Overheating

A warming climate, increasing frequency and severity of extreme heat events, and the heat island effect are cumulatively expected to exacerbate climate thermal loading on urban buildings. This in turn could lead to increased summertime overheating risk, with any active means for addressing this likely to influence future energy consumption and CO2 emission patterns. This paper examines how the microclimatic loading presented by the heat island (UHI) effect influences summertime adaptive comfort in traditional urban residential buildings. The method for addressing this utilises the novel approach of coupling a computationally efficient urban climate model with an established building energy model to simulate a residential street canyon within the London heat island. Key findings highlighted adaptive capabilities to achieve summertime ‘comfort’ in most rooms without the need for energy intensive mechanical cooling. The alternative of using indiscriminate and widespread mechanical cooling within the canyon length is estimated to result in a 0.4 K increase in nocturnal canyon temperatures, and an additional 4.4% of CO2 released to the climate. In contrast, a targeted approach of cooling rooms where adaptive capacity is insufficient more than halves the canyon CO2 emission estimate; which in turn highlights the necessity for detailed overheating assessments in managing energy use in such traditional residential neighbourhoods within UHIs.

A c c e p t e d M a n u s c r i p t Highlights We simulate demand of energy efficient house, focusing on influence of occupants. New complex view of occupant's influence on PE demand of the building is proposed. For simulations we used dynamic building energy simulation tool Design Builder. Various occupancy, lighting and HVAC system management scenarios were analysed. Realistic assumptions on occupants' characteristics raise the accuracy of results.

The article presents a verbal and mathematical model of medium-term business cycles (with a characteristic period of 7–11 years) known as Juglar cycles.
The model takes into account a number of approaches to the analysis of such cycles; in the meantime it also takes into account some of the authors' own generalizations and additions that are important for understanding the internal logic of the cycle, its variability and its peculiarities in the present-time conditions. The authors argue that the most important cause of cyclical crises stems from strong structural disproportions that develop during economic booms. These are not only disproportions between different economic sectors, but also disproportions between different societal subsystems; at present these are
also disproportions within the World System as a whole.
The proposed model of business cycle is based on its subdivision into four phases:
– recovery phase (which could be subdivided into the start sub-phase and the acceleration sub-phase);
– upswing/prosperity/expansion phase (which could be subdivided into the growth sub-phase and the boom/overheating sub-phase);
– recession phase (within which one may single out the crash/bust/acute crisis sub-phase and the downswing sub-phase);
– depression/stagnation phase (which we could subdivide into the stabilization sub-phase and the breakthrough sub-phase).
The article provides a detailed qualitative description of macroeconomic dynamics at all phases; it specifies driving forces of cyclical dynamics and
the causes of transition from one phase to another (including psychological causes); a special attention is paid to the turning point from the peak of over-heating to the acute crisis, as well as to the turning point from the downswing to recovery.
The proposed mathematical model of Juglar cycle takes into account the following effects that are typical for the market economy:
• positive feedbacks between various economic processes;
• presence of a certain inertia, time lags in reactions of the economic subsystem to the change in conditions;
• amplification by the financial subsystem of positive feedbacks and time lags in the economic subsystem;
• excessive reaction to changing conditions during the acute crisis sub-phase.
The authors suggest that the current crisis turns out to be rather similar to classical Juglar crises; however, there is also a significant difference, as the current crisis occurs at a truly global scale. Yet, due to this truly global scale of the current crisis, the possibilities of regulation with the national state's measures have turned out to be ineffective, whereas the suprastate regulation of financial processes hardly exists. It is shown that all these have led to the reproduction of the current crisis according to a classical Juglar scenario.

Extreme weather events, including heat waves, are predicted to increase in both frequency and severity over the coming decades. Low house building rates and a growing population mean there is a need to adapt existing dwellings. Research presented here uses dynamic thermal simulation to model the effect of passive heat wave mitigating interventions for UK dwellings. Interventions include a range of additions and modifications to solar shading, insulation and ventilation.

Building interiors daylighting is a crucial aspect for occupant comfort and energy efficiency. Standards and requirements exist to guarantee minimum levels of natural illumination in new buildings on the basis of different metrics. Some rely only on interiors static characteristics, others additionally take into account location climate. The main aim of the present study is to investigate the validity of the static Daylight Factor (DF) requirement of the Estonian daylight standard against more reliable climate-based daylight simulations using the approved method Spatial Daylight Autonomy. Results show the weakness of DF in predicting appropriate daylight availability of building interiors for the city of Tallinn. Evaluations of DF in relation to overheating regulation is also presented.

The Passivhaus strategy employs super insulation to reduce the heat transfer through the building envelope. It has been argued that super insulated homes are vulnerable to summer overheating risks, even in the current climate. The UK is expected to experience hotter and more extreme summers in the coming decades and the risk of buildings overheating may become very significant in future climate scenarios. The Passivhaus approach can use much of the solar energy from its relatively large glazing in south facade but this large glazing may eventually lead to overheating in summer time. The study used parametric design modelling to generate differently inclined facade geometries for south elevations. Each elevation was then simulated by means of dynamic building simulation software in order to examine to what extend inclined wall mitigate summer overheating risk for Passivhaus dwellings in the UK under alternative future weather projections.

Daylight is of interest in architecture for two reasons: On one
hand it is appreciated and requested to make the interiors of
buildings pleasant and comfortable and to save energy for
electric lighting and heating. On the other hand excessive
direct solar exposure can cause occupant discomfort and
harm the energy efficiency of buildings causing overheating
during the warm season. In Estonia, a daylight ordinance
establishes the minimum average Daylight Factor for
residential buildings and an energy efficiency ordinance sets
the maximum acceptable degree hours of overheating. The
two requirements are potentially conflicting. The recent
architectural trend in Estonia is to use very large windows in
residential building design. Even in the Estonian heating
dominated climate this causes overheating issues that lead to
the previously mentioned regulations. This paper explores
the relationship of opening ratios, daylighting and
overheating potential analyzing 7812 design variants taking
into account room, windows and external wall sizes,
presence of shading or balconies and different types of
ventilation. It is shown that the overheating potential can be
contained and both requirements can be satisfied only using
measures such as shading and ventilation.

In a changing climate there is increasing concern about the risk of overheating in UK buildings, particularly those with a low-carbon footprint which cannot rely on mechanical cooling. This gives rise to concern among building professionals about how overheating risk can best be assessed. Current Chartered Institution of Building Services Engineers (CIBSE) guidance uses a simple definition of overheating as the exceedance of 288 8 8 8 8C for more than 1% of occupied hours, based on simulations using weather files from a 'design summer year' (DSY). There is increasing evidence that this criterion is both insensitive and open to abuse. This paper uses field surveys of thermal (dis)comfort and the adaptive thinking behind the British and European Standard BS EN15251 to propose a new approach. It takes account of the effect of indoor and outdoor climate on the dissatisfaction of building occupants. An alternative definition of overheating in buildings is proposed, along with an approach to predicting the magnitude and/or frequency of occurrence of overheating in buildings.

Learning performance is strongly related to thermal comfort and lighting conditions
of classrooms. Poor facade design can result in high indoor temperatures or insufficient access
to natural light. To maintain the required temperatures and illuminance levels in such rooms may
require intensive use of artificial lighting and active cooling systems, which are energy-intensive,
costly to install, operate and maintain. The purpose of this study was to determine essential
parameters and facade design options that ensure overheating prevention and fulfil daylight
requirements in classrooms without mechanical cooling. The present study is based on
simulations of a parametric room model with variable dimensions and orientations. Facade
glazing solutions with optimal combination of solar factor and visible light transmittance were
used to minimize overheating risk and maximize natural lighting impact. For east, south and west
oriented facades, the effect of horizontal shading was also analysed. Overheating assessment
through indoor temperature simulations was conducted with dynamic simulation software IDA
ICE, daylighting was simulated with DIVA4 coupled with Grasshopper software. Results show
that classrooms without mechanical cooling require in depth analysis to determine satisfying
solutions for both overheating and daylighting criteria. The results of this paper can be used for
early stage facade design guide for school buildings or similar use free-running buildings.

The article presents a verbal and mathematical model of medium-term business cycles (with a characteristic period of 7–11 years) known as Juglar cycles. The model takes into account a number of approaches to the analysis of such cycles; in the meantime it also takes into account some of the authors' own generalizations and additions that are important for understanding the internal logic of the cycle, its variability and its peculiarities in the present-time conditions. The authors argue that the most important cause of cyclical crises stems from strong structural disproportions that develop during economic booms. These are not only disproportions between different economic sectors, but also disproportions between different societal subsystems; at present these are also disproportions within the World System as a whole.
The proposed model of business cycle is based on its subdivision into four phases:
– recovery phase (which could be subdivided into the start sub-phase and the acceleration sub-phase);
– upswing/prosperity/expansion phase (which could be subdivided into the growth sub-phase and the boom/overheating sub-phase);
– recession phase (within which one may single out the crash/bust/acute crisis sub-phase and the downswing sub-phase);
– depression/stagnation phase (which we could subdivide into the stabilization sub-phase and the breakthrough sub-phase).
The article provides a detailed qualitative description of macroeconomic dynamics at all the phases; it specifies driving forces of cyclical dynamics and the causes of transition from one phase to another (including psychological causes); a special attention is paid to the turning point from the peak of overheating to the acute crisis, as well as to the turning point from the downswing to recovery.
The proposed mathematical model of Juglar cycle takes into account the following effects that are typical for the market economy:
•positive feedbacks between various economic processes;
•presence of a certain inertia, time lags in reactions of the economic subsystem to the change in conditions;
•amplification by the financial subsystem of positive feedbacks and time lags in the economic subsystem;
•excessive reaction to changing conditions during the acute crisis sub-phase.
The authors suggest that the current crisis turns out to be rather similar to classical Jug-lar crises; however, there is also a significant difference, as the current crisis occurs at
a truly global scale. Yet, due to this truly global scale of the current crisis, the possibilities of regulation with the national state's measures have turned out to be ineffective, whereas the suprastate regulation of financial processes hardly exists. It is shown that all these have led to the reproduction of the current crisis according to a classical Juglar scenario.

This paper presents one of the first national scale studies of summertime temperatures in English dwellings. Living room and bedroom temperatures were recorded in 207 homes across the England during the cool summer of 2007. Data was also collected by face-to-face household interviews. Fourteen homes (7%) were observed to be heated for part or all of the analysis period (July to August). Based on the BSEN15251 adaptive thermal comfort model, the 193 free-running dwellings would, in general, to be considered as uncomfortably cool. Over 72% of living rooms and bedrooms had more than 5% of hours below the BSEN15251 Cat II lower threshold, with over 50% having more than 5% of hours below the Cat III threshold. Detached homes and those built before 1919 were significantly cooler (p < 0.05) than those of other type and age. Static criteria revealed that, despite the cool summer, 21% of the bedrooms had more than 5% of night time hours over 26 C; which is a recommended upper limit for bedrooms. The bedrooms of modern homes, i.e. those built after 1990 or with cavity walls, were significantly warmer (p < 0.05). The bedrooms in homes built prior to 1919 were significantly cooler (p < 0.05). The living rooms of flats were significantly warmer than the living rooms in the other dwelling types (p < 0.05). The incidence of warm bedrooms in modern homes, even during a cool summer, is of concern, especially as there is a strong trend towards even better insulation standards in new homes and the energy-efficient retrofitting of existing homes.

The main reason for the existence of superalloys is their outstanding strength at high temperatures, which make them suitable for the fabrication of gas turbine components. Contributing factors are the high modulus of their close packed FCC lattice and the presence of elements, like aluminum and titanium, which enable the formation of c 0 phase, Ni 3 (Al,Ti), that dispersed in the c matrix has a hardening effect. The presence of chromium is essential to guarantee oxidation resistance and other alloying elements are important to impart high-temperature strength. Carbon content is usually sufficient to allow the formation of carbides which improve creep resistance. In this work, two failure cases of nickel base superalloy components were analyzed by scanning electron microscopy (SEM). The microstructural aspects provided sufficient evidences to conclude that, in the first case overheating led to failure and in the second case the significant microstructural degradation of the surface can lead to failure.

European Building Codes have transitioned towards Net Zero Energy Building (NZEB) requirements in new constructions, demanding high levels of insulation and airtightness derived from research and standards developed in Northern and Central Europe. The use of these principles in Southern Europe, where solar radiation is greater and building typologies and user behaviour are different, may have had a negative impact in Thermal Comfort and Energy Demand and Consumption. In this study, six dwellings located in a 2018 27-storey Passivhaus-certified building were monitored for a period of 9-18 months in 2019 and 2020. In the spirit of a complete Post-Occupancy Evaluation, a User Comfort Survey was carried out. The obtained data were analysed and fixed-limit and adaptative comfort models were used to assess the compliance of several European Comfort Standards, namely, EN ISO 7730, EN 15251, CIBSE TM:52, CIBSE TM:59 and CIBSE Guide A. Experimental results confirmed the issues reported by occupants in the Comfort Survey, making evident a severe overheating problem which we were able to quantify. In addition to presenting the obtained data and its analysis, this paper discusses the plausible causes and health-related implications of excess heat in NZEB Housing in the Northern Spanish climate.

The degree of overheating of a melt often plays an important role in determining its solidification behavior and the quality of the final product. However, the relationship between the level of melt overheating and the resulting undercooling is far from being understood, especially in rapid cooling processes. The undercooling dependence on overheating of a pure Sn single micronsized particle is successfully investigated by differential fast scanning calorimetry with cooling rates from 500 to 10,000 K/s. It is shown that two levels of behavior exist. First, the undercooling increases gradually with increasing overheating and reaches an undercooling plateau. Second, the undercooling increases with increasing cooling rate initially. However, above a certain cooling rate the undercooling decreases strongly with increasing cooling rate. For overheating levels above that for the onset of the undercooling plateau the undercooling increases with increasing cooling rate. Considering the cavity heterogeneous nucleation mechanism, a theoretical analysis is developed on this specific feature.

In a changing climate, there is increasing concern about the risk of overheating in buildings, particularly those with a low-carbon footprint leading to concern among building professionals about how overheating can best be assessed. Current CIBSE guidance uses a simple definition of overheating as the exceedance of 28 o C for more than 1% of occupied hours, based on simulations using weather files from a 'design summer year' (DSY). There is increasing evidence that this criterion is both insensitive and open to abuse. This paper uses field surveys of thermal (dis)comfort and the adaptive thinking behind the British and European Standard BS EN15251 to propose a new approach. This takes account of the effect of indoor and outdoor climate on the dissatisfaction of building occupants. An alternative definition of overheating in buildings is proposed, along with an approach for the way to predicting the magnitude and/or frequency of occurrence of overheating in buildings.