wearable devices, it can validate or challenge prior assumptions about the evolution of a place, spatial factors affecting human and environmental health and the public health status across demographic segments and geographies.”.

The implications for health impact assessments are clear:

“This process can not only inform policymakers about the “diagnosis” of environmental or social health challenges but can also enable them to propose and monitor interventions – akin to creating treatment plans. When spatial interventions prove effective, confirmed through multiple data sources, satellites, sensors and analyses, the “treatment” can be replicated across other cities.”

Second, take the “do no harm” principle seriously. As I argued three years ago, this principle lies at the core of medical training and practice, guiding all those who practice medicine and have the most direct impact possible on human health. But it is rarely acknowledged or adhered to in a unified or standardised way when it comes to non-medical practice, even when that practice has a significant impact on human health. Designing, creating and maintaining our built environment is one such practice.

Despite a growing body of evidence on the impacts our built environment incur on human health, the “do no harm” principle does not often play a central role in the planning and development process. When "harms" are identified, they are usually defined vaguely and subjectively, and often never adequately addressed. An adundance of evidence and data means we can measure  harm – it isn’t debatable and we can’t wish them away.

Third, go beyond the do no harm and aim for health net gain – that is, develop a building or place that has a positive health impact, and actually improves the health and wellbeing of inhabitants. This is no longer an unattainable goal  - the evidence and data are here to identify and measure baselines and explore approaches and interventions to improve health outcomes.

These changes in approaches to and practice of place development are becoming increasingly urgent as appreciation of the connection between place, building and health spread beyond the professional discourse and into the general public. This past week of extreme heat and the conversational shift to the (in)ability of our homes, buildings and infrastructure to cope demonstrate this.

Those that embrace the evidence and embark on changes to practice are also likely to find less resistance and more local support for their projects. Not surprisingly, you often get more people on board when you focus on their health and wellbeing.

Clare Delmar

Listen to Locals

29 June 2026