2.1. Simulating the future climate projections

Current condition (baseline) and future climate weather year (FWY) files are used to simulate climate impact. These weather files, created using the Weather Generator of the UK Climate Projections 2009 (UKCP09), have been obtained from a catalogue of weather files developed by the PROMETHEUS project from the University of Exeter (Eames, Kershaw, and Coley Citation2011).

The selection of suitable weather year (WY) files for the DTS was based on four factors:

1. Location: WY file sets are selected for their proximity to the case study locations, all within five miles of the case study with the exception of case study B which is 20 miles from the nearest weather station.

2. Climate periods: UKCP09 provides projections for seven climate periods (30-year time periods). Three time periods have been selected to represent: Short (2030s), medium (2050s) and long-term climate conditions (2080s). New buildings constructed today typically require building services replacement every 15–20 years (short term). They would have minor refurbishment after 35–45 years (medium term), and major refurbishments would occur after 60–100 years (long term).

3. Carbon emission scenarios: UKCP09 offers climate projections based on three emission scenarios: low, medium and high. The high carbon emission scenario has been selected, as observed emissions have been following this path (EEA Citation2012). In addition, building adaptations would still be effective under the medium or low emission scenarios.

4. Risk percentiles: UKCP09 offers climate projections based on a probabilistic approach. Of the most commonly cited probabilities, 10% (more likely to be greater than), 50% (central estimate) and 90% (less likely to be greater than) (UKCP09 Citation2012), 50% probability was used in the research.

1. current conditions, that is, baseline weather year (BWY)

2. 2030s climate period, high emissions scenario, 50% probability (FWY)

3. 2050s climate period, high emissions scenario, 50% probability (FWY)

4. 2080s climate period, high emissions scenario, 50% probability (FWY)

2.2. Modelling the care homes and the users

For each case study, the plan involved assessing two bedrooms (in care homes), two flats (in extra-care homes), an office and the public lounge. To collect data on the case study buildings, construction drawings and material and system specifications were collected from the owner and/or architect as most buildings were constructed recently. In the case of the pre-1919 building, a renovation was planned; therefore, as-built drawings were submitted and available from the local planning office. In addition to drawings, site visits were made to complete building survey forms developed for the study to verify or collect additional information needed for modelling purposes. This information included, heating, air conditioning and ventilation system models, seasonal set-points, occupancy count and times, heating set-points and times, window opening patterns, and other information regarding personal shading devices, equipment or fans not found on the drawings.

2.3. Assessing current and future overheating

Gupta, Barnfield, and Gregg (Citation2016) critically review the evolving understanding of overheating, thermal comfort and appropriate thresholds in the UK and the various methods for assessing overheating and health-temperature thresholds in the UK for the different sub-sectors of the building stock, particularly in the care sector. From this review, overheating and heatwave vulnerability were assessed through two primary metrics: overheating as defined by CIBSE (Citation2006, Citation2013) and vulnerability to heatwaves as defined by the Met Office (Citation2015) and the Heatwave Plan for England (PHE Citation2014b). Due to the hybrid nature of care sector buildings (both residential and work places), it was considered appropriate to use both of CIBSE’s static and adaptive overheating methods for assessment. To summarize the methods used to evaluate the climate impact, Table 2 lists relevant details of the overheating methods used in the study which are relevant to the care sector.

2.4. Assessing adaptation options

Following the review of the D4FC and BPE studies, the following adaptations were selected for assessment to mitigate or reduce risk:

• passive: green roof, reflective roof and walls, canopy cover over courtyards (where possible), green cover, external shutters, interior blinds, improved glazing, solar film, exposed thermal mass;

• semi-active: managed natural ventilation;

• active: ceiling fans.

3.1. Occurrence of overheating

Figure 1 shows the overheating results for the case studies using the static method and Table 3 shows the overheating results using the adaptive method. Though the 2030s climate period was assessed along with 2050s and 2080s, the latter are the focus of the paper due to the low occurrence of overheating in 2030s or earlier. It should be noted, however, that Case C simulation demonstrated some overheating in the 2030s and BSY.

Figure 1. 2050s (left) and 2080s (right) climate period overheating results using the static method.

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In the figures below the darker zone above 1% shows the zone of overheating, that is, below 1% is not overheated. In the table showing the adaptive method results, where two or more criteria failed, overheating is occurring.

Table 4 presents the heatwave thresholds and counts for the case study locations. Note that Leeds experiences heatwaves before others (2030s and 2050s) (partially attributed to the lower threshold) but the other locations have heatwaves with much higher peak temperatures at 2080s.

3.2. Adaptation measures

From the adaptation options testing, it was concluded that the most effective passive adaptation options include shading, for example, with shutters (allow greatest seasonal variation), reflective roofing material, thermal mass (only where applicable – Case D), and in some instances interior blinds. Figure 2 shows the effectiveness of three adaptation measures in the lounge of the case studies in the 2080s climate period using the static method. Shutters are most effective for two case studies but Case B and Case C are more responsive to other options. In some spaces, singular simple measures are effective in mitigating overheating risk; however, in other spaces packages of measures will be required and in some instances at 2080s climate period no (tested) combination of passive measures were effective in eliminating overheating, for example, Case C lounge.

Figure 2. Most effective single passive adaptation measures for the case studies’ lounges.

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Management of natural ventilation (ventilation dependent on external conditions) can be either passive or active depending on how it is controlled. In some cases, appropriate natural ventilation management (in this study, closing windows when the external temperature is >25°C) is effective alone in eliminating overheating risk. Intelligent natural ventilation management will require carers, building managers, or building management systems to be involved in temperature monitoring, and window opening and closing management or supervision.

The building survey revealed that several residents are already using mobile electric fans as a ‘quick-fix’ to keep cool, wherein some cases, residents or their family members were required to provide these. Ceiling fans are an effective, low energy and inexpensive integrated option. As an example, in Case A – first floor (FF) bedroom for all hours over 25.5°C between 19:00 and 07:00 fan energy consumption can range between 0.9 and 1.8 kWh (depending on fan selection) for the entire summer. Alternatively at 24-hour occupancy, this would be 3.5–7 kWh (EEC Citation2015).

Figure 3 shows the impact of using fans to improve the comfort of occupants during the peak temperature period of a heatwave (2080s climate period). The ‘most effective single measure’ refers to the respective measures shown in Figure 2. For Case C, the internal temperature is too high for increased air velocity to improve thermal comfort. For the other case studies, the addition of a fan is helpful but the case studies are unable to satisfy PMV for Category I (PMV = 0.2). Again, integrating more measures would be helpful. Note also that though the shutters mitigate overheating using the static method in Figure 2, for Case A during the heatwave, shutters are not enough to satisfy thermal comfort demand using the PMV method; however, adding the fan is necessary to do so.

Figure 3. Most effective adaptation measures in combination with ceiling fans for the case studies’ lounges.

Note: whereas the static method shown in the previous image indicates the impact on the seasonal overheating of the spaces, the PMV looks particularly at the impact of measures on the predicted thermal comfort of individuals during the peak temperatures of a heatwave in the selected climate period.

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3.3. Adaptation packages

Figure 4 shows the impact of select adaptation measures and a ‘full adaptation package’ on the internal temperatures of a selected space during a heatwave period; Table 5 shows the same for the overheating methods. The full adaptation package in the following example is comprised of exterior shutters, exposed thermal mass and managed natural ventilation.

Figure 4. TF living room internal temperatures during a heatwave in the 2080s climate period.

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In this case, the most effective adaptation measures are external shutters, canopy cover and green cover. This list suggests that the third floor (TF) flat is overheating as a result of too much incident solar gain. As can be seen in Figure 4 and Table 5, managed ventilation alone would be a hindrance to the TF flat, locking in gain and not allowing the temperature to drop internally to be ventilated. Note that though managed ventilation appears to be problematic as a singular measure, it is essential to the success of the full adaptation package to provide temperatures below 26°C during the heatwave. That is, if managed ventilation were removed from the full adaptation package, the external shutters and exposed thermal mass would be the result, that is, far less effective than the full adaptation package (difference of 2.5°C during heatwaves in the 2080s projection). In contrast to heatwave considerations, external shutters alone are sufficient in completely mitigating overheating risk.

To summarize the findings for the selected space presented, by 2030s no adaptation is needed, by 2050s it is suggested that ceiling fans are installed or no adaptation is needed, by 2080s external shutters would be entirely sufficient to mitigate overheating; however, more action is needed to either bring down the internal temperature or cool the individual during a heatwave; therefore, either the full adaptation package or a shutters and ceiling fan package is recommended.

For all cases, the resultant suggested adaptation packages are marked in Table 6. The measures could be phased over time according to the FWY data; where temperature/ thermal comfort monitoring may prove a more immediate need, it may be suggested that measures (or even entire packages) are installed now, in a step-wise method, observing the impact over time.

3.4. Design interviews

Interviews with design team shows that there appeared to be a general lack of awareness of the risks of climate change particularly related to overheating for care settings. In addition, designers were generally unaware of the formal Heatwave Plan for England guidance. As one interviewee stated, when designing and developing the briefing for care schemes, overheating is ‘the poor sister … to other aspects of climate change’. Furthermore, planning for future overheating is not seen as a priority for care and housing providers who tend to focus on the near future rather than long term, for example, the impact of climate change within the next 30 years or beyond. While all interviewed considered designing for overheating to simply be ‘good environmental design’, one designer stated that, ‘We need to understand it a little bit more … we’re (the industry as a whole) not as familiar with the solutions … ’ There was also an underlying attitude among both designers and managers that emphasized a culture of ‘warmth’; cold is seen as the issue, and as such there was a focus in both the design and briefing documents for new schemes on provision of warmth, rather than a provision of cooling and/or adequate ventilation strategies.

Modelling and relevant overheating standards was an area of focus within the interviews. Interviewees commented on the fact that there is no clear definition or guidance on overheating to which designers can both design and refer clients. There has been an increase in standards and guidance (such as CIBSE TM52 2013 and Building Regulations Part L2A 2013 (non-domestic but includes provision for domestic buildings that fall outside Part L1A such as care homes)) in terms of assessing the overheating risk in new buildings since all the case studies were constructed. However, there is still no definitive regulatory requirement in the building sector. In addition, two out of the three design practices interviewed left the design of services, and modelling of thermal comfort with either environmental consultants, or mechanical and electrical (M&E) engineers, which appears to have led to a lack of a joined-up approach between overall design of the care scheme buildings and services (heating, hot water, electrical systems) design.

4.1. Assessing the risk of and response to overheating

The static method was found to be more sensitive to overheating throughout the results, meaning that more spaces overheated within a particular projection and at earlier projections using the static method. As the BWY DSY files do not indicate heatwaves or overheating in most cases this may suggest that the DSY WY files for the current climate are not sufficient when designing for people of higher vulnerability to health risk.

Table 6 above demonstrates the findings of this study which can be summarized in the following considerations on how to apply adaptation measures to mitigate overheating:

1. Adaptation measures may not be universally effective, that is, many existing conditions of buildings cause the results to vary widely between buildings

2. Measures may not be universally effective even at the building level, that is, bedrooms can respond differently than offices, etc. Measures that mitigate overheating risk or enhance resilience will need to be tailored to each building’s construction and location, and each individual space’s orientation and occupancy pattern.

3. In some cases measures that are effective for long-term overheating (as assessed through either the adaptive or static methods) may not be effective during heatwaves and vice versa; therefore, design and adaptation should consider both overheating and heatwave risks as separate conditions.

4.1.1. Identifying influencing factors in overheating

Building characteristics that contribute to overheating include large proportion of exposed glazing (example: Case C lounge), building age, inadequate ventilation, high internal gains, location and orientation. The impact of the age of a building is most seen in the contrast between Case B and the other modern homes. Simply put, Case B overheats more than it should in a future climate due to being a leaky building with single glazing (as modelling the opposite conditions demonstrated improvement).

Modelling informed by case study observations demonstrate that inadequate ventilation of rooms (lack of window opening and closed trickle vents as observed during the building survey), increases the risk of overheating. Likewise, in a residential BPE study, combining supplemental ventilation and window ventilation particularly in kitchens was found to be important for reduction of overheating (QCHA and MEARU Citation2015). Also, in line with D4FC projects modelling found that single-sided ventilation (common to all case studies in this work and to the care sector in general) is significantly more prone to overheating as compared to cross-flow ventilation.

Often the design of the heating and ventilation systems is commissioned to M&E services engineers and consultants, as in Case Study A where the architects were reliant on the consultants hired to undertake all the commissioning, testing and checking but who were not responsible for the handover of the building to the end users. This can result in a lack of information provided to the end users in how to operate systems, and subsequently a lack of knowledge within the end users in how the systems work. Poor management of heating controls can result in localized heating being left on, for example, in Case D each room has thermostatic control; the bathroom’s control in a number of flats was discovered to be set to 30°C throughout the summer (with the main heating also on serving hot water supply). Though comparatively modelling both scenarios demonstrated a significant difference, the evaluation of adaptive responses assumed appropriate management of heating systems as a baseline.

The impact of location can vary greatly on overheating risk. To demonstrate an example of this, the Case A building was simulated in all four locations. Figure 5 shows the difference location plays in overheating potential for the 2080s climate period. Bristol appears to present the highest overheating risk followed closely by Reading. This demonstrates that though Case C has a large glass to wall ratio which contributes to overheating, the climate in Bristol is also a significant contributor to consider. Interestingly, the slight difference between Reading and Bristol is reversed when assessing the results using the adaptive method; however, understanding why this difference exists is outside the scope of this study.

Figure 5. Location simulation results.

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Overall, Case study A in NE England shows the least overheating. Location will impact significantly on need for overheating resilience as homes in the south of England will become more susceptible to overheating in future climate. For this reason, it may be necessary to focus more immediate effort in the south of England. By the 2050s, passive strategies for tackling overheating will likely be necessary for all building types in the south of England. By 2080s, passive strategies for tackling overheating will likely be necessary for most locations and building types in the UK.

Figure 6. Orientation variations for Case C.

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Table 7. Orientation change for Case C results.

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Orientation of certain spaces can also have an impact on overheating results in the way that the solar angles and wind direction can be embraced or shunned depending on need. For new construction, consideration of orientation is very important to programming a building where sustainability is seriously considered. Obviously in existing buildings, orientation can be difficult to change; however, if there is flexibility, understanding orientation can guide where to place certain individuals based on vulnerability or where to focus partial adaptive renovations if work must be phased over a long period. To demonstrate an example of this impact on overheating results, Case C was simulated in four additional orientations (Figure 6). Table 7 shows the difference orientation plays on overheating potential for the 2080s climate period. The only variable changed in the equation is orientation. This test demonstrates (as far as overheating risk is concerned) that:

• The lounge was correctly orientated (south) though it overheats significantly. This problem appears to have been understood from the beginning as the lounge has air conditioning installed.

• All other spaces would have benefited from northeast or north orientation.

• Bedrooms (spaces occupied at evening and night) would benefit from avoiding west (including southwest, northwest) orientations due to the late solar gain, whereas, spaces occupied during the daytime, for example, offices and living rooms are more susceptible to overheating when facing southeast and east.

4.2. Integration of physical adaptation measures with management and care practices

The most effective single passive measure across all case studies is external shading, that is, shutters as modelled in the current project. In addition, however, there is a need to build resilience in the care sector, to extend both awareness and understanding of heat-related risks for older people among all of those involved in the provision of care. Though the adaptation responses focussed primarily on physical change to the buildings, neither design or management/care changes are deemed sufficient responses on their own.

It is particularly important that internal heat gains are minimized during heatwaves. This is to ensure that the heating system is completely switched off, not just in terms of room temperature controls but any circulation of hot water through the heating system. Building surveys of the case studies found that heating systems were still on during hotter weather, in part this is suspected because of the general culture of ‘fear of the cold’ and potentially a readiness for unexpected cold weather, but also due to a lack of clarity as to whose role it is to be in charge of the heating system and its use. It follows that management should be proactive in understanding (or trusting the capability of technical staff to operate) the mechanical systems and how they should be operated seasonally. At both building and room level checks should be performed to avoid internal heat gain in summer.

As part of raising awareness about heatwaves and summertime thermal comfort more generally all staff should be educated about solar gain impact, internal gains from heating systems and ventilation. This will require education on how to operate heating systems, shading devices (internal or external) and ventilation systems seasonally. Essentially, as an additional job task, care staff may be expected to operate shading elements (e.g. open shutters) and open and close windows for ventilation. This can be considered a part of caring for the resident as thermal comfort has an impact on health. For extra-care homes, education can extend to the residents and their frequently visitors.

Finally, understanding orientation can guide where to place certain individuals based on vulnerability. As an example, north-, east- and northeast-facing bedrooms were found to overheat less. More vulnerable or bed-bound residents should be placed in these bedrooms where less is required to reduce the overheating risk. It is however, understood that there are other factors limiting resident placement.