Building Thermal Performance and Sustainability

The book ‘Building Thermal Performance and Sustainability’ as part of ‘Lecture Notes in Civil Engineering’ highlights the various aspects of architectural research in the domain of Building Thermal Performance leading to a sustainable built environment. The book has chapters based on the sections pertaining to (i) heat stress in buildings, (ii) methods of assessing thermal performance in buildings, and (iii) smart materials and nanotechnology in architecture. The chapters under each of the sections present various aspects of architectural research based on real-time data obtained through field studies. The first section deals with the issues that the rural houses face due to heat wave and the impact on heat stress due to the envelope building materials. The second section focuses on the various ways to assess the performance of the buildings which can enable conscious design decisions at early stages. The third section addresses the way in which correctives can be carried out using nanotechnology with the case study. The research papers are a result of systematic research conducted after the identification of a research gap through the latest review of the literature and present new knowledge which can help in making performance-based design decisions, especially building in a hot-humid climate. The book also presents chapters that are ‘methodology’ based. The methodology can be applied in other contexts to achieve desired results. This book is a valuable reference for postgraduate and doctoral students of architecture and professionals interested in the built environment and allied fields to understand the strategies, tact, and methods of a scientific approach to assess building performance.

Global warming is on the rise, and the occurrence of heat stroke due to exposure to high temperature and humidity has become more prevalent. The country over the years has experienced severe heat wave with implications of illness and death. Most of the studies on heat stress have been assessed in urban areas. In contrast, there is very less research on the impact and significance of heat stress on rural habitations. The United Nations and Red Cross have warned that due to heat wave, human life may become unsustainable in the coming years. This study aims to look at the impact of heat stress on human life and the appropriate index to measure heat stress. A detailed study has been made to understand the current Indian scenario. Various methods of assessing heat stress and indices such as rational, empirical, and direct indices are studied to understand the best assessing method for assessing its impact in rural homes. An extensive assessment should be made for various geographical locations to understand the climate parameters and physiological needs to combat heat stress as heat stress indicators cannot be generic. It is found that Wet Bulb Globe Temperature (WBGT) is the best index for measuring that stress.

Heat stress results in human distress and sometimes mortality. This is significant in the rural context where the economically vulnerable have no access to active means to enhance indoor comfort. This study deals with assessing the Heat Stress Index of five house types. Four houses have reed roofs and different walling materials in rural Andhra Pradesh, while one house is made of conventional building materials. Field measurements of indoor climatic parameters of the five houses are captured using data loggers. Heat Stress Index and Wet Bulb Globe Temperature (WBGT) are assessed using the Bernard and Pourmoghani method on August 27, 2019, from 5.00 am to 9.00 pm. The indoor heat stress is compared with a conventional house from the same location. It is found that occupants of houses built with concrete roofs are more vulnerable to heat stress than the reed roof for the same walling material. The WBGT of the brick wall with a reed roof is lower than other walling materials for most parts of the day. The WBGT of the houses shows a difference of up to 2 °C. Occupants’ thermal sensations through closed format rating scale questionnaire show that the house of reed wall felt most uncomfortable for most parts of the day as expressed by 100% of the occupants. The time of discomfort sensation and the WBGT limits correlate. Since the intensity of discomfort reported is high, in-depth assessments of WBGT are required for heat wave-specific geographic locations to avert the adverse effects of heat stress for millions of rural population.

Buildings are responsible for approximately 30% of CO₂ emissions and about 40% of the world’s energy usage. This energy is mainly used in buildings for thermal comfort. Built structures are one of the major energy consumers that are eventually to blame for environmental degradation in these times of escalating environmental concerns. Dealing with the building’s energy demand will help us mitigate this issue. Heat transfer from the outside to the inside occurs within the building envelope, and the quantities are determined using some fundamental ideas. To better understand the building’s energy requirements, the thermal performance of the structure can be evaluated a number of methods. The goal of this research is to investigate the suitability of various methodologies for evaluating the thermal performance of buildings. To comprehend their applications and adaptability, the three methods of evaluating thermal performance—numerical, simulation, and physical data—have been investigated.

Vegetation coupled with buildings proved to be efficient in mitigating excessive cooling, heating loads of buildings through achieving thermal comfort, microclimatic cooling, and control of insolation through the building envelope. This is possible through the shading effect, insulation, cooling by evapotranspiration, and wind barrier effects of the foliage layer. This study focuses on assessing the thermal resistance of the façade generated through the addition of vertical greenery systems in a steady state adopting a theoretical approach. A total of nine construction types are considered of varying insulation and vegetation strategies, and the influence of thermal insulation of the structure upon the resistive capacity of the façade improved by vertical greenery systems is evaluated. It is found that the effect of foliage in increasing the resistive capacity in cases with less insulated envelope is greater with a green façade showing 12.76% and living wall system showing 93.6%, and with the increase in the insulation of the construction type, the greening measures showed less impact in increasing the resistive capacity. The percentage increases system, respectively. The theoretical approach is adopted due to the complex metabolic processes in plants. This theoretical approach does not consider any other effect caused by the plant layer except the resistance generated by foliage when used in vertical greenery systems. Further, this study tries to explore conventional, vertical greenery system facades and their influence on material efficiency. The results will be useful to architects in designing energy-efficient and sustainable buildings.

The thermal performance of roof envelopes is one of the major contributors in a building to the indoor temperature and its associated comfort level. Roof envelopes by alternative construction techniques with the involvement of renewable materials like bamboo and stabilized mud are studied and incorporated to achieve the required thermal comfort. In Kerala with its Warm and Humid climate, even though reinforced cement concrete roofs are majorly constructed for residential buildings in recent times, as per research, it does not achieve the required thermal performance with respect to adverse impacts of an increase in temperature, which further pave the way to attain higher heat gain during the summer season. This study is done with respect to the comparative analysis of the thermal performance in real time of flat RCC filler slab roofs and bamboo-mud made flat slabs in two residential buildings in Kerala. Using the required parameters, thermal performance is evaluated through field study, and comparative analysis is carried out. Due to the lower decrement factor of 0.36, a time lag of 6 h and TPI of 76.25%, lower surface temperature, higher outdoor to indoor air temperature variation with 2–3 °C (during peak hot hours), and presence of more air cavity inside bamboo poles than in the filler material of filler slabs, flat bamboo-stabilized mud roof envelope exhibits better thermal performance than flat roof filler slab. This research can add more value to the usage of alternative construction methods over conventional, ones to achieve required thermal performance as well as to minimize overconsumption of non-renewable resources.

This study attempts to investigate a parametric model to assess the thermal performance of naturally ventilated residential buildings for various parameters. A predictive model using DesignBuilder and Rhino is generated for 14 opening sizes in rooms along eight orientations in the hot-humid climate of Chennai city. The results of indoor temperature simulated from the model and collected from field measurements are compared and found to correlate well. The model is validated with two commonly used influencing factors, namely ceiling fan and flyscreen, and is found to correlate well with field measurements. The South-West room showed better thermal performance. For the same opening size in different room orientations, there is a temperature variation of 4 °C. The indoor average temperature is higher in rooms oriented along the cardinal directions than in the semi-cardinal directions. There is not much variation in indoor temperature for openings below 35%. Precautions must be taken to ensure that the outdoor temperature at site correlates with the EPW data. The model can be used to test the implications of the affecting factors to arrive at an optimized design at an early design stage resulting in enhanced thermal comfort. The results are useful in assessing the implications of changing one or more parameters on the indoor thermal performance in rooms with varying orientation and opening size. Since the model is based on the most prevailing and preferred building configurations, the study will assist architects and designers in optimizing for the most effective design of naturally ventilated buildings.

This study explores the impact of changing ceiling height on the indoor thermal performance of a building for various combinations of room orientation and opening sizes. The methodology followed is building simulation and validation with field study data for some ceiling heights. This study uses the predictive model established in Chap. 7. Thermal performance of rooms along 8 different orientations for 11 opening conditions and 10 different ceiling heights is assessed using the predictive model. The results are validated by examining the indoor thermal performance of real-scale rooms with varying ceiling heights. For the first time, the indoor thermal performance due to varying ceiling height, opening size, and orientation is examined in naturally ventilated rooms in a hot-humid climate. It is found that for every 30 cm rise in ceiling height, there is a change of up to 0.1 °C. The indoor temperature at the working level increases by 0.5 °C when the ceiling height is increased from 3.0 to 6.0 m. The percentage of indoor air temperature difference reduces exponentially as ceiling height increases. For any ceiling height, the indoor temperature is the same two times a day. Conditioned rooms with large ceiling heights consume more energy to be cool. This study can direct the vent of the air conditioner at various levels for optimized cooling. In this manner, this study is useful in the design of air conditioner vents and the location of goods in warehouses and silos for minimizing energy use.

Integrating a building with a more efficient natural ventilation and daylighting system reduces the dependency on artificial lighting and HVAC systems that account for more than 50% of the total building energy. As commercial buildings are one of the main typologies of buildings that are largely dependent on active systems, maximizing the natural ventilation and daylighting potential can make the building more resilient. For this study, the atrium space, which forms a central connectivity point in a commercial space, is selected and optimized for maximum natural ventilation and daylighting while maintaining occupant comfort. A field study of an existing commercial building, similar to the proposed case, is conducted and data is collected for validation. A quantitative analysis is done to study the impact of various natural ventilation and daylighting strategies on indoor thermal and visual comfort through simulations. It is found that among the 11 design variables selected, the window-to-wall ratio and the type of glazing have the most impact on the daylighting and thermal comfort of the space. The opening schedule, vent area, and the size of the opening have the maximum impact on natural ventilation.

Ecological sustainability should be a holistic approach, where we consider all the biotic and abiotic factors of an ecosystem. Due to climate change, changes in vegetation patterns, a rapid increase of urbanization, depletion of resources, etc., in many ecological cases, we have crossed the line of conservation and now we face the phase of rejuvenation or revival of an eco-sensitive space. For the benefit of flora and fauna, environment much research is done, but the consideration of other species is very less. Sanctuaries being home to 80% of the migratory and native birds has to be rejuvenated by making them a vital space for avian habitat. This paper deals with the impact of buildings in a bird sanctuary on the indoor thermal performance of humans and the impact on birds (breeding temperature) due to human intervention. The site chosen for this study is the Chitrangudi Birds Sanctuary in Tamil Nadu, India. To achieve the optimal thermal conditions for the birds in and around a bird sanctuary, many stages of analysis and strategies benefiting both humans and birds have to be considered. The strategies derived after analysis for the site considering human adaptive thermal comfort and bird breeding temperature of each species are—roof, WWR%, shading device, the shape of the building, and jaali. Quantification of different passive strategies that balance both indoor comfort for humans and outdoor comfort for birds is carried out. The various conditions for which iterations are carried out are Orientation and form—10 conditions, aspect ratio:11 ratio each for two perimeter conditions (22 conditions of aspect ratio), roof structure and material—15 conditions of various pitch angles and overhang, WWR and Height—20 Opening condition of WWR, building height—7 height conditions, 5 Sill Heights and 5 Window heights, level of openings—8 conditions, perforated screens—6 configurations, and shading devices—8 conditions for optimizing indoor air temperature as well as lighting levels. Future studies can include noise. This study establishes a methodology for optimizing indoor comfort for humans with minimum disturbance to the requirement of avian microclimate in a bird sanctuary. This methodology can be followed in other sanctuaries to ensure safe human interventions to assist flora and fauna.

With advances in material research, there is a growing interest in the knowledge of smart materials and their application in improving energy efficiency and the indoor environmental quality of a building. Smart materials can sense and react to their environment, and thus, they behave like living systems. Smart materials and technology produce useful effects in response to an external condition. They can be combined to provide changing and dynamic solutions for problems encountered while designing for energy efficiency. This paper is an introduction to the characteristics of smart materials and their application in the construction industry. Due to their small scale, smart materials enable us to design dynamic thermal environments. Smart materials are applied for façade systems, lighting systems, and energy systems. By focusing on the phenomena rather than the material artifact, the use of smart materials has the potential to dramatically increase the sustainability of buildings. We can save energy by operating discretely and locally only when necessary.

The Indian state of Andhra Pradesh experiences intense heat wave in the summer months. It is important to assess the indoor comfort hours of rural houses which are built with locally available materials because of economic constraints. This study aims to gauge the embodied energy and heat conductance of the houses in the heat wave-prone hot and humid climate of Vijayawada, Andhra Pradesh, and suggest retrofit to better the indoor thermal environment. A field study of four houses with different walling materials and the same roofing material of a typical village is carried out, and their embodied energy and thermal performance are compared with a conventional modern house from the same location. HTC-AMV06 Thermometer is used for field measurements of indoor dry bulb temperature and humidity, and the globe thermometer is used for outdoor temperature data on a summer day in April. Thermal energy models are simulated in energy plus and correlated with recorded data to validate the models. Validated models are used for computing indoor comfort hours. Embodied energy analysis shows that a house made with a reed wall and mud plaster with a reed roof has the lowest embodied energy (473.5 MJ/m²). It is only 9.47% of the conventional house which has very high embodied energy (5002.2 MJ/m²). Comfort hours for all the houses lie in a narrow range of 51.4–47.18% irrespective of the variation in embodied energy. Aerogel, when used as an insulation material, reduces indoor temperature by 11.09 °C in cement block houses and 6.17 °C in random rubble houses.