Dr Eric Laurentius Peterson (Visiting Research Fellow, University of Leeds)              HRSC0069

Additional written evidence submitted by Dr Eric Laurentius Peterson

Heat resilience and sustainable cooling - additional evidence submitted 31st October 2023             

Further to the House of Commons’ Environmental Audit Committee 18th September 2023 hearings - heat resilience and sustainable cooling. It was my pleasure to have attended these hearings in person.  I have since reflected deeply on the synergies expressed by MPs and the expert evidence provided by all members of both panels.  So, I hereby submit follow-up evidence with scholarly citations in three areas:

(A) Heat-Alert messaging regarding local accessibility of cool relief and individual health condition. 

(B) All green spaces are not equal – cool roofs and shade trees are superior to lawns.

(C) Passive Survivability of Existing Buildings –public health policy for retrofit of existing dwellings.

Re: Health impacts, avoidance of un-necessary air-conditioning, and practical measures

I am Dr Eric Laurentius Peterson, M-CIBSE, CEng, Professional Engineer (Mechanical and Environmental) licenced in as required to practice in certain US states as well as Australia, Visiting Research Fellow (Bioclimatic Design) at the University of Leeds, and Secretary of ASHRAE (American Society of Heating Refrigeration and Air-Conditioning Engineering) Technical Committee on Climatic Information (TC4.2). I post relevant design charts and tables at http://BioClimatic.GitHub.io/UK .

Immobile health-compromised elders may benefit from air-conditioning only as long as electricity works. Figure 1 below illustrates effective adaptation by taking refuge in suitable outdoor microclimates when buildings overheat due to poor design or failure of air-conditioning.  A shaded outdoor refuge, such a covered balcony, should be readily accessible to occupants from buildings which overheat during heat waves. Sadly such cooling relief is not available in many communities.

Figure 1: Elderly man sitting under a tree in Indonesia 26 October 2023 by Prandito Simanjuntak

(A) Heat-Alert messaging regarding local accessibility of cool relief and individual health condition. 

Heat-alert messaging policies in England employ a “traffic light system” developed to prepare health and social care professional to manage their elderly and unhealthy clients during the summer months, starting with a “green” (preparation) signal.  Sussex Air Quality Partnership (Sussex-air 2023) reveals that the UK Health Security Agency (UKHSA)’s Adverse Weather Heat Plan 2023-2024 declares “yellow” (response) when the UK MetOffice forecasts at least 60% chance of a heat-wave in the next 2 to 3 days.  “Amber” (enhanced response) is nationally flagged when MetOffice observes a daily maximum of at least 31°C or a nightly minimum of at least 16°C at any location in England. 

Decisions to go to “red” (warning of significant risk of mortality among vulnerable populations) are co-ordinated by Civil Contingencies Secretariat (Cabinet Office). The UK Met Office website defines a “heat wave” on the basis of three subsequent observations of daily maximum  temperature above a threshold.  That threshold varies from 25°C to 28°C depending on location. The 25°C threshold applies only in Northern Ireland, Scotland, Wales, Cornwall, Devon, and northern parts of northern England, and increments up to 28°C in Cambridgeshire and metropolitan London. 

The MetOffice’s National Severe Weather Warning Service as well as the associated UKHSA system are evolving based on evidence in practice.  Monitoring and modelling of overheating in British dwellings (Sameni, Gaterell et al. 2015, Baborska-Narożny, Stevenson et al. 2017, Morey, Beizaee et al. 2020) found that overheating varies considerably between dwellings, owing to occupant behaviour more than construction, and that overheating was not generally worse in poorly insulated buildings. As an example of indoor monitoring methods, consider Canadian Broadcasting Corporation (CBC)'s investigation this past summer (Carman, Ward et al. 2023).  CBC deployed fifty temperature/humidity loggers in un-air-conditioned flats and followed a number for very stressful stories, of which one was most tragic.

As a point of comparison, Canada’s heat warning system (ECCC 2023) varies among 24 regions, such as southwest Ontario (Essex and Chatham-Kent Counties). SW Ontario Heat Warnings are issued when forecasts indicate maximum temperatures ≥ 31°C for 2 consecutive days with an overnight minimum temperature ≥ 21°C.  SW Ontario Heat Warnings could also be issued if forecast “humidex” ≥ 42°C.  Humidex (CCOHS 2023, ECCC 2023) has been a Canadian characterisation of how hot, humid weather feels to “average” people but is not used in any other country.  Humidex values are tabulated in 5% increments of relative humidity versus one-degree increments of temperature (°C).  For example UK’s record temperature of 40.3°C while humidity was 25% (Timperley 2022) corresponded to a humidex of 46 (for less than an hour), with humidex’s associated warning at the border of “Dangerous; heat stroke possible”. Canadian Humidex tables do not depend on the impact of shade (or sun) and do not consider the potential for evaporative and convective cooling that are dynamically assessed in accordance with internationally recognised standards (BS-EN-16798-1 2019, ANSI/ASHRAE-55 2020) by University of California at Berkley CBE Thermal Comfort Tool (Tartarini, Schiavon et al. 2020).

To facilitate comparative learning and adaptation, it would be helpful if UK MetOffice heat messaging were based upon internationally recognised metrics.  For example, The Government of Singapore (MSE and NEA 2023) has now followed the Japanese national Heat Illness Prevention Information system launched ten years ago - based upon forecast and observed wet-bulb globe temperature (WBGT)(Lemke and Kjellstrom 2012).  Heat Stroke Alerts are issued when the Japan Meteorological Agency (JMA) forecasts WBGT above 33°C (MoE 2020).  Evidence suggests the alert-threshold could be adjusted according to regionality and age group (Oka, Honda et al. 2023, Oka, Honda et al. 2023).

Other national weather services also provide forecasting of WBGT exposure outdoors, including Greece (HNMS 2020) and USA (NWS 2023). Meanwhile Australian meteorologists provide daily reports of WBGT in both cases of sun and shade (BoM 2005, BoM 2023).

Under both circumstances of sun and shade WBGT extreme events have been projected mid-century in thousands of locations around the globe in an interactive expose (Kommenda, Osaka et al. 2023) served from the Washington Post website using open-access data and algorithms (Chegwidden and Freeman 2023), finding the worst major city on earth is Pekanbaru, Indonesia.  This city already averages over 300 days of very dangerous heat each year (WBGTsun > 32°C).  Fortunately, the Post/CarbonPlan analysis for Indonesian locations shows that outdoor conditions have been tolerable in the shade.  This Indonesian city may exceed the threshold a couple of days per year circa year 2050.  Also, their analysis shows there is no city in the UK that would generally exceed 32°C WBGT in shade, nor in sun.  In an associated article Washington Post reported that spending more than 15 minutes beyond that limit “exacts a harsh toll on even a healthy adult; many deaths have occurred at much lower levels” (Gowen, Kommenda et al. 2023).  Many governments legislate or promulgate regulations that employers monitor WBGT within working environments (Qatar MoL 2023) and supposedly respond appropriately to avoid this threshold.  The Post/CarbonPlan on-line tool shows that worse conditions already persist about 50 days/year in the shade in the Qatar capital Doha, where there are usually over 150 days/year when conditions in the sun are unacceptable.

The Guardian (Carrington 2023) publicised maps of future “noncompensatable heat” (Powis, Byrne et al. 2023) which are more conservative that the Washington Post/CarbonPlan tool, flagging more risk for UK cities in the future.  This was based upon research tasking young adults to exert a continuous low load of physical activity found a 31.5°C wet-bulb temperature (WBT), which drops further in lower-humidity environments (Vecellio, Wolf et al. 2022).  This is consistent with policy conceived 50 years ago of weighting of radiant and convective heat together with humidity with a threshold of 88°F (31.1°C) wet-bulb globe temperature (WBGT) to replace work with rest and rehydration (Yaglou and Minard 1956).

Figure 2: Heat-Alert Messaging audiences – age or unhealthy conditions vs accessibility of coolth.

Different audiences deserve uniquely appropriate messaging to be provided with forecasted heat waves, so we should attempt to disaggregate distinct vulnerability demographic groups, - perhaps along the horizontal and vertical axes of Figure 2 above.  Here I use a “RED” code to identify those are at the intersection of multiple health conditions and/or aged dwelling in an overheating dwelling (vertical axis) and unable to access cooling relief (horizontal axis).  Emergency intervention by caregivers should respond by evacuation of the most vulnerable into cooling shelters, while longer term policy should be framed to implement preventative measures to provide cooling relief at home would change this group’s circumstances to a “BLUE” code.  Measures could be as simple as installing motorised external awnings on southern and western windows (Cumming 2017), and intelligent night purge ventilation strategies (Fosas, Coley et al. 2018), but in some situations, air-conditioning may be justified (DLUHC 2022).

A symbolic small step in the direction changing circumstances from “RED” to “BLUE” is the Japanese tradition of Uchimizu (DavideGorla 2017, Bissoux 2018, Solcerova, Van Emmerik et al. 2018) – the summer ritual of sprinkling of water on streets and doorsteps, encouraging inter-generational dialogue to mitigate urban heat islands.  Another example of measures than can provide accessible immediate relief is the Australian State Government of Queensland incentivises to provide 12m² outdoor living area with insulated roof, ceiling fan, and natural cross ventilation (QDC 2023) adjoining indoors living areas.

Figure 3: Uchimizu, Kyoto by DavideGorla October 17th 2015 photograph (CC BY 2.0 DEED https://creativecommons.org/licenses/by/2.0/)

Another disadvantaged group are the healthier individuals (which may include physically active elders) who are unfortunate to dwell in built environments which overheat without local access cooling.  Fig 2 illustrates an “AMBER” code that could message such citizenry to improve their dwellings’ resilience to heat and to collaborate in accessing local community green spaces that include outdoor shade.  In which case their status would be upgraded to a “GREEN” code.   More youthful and active elders (Figure 1) can readily adapt to the build-up of indoor heat if they have access to shade, breeze, rest, and refreshments.  In many hot countries cooking is physically separated by outdoor space from living and sleeping areas. 

(B)         Outdoor green spaces and shade - local availability for cool relief outside the dwelling.

Mitigating urbanisation-amplified heat waves is of critical importance for millions worldwide. Consequently, I hereby reiterate points from my contribution to the ASHRAE Winter Conference Seminar “Hotter Cities, Hotter Climates: Modelling and Measuring Urban Heat Island Effects Around the World” (Peterson 2021).

Case studies are important to assess the efficacy of measures that have been promoted to mitigate the impact of urban heat islands. In any case study, one should ask if local landscape measures are sufficient to prevent pedestrians needing shelter indoors in air-conditioned premises? Green roofs may serve building occupants, but do not directly impact pedestrian comfort, whereas street trees provide immediate relief from sun as well as providing a visually aesthetic presentation.

My seminar reviewed case studies of microclimates associated with water features and green infrastructure around the world, compared with a living laboratory set among the “Brutalist” concrete canyons developed in late 20th century at the University of Leeds in the United Kingdom.

Understand how the intensity of the UHI may vary between precincts and microclimates within a metropolitan area, by reference to Figure 4.  Urban heat island temperature is typically most elevated above the surroundings afternoon and into the evening.

Figure 4: Urban heat island intensity of University of Leeds rooftop weather station relative to LBA (Leeds-Bradford International Airport) in March 2018.  Subtracted adiabatic lapse altitude effect, heat island intensity attributable to anthropogenic effect of the urban system.

Micro-climate heat intensity of Roger Stevens Cooling Pond (blue infrastructure) is illustrated in Figure 5.  Here the correlation R² is showing that some variability is associated with the time of day.  University of Leeds Chancellor’s Court (green infrastructure) micro urban heat island intensity (µHII) drops during the afternoon as sun is shaded by the Staff Centre Building.  The pondside, NW corner of the School of Food Science Building remains exposed to afternoon sun, directly and reflected by the pond, and so has a fractionally elevated µHII.

Figure 5: Micro-climate heat intensity performance Roger Steves Cooling Pond (µHII relative to rooftop University of Leeds) - sensor located in NE corner of this example of “blue infrastructure”.