Portrait of Dr Giridharan Renganathan

Dr Giridharan Renganathan

Senior Lecturer
Chief Examiner
Director of CASE Research Centre

About

Qualifications: B.Arch(IIT); M.Ur. Dgn (HKU); PhD (HKU); AIA (SL)

Giridharan Joined University of Kent in 2012. He received his B.Arch (1994) degree from IIT Kharagpur, India. He did his M.Ur.Design (1997) and PhD (2005) degrees at the University of Hong Kong. He has both academic and professional consultancy work experience. He has held research appointments at University of Hong Kong (2006), Brunel University (2007) and Loughborough University (2009). Prior to taking up the academic career, he had worked for organisations such as State Engineering Corporation, Urban Development Authority and Avant Garde Urban Design Partnership in Sri Lanka. In practice, he has designed personalised houses as well as large scale institutional and commercial projects. He also designed small scale interventions in towns to mega urban development projects in Sri Lanka.

His research focus is on Urban Morphology and Climatology (environmental design), with specific interest in Urban Heat Island effect and indoor overheating. He has secured large research grants from RGC (Hong Kong SAR) and EPSRC (UK), and small grants from European Union Regional Development Fund (EU), Herritage lottery fund/Kent County Council (UK) and University of Moratuwa (Sri Lanka). He has over 25 peer reviewed publications and 3 book chapters. He has also reviewed research papers for journals such as Building and Environment, Energy and Buildings, Building Research and Information, habitat International, Urban Forestry, Applied Meteorology and Climatology, Environmental Management, International Journal of Climatology, Theoretical and applied climatology, Energy for Sustainable Development and Environmental Engineering Science.

Appointments and affiliations

  • Associate member of Sri Lanka Institute of Architects (Chartered Architect, SL)
  • Fellow of Higher Education Academy, UK
  • Member of European Cool roof Council
  • Member of International Association of Urban Climate

Prizes and Honours

  • Carter Bronze Medal (2016) by Chartered Institute of Building Services Engineers (CIBSE)
  • Research Paper of the Year (2015), 'Highly Commended Certificate', Loughborough University Energy Medal, Loughborough University
  • Asian Development Bank Scholarship (1995)

Research interests

His research focus is on Urban Morphology and Climatology (environmental design), with specific interest in urban heat island effect, urban albedo, outdoor thermal comfort, summer time over heating in buildings, passive ventilation strategies, use of cool materials, urban albedo and dynamic thermal modelling.

Research grants

  • EPSRC Grant, 2017. Urban Albedo computation in high latitude locations: an experimental approach. Capacity: Co-Investigator; Amount: £900,000.00; Duration: 3 Years
  • University of Moratuwa Senate Research Committee short term grants, 2016. Thermal Comfort in Tsunami Housing Developments in Southern Coast of Sri Lanka. Capacity: Co-Investigator; Amount SLRs 250,000.00; Duration: 1 Year.
  • Heritage Lottery Fund / Kent County Council Grant, 2015. Environmental monitoring of large Victorian house in Dalby Square, Margate. Capacity: Co-Investigator; Amount: £73,550.00 (overall); Duration: 1 Year.
  • European Union regional development fund, Environmental innovation network grant, 2015. Detailed thermal simulations of a heritage townhouse. Capacity: Principal Investigator; Amount £700.00; Duration: 1 Year.
  • Hong Kong SAR Government Research, 2004. Urban design approach to lower the space conditioning energy in inner city mixed use residential street blocks in Hong Kong. Capacity: Co-Investigator; Amount: HK$ 1.1M; Duration: 3 Years.
  •  Hong Kong SAR Government Research Grant, 2003. Urban design approach to lower the space conditioning energy in coastal area residential developments in Hong Kong. Capacity: Co-Investigator; Amount: HK$ 1.2M; Duration: 3 Years.

Research Projects (member of research team)

  • Local Urban Climate Model and its application to the Intelligent Development of Cities (LUCID-London). EPSRC funded. June 2007 - May 2009.
  • European Cool Roof Project. European Council funded. June 2009 to October 2009.
  • Design and Delivery of Robust Hospital Environment in a Changing Climate (DeDeRHECC). EPSRC funded. November 2009 to October 2012.

Teaching

Module CodeModule TitleInformation
AR545Architectural DesignTutor
AR554Urban InterventionTutor
AR546Technology 4Module Convenor
AR597DissertationTutor
AR602MArch DissertationTutor
AR899MSc Architecture and Sustainable Environment DissertationTutor
AR829Monitoring and Modelling of Environmental PerformanceTutor
AR830Sustainable Design ProjectModule Convenor


Supervision


Professional

Appointments and affiliations

  • Associate member of Sri Lanka Institute of Architects (Chartered Architect, SL)
  • Fellow of Higher Education Academy, UK
  • Member of European Cool roof Council
  • Member of International Association of Urban Climate

Prizes and Honours

  • Carter Bronze Medal (2016) by Chartered Institute of Building Services Engineers (CIBSE)
  • Research Paper of the Year (2015), 'Highly Commended Certificate', Loughborough University Energy Medal, Loughborough University
  • Asian Development Bank Scholarship (1995)

Publications

Article

  • Catt, M. and Giridharan, R. (2018). The Reality of Wellbeing-Focused Design in Dementia Care – A Case Study of Acute Dementia Wards in the UK. Health Environments Research & Design Journal [Online]. Available at: https://doi.org/10.1177/1937586718779172.
    Objective. The study explored design for wellbeing within dementia-care by investigating the adoption of wellbeing-focused design in real-world practice, through observing NHS wards.
    Background. Design for wellbeing is an approach that considers the psychological and physiological effects of architecture to improve health and wellbeing. The high psychological care requirement for dementia patients makes them a significant group to study in the evaluation of current hospital facilities.
    Methods. A literature review was conducted, to frame the current theoretical perception of the key characteristics of a good environment for dementia care. A framework was generated to summarise, and used as an assessment tool in a series of observational visits to NHS wards. Interviews with clinical staff focused on care outcomes and practicalities of implementing wellbeing-focused design, considering the historical and economical context. Key findings from the observations and interviews were analysed for recurring themes.
    Results. The ward observations and interviews provided insight to the current progression of wellbeing-led design in NHS hospitals in England. The research highlights key areas of success, and factors that inhibit further progression.
    Conclusions. The case studies showed a good degree of ambition to utilise wellbeing-focused design, with belief among staff that the physical environment has a substantial role in the health and wellbeing of patients. Staff also felt that this approach is most effective for those in the less advanced stages of dementia. Despite the high level of support, the current degree of implementation appears to be varied.
  • Giridharan, R. and Emmanuel, R. (2018). The impact of urban compactness, comfort strategies and energy consumption on tropical urban heat island intensity: a review. Sustainable Cities and Society [Online] 40:677-687. Available at: https://doi.org/10.1016/j.scs.2018.01.024.
    The importance of studying tropical urban climate was recognised by the World Meteorological Organisation (WMO) as early as in 1981 but substantial improvements were seen only in the last two decades. However specific knowledge of tropical urban climate still lags behind that of temperate climate. In this paper, authors review the state of the art in tropical heat island intensity, its influence on building energy consumption and the effect of urban compactness in the tropics. The review is limited to peer-reviewed journal publications found on four databases: Web of Science, Scopus, Google Scholar and Science Direct.
    The review indicates that although the tropical belt has large variations in topography, forest cover, land mass and development patterns, much of the current work is confined largely to Far East Asia, South Asia and South America. Future studies should focus on protocol for parameterisation and standardisation of measurement, in depth and scientific understanding of the influence of vegetation, water and topography, survey and monitoring of the context specific relationship between UHI and energy consumption, development of database for numerical model validation and improvement, and the context specific development of LCZ based institutional framework to integrate UHI mitigation strategies with environmental design guidelines.
  • Fifield, L. et al. (2018). Hospital wards and modular construction: Summertime overheating and energy efficiency. Building and Environment [Online] 141:28-44. Available at: https://doi.org/10.1016/j.buildenv.2018.05.041.
    The UK National Health Service (NHS) is continually under pressure to provide more bed spaces and to do this within a tight budget. Therefore, NHS Trusts may turn to modular buildings, which promise faster construction and low energy demands helping the NHS meet its stringent energy targets. However, there is growing evidence that thermally lightweight, well insulated and naturally ventilated dwellings are at risk of overheating during warm UK summers.
    This paper examines the energy demands and internal temperatures in two 16-bed hospital wards built in 2008?at Bradford Royal Infirmary in northern England using modular fast track methods. The two-storey building used ceiling-mounted radiant panels and a mix of natural and mechanical ventilation with heat recovery to condition patients' rooms. Monitoring showed that the annual energy demand was 289?kWh/m2 ±16%, which is below the NHS guidelines for new hospital buildings.
    It was observed that the criterion given in Department of Health Technical Memorandum HTM03-01 can lead to the incorrect diagnosis of overheating risk in existing buildings. Assessment using other static and adaptive overheating criteria showed that patient rooms and the nurses' station overheated in summer. To maintain patient safety, temporary air conditioning units had to be installed during the warmest weather.
    It is concluded that thermally lightweight, well insulated, naturally ventilated hospital wards can be low-energy but are at risk of overheating even in relatively cool UK summer conditions and that this needs to be addressed before such buildings can be recommended for wider adoption.
  • Gana, V., Renganathan, G. and Watkins, R. (2017). Application of Soft Landings in the Design Management process of a non-residential building. Architectural Engineering and Design Management [Online]. Available at: http://dx.doi.org/10.1080/17452007.2017.1324400.
    A study into the design processes involved in Soft Landings is an important aspect to realising energy efficiency and
    environmental sustainability in buildings. Previous Soft Landings papers have focused mainly on post occupancy evaluations
    and aftercare. No comprehensive study has been attempted with respect to Soft Landings at the design stage. In response
    to this gap, this paper investigates the application of Soft Landings during the design stage of a central government building
    in London. It provides an insight into the working processes of a Soft Landings design team and its interaction with other
    team members and end users. Information from interviews with the design team, minutes of meetings, walk-through in the
    designed spaces were used to explore how design decisions were reached. It highlights the role the Soft Landings Champion
    played to ensure that the environmental sustainability objectives of the project were carried from design to construction. The
    paper also explains the fundamentals of Soft Landings and its potential as a client-driven management tool. The paper
    concludes by highlighting the implications of the result to designers, contractors and clients.
  • Iddon, C. et al. (2015). The influence of hospital ward design on resilience to heat waves: An exploration using distributed lag models. Energy and Buildings [Online] 86:573-588. Available at: http://dx.doi.org/10.1016/j.enbuild.2014.09.053.
    Distributed lag models (DLMs) to predict future internal temperatures have been developed using the hourly weather data and the internal temperatures recorded in eleven spaces on two UK National Health Service (NHS) hospital sites. The ward spaces were in five buildings of very different type and age. In all the DLMs, the best prediction of internal temperature was obtained using three exogenous drivers, previous internal temperature, external temperature and solar radiation. DLMs were sensitive to the buildings’ differences in orientation, thermal mass and shading and were validated by comparing the predictions with the internal temperatures recorded in the summer of 2012. The results were encouraging, with both modelled and recorded data showing good correlation. To understand the resilience of the spaces to heat waves, the DLMs were fed with weather data recorded during the hot summer of 2006. The Nightingale wards and traditional masonry wards showed remarkable resilience to the hot weather. In contrast, light-weight modular buildings were predicted to overheat dangerously. By recording internal temperatures for a short period, DLMs might be created that can forecast future temperatures in many other types of naturally ventilated or mixed-mode buildings as a means of assessing overheating risk
  • Short, C., Renganathan, G. and Lomas, K. (2015). A medium-rise 1970s maternity hospital in the east of England: Resilience and adaptation to climate change. Building Services Engineering Research and Technology [Online] 36:247-274. Available at: http://dx.doi.org/10.1177/0143624414567544.
    The late 1970s design for the Rosie Maternity Hospital on the Addenbrookes campus in Cambridge is a
    recurring type across the UK National Health Service, a framed three-storey courtyard configuration in
    brick masonry. It was selected as a case study project for the ‘Design and Delivery of Robust Hospitals in a
    Changing Climate’ project, pursuing the methodology developed for that research. Temperature data
    were collected in representative spaces within the hospital, over a two-year period. These revealed
    overheating in mild conditions relative to an observed 24C threshold for sleep but concealed within
    the customary 28C threshold marking the upper limit of acceptable conditions. The building was modelled
    using current climate data to predict 2010 conditions. The model was then calibrated against the
    observed 2010 data and used to predict the likely internal temperatures in current and 2030s. The results
    indicated an increase in peak temperatures. Four adaptive intervention schemes were subsequently
    developed: an ‘enlightened’ industry standard ‘Passivhaus’-type option providing superinsulation, sealed
    glazing and heat recovery; a lower technology-based scheme promoting natural cross-ventilation by
    providing greater opening glazing area, opening up the plan, sunshading and additional insulation; an
    enhanced natural ventilation scheme glazing over the courtyards to provide supply air winter gardens,
    and an advanced natural ventilation option pursuing passive downdraught cooling. All four schemes were
    modelled using the projected current and 2030s weather data and their performance was compared. The
    schemes were fully costed to yield relative ‘value for money’ guidance to National Health Service Trusts.
    Practical application: The Heat wave Plan for England 2014 warns National Health Service (NHS)
    organisations of the risks to patients, particularly the very young, the elderly and the seriously ill, from
    extreme summer heat events.1 The Chief Medical Officer in her introduction challenges each NHS locality
    to plan well in advance of hot spells, as appropriate. This paper describes the likely extent of overheating
    risk and a series of potential adaptation plans for a recurring NHS hospital building type. As a consequence,
    estates and facilities decision makers in NHS organisations and Public Health England officers charged with the mitigation of risk resulting from overheating of wards and clinical spaces will benefit directly in their necessary decision making from the findings. Policy makers in the Department of Health and policy advisors in the NHS Sustainable Development Unit and the Climate Change Committee Adaptation Sub-Committee will benefit from the evidence presented in advising the NHS and
    Department of Health.
  • Kolokotroni, M., Gowreesunker, B. and Giridharan, R. (2013). Cool roof technology in London: An experimental and modelling study. Energy and Buildings [Online] 67:658-667. Available at: http://dx.doi.org/10.1016/j.enbuild.2011.07.011.
    One of the primary reasons for the application of cool materials is their energy and associated environmental impact on the built environment. Cool materials are usually applied on the roof of buildings to reduce cooling energy demand. The relative benefits of this reduction depend on the construction of the building, external weather conditions and use of the building. This paper examines the impact from the application of a reflective paint on a flat roof in a naturally ventilated office building in the area of London, UK where the climate is moderate with high heating demand by buildings. The environmental conditions (internal/external air and surface temperatures) of the building were monitored before and after the application of the cool roof during the summer. It was found that internal temperatures were reduced after the application of the cool roof. The building was modelled using TRNSYS and the model was calibrated successfully using the measurements. A parametric analysis was carried out by varying the reflectivity and insulation of the roof and ventilation rate; the heating and cooling demand for a year was calculated using the Summer Design Year for London as the weather file. It was found that cooling demand is significantly reduced, heating demand is increased and the total energy savings vary between 1 and 8.5% relative to an albedo of 0.1 for the same conditions. In free floating (naturally ventilated) buildings summer comfort is improved but there is a penalty of increased heating energy during the winter. Thermal comfort can be improved by an average of 2.5 °C (operative temperature difference for a change of 0.5 in albedo) but heating demand could be increased by 10% for a ventilation rate of 2 air changes per hour. The results indicate that in the case of temperate climates the type, operation and thermal characteristics of the building should be considered carefully to determine potential benefits of the application of cool roof technology. For the examined case-study, it was found that a roof reflectivity of 0.6–0.7 is the optimum value to achieve energy savings in a cooled office, improve summer internal thermal conditions in a non-cooled office (albeit with some heating energy penalty). It indicates that it is a suitable strategy for refurbishment of existing offices to improve energy efficiency or internal environmental conditions in the summer and should be considered in the design of new offices together with other passive energy efficient strategies.
  • Maciel, C. et al. (2013). The impact of surface characteristics on ambient temperature at urban micro scale: comparative field study in two climates. International Journal of Low-Carbon Technologies [Online] 10:165-175. Available at: http://dx.doi.org/10.1093/ijlct/ctt016.
    This paper presents the results of two field studies to examine the differences in ambient temperatures in a micro-scale environment (at distances of 50–200 m between measuring points) in two different climates during typical summer weather conditions at two similar sites in terms of construction and activities. The analysis considered the land use around the measuring locations split into three categories (built, green and open) as well as climatic conditions and studied the effect of these on ambient temperature at each measuring location. It was found that, similarly to macro-scale studies at the urban level, measuring locations with a higher green cover have a lower ambient temperature compared with measuring locations with a higher built and/or open land cover. The results provide measured evidence in two different climates that small green areas distributed within the urban environment can provide a reduction in the ambient temperature thus contributing to the mitigation of urban heat island.
  • Giridharan, R. et al. (2013). Performance of hospital spaces in summer: A case study of a ‘Nucleus’-type hospital in the UK Midlands. Energy and Buildings [Online] 66:315-328. Available at: http://dx.doi.org/10.1016/j.enbuild.2013.07.001.
    Nucleus-type Hospital in Glenfield comprises connected cruciform blocks with numerous small courtyards between. The hospital has mechanical ventilation and perimeter heating. The wards have a hybrid ventilation strategy with a low rate of mechanical ventilation. Ventilation through windows is the main source of summer time cooling. This paper investigates the summer time performance of spaces that are mechanically ventilated but passively cooled. The paper presents the measured indoor temperatures in selected hospital spaces and compares them with thermal comfort criteria. Finally, future summer conditions for the ward space are predicted using a calibrated multi zone dynamic thermal model.

    During June to September 2010, the maximum indoor temperatures in the case study spaces varied between 27.3 °C and 29.3 °C. The nurse station was found to be the hottest area. During this period the performance of most of the monitored spaces was reasonably within the thermal comfort threshold as defined by HTM03-01. The simulation results demonstrate that light-touch low carbon interventions could produce comfortable conditions in bedrooms into the 2050s in UK Midlands.
  • Short, C. et al. (2012). Building resilience to overheating into 1960's UK hospital buildings within the constraint of the national carbon reduction target: Adaptive strategies. Building and Environment [Online] 55:73-95. Available at: http://dx.doi.org/10.1016/j.buildenv.2012.02.031.
    The National Health Service (NHS) Estate in England includes 18.83 Mm2 of acute hospital accommodation, distributed across 330 sites. Vulnerability to overheating is clear with 15,000 excess deaths occurring nationally during the July 2003 heatwave. The installation of mechanical cooling in existing hospitals appears to be the inevitable recommendation from NHS patient safety risk assessments but the carbon implications would undermine the NHS Carbon Reduction Strategy. NHS CO2 emissions constitute 25% of all public sector emissions, equivalent to 3% of the UK total. In the post-2008 economic climate, the likelihood of wholesale replacement of the NHS Estate is significantly diminished; refurbishment is now of increasing interest to the Trusts that together make up the NHS. The research project ‘Design and Delivery of Robust Hospital Environments in a Changing Climate’ seeks to understand the environmental performance of the current NHS Estate and, from this, to establish its resilience. To this end, hospital buildings operated by four NHS Trusts are being monitored and simulated using dynamic thermal models calibrated against measured data. Adaptive refurbishment options are proposed and their relative performance predicted against the existing internal conditions, energy demands and CO2 emissions. This paper presents findings relating to one representative type building, a medium-rise ward block dating from the late 1960s. It shows that this particular type may have more resilience in the current climate than might have been expected, that it will remain resilient into the 2030s, and that relatively non-invasive measures would extend and increase its resilience whilst saving energy
  • Lomas, K. et al. (2012). Resilience of 'Nightingale' hospital wards in a changing climate. Building Services Engineering Research and Technology [Online] 33:81-103. Available at: http://dx.doi.org/10.1177/0143624411432012.
    The National Health Service (NHS) Estate in England comprises more than 30?Mm2 with 18.83?Mm2 of acute hospital accommodation on 330 sites. There is concern about the resilience of these buildings in a changing climate, informed by the experience of recent heatwaves. However, the widespread installation of air conditioning would disrupt the achievement of ambitious energy reduction targets. The research project ‘Design and Delivery of Robust Hospital Environments in a Changing Climate’ is attempting to estimate the resilience of the NHS Estate on the basis of current and projected performance, using an adaptive comfort model. This paper presents results relating to a 1920s traditionally built block with open ‘Nightingale’ wards, a representative type. The paper demonstrates the relative resilience of the type, and illustrates a series of light-touch measures that may increase resilience while saving energy.
  • Lomas, K. and Giridharan, R. (2012). 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 [Online] 55:57-72. Available at: http://dx.doi.org/10.1016/j.buildenv.2011.12.006.
    In view of the warming climate, there is increasing concern about the likelihood of overheating inside UK buildings that are not mechanically cooled. A number of studies are examining this matter, of which the DeDeRHECC project is one. The recent availability of the UKCP09 future climate data projections has acted as a stimulus to such work. This paper illustrates how field measurement, thermal modelling and the generation of current and future typical and extreme weather years, can be used to provide a picture of the resilience of buildings to climate change. The unified framework for assessing both measurements and current and future predictions that is offered by the BSEN15251 thermal comfort standard is a crucial component. The paper focuses on internal temperatures during the day and at night in wards within the tower building at Addenbrooke’s hospital, which has a hybrid ventilation strategy. The maintenance of thermal comfort in such spaces is critically important and installing air-conditioning in response to climate change is expensive and potentially energy intensive. Fans appear to be a simple retrofit measure that may substantially improve the wards’ resilience to climate change even in extreme years. Whilst healthcare provides the back cloth, the methodology developed has a much wider utility for assessing thermal comfort in buildings in the current and future climate of the UK.
  • Mavrogianni, A. et al. (2011). The comfort, energy and health implications of London's urban heat island. Building Services Engineering Research and Technology [Online] 32:35-52. Available at: http://dx.doi.org/10.1177/0143624410394530.
    The urban heat island (UHI) is a well-known effect of urbanisation and is particularly
    important in world megacities. Overheating in such cities is expected to be exacerbated in
    the future as a result of further urban growth and climate change. Demonstrating and
    quantifying the impact of individual design interventions on the UHI is currently difficult
    using available software tools. The tools developed in the LUCID (‘The Development of a
    Local Urban Climate Model and its Application to the Intelligent Design of Cities’) research
    project will enable the related impacts to be better understood, quantified and addressed.
    This article summarises the relevant literature and reports on the ongoing work of the
    project.
    Practical applications: There is a complex relationship between built form, urban
    processes, local temperature, comfort, energy use and health. The UHI effect is significant
    and there is a growing recognition of this issue. Developers and planners are seeking advice
    on design decisions at a variety of scales based on scientifically robust, quantitative
    methods. The LUCID project has thus developed a series of tools that (1) quantify the effect
    of urbanisation processes on local environmental conditions, and (2) quantify the impact of
    such conditions on comfort, energy use and health. The use of such tools is vital, both to
    inform policy but also to be able to demonstrate compliance with it.
  • Kolokotroni, M., Zhang, Y. and Giridharan, R. (2009). Heating and cooling degree day prediction within the London urban heat island area. Building Services Engineering Research and Technology [Online] 30:183-202. Available at: http://dx.doi.org/10.1177/0143624409104733.
    This paper describes the London Site Specific Air Temperature prediction model, which comprises of a suite of artificial neural network (ANN) models to predict site-specific hourly air temperature within the Greater London Area (GLA). The model was developed using a back-propagation ANN model based on hourly air temperature measurements at 77 fixed temperature stations (FTS) and hourly meteorological data (off-site variables) from Heathrow; it also includes six on-site variables calculated for each FTS. The temporal and spatial validity of the model was tested using data measured 7 years later from the original dataset, which include new FTS locations. It was found that site-specific hourly air temperature prediction is within accepted range and improves considerably for average daily and monthly values. Therefore, the model can be used with confidence to predict daily and seasonal variations of air temperature within the GLA and in particular for the calculation of monthly and annual heating degree days (HDD) and cooling degree hours (CDH). It was found that as expected HDD increase and CDH decrease with distance from the urban heat island centre point; however, all variations cannot be explained with distance and six key on-site variables namely aspect ratio, surface albedo, plan density ratio, green density ratio, fabric density ratio and thermal mass have been identified to explain the remaining variation.
    Practical applications: Research studies have confirmed the extent of Urban Heat Island (UHI) within many cities in Europe. Studies have also confirmed the impact of the UHI on energy demand by buildings. There is therefore need to consider this in the design of building by using site-specific external temperatures in the energy calculations for urban buildings. This paper describes the development of a model, which can generate site-specific air temperature in a large number of locations in London. The model's predictions can be used for the calculation of HDD and CDH for any base temperature across London using any Heathrow weather file for a specific year, design years or future climate years; such values can be used for the calculation of site specific building heating and cooling loads.
  • Giridharan, R. and Kolokotroni, M. (2009). Urban heat island characteristics in London during winter. Solar Energy [Online] 83:1668-1682. Available at: http://dx.doi.org/10.1016/j.solener.2009.06.007.
    This paper presents results characterising the urban heat island intensity (UHI) in London during the peak winter season. Most UHI studies focus on the phenomenon during the summer as this is the period when temperature peaks are observed. However, for urban planning mitigation strategies and building energy demand design, the heating season should be also considered, since proposed measures to alleviate the summer UHI might have a negative effect during the winter or intermediate seasons.

    The study carries out trend and regression analysis by controlling climatic and geographical variations in the data set following a methodology developed for studying summer UHI [Kolokotroni, M., Giridharan, R., 2008. Urban heat island intensity in London: an investigation of the impact of physical characteristics on changes in outdoor air temperature during summer. Solar Energy 82, 986–998]. It was found that average nocturnal UHI of winter periods are of similar magnitude to the summer periods but the peak winter UHI trends are not as regular as summer giving a first indication that the effect of climate and urban parameters is different. The regression analysis in this research uses six on-site variables namely aspect ratio, surface albedo, plan density ratio, green density ratio, fabric density ratio and thermal mass to carry out impact investigation in six data sets, categorised by three geographical location within London and three sky conditions and regional wind velocity. The above variables do not explain the changes in outdoor temperature as much as they did during summer period models. However, unlike summer, the winter climate control models have the same R2 indicating that most of changes in outdoor temperature are caused by climate factors and not the on-site variables.
  • Giridharan, R. et al. (2008). Lowering the outdoor temperature in high-rise high-density residential developments of coastal Hong Kong: The vegetation influence. Building and Environment [Online] 43:1583-1595. Available at: http://dx.doi.org/10.1016/j.buildenv.2007.10.003.
    This paper investigates the impact of on-site variables on the influence of vegetation in lowering outdoor temperature. The study uses six critical on-site variables such as surface albedo, sky view factor, altitude, shrub cover, tree cover and average height to floor area ratio to carry out analysis in five data sets. The climatic parameters and physical characteristics were measured and surveyed, respectively in 216 stations in high-rise high-density residential developments of coastal Hong Kong. The data set is mainly categorised into peak summer clear sky days (PSCS-days), peak summer partially cloudy days (PSPC-days) and late summer days to address the issues related to cloudy sky conditions in Hong Kong. The trend analysis shows that at a lower sky view factor, ranging from 0.1 to 0.25, shrub cover as low as 10–15% in a 1000 m2 open area is more effective in reducing outdoor temperature than the same level of tree cover in a location with a higher sky view factor (0.4 or above). The regression models used in this study were able to explain the influence of on-site variables on vegetation in lowering the outdoor temperature within the respective urban settings. In high-rise high-density environments, on-site variables such as sky view factor and altitude have a substantial impact on the influence of vegetation in lowering outdoor temperature. However, off-site variables such as high urban density and anthropogenic heat could negate the behaviour of sky view factor and altitude. The study suggests that increasing the tree cover from 25% to 40% in the pocket parks in coastal area residential developments of Hong Kong could reduce daytime urban heat island intensity (UHI) by further 0.5 °C.
  • Kolokotroni, M. and Giridharan, R. (2008). Urban heat island intensity in London: An investigation of the impact of physical characteristics on changes in outdoor air temperature during summer. Solar Energy [Online] 82:986-998. Available at: http://doi.org/10.1016/j.solener.2008.05.004.
    The study looks at the potential of physical characteristics in mitigating the urban heat island intensity (UHI) in London during summer. This research uses six on-site variables namely aspect ratio, surface albedo, plan density ratio, green density ratio, fabric density ratio and thermal mass for the investigation in six data sets. The climatic variations in summer are controlled by classifying the data into clear sky, partially cloudy and cloudy periods. Geographical variation is controlled by classifying the data into core, urban and semi urban areas. Maximum daytime UHI of 8.9 °C is found in semi-urban area during partially cloudy period while maximum nocturnal UHI of 8.6 °C is found in urban area during clear sky period when the wind velocity is below 5 m/s. The most critical climate and geographical location in determining the changes in outdoor air temperature in London are partially cloudy periods and urban areas respectively. Among the variables studied, most critical variable that determines the daytime and nocturnal changes in outdoor air temperature is surface albedo.
  • Giridharan, R. et al. (2007). Urban design factors influencing heat island intensity in high-rise high-density environments of Hong Kong. Building and Environment [Online] 42:3669-3684. Available at: http://doi.org/10.1016/j.buildenv.2006.09.011.
    Previous research on Urban Heat Island Intensity (UHI) in Hong Kong was limited to 4 weeks of field measurements during the summer in 3 major coastal housing estates. The current study extends this work to 6 months enveloping 3 “seasons” and 7 different locations within the coastal area. Variations in UHI in the range ?1.3 ° to 3.4 °C were recorded. The study reveals seasonal changes are in general more influential on UHI than changes due to geographical characteristics. Among the seasonal models, the peak summer clear sky day's daytime and nocturnal models examined separately were found to provide the clearest indicators of the impact of urban design variables on UHI with R2value of 0.7 and 0.8, respectively. Sky view factor, surface albedo, altitude, vegetation above 1 m in height, average height to floor area ratio, location quotient and proximity to sea are critical variables in mitigating both daytime and nocturnal UHI. Combining daytime and nocturnal data dilutes the impact of extreme values on UHI, by up to 50%, and is not useful for design solutions. Ideally design solutions may respond to the adverse impacts recorded in peak summer clear sky daytime at the concept design stage, and then have the design manipulated and validated for other seasons.
  • Giridharan, R., Lau, S. and Ganesan, S. (2005). Nocturnal heat island effect in urban residential developments of Hong Kong. Energy and Buildings [Online] 37:964-971. Available at: http://dx.doi.org/10.1016/j.enbuild.2004.12.005.
    In hot humid climate, mitigating summer time nocturnal Urban Heat Island (UHI) effect is important in order to reduce the space-conditioning cost. Case studies of Belchers, Wah Fu-1 and -2 reveal the maximum nocturnal UHI in the order of 1.3 °C within an estate, and 0.4 °C between estates. The variables such as surface albedo, height-to-floor area ratio, sky view factor (SVF) and altitude are capable of explaining the nocturnal UHI in the case study areas with an explanatory power of 0.8. Although, during summer, the nocturnal UHI intensity is low relative to daytime UHI, thermal distress is high in night especially in Wah Fu-1 and -2. The paper will discuss the influence of the design variables on nocturnal UHI and its significance in relation to daytime UHI in the case study areas.
  • Lau, S., Giridharan, R. and Ganesan, S. (2005). Multiple and intensive land use: case studies in Hong Kong. Habitat International [Online] 29:527-546. Available at: http://doi.org/10.1016/j.habitatint.2004.04.007.
    Multiple Intensive Land Use (MILU) achieves intensification of land use through mixing residential, commercial and other uses at higher densities at selected urban locations, while being supported by an efficient public transport and pedestrian network. Successful case studies in Hong Kong have more than five uses, i.e. Residential, Commercial, Recreational, Community facilities and Transport facilities. The residential component in these projects is usually between 30% and 65% of the total gross floor area. The MILU concept is being implemented in subsidized public housing projects as well. Multiple land uses within the podium, together with access to five or more modes of public transport and an accessible network of multilevel pedestrian links create the necessary variety, vitality and viability. The paper examines three different generations of MILU fabric and discusses the integrating design variables, while focusing on the life style and design approaches of Hong Kong
  • Giridharan, R., Ganesan, S. and Lau, S. (2004). Daytime urban heat island effect in high-rise and high-density residential developments in Hong Kong. Energy and Buildings [Online] 36:525-534. Available at: http://doi.org/10.1016/j.enbuild.2003.12.016.
    Nearly 60% of electrical energy use in Hong Kong is for space conditioning during summer months. The paper investigates the impact of design-related variables on outdoor micro level daytime heat island effect in residential developments in HongKong. The paper hypothesizes that the differences in outdoor temperatures within and between residential developments can be explained by the impact of design-related variables on the overall environment. Case studies of three large housing estates reveal urban heat island effect (UHI) in the order of 1.5 ?C within an estate, and 1.0 ?C between estates. The results indicate that energy efficient designs can be achieved by manipulating surface albedo, sky view factor and total height to floor area ratio (building massing) while maximizing cross ventilation.
  • Lau, S., Giridharan, R. and Ganesan, S. (2003). Policies for implementing multiple intensive land use in Hong Kong. Journal of Housing and the Built Environment [Online] 18:365-378. Available at: http://dx.doi.org/10.1023/B:JOHO.0000005758.41003.19.
    The entire Hong Kong SAR acts as a network of primary, secondary and tertiary Multiple Intensive Land Use (MILU) zones linked by relatively cheap and speedy public transport. The MILU forms of Hong Kong have been developed as an efficient design response within a small city-state to population growth and shortages of buildable land. However, planning guidelines and development control instruments and policies have promoted public and private sector cooperation and achieved a high degree of integration of residential, commercial and other uses. This paper discusses the design approaches in Hong Kong and examines the basic characteristics of the Hong Kong model of mixed-use development, planning mechanism and relevant policies.

Book section

  • Giridharan, R. (2016). Urban Climate Modelling: Challenges in the Tropics. in: Emmanuel, R. ed. Urban Climate Challenges in the Tropics. World Scientific / Imperial College Press. Available at: http://www.worldscientific.com/worldscibooks/10.1142/p1048.
    Among the places worst hit by climate change are areas of high urban growth in the warm, humid tropics of Asia and Latin America. In these places, the global trend of rapid urbanisation and conditions of local warming compound the effects of climate change.

    This three-part book explores the unique local climate consequences of urban growth trajectories of tropical cities and provides strategies and design approaches to enhance the quality of life of tropical urban dwellers in the face of urban warming. Part One considers the philosophical basis of the climate challenge in this context and investigates tropical urbanism from the viewpoints of urban activity patterns and the notion of 'thermal pleasure'. Part Two explores specific, practical techniques in enhancing ventilation, shading and greenery as well as the challenges in local climate assessment in the tropics. Part Three explores the barriers and future opportunities for climate-sensitive urban planning and presents specific examples of good practice, contextualized within the wider global debate on adapting to climate change. Urban Climate Challenges in the Tropics is an indispensable companion for planners, designers, architects and students of all levels.
  • Lau, S., Wang, J. and Giridharan, R. (2005). Smart and sustainable city- A case study from Hong Kong. in: Yang, J., Brandon, P. S. and Sidwell, A. C. eds. Smart and Sustainable Built Environment. USA: Wiley-Blackwell, pp. 33-42.
    This book brings together a group of international specialists to explore the current state of the art and future potential for encouraging, developing and implementing smart and sustainable built environment strategies.
    It covers a broad spectrum of issues, ranging from technological advancement, through the assessment of past experiences, to communication and education requirements and future strategies.

    - provides a snapshot of current methods and technologies for developing smart and sustainable built environment strategi
    - over 30 fully refereed chapters from international experts
    - addresses the particular requirements and problems of difference areas and climatic regions
  • Lau, S., Wang, J. and Giridharan, R. (2005). High-density, High-rise and Multiple Intensive Landuse in Hong Kong: A future forms and design for sustainable cities. in: Jenks, M. and Dempsey, N. eds. Future forms and designs for sustainable cities. Routledge.

Conference or workshop item

  • Giridharan, R. (2017). Heat stress in hospital ward spaces: An investigation on a naturally ventilated hospital building in UK. in: Passive Low Energy Architecture 2017 (PLEA). pp. 3762-3769. Available at: https://plea2017.net/#programmes-container.
    In the context of climate change, there is increasing concern about the likelihood of overheating in hospitals in UK, especially in buildings which are not mechanically cooled. A number of studies have examined this issue in different hospitals in UK. On most occasions these studies have focused on overheating and evaluated the performance of the spaces using adaptive thermal comfort criteria. Adaptive criteria is not a good indicator of actual heat stress. Further, the adaptive criteria cannot be applied to spaces that have no operable windows. However, in hospital, substantial number of spaces are without windows, especially nurse stations. This paper will assess the heat stress in ward spaces using Wet Bulb Globe Temperature (WBGT) heat index in order to explain the occupant’s vulnerability while looking at the potential of combining this index with adaptive thermal comfort criteria (BSEN15251). The paper will focus on naturally ventilated Runcie ward building at St Albans city hospital and assess its thermal performance for summer 2011. During summer 2011, the maximum WBGT varies between 21.5?C and 23.8?C while the minimum was between 13.6?C and 14.3?C. The paper proposes WBGT of 23?C as a heat stress threshold for sick and vulnerable.
  • Victoria, G. and Giridharan, R. (2017). Soft Landings Driven Design Management process: Achieving sustainability in a school building in the UK. in: Passive Low Energy Architecture 2017 (PLEA).. Available at: https://plea2017.net/#programmes-container.
    One of the challenges facing the industry is closing the energy performance gap in non-residential buildings. Despite various recommendations and introduction of new technology, the problem remains widespread. Debate on how designers and architects can contribute to finding solutions to this problem continues. Soft Landings has been on the forefront of encouraging the delivery of buildings where estimated energy targets align with actual targets. This paper investigates the working processes of a Soft Landings design team; using Interviews, walk-throughs and contract documentation of the project. The paper explores the design management side in a Soft Landings process. How end users and sub-contractors were involved during the design stage of the project and how decisions taken affected the outcome of the project. The study discovers that learning from past projects plays an important role for new projects in achieving their goals with respect to energy efficiency and sustainability. Participation of the end users need to be coordinated to maximise their advantage without sacrificing time and cost. Additionally, practical implications are presented for architects about the involvement of end users in a Soft Landings project.
  • Watkins, R. et al. (2015). The Performance of Natural Ventilation In A Dance Studio – Lessons From Tracer Gas Measurements And Control Integration. in: 31st International PLEA Conference, Passive Low Energy Architecture.
    The naturally ventilated, three storey School of Arts Jarman Building provides two dance studios, an exhibition gallery, teaching rooms, video editing suites and offices. The main dance studio is double-height, has underfloor heating and accommodates sixty people. Fresh air enters from low level perimeter louvres and exits at high level through a stack that rises through the third storey to a stack terminal with motorized louvres. Tracer gas (CO2) measurements were used to measure the ventilation rate in conjunction with hot-wire anemometry in the stack tower. The results showed that when all air inlet and exit louvres were set to closed, the residual air flow up the stack was 0.33m3/s representing a potential heat loss of 9kW in winter at 0°C outside. When the louvres were all open, the air flow increased to between 0.49 and 0.62m3/s, a level consistent with the studio’s design occupancy. It was found that the studio’s 4m high perimeter curtains represent a barrier to fresh air entering the main room space and cause the incoming air to migrate upwards towards the stack exit and effectively bypass the central part of the studio. Tracer gas decay rates showed that the main space experienced an air exchange rate 50% less than that for the overall studio. An investigation of the controls also revealed that the underfloor heating system operated independently of the control of the stack ventilation system, leading to simultaneous heating and venting. The research shows the vital importance of prescribing contractually that key controls are integrated, that fresh air dampers are well-sealed when closed, and the importance of designing a fresh air supply that matches the way a space is used.
  • Kolokotroni, M. and Giridharan, R. (2010). The significant of urban heat island within and between geographical zones of London. in: 3rd International Conference on Passive and Low Energy Cooling for the built Environment (PALENC) - 2010.
  • Giridharan, R. and Kolokotroni, M. (2008). Daytime urban heat island in London during winter season. in: Passive and Low Energy Architecture conference 2008.
  • Giridharan, R., Ganesan, S. and Lau, S. (2006). Impact of on-site variables on the influence of vegetation in lowering outdoor temperature in high rise high density environmnets. in: Passive and Low Energy Architecture Conference 2006.
  • Giridharan, R., Ganesan, S. and Lau, S. (2004). Nocturnal heat island effect in urban residential development of Hong Kong. in: Sustainable Communities Conference 2004.

Forthcoming

  • Coorey, S. et al. (2017). Thermal Comfort Study in Post Disaster Housing in the Southern Coast of Sri Lanka. University of Moratuwa.
    The Indian Ocean Tsunami in 2004 had a great impact on the local land formation, vegetation and settlement patterns in Sri Lanka. The re-housing developed to settle the displaced people were carried out in mass scale over a period of two to three years. By and large the criteria for re-settlement had little or no consideration for thermal comfort and climate change. This study was conducted with the aim of identifying the features in the building that causes overheating and features that has the potential to mitigate overheating.
    A thermal comfort field survey was conducted in selected house types in Boosa and Dadella in Galle, Madihe in Matara and Kirinda in Tissamaharama during the months that presented the most extreme climate conditions during the year. The physical characteristics of thirteen houses were explored; indoor thermal conditions were monitored with the aim of assessing the overall thermal performance of the houses.
    Findings showed the need to start at the neighbourhood level and the importance of the building envelope in achieving thermal comfort. Implications for design focus on guidelines for controlling the negative effects of the microclimate into the interior habitable spaces, together with the need for prescriptive thresholds for the building envelope.
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