Dr Jonathan Webb and Professor Aimee Ambrose, Centre for Regional, Economic and Social Research, Sheffield Hallam University, and Dr Sally Shahzad, Sheffield School of Architecture, University of Sheffield HRSC0050
Written evidence submitted by Dr Jonathan Webb and Professor Aimee Ambrose, Centre for Regional, Economic and Social Research, Sheffield Hallam University, and Dr Sally Shahzad, Sheffield School of Architecture, University of Sheffield.
Author Note
This evidence draws upon our research and expertise across energy policy, housing policy and the built environment.
Introduction
At current summer temperatures, a fifth of homes in the UK overheat. However, one third of homes in England have attributes that put them at risk of overheating in the future (Marshal 2023). This overheating adversely impacts health and reduces both productivity and educational attainment (CCC 2022). This means that overheating has significant health, economic and social impacts.
Overheating in homes is likely to become a much bigger problem if no action is taken. The UK government’s Adaptation Programme will be a crucial tool for addressing the problem of overheating across a range of areas. Alongside this, current and future home standards will need to draw upon the general guidance of the Adaptation programme, while devising specific standards for homes in England to minimise overheating in buildings. Taken together, these will form key policy instruments and support an effective overheating strategy. As a result, the effectiveness of these instruments should be reviewed. Any specific overheating strategy will need to work in tandem with ongoing policies designed to decarbonise heat in homes, as well as existing and proposed planning reforms.
Our submission responds to the questions outlined by the Environmental Audit Committee and draws on our collective research and policy expertise. We emphasise the need to create greater cohesion between existing and proposed policy instruments, the importance of fabric changes to reduce overheating in buildings, the role that heat pumps can play and the urgency required to address overheating in homes.
Reducing overheating in homes will require government to work closely with the public, engaging them in the transition to more resilient net zero homes and a more pro-active and nuanced policy response are all necessary to develop an effective heat resilience strategy.
Response to questions
1. What evidence exists on the relationship between heat and human health (mortality and morbidity), and which communities are worst affected?
Temperature is the key climatic factor affecting poor health and mortality rate. Children and older people are more vulnerable to extremes of temperature, including high heat. Amongst these groups, there is little research focusing on the vulnerability of children. However, many researchers have investigated the impact of high and low temperatures on morbidity and mortality of older people. Their conclusions suggest a significant relationship between extreme temperatures and morbidity/mortality (Kenny et al 2019).
Older people don’t cope well with extremes of the weather, resulting in higher death rates and more health issues. This is due to their impaired functions of the thermoregulatory processes, cardiovascular, respiratory, neuromuscular, and gastrointestinal functions as well as malnutrition.
Analysis based on Office for National Statistics throughout the years suggest that when the outdoor temperatures drop below 10°C or above 23°C in the UK, the excess death rate significantly increases for older people over the age of 70 and particularly above 80 (ONS 2022).
Climate change and ageing may increase the risk of various diseases, such as diabetes, infectious disease and heat related morbidity. Most of the key diseases affecting older age, such as respiratory diseases, are indirectly impacted by low temperatures and particularly living in cold conditions.
In summary, due to climate change and increased temperatures, the impact of heat wave on mortality is significant. However, the majority of excess mortality rate still happens in winter in the UK. This should be considered when devising policy responses.
2. How can sustainable cooling solutions and adaptation strategies be implemented in such a way as to minimise overheating, reduce energy consumption and prevent overloading of the electricity grid during peak demand?
There are multiple options for tackling overheating in buildings. Active cooling, such as air conditioning, can effectively address overheating in buildings. However, active cooling works best in combination with optimised building fabric. Improving the design of England’s homes through a ‘fabric first’ approach would likely be the best strategy for reducing overheating in homes. Many fabric changes, such as improving wall insulation, will help keep a home cool in the summer while allowing it to retain heat in winter. Fabric improvements also generally cost less than active cooling solutions. At scale, fabric improvements have a positive impact on energy consumption, reducing the need for heat input in winter and cold input in summer.
Modern ‘split’ air conditioning units or air-to-air heat pumps are the primary technology for providing active cooling in buildings. Further comment on their use is provided in response in question seven. The impacts of widespread active cooling on the UK’s electricity grid could be significant. This is because active cooling technologies require electricity to operate. The UK’s grid is not yet capable of meeting future demand for electricity use in line with the government’s plans to push forward with the electrification of heat in homes. Active cooling demand will also require greater generation, distribution and control capacity from the UK’s power system.
The UK government is committed to a primary strategy of electrification to decarbonise heat in homes. This has seen air-to-water heat pumps rightly prioritised as the primary technology for achieving this goal. This strategy will require significant and large-scale modifications and upgrades to the UK’s electricity grid. At the same time, heat pumps will only be zero carbon if the energy they use is produced from renewable sources. Renewable energy generation will need to be expanded alongside infrastructure upgrades to the grid if the government is to achieve its vision.
While there is an absence of primary evidence on the impact active cooling at scale would have on the grid, the impact it could have could be effectively minimised. It is unlikely the energy demand for cooling, even in the most extreme temperatures would be greater than the maximum demand on the grid in a hypothetically old winter. A combination of high energy generation in summer from solar power and wind, coupled with the ability of heat pumps to perform efficiently at high temperatures, means that any extreme heat summer scenario is likely to demand less energy than an extremely cold winter scenario. Even if the energy demand and efficiency rates of heating and cooling are assumed to be comparable, energy generation is far more likely to be abundant in summer.
An active cooling approach will largely follow the same blueprint for upgrading the grid infrastructure as the electrification of heat in homes. The CCC’s recommendations for delivering a decarbonised power system offer strong guidance on the policy measures needed to ensure the UK’s future energy system delivers adequate renewable energy and that the grid can effectively operate in line with the electrification of heat (CCC 2023). These recommendations would help enable active cooling measures too.
Sustainable strategies for reducing energy use in homes must adequately consider ways to reduce heat demand during winter and provide respite from heat in the summer. Mixed mode buildings are suitable solutions for building resilience towards climate change. These should be considered as a primary tool for reducing overheating. These buildings will mainly run naturally (e.g. natural ventilation and passive solar strategies) without any cooling or heating as much as possible and are able to do run without both for about half of the year. Cooling and heating are only turned on, when needed. A smart design of the building is required to ensure the efficiency of the system, otherwise it may result in a much more energy use than a heating, ventilation and air conditioning (HVAC) building. For example, sensors on windows can alert the system to turn off heating or cooling, in case the occupants open the windows.
Zoning is another solution to combat the periods of extreme heat or cold spells in the building. The design of the building is arranged in layers. Certain areas, usually at the heart of the building, are designed to be comfortable all year round and usually equipped with heating and cooling systems. Essential activities are usually allocated in these areas. The outer layer of the building runs naturally and it is expected to be uncomfortable during the extreme temperatures; and thus, dedicated to non-essential activities.
Designing refuge areas in the building can be a practical solution particularly for small buildings and individual houses or flats. One space in the building will be designed to cope with extremes of the temperature. This space can be isolated from the rest of the building and it is equipped with heating and cooling. This is an effective strategy particularly for vulnerable people, such as older people. Also, it allows the rest of the building to be designed mainly based on passive and natural strategies to use less energy.
3. What actions can be taken to protect those most vulnerable to the impacts of extreme heat?
A better targeting of active cooling policy needs to take place. Action should prioritise households with vulnerable people (such as older people and children) and offer discounted or grant funded building fabric improvements, as well as support to access active cooling solutions. These households would also be a sensible place to prioritise the installation of active cooling measures, such as heat pumps.
Poorer households are likely to struggle with the costs of active cooling because of high energy prices. In the same way that Warm Hubs have been introduced to help people in winter, ‘Cold Hubs’ should be created and made available for those who need them in the summer.
There are also specific strategies that can be deployed to reduce overheating in homes. This includes:
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4. To what extent do the Government’s Climate Change Risk Assessment and National Adaptation Programme (as well as other related strategies such as the Net Zero Strategy and Heat and Buildings Strategy) identify and address the risks from extreme heat? (Note: The third NAP, covering the five-year period from 2023-2028, is expected to be published in the summer of 2023)
The National Adaptation Programme (NAP) currently emphasises the importance of nature-based solutions for reducing extreme heat. Beyond this, the NAP currently offers very little by way of strategies for reducing overheating in homes. As a result, the current ongoing work across government departments to identify the scale of overheating in homes and identify vulnerable households should be accelerated.
The Heat and Building Strategy identifies the importance of good building design and adequate natural ventilation to reduce overheating in new homes. However, this strategy also lacks a specific focus on delivering more of the types of measures that could tackle overheating in new homes. For example, eliminating overheating as a result of poor building design or an ambitious plan to expand active cooling methods in new properties that are prone to overheating, such as flats.
The Net Zero Strategy also says little about promoting and expanding active cooling. It can be summarised that the key planks of government strategy currently fail to realise the potential problem of overheating, nor do they promote more detailed and ambitious plans to ensure cooling of existing and future homes.
5. Does the current planning framework do enough to encourage heat resilience measures such as cooling shelters, water bodies, green infrastructure and shading to be integrated into urban planning? Where such measures are incorporated, how accessible and successful are they?
The current planning framework gives little consideration to overheating. A strong focus on heat loss in new buildings has reduced window size and placement in new buildings. Beyond basic ventilation requirements, new buildings are not required to strongly consider the challenges of overheating.
Inconsistencies in planning guidance mean that while air-to-water heat pumps are often permissible under permitted development rights, air-to-air heat pumps are far more likely to require planning permission. This is the case despite the almost identical appearance of the units, similar noise outputs and minimal impact that both have on the external environment.
Trends towards steel and glass particularly in dense urban areas are unhelpful and present challenges to cooling the interior and exterior environment. Air conditioning is assumed as standard, favoured over more passive cooling measures such as planting (around and up buildings), window shades, less heat absorbing materials and natural ventilation. Solar control glass is also emerging as a possibility.
6. What can be done to protect the UK’s existing public and private sector housing stock from the impacts of extreme heat while ensuring that homes are sufficiently warm in the winter months?
Overheating is a very real and growing concern in both new build and retrofit projects. Overheating prevention is only covered by Part O of the Building Regulations for new build properties, which requires limited glazing.
Overheating can be exacerbated by high indoor humidity, which in winter causes dangerous mould outbreaks, therefore maintaining ventilation all year round is vital. Those who have mechanical ventilation must be discouraged from turning this off due to energy affordability concerns or blocking up vents to avoid draughts and thus cutting off ventilation or disrupting cross- ventilation. See the important work of Jenny Brierley (2021) in relation to this behavioural issue.
Investing in renewable energy systems, such as solar panels, to make running active cooling systems more affordable will be important. Providing grants for effective retrofit of the existing building stock and to equip them with solar panels and renewable energy resources is a useful strategy to encourage building owners to make their buildings resilient for climate change, produce energy and move towards net zero. Encouraging retrofit through reducing taxes, providing grants and other awards can be useful to encourage the public and home and building owners to enhance the performance of their buildings.
7. What role might reversible heat pumps (which can act as both heating and cooling systems) and other emerging technological solutions, such as the development of smart materials, play in meeting future cooling demands?
Heat pumps as a technology are now relatively mature, cost-effective and workable in most types of buildings. These technologies operation at high levels of efficiency, often over 300 per cent. This means for every 1kw of energy they use, they’re capable of producing on average at least 3kw of energy for heating or cooling. Unlike air-to-water heat pumps, air-to-air heat pumps currently do not benefit from government grants to support their uptake. A peculiar inconsistency in current planning guidance means that while an air-to-water heat pump will not require planning permission, in most cases an air-to-air one will. While air-to-water to heat pumps are usually acceptable under permitted development, air-to-air ones will usually require planning consent. Overall, planning guidance on this matter is outdated and assumes air-to-air units could pose a noise nuisance. Significant technological changes in recent years mean this is highly unlikely to be the case and there is no reason that the permitted development rules for air-to-water heat pumps (which include updated requirements on boundary proximity and noise levels) should not be applied to air-to-air heat pumps.
Many air-to-water heat pumps can theoretically provide cooling too. Problems can arise when the cooling function is used due to condensation building up around pipework. This can lead to adverse consequences, such as the development of damp and mould. The installation of proper cooling systems that can work in tandem with air-to-water heat pumps can address this problem. This includes new products such as wall, floor and ceiling materials that can be fitted with flexible aluminium and plastic piping that avoids condensation forming. Cold water can then be sent through the pipes to provide cooling in high temperatures. This combination of smart materials and air-to-water heat pump use could present a solution for heating and cooling in homes.
Where a fabric first option (minimising glazing, maximising passive cooling) is not sufficient, reverse cycle heat pumps should provide a vital safety net. Heat pumps capable of cooling could be mandated through Building Regulations. Currently they are not.
Integration of both passive and active strategies are required for dealing with extreme temperatures is important. Although the use of low energy passive strategies should be prioritised, they may not be sufficient when dealing with extreme climatic conditions. Thus, the use of advanced, smart and innovative strategies are essential for current and future building resilience.
8. How can cleaner refrigerants with low or zero global warming potentials support the UK’s cooling needs while contributing to the national emission reduction targets?
Unintended leaks from F-gases or refrigerants can pose a risk to the environment. Refrigerant use in heat pumps is unlikely to cause significant adverse climate impacts globally and the use of heat pumps for heating and cooling would still result in significant reduced emissions compared to alternative technologies (IEA 2022). As with any electrification solution, heat pumps are only as green as the source of electricity generated to power them. Expanding renewable energy generation is necessary to ensure they achieve their full green potential.
9. Does the Government’s Future Homes Standard adequately consider overheating in homes? If not, what additional elements should it include?
Overall, the Future Homes Standard does not adequately consider overheating in homes. Document O (Overheating) has been introduced into the Future Home Standards and requires all new homes to have undergone an overheating assessment. These have focused on minimising solar gain. There is a broader problem with building regulations and the future homes standard. While on paper, housebuilding standards in England are set to a high standard, the sign off process often allows housebuilders to underperform against these standards. The privatisation of building regulations sign off and other changes such as self-certification at key stages, has reduced quality control when it comes to building homes in line with standards. Building high quality and resilient new homes will require not only strong standards on paper, but designing better accountability mechanisms to ensure they are delivered in practice.
10. How effectively is the Government working across departments and with local authorities to ensure a coordinated approach is taken to heat resilience?
The government currently works across departments and with local authorities tot tackle climate change. This includes coordinating and promoting efforts to decarbonise homes and build homes fit for the future. Collaboration to date to tackle overheating has been comparatively weak. This is likely a result of the current lack of focus on overheating and the absence of strategic detail within major government strategies.
11. Does the UK need a dedicated Heat Resilience Strategy? What lessons can be learned from other nations when it comes to national strategies for heat resilience?
The government should have a tangible strategy – whether that be a standalone Heat Resilience Strategy or ensuring the better integration of overheating strategies within existing strategies to decarbonise heat in homes, promote new building standards and reform the planning system. The UK should prioritise decarbonising its housing stock and improving housing quality. Other countries where heat pumps are a feature of everyday life (such as Sweden) or where heat pump uptake has rapidly accelerated (France) can provide useful lessons. Countries such as Germany have much stronger design codes and actively balance heating and cooling demands in buildings. The UK could also learn from this.
August 2023
References
Committee on Climate Change [CCC] (2023) ‘Delivering a reliable decarbonised power system’. https://www.theccc.org.uk/wp-content/uploads/2023/03/Delivering-a-reliable-decarbonised-power-system.pdf
Committee on Climate Change [CCC] (2022) ‘Risks to health, wellbeing and
productivity from overheating in buildings.’ https://www.theccc.org.uk/wp-content/uploads/2022/07/Risks-to-health-wellbeing-and-productivity-from-overheating-in-buildings.pdf
International Energy Agency [IEA] (2022)’Executive summary: the future of heat pumps.’ https://www.iea.org/reports/the-future-of-heat-pumps/executive-summary
Kenny, G. P., Flouris, A. D., Yagouti, A., & Notley, S. R. (2019). Towards establishing evidence-based guidelines on maximum indoor temperatures during hot weather in temperate continental climates. Temperature, 6(1), 11-36. https://www.tandfonline.com/doi/abs/10.1080/23328940.2018.1456257
Marshal J (2023) ‘It’s getting hot in here’. Resolution Foundation. https://www.resolutionfoundation.org/app/uploads/2023/08/Its-getting-hot-in-here.pdf
Office for National Statistics [ONS] (2022) ‘Excess mortality during heat-periods: 1 June to 31 August’ 2022https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/deaths/articles/excessmortalityduringheatperiods/englandandwales1juneto31august2022