Cool roof technology in London: An experimental and modelling study

This is the post-print version of the final paper published in Journal of Energy and Buildings. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2011 Elsevier B.V.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.Intelligent Energy Europe (IEE

The Performance of Natural Ventilation In A Dance Studio – Lessons From Tracer Gas Measurements And Control Integration

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

The influence of hospital ward design on resilience to heat waves: An exploration using distributed lag models

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 ris

The impact of urban compactness, comfort strategies and energy consumption on tropical urban heat island intensity: a review

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

Assessing heat stress in hospital wards using Wet Bulb Globe temperature: A case study in Mediterranean climate

In the context of climate change, there is increasing concern about the likelihood of overheating in hospitals. The aim of this paper is to investigate the heat stress exposure through the Wet Bulb Globe Temperature (WBGT) heat index in four different rooms of the 1st Internal Medicine Department of the American Hellenic Educational Progressive Association (AHEPA) hospital located in Thessaloniki, Greece. In hospital environments patients usually have restricted adaptive opportunity. Thus, the need for an indoor heat-safety metric is imperative. This study proposes thresholds of 24oC and 26oC to assess critical ward spaces as these are the initial warning points for nighttime thermal discomfort of healthy individuals in ‘normal’ environments. In this context, the internal temperatures measured in the patients’ rooms were plotted against the indoor WBGT thresholds for a low wind velocity of 0.1m/sec. Between the 13th and the 22th of June 2017 the most extreme temperatures were recorded in room 3, while the mildest conditions occurred in room 1. WBGT ranged between 19⁰C and 25.46⁰C. The recorded WBGT in three rooms exceeded the threshold of 24oC for approximately one-third of the time, while in one room it was marginally below the proposed threshold

Bovine Model of Doxorubicin-Induced Cardiomyopathy

Left ventricular assist devices (LVADs) constitute a recent advance in heart failure (HF) therapeutics. As the rigorous experimental assessment of LVADs in HF requires large animal models, our objective was to develop a bovine model of cardiomyopathy. Male calves (n = 8) were used. Four animals received 1.2 mg/kg intravenous doxorubicin weekly for seven weeks and four separate animals were studied as controls. Doxorubicin-treated animals were followed with weekly echocardiography. Target LV dysfunction was defined as an ejection fraction ≤35%. Sixty days after initiating doxorubicin, a terminal study was performed to determine hemodynamic, histological, biochemical, and molecular parameters. All four doxorubicin-treated animals exhibited significant (P < 0.05) contractile dysfunction, with target LV dysfunction achieved in three animals. Doxorubicin-treated hearts exhibited significantly reduced coronary blood flow and interstitial fibrosis and significantly increased apoptosis and myocyte size. Gene expression of atrial natriuretic factor increased more than 3-fold. Plasma norepinephrine and epinephrine levels were significantly increased early and late during the development of cardiomyopathy, respectively. We conclude that sequential administration of intravenous doxorubicin in calves induces a cardiomyopathy with many phenotypic hallmarks of the failing human heart. This clinically-relevant model may be useful for testing pathophysiologic responses to LVADs in the context of HF

Neurochemical Effects of Sepsis on the Brain

Sepsis is a life-threatening organ dysfunction triggered by a dysregulated host immune response to eliminate an infection. After the host immune response is activated, a complex, dynamic, and time-dependent process is triggered. This process promotes the production of inflammatory mediators, including acute-phase proteins, complement system proteins, cytokines, chemokines, and antimicrobial peptides, which are required to initiate an inflammatory environment for eliminating the invading pathogen. The physiological response of this sepsis-induced systemic inflammation can affect blood-brain barrier (BBB) function; subsequently, endothelial cells produce inflammatory mediators, including cytokines, chemokines, and matrix metalloproteinases (MMPs) that degrade tight junction (TJ) proteins and decrease BBB function. The resulting BBB permeability allows peripheral immune cells from the bloodstream to enter the brain, which then release a range of inflammatory mediators and activate glial cells. The activated microglia and astrocytes release reactive oxygen species (ROS), cytokines, chemokines, and neurochemicals, initiate mitochondrial dysfunction and neuronal damage, and exacerbate the inflammatory milieu in the brain. These changes trigger sepsis-associated encephalopathy (SAE), which has the potential to increase cognitive deterioration and susceptibility to cognitive decline later in life

Thermal Comfort Study in Post Disaster Housing in the Southern Coast of Sri Lanka

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

Case series: Pediatric Pineoblastoma (PNETs) - radiological, and clinicopathological studies

A rare type of brain tumor, pineoblastoma (PNET) is found in young adults and children. PNETs are rarest representing under 1% of all cerebrum cancers. The most common type of this type of tumor starts at the pineal glands, a small gland located at the base of the brain. Pineoblastomas make up approximately 50% of all pineal gland tumors. These tumors can be challenging to treat because of their location in the brain. The five-year endurance of patients of PNETs or pineoblastoma is around 50-60%. Infants and children who have had partial surgical removal and a poor response to radiation therapy have less favorable outcomes