Design and Health World Health Design
 













Robust hospitals in a changing climate

The Climate Change Act aims to cut 80% of the UK’s emissions by 2050 – a target it is hard to see being reached. A series of research projects, led by the University of Cambridge, explore how the NHS’s new and existing estate can make a serious contribution

C. Alan Short MA (Cantab) DipArch RIBA, University of Cambridge, Kevin Lomas BSc (Hons) PhD, University of Loughborough; Alistair Fair BA (Hons) MA PhD, University of Cambridge; Catherine Noakes BEng (Hons) PhD, University of Leeds; Giridharan Renganathan BArch MUrDgn PhD AIA (SL), University of Kent; Sura Al-Maiyah BSc MSc PhD, Portsmouth School of Architecture

The UK’s National Health Service (NHS) currently confronts a conundrum of global consequence: how can it deliver safe environments in a changing climate while at the same time dramatically reducing its carbon emissions? The UK Climate Impacts Programme predicts the increasing incidence of extreme heat events in England, particularly within large conurbations, where the impact of summer heatwaves is amplified by the ‘urban heat island’ effect. The UK heatwave of June/July 2006 is thought to have led to an increase in deaths over baseline mortality of 4%, and there were approximately 300 excess summer deaths after the 2009 heatwave between 30 June and 2 July.1 In the aftermath of the 2006 heatwave the Department of Health concluded, regretfully: “During relatively mild heatwaves, excess death rates are significantly, but avoidably, higher in this country.”1 We have a particular research interest in the maintenance of thermally safe, comfortable environments in hospitals.

NHS environments accommodate 1.4 million employees, 5% of the UK workforce; they receive one million visitors every 36 hours.2 The NHS generates 18% of the carbon emissions of the UK non-domestic stock, 25% of UK public sector emissions and 3% of total UK emissions3 at an annual cost of almost £600m.4 NHS carbon reduction targets are mandatory, but the NHS Sustainable Development Unit regularly tells us that the NHS is dramatically missing its targets. In 2013 the prognosis is exactly as it was in 2008; there has been little or no progress.5 A strategy of installing more mechanical cooling in more NHS buildings might lower temperatures, but it will not deliver the energy savings – quite the reverse. The NHS estate is immense. Within England alone, it comprises 28m square metres; there are 330 acute hospital sites with a gross floor area of 18.83m square metres.6 Our observations of the estate in England using aerial views reveals that some 70 sites still have significant numbers of pre-1939 buildings – which presents opportunities, as we shall see.

In a typical UK hospital, 44% of the energy used can be attributed to air and space heating.7 NHS organisations have ambitious targets for delivered energy of 35–55GJ/100m3 in new buildings and 55–65GJ/100m3 when refurbishing existing facilities; this covers all building uses, including space heating, hot water, lights, appliances and catering.8 However, the energy use of the majority of NHS trusts in England is significantly higher, being in the range of 44.8–98.0GJ/100m3 for 2004/05, peaking at 125GJ/100m3. It has been summarised in a film which may be streamed or downloaded at http://sms.cam.ac.uk/media/1446036.

New-build hospitals: implications
There is no viable strategy for resolving this dilemma at the time of writing. We believe it requires a fundamental reinvention of the hospital form, but neither the industry nor central government are resourced to conduct this scale of reinvention as they were in the 1950s and 1960s. In our research, very much ongoing, the hospital form is fundamentally reconsidered through work funded by the National Institute of Health Research (NIHR), ‘Design strategy for low energy ventilation and cooling of health buildings’ (project B(06)03).9

The current tendency to devise deep hospital plans, tessellating clinical departments, has been developed over perhaps 40–50 years. Deep plans are mechanically conditioned using strategies originally designed to maintain comfortable internal conditions artificially in fierce continental climates. One might question their appropriateness in a more temperate climate, especially one that might be warming. A recent hospital in London lauded for its excellent medical planning is 50 rooms deep between one window wall and the next at ground and first floor levels. However, our work suggests that a significant proportion of hospital spaces might be naturally ventilated: why impose the air conditioning needed only in a small part of the building onto the whole?




Figures 1 and 2 depict our proposed alternative. The Consulting/examination/treatment rooms are arranged around an external courtyard (7.2m x 21.6m) attenuated east to west, to offer predominantly south-facing elevations. The L-shaped accommodation to the north and east of the courtyards fits into a ‘slipped’ tartan grid of circulation routes, directly adjacent to the courtyard on the south and west sides. These circulation routes thus enliven what will inevitably be long corridors and aid navigability. The plan yields ‘dark’ locations for services, support rooms, and other largely unoccupied spaces. To the north of the rooms adjoining the courtyard lies a further range of rooms, facing the next courtyard to the north across a lateral circulation route.

Circulation routes are naturally ventilated directly from the courtyards. Rooms adjacent receive supply air ducted within a deep facade and exhaust back into further ducts within the facade. The facade depth shields the south-facing glazing from summertime solar gain. The inboard rooms receive supply air from the courtyard to the north across a lateral circulation route. Supply air enters the rooms through an acoustically attenuated transfer duct. The exhausts are coupled together via a lateral high-level extract duct, connecting into exhaust stacks at regular intervals. As the tartan pattern builds, envisaged on three storeys, the 7.2m and 10.8m planning module develops 14.4m-deep floorplates on the north-section axis, 21.6m deep on the east-west axis. While North American hospital planning tends to develop a minimum of 35.0m-deep packets of floorplate, much contemporary UK hospital planning is achieved in 25m plan depth.

The cross-section (Figure 2) depicts supply air passing through a concrete labyrinth lined in anti-fungicidal surface treatment below the courtyard, feeding supply ducts within a double facade, delivering to three floors. Exhaust is provided by stacks spliced onto the supply ducts below, a simple ‘edge-in/edge-out’ strategy delivering pre-cooled (or pre-warmed) supply air. Across the courtyard, air is admitted in the circulation zone and across adjacent rooms, exhausting through a central duct, connecting, as described, to stacks. All the stacks indicated are provided with fan assistance, operated by flow sensors to prevent flow reversal.

We have developed a five-category coding system to denote the proposed environmental control strategy for each space. The principle is to employ the simplest, least energy-intensive strategy to deliver the airflow performance required by the Department of Health for each space:

Simple natural ventilation (SNV) all the time (opening windows): the ventilation of outdoor air directly into the space through occupant-controlled windows. The flow of air out of the space may be through the same window, other windows or via stacks. It is uncontrolled, except by the immediate occupant for the least sensitive spaces.

Advanced natural ventilation (ANV) with passive cooling: outdoor air is supplied via stacks fed from below-ground concrete plena providing passive cooling/warming depending upon the season. Air leaves the space via ventilation stacks. It is ‘advanced’ because of the possibility of optimised central control. Air flow rates are managed by Building Management System (BMS)-controlled dampers at the inlet and outlet locations to each space. It entails equipment to maintain and there are controls to master. Occupant override will compromise energy efficiency but may enhance ‘wellbeing’.

Hybrid ventilation: combined natural and mechanical ventilation (including passive downdraught cooling (PDC)) and mixing ventilation strategies. This option adds robustness to an ANV system. The supply of outdoor air is made directly into the space via damper-controlled inlets. The flow of air out of the space is via exhaust stacks. During peak load (warm) conditions, fans are used to increase the ventilation cooling potential. PDC, encouraging air to fall through chilled water pipes at a high level, may also be used to provide additional cooling where and when necessary. Mixing ventilation, using exhaust flows to warm incoming supply air in winter, is also included in this category. Higher energy consumption is tempered by increasing the efficiency of fans. Sensors and controls are employed to detect down-draughting and flow reversals.

Full mechanical ventilation: The need for this option is when ANV and hybrid systems are unable to deliver required constant airflow rates. Air flow into and out of the space is driven by variable speed fans providing full control over ventilation rates, but no mechanical cooling. The system enables heat recovery via an air-handling unit (AHU).

Full air-conditioning and filtration: This provides reliable, very clean, temperature- and humidity-controlled environments. Air is supplied to and exhausted from spaces via high-efficiency particle arrestor (HEPA) filters, driven by a central (AHU) controlling temperature and humidity according to the requirements of each space. It is impossible to overcome filter resistances with naturally driven airflows.



A representative quadrant of the notional hospital plan was assembled (Figure 3). The lighter the shading on the plan, the more ‘natural’ the environmental strategy. Simulations were conducted on the northwest quadrant. It has a higher proportion of spaces requiring controlled mechanical ventilation and cooling than is the case for the rest of the design; the results gained may be pessimistic in the context of the whole hospital. The first-floor quadrant revolves around the operating theatres, recovery and support spaces. The theatres shown adopt a hybrid environmental strategy; we hope to develop this concept with colleagues at Imperial College. A pathology laboratory is included, the actual laboratories ventilated mechanically, of course, to UK Home Office standards.

The component plan elements were then developed into a full 35,000sqm, 180-bed, acute hospital. The first floor plan is shown as Figure 4. It indicates the tartan mat unrolled to accommodate the principal departments and ancillary functions of a small- to medium-sized acute hospital. As discussed, compact planning is favoured by clinicians and managers over shallow, linear planning because it offers a greater frequency of closer medical adjacencies. However, this theoretical deep plan will be liberally punctured to offer fresh air, using garden courtyards as daylit navigation landmarks. There is no need for the courtyards to be similar or for the plan to be orthogonal throughout, although extended west-facing elevations are avoided to mitigate solar gains. Again, the plan is coded to indicate the distribution of the five environmental strategies to cope with the present-day climate of southern England, which may become the future climate of the English Midlands, as the simulations indicate. The relative proportions of the five broad environmental strategies is indicated in Figure 5. Surprisingly perhaps, some 70% of the total floor area is indicated as naturally ventilated, simply or in a more contrived way.

The computer simulations predicted the following annual energy consumptions for the four climatic conditions considered:
• 2005 climate: 377kwh/m2 or 38.0GJ/100 m3
• 2020 climate: 379kwh/m2 or 38.5GJ/100m3
• 2050 climate: 370.2kwh/m2 or 37.6GJ/100m3
• 2080 climate: 361.7kwh/m2 or 36.7GJ/100m3.

These results suggest a near halving of typical achieved figures. As the study from which they are taken was calibrated against energy use predictions based on current hospital designs and construction, it is clear that significant energy savings can be achieved. However, the exercise reveals that delivering the lowest best target of 35GJ/100m3 will be very demanding. Medical equipment heat loads will be required to be significantly reduced at source. There is little evidence that this is a procurement priority.

Could renewable energy technologies solve this conundrum, restricted to those technologies that do not burn fossil fuels on site? The base case prediction on 2005 data of 376.7kwh/m2 yields a total energy consumption of 467,485kwh. Even a 10% contribution (46,749kwh) requires a total of 234 wind turbines with a 3.2m blade diameter, rated at 1.5kw and assuming an average wind speed of 2m/s. This is infeasible in development control terms alone. Environmentally responsive design is much more effective.



The potential of refurbishment
Funded by the Department of Health and the Engineering and Physical Sciences Research Council, the next stage of our work was entitled ‘Design & delivery of robust hospital environments in a changing climate’ (De2RHECC, grant reference EP/G061327/1). The research asked whether the same concepts could be applied to the existing acute estate to increase resilience. By increasing resilience, would energy consumption rise? Would effective adaptation be prohibitively expensive?
How can one possibly comment on a distributed estate this size? Although vast, the NHS estate comprises a recognisable number of repeating ‘type’ building forms/plans of different eras. The first type comprises pre-1939 buildings, typically with ‘Nightingale’ wards arranged as finger-like pavilions. Subsequent 1950s/early 1960s ‘Nuffield’-type ward buildings may be high or low rise, of heavyweight or lightweight construction. A tower of Nuffield-type wards can be combined with a lower podium as the so-called ‘matchbox on muffin’ type. 1970s and 1980s hospitals are, in many cases, lower rise buildings punctured by courtyards; over 100 such schemes were built using the Department of Health’s ‘Nucleus’ template planning system. Very few existing buildings on the NHS estate were designed to be air-conditioned. Many are poorly insulated and often over-glazed, leading to increased risk of summertime overheating, even in relatively recently completed buildings.10

We selected one or more of each type from four partner NHS trust campuses. Here we report on two particularly revealing investigations exploring the potential to achieve the Department of Health’s target of 55–65GJ/100m3 for exemplary refurbishments.

Addenbrooke’s Hospital ward tower is in Cambridge, in the east of England. It was built between 1967 and 1972 comprising a 10-storey slab block (Figure 6).11-13 An initial survey of NHS hospital sites by the authors identified at least 50 buildings of this basic type. The tower is 120m long on its southwest/northeast axis and variously 14.1m and 18.3m deep. All floors have the same overall geometry, a long central corridor to which, on the south side, multi-bed wards (10.2m deep from corridor to window wall) occupy the wider end parts of the building. Private rooms and offices face north. The occupied levels have a structural floor-to-ceiling height of 3.66m with, as designed, a 0.90m void above the suspended ceiling. Figure 7 shows a cross-section through a typical floor, showing the relative proportions of the single- and multi-bed spaces and also the relative height of the wards.


The windows run as a continuous ribbon at all levels on both facades, a facade-glazing ratio of 57%, incorporating opaque panels. Precast concrete panels form the spandrels. The original fenestration comprised large centre-pivot windows, offering prodigious opening area if required, but these windows were replaced with double glazing in the 1990s, which are restricted to 100mm opening, radically disrupting the natural ventilation opportunities. The continuous glazing here was intended to maximise views. Sun shading was planned, but omitted during construction. The priority was to achieve adequate winter heating (the 1962–63 winter had been brutal). Air was mechanically supplied from a central plant room into the central corridors. There is no organised exhaust except in bathrooms and utility rooms. Patent radiant ceilings, still in operation, helped to heat wards to 18.3°C (65°F) when the external temperature was -1°C (30°F).

Two floors were monitored by the research team. The building emerges as pretty resilient. Level 8 ward temperatures varied between 21.4°C and 28.5°C. Forty-five per cent of the hours during a mid-summer measurement period (1 July–15 August 2010), had internal temperatures over 25°C, which for healthy people is seen as the value above which thermal dissatisfaction will occur, with 28°C being the upper limit of thermal comfort acceptance. There were 38 night-time hours (taken as 21:00 to 06:00) above 26°C (ie 8% of the total). The nurses’ stations mid-plan were consistently warmer. Temperatures were arrested by the very high air leakage from the building’s construction, while the windows were observed to be continuously open, so that energy consumption is close to the maximum recorded in the NHS, more than 100GJ/100m3.


Five refurbishment options were devised by the team, ranging from the industry-standard PassivHaus-type approach (sealing the building within a heavily insulated jacket, with very efficient heat recovery) of Option 1 to hybrid Options 2 and 3, and more innovative passive schemes 4 and 5. Each is described in turn in what follows.

Option 1: sealed building, mechanical ventilation with heating and cooling (SMVHC). This depicted in Figure 8. The external envelope is overclad to substantially improve air-tightness and U-values. The relatively recent thermal-break aluminium double glazing is retained to save cost. The ventilation system operates at 6 AC/h, as required by the Department of Health’s document Health Technical Memorandum (HTM) 03-01. Windows are sealed and a third layer of glazing added internally. The glazing is shielded by new interstitial blinds. Resilience to overheating is provided by increased mechanical ventilation with mechanical cooling for peak lopping when required. Modelling showed few summertime hours above the thresholds given in HTM 03-01 or those suggested by the Chartered Institution of Building Services Engineers (CIBSE): see Table 1. The annual predicted energy demands and emissions were 59GJ/100m3, so within the DH target, and 137kgCO2/m2 respectively (Figures 9 and 10). These figures exclude delivered energy, which would add to this figure. Relatively little energy was used for cooling but the ventilation energy demand to deliver the high airflows was significant.

Option 2: sealed mechanically ventilated environment, radiant ceilings active in winter (heating) and summer (cold water for cooling) and heat recovery (SMVRHC). This option exploits the radiant action of the ceilings both in heating and cooling mode, thermally upgrades the envelope as Option 1, and retains the double glazing but adds solar shading. The mechanical supply delivers the fresh air requirement only so that it is below 6 AC/h and heat recovery is provided. The original radiant ceiling installation is refurbished to provide additional radiant heating. The simulations indicated an insignificant number of summertime hours above each of the HTM 03-01 and CIBSE thresholds (Table 1). The annual predicted energy demands and emissions were 46GJ/100m3 and 102kgCO2/m2 respectively (Figures 9 and 10). This represents a further improvement.

Option 3: natural ventilation and concurrent mechanical ventilation supply, heat recovery, opening windows and perimeter heating (NVMVPH). This hybrid option adopts a similar thermal upgrading of the envelope, retaining the current double glazing. All of the glazing can be opened by the occupants in peak summer periods, an important contribution to the overheating defence strategy of this option. In addition, the suspended ceilings are cut back as far as the supply ductwork allows, in order to expose the thermal mass of the concrete soffits. It performs well. There were no predicted summertime hours above the CIBSE or HTM 03-01 thresholds, or indeed the recent adaptive comfort British Standard, BS EN 15251, which allows for occupants to become accustomed to raised temperatures over a period of time (Table 1). The annual predicted energy demands and emissions were 40GJ/100m3 and 111kgCO2/m2 respectively (Figures 9 and 10), with ventilation energy (to deliver 4 AC/h) being about 40% of the whole.

Option 4: natural cross-ventilation, perimeter heating (CVPH). This option (Figure 11) dispenses with the mechanical ventilation system altogether. It enables cross-ventilation by threading crossover ducts in alternating directions across the width of the floorplate and upgrades the external envelope to the standard of Options 2 and 3. Perimeter heating is provided with actuated trickle vents below fully operable occupant-controlled windows, adapting the existing installation. Effective night ventilation will be important. All suspended ceilings are removed to expose the full flat concrete soffit above all patients so that vigorous night ventilation will cool the soffits. In this entirely naturally driven scheme there were no predicted summertime hours above each of the thresholds (Table 1) and the annual predicted energy demands and emissions were just 20GJ/100m3 and 44kgCO2/m2 respectively (Figures 9 and 10), the omission of fans being the key to such low energy demand.

Option 5: natural stack ventilation with perimeter heating (SVPH). This option (Figure 12) adds external exhaust stacks to develop more reliable air flows as required. A potential difficulty is the effectiveness of stub stacks on the windward face in which the flows may reverse with a reversing flow regime set up on each floor. In a hospital where the avoidance of the risk of airborne infection spread is clearly important, reversing flow regimes are unacceptable. This option removes the envelope of a floor at mid-height to provide a free air environment in which the stacks to the lower four floors can terminate. The stacks are strictly dedicated to one space per cell, as the part elevation/section reveals. The occupation of the elevation by deep stacks reduces the glazed area beneficially and the depth also shades the glazing through the critical summer overheating period. All windows are rendered operable and the cross-ducts of Option 4 are introduced below a fully exposed flat concrete soffit. The intention would be to vigorously night-ventilate within the comfort parameters of sleeping patients and patrolling medical staff.



All five schemes dramatically improve performance, but these predictions do not include energy use for matters unconnected with space conditioning (small power, medical equipment, restaurants etc), which can be 44% of the total. Given this, it is likely that only Options 2 to 5 could plausibly meet the NHS energy target and CO2 emissions benchmark of 55–65GJ/100m3. Importantly this excludes Option 1, which has a mechanical supply of 6 AC/h as stated in HTM 03-01.
Predictions of future performance used Test Resultant Year (TRY) and Design Summer Year (DSY) data for 2030, 2050 and 2080 supplied by the Prometheus project at Exeter University using the UKCP09 Weather Generator assuming the benign A1B scenario, which is now less credible due to the unexpectedly rapid rise in atmospheric carbon concentration. The existing building will ‘go off the rails’ by the 2030s. Table 2 shows that that Options 1 and 2 can eliminate overheating hours, but in the case of Option 1 this is done at a prodigious energy cost. Radiant cooling is much more effective. In extreme years, the hybrid Option 3 can maintain comfort to 2050 but clinical spaces are in difficulties by 2080. In standard TRY years, the natural ventilation Options 4 and 5 are remarkably robust but in extreme years performed well, as judged by the BS EN 15251 adaptive comfort method, in the 2030s but by the 2050s performance is unacceptable in Cat I spaces, the clinical spaces for the vulnerable, and by the 2080s also in Cat II spaces for less vulnerable patients.
In these extreme years, the number of hours internal temperatures exceeded 28ªC was greater than exceeded externally, suggesting that passive night-time cooling will be less effective in future extreme years.
The answer, then, is a naturally ventilated option with the capacity to install cooling in the future.



The UK’s pre-1939 stock
A parallel De2RHECC investigation suggests the masonry-built ‘Nightingale’ ward type is exceptionally resilient and has the potential to contribute to the solution of the conundrum if fundamentally reconfigured to deliver NHS modernisation policy goals.14 In the early 2000s, the NHS was directed to abandon the traditional collective healthcare model of an open shared ward and adopt the single room model hitherto reserved for the very unwell and the privately insured. Pre-1948 wards built to Florence Nightingale’s original, very detailed specifications were condemned by the British government.15 Nightingale wards in Britain comprised open dormitories for, on average, 24–30 patients.

The De2RHECC research team has measured and modelled the Nightingale wards at Bradford Royal Infirmary since 2009. These are four-storey ward buildings, a little narrower than the typical Nightingale ward, but in all other respects they conform to the type. The original Nightingale glazing configuration offered prodigious free areas for cross-ventilation, quadruple-banked hopper windows alternately top- and bottom-hung. Internal temperatures in two full wards were recorded using calibrated data-loggers. During the monitoring period (1 June–11 August 2010), the ambient temperature reached a maximum of just 24.1°C. In mid-June, external night-time lows of just over 5°C were recorded. Across all eight measuring points in the first ward measured, the temperature only varied from 20.1°C to 27.4°C with a mean of 23.7°C. The mean night-time temperature was 23.2°C and the maximum diurnal swing recorded was just 5.2°C. The temperatures in a second ward were similar.

Overall, the temperatures in all the spaces were well controlled and well within the wide range recommended for wards by HTM 03-01 of 18–28°C. The predicted energy demand in 2010 was 14GJ/100m3 with over 90% of this being for space heating. Assuming national norms for the adjusted energy demand of about 25GJ/100m3 is significantly below the NHS target of 55–65GJ/100m3 for refurbished buildings and significantly below the target of 35–55GJ/100m3 for new buildings. In other words, it delivers the NHS carbon reduction target. Concerning CO2 emissions, the predicted value for energy use to sustain the clinical function is about 30kgCO2/m2, which would uplift the total to about 53kgCO2/m2, just below the best Department of Health target. It is this level of provision that the target implies.

Three incremental refurbishment options were devised for the Nightingale wards (Figure 13). The first adds 100mm of insulation to the walls and 300mm to the roof; opens up the triple-light windows and protects occupants with an architectural external steel grillage; and provides a sunshade at each opening. Fresh air supply in winter is provided by the reopening of a trickle vent behind a perimeter heating element. The second option adds ceiling fans operable by the patients to this strategy, while the third option introduces 100mm-diameter high-level air inlets above each bed space, between each window, with a damper, and a simple convective heating device fixed to the internal face to enable supply air to be pre-heated and/or recirculation within the space. Primary heating and cooling is delivered through the installation of radiant panels. The addition of radiant cooling eliminates entirely the risk of overheating. The further adaptation work reported here takes the second option as the base treatment of the envelope.

For each option, the annual energy demands and CO2 emissions were predicted (Figure 14). For the first option the space heating demand dropped from about 13GJ/100m3 to an extremely low value of about 5GJ/100m3; lighting and small power gains remained unchanged. The CO2 emissions were about 15kgCO2/m2. Clearly the added insulation has an impact. There were just 196 hours above the BS EN 15251 Cat I upper threshold, which represents about 5.3% of the total for the summer period (May to September) modelled. Assuming that the heating system is appropriately controlled during the wintertime so there is no overheating, then over a year there will be just 2% of hours over the Cat I envelope, which is well within a suggested BS EN 15251 limit of 5%. The refurbishment reduces the impact of higher ambient temperatures and solar gain, resulting in a reduction in the peak temperatures. This effect may well yield benefits as the climate warms (see below). Full removal of the suspended ceiling might result in greater benefits still.

The second option’s slow fans are set at 0.3m/s air speed, well inside the allowable upper limit of 0.8m/s, to give an operative temperature depression of 1.2ºC, at an assumed fan power of 70 watt per fan. The fans resulted in very little change to the occurrence of elevated summertime temperatures, there being about 5.2% of summertime hours above the Cat I upper threshold. Neither was there much difference in the energy demand and CO2 emissions. This is because the predicted internal temperature rarely exceeded 26ªC, the temperature at which the fans were set to switch on.

Internal temperatures were predicted for current and future typical and extreme temperature years as represented by TRYs and DSYs for current and future conditions, developed for Bradford by the University of Exeter using the customary CIBSE methods, as for the Addenbrooke’s exercise. Simulations were undertaken with all eight weather years for 2010, 2030, 2050 and 2080. Predictions of the likely air and operative temperatures were compared with the CIBSE, HTM 03-01 and BS EN 15251 overheating criteria (Table 3) as appropriate. The results clearly indicate that neither the existing or refurbished building will overheat in typical years, as judged by the HTM 03-01 and BS EN 15251 criteria. However, in the 2050s warmer night-time temperatures may be experienced (although these might be ameliorated easily with a refined window-opening regimen if the windows are openable to a useful degree in sufficient numbers). In the extreme temperature years (ie the DSYs), however, HTM 03-01 shows overheating will occur in the existing building and in refurbishment Option 1 as early as the 2030s. Options 2 and 3 are resilient.

The highly resilient Option 2 was then taken as the basis for exploring reconfiguration possibilities with staff at the Bradford Royal Infirmary. The aim was to couple this resilient envelope with an internal layout better suited to privacy, though evidence from the hospital suggests the value of open wards for geriatric patients. Figure 15 shows:
a) The original Nightingale layout
b) Partitions: Subdivided into one-bed cubicles, the full 16 feet in height, with the addition of external bathroom towers
c) Pullman: An arrangement like a compartmentalised railway carriage, with the incorporation of an internal corridor and subdivision into six two-bed rooms served by split bathroom towers
d) Zig-zag: Preserves the full open volume but configures the beds either side of a wardrobe-high central partition set out to a zig-zag plan, offering visual if not acoustic privacy with five external bathroom towers
e) External corridor: The recovery of more usable floorspace by adding an external corridor to each floor, enabling ward rooms of three to five beds.
The options were modelled to assess airborne infection implications by our colleagues at Leeds. They perform well, and the results will be published in early 2014. The British government Cabinet Office is enthusiastic about the zig-zag arrangement, almost a kind of aeroplane ‘business class’, rethought for NHS patients.

Conclusion
In addition to the projects reported here, other types of hospital building have been modelled. They include an early 1970s medium-rise maternity wing, a low-rise 1980s maternity hospital, and a Nucleus hospital (which is highly resilient because of its recurring courtyards, but is dramatically impaired if courtyards are infilled). Work on modular buildings suggests they merit concern: being fundamentally lightweight, they have inherently low resilience.
All the schemes have been costed in detail. The new-build scheme is costed at £5,360/m2 by AECOM Davis Langdon. This figure can be compared, perhaps harshly, with capital costs for notional best upper and lower target hospitals at £5,060/m2, but these targets are not achieved at this scale in reality. However, in payback terms, the new-build option comes into its own in the 2030s as ‘business-as-usual’ hospitals suffer radical air-conditioning refits. The Addenbrooke’s refurbishment schemes costed between £1,000 and £1,300/m2. The Nightingale adaptation schemes are very similar, ie within current NHS refurbishment norms. The new director of the Department of Health Estates and Facilities Policy believes the optimal adaptation schemes could be rolled into the annual backlog maintenance operation across the NHS. These are grounds for optimism and action.

Authors
C Alan Short MA (Cantab) DipArch RIBA is professor of architecture at the University of Cambridge and a fellow of Clare Hall, Cambridge; Kevin Lomas BSc (Hons) PhD is professor of building simulation at the University of Loughborough; Alistair Fair BA (Hons) MA PhD is a research associate in the Department of Architecture at the University of Cambridge; Catherine Noakes BEng (Hons) PhD is reader in infection control engineering at the University of Leeds; Giridharan Renganathan BArch MUrDgn PhD AIA (SL) is lecturer in architecture at the University of Kent; Sura Al-Maiyah BSc MSc PhD is senior lecturer at the Portsmouth School of Architecture.

References
1. National Health Service. Heatwave Plan for England: Protecting health and reducing harm from extreme heat and heatwaves. 2011 [Accessed 11 June 2013]. Available from: www.nhs.uk/Livewell/Summerhealth/Documents/dh_HeatwavePlan2011.pdf
2. National Health Service. NHS Workforce, Summary of staff in the NHS: Results from the September 2012 census. 2013 [Accessed 14 May 2013]. Available from:  www.hscic.gov.uk/catalogue/PUB10392
3. National Health Service Sustainable Development Unit. Saving Carbon, Improving Health. London: NHS; 2008.
4. National Health Service. Improving Energy Efficiency in the NHS: Applications for capital funding 2012-13. London: Department of Health; 2012.
5. NHS Sustainable Development Unit. Sustainable Development Strategy for the Health, Public Health and Social Care System. Consultation document. 2013.
6. National Health Service Information Centre. Hospital Estates and Facilities Statistics. 2010. [Accessed 14 May 2013]. Available from: www.hefs.ic.nhs.uk
7. Department of Health. Health Technical Memorandum 07-02: EnCO2de: Making energy work in healthcare. London: The Stationery Office; 2006.
8. Department of Health. Health Technical Memorandum 07-07: Sustainable health and social care buildings. London: The Stationery Office; 2009.
9. This section summarises Short CA, Al-Maiyah S. Design strategy for low-energy ventilation and cooling of hospitals. Build Res Inf 2009; 37(3): 264-92.
10. Hall C. Babies swelter in 90ªF at new hospital. The Telegraph; 21 June 2006 [Accessed 14 May 2013]. Available from:  www.telegraph.co.uk/news/1524435/Babies-swelter-in-90F-at-new-hospital.html
11. The work on Addenbrooke’s Hospital is reported in Short CA, Lomas KJ, Giridharan R, Fair AJ. Building resilience to overheating into 1960s UK hospital buildings within the Constraint of the National Carbon Reduction Target: Adaptive strategies. Building and Environment 2012; 55:73-95.
12. Animations of the models can be found in our film: Cook P (dir). Robust Hospitals in a Changing Climate. Cambridge: Screenspace Productions; 2013 [Accessed 14 May 2013]. Available from:  http://sms.cam.ac.uk/media/1446036
13. Details of the monitoring strategy may be found in Lomas KJ, Giridharan R. Thermal comfort standards: Measured internal temperatures and thermal resilience to climate change of free-running buildings: A case study of hospital wards. Building and Environment 2012;
55:57-72.
14. The Bradford work is reported fully in Lomas KJ, Giridharan R, Short CA, Fair AJ. Resilience of ‘Nightingale’ hospital wards in a changing climate. Build Serv Eng Res & Tech 2012; 33/1:81-103.
15. Nightingale F. Notes on Hospitals: Being two papers read before the National Association for the Promotion of Social Science with evidence given to the Royal Commissioners on the State of the Army in 1857. London: John Parker and Son; 1859.








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