Enhancing Indoor Environment through efficient & effective building envelope design

Building envelope is one of the most important systems in a building that helps with energy efficiency, safety, and indoor environmental quality. In addition to the insulation, roofing, and weatherproofing, the fenestrations in the building envelope are key elements to enhance its functionality, aesthetics, and occupant wellbeing. Thoughtfully designed and placed windows, doors, and openings can boost natural daylighting, ventilation and protection from the external elements.

Some of the sustainable design principles we follow today are realised from centuries-old design practices which respond to a building’s geographical location and the local weather conditions. These designs reflect indigenous materials and practices which shield them from severe weather conditions like winter winds and blizzards, heavy tropical rains and summer heat.

Some examples are the sloppy roofs and stone walls of Kashmir which protect the inmates from temperate weather conditions, and open verandas and Nalukettu of Kerala, suitable for humid and rainy geography. The chajjas and Jhaalis of Rajasthan protect occupants from the extremely hot and dry weather of the region. In desert regions, buildings utilise shading features to cool interiors and provide comfortable spaces to escape the heat. Informed by traditional design, sustainable buildings benefit from significant advances in window and door technology.

Sustainably designed buildings today combine vernacular design principles with advanced building technologies. Structural glazing continually becomes more architecturally sophisticated and technically complex, allowing building design to follow the imagination of engineers and architects. As architects and engineers work to meet design and energy requirements, the builders and consultants use tools that allow them to minimise building energy consumption and also monitor the same in the later stages.

This edition’s cover story seeks to discuss sustainable façade design methodologies, and identify the aesthetic perception of façades and fenestrations by the users of India, with the view of improving occupants’ comfort and building attractiveness. In achieving this, the cover story also discussed the design strategies, characteristics, and properties of sustainable façades.

APPROACH TO FAÇADE AND FENESTRATIONS DESIGN IN VARIED ENVIRONMENTS

Based on the geographical areas & climatic conditions, the designs & materials for the façade and fenestration are chosen.

Ar. Indrajit Kembhavi, Principal Architect, Kembhavi Architecture Foundation, says that in diverse environments, they prioritise a holistic approach to façade and fenestration design that integrates seamlessly with the surrounding context. Understanding the geographical area and climatic conditions is crucial for selecting appropriate materials and design strategies. For instance, in hot climates, shading elements and high-performance glazing can help mitigate solar heat gain, while in colder regions, insulation and air-tightness are emphasised.

“We are very conscientious about the context that we design for, and the façade is always studied, analysed and then proposed”, says Ar. Shridhar Rao, Partner at R+D Studio. It is the balance between the architecture and the contextual parameters that lead to the final design. “For example, in the arid deserts of UAE projects, we go for smaller fenestrations or screens in front of our larger openings as protection from the harsh sun; whereas for one of our projects, the Dichotomous House, we wanted to include the farm context in the planning of the house. Thus we went with larger openings so that the occupants are visually connected with the greens”.

In approaching façade & fenestrations across diverse environments, geography, and climates, our design philosophy revolves around integrating regional context into our concepts, adds Ar. Vivek Bhole, Chairman & Managing Director, Vivek Bhole Architects. We meticulously select materials that not only complement the aesthetic vision but also respond effectively to climatic conditions. In tropical regions with abundant sunlight, we employ shading devices, smaller windows, and reflective cool whites to mitigate heat gain. Conversely, in colder climates, maximising sunlight penetration with south-facing glazing and high- performance insulation is key.

According to Er. Rohit Rajpoot, Assistant Manager-Façade, Group-108, in diverse environments and climatic conditions, his approach to façade and fenestration design integrates local context, climate considerations, and architectural aesthetics. “I prioritise materials like GRC, ACP, and zinc cladding for their durability and adaptability. For regions prone to extreme weather, such as heavy rain or high winds, I emphasise structural integrity in curtain walls and unitised glazing, collaborating closely with engineers.

My design ethos incorporates the local architectural vernacular while meeting client preferences and project goals,” points out Rajpoot. “By balancing functionality, aesthetics, & sustainability, I ensure façades withstand environmental challenges while enhancing the building’s overall design. As a façade manager, I lead teams to execute projects that seamlessly blend form and function, delivering solutions that endure varied climates and geographical conditions”, he adds.

Beyond sustainability, the façade being the primary identity of a building, it needs to respond to the Geography, climate, culture of the region, and typology of the building. “The geography & topography affects fenestration design and orientation. Climate affects every aspect of the façade. Culture affects the material, aesthetic and graphics of the façade. Typology affects window wall ratio, technology, materials and cost of the façade design”, says Sriram. R, Principal Architect, FHD India, Bengaluru. In our projects, we try to reflect the character of nature and culture through the façade thereby creating unique and responsive projects, he adds.

Sumesh Sivasankar, Associate Director – Project Services, Vestian Global Workplace Services Private Limited considers the below-mentioned aspects for façade and fenestrations in different environments in terms of design & materials:

• Easily available façade & fenestration materials in that geography.
• Availability of services after installation.
• Natural Ventilation.
• Natural/daylight and
• Energy conservation and above all
• Design matching to the local environment and not just for aesthetics.

ARE LARGE GLASS WINDOWS A SUSTAINABLE SOLUTION?

Large glass units are increasing in demand as they allow homeowners to better blend the inside of their homes and offices with the natural surroundings outside. The indoor- outdoor lifestyle trend gained popularity over the past few years. But how sustainable are these options considering exposure to sunlight and heat and energy spent on cooling and ventilation?

To meet clients’ desire for large glass windows sustainably, advanced glazing technologies that balance aesthetics with energy efficiency are used, says Ar. Kembhavi. This includes low-emissivity coatings, insulated glass units, and dynamic shading systems. Additionally, incorporating passive design strategies such as orientation optimisation and natural ventilation can further enhance sustainability.

Is so much use of glass agreeable? Ar. Rao from R+D Studio replies that glass is actually a sustainable material, as it can be recycled back to form a new one. However, the kind of glass, specifications, and opening sizes, are what one needs to be aware of while designing. Insulated glass can help prevent noise, and has thermal properties which can reduce energy costs. In India, south-side exposure tends to bring in a lot of heat which is not preferred, so doing a solar path and wind studies for any building should help in proposing the right kind of fenestrations, thereby making it more sustainable in terms of design as well, Rao explains.

Sustainable design for large glass windows involves a multi-faceted approach, points out Ar. Vivek Bhole. Employing double or triple glazing with low-emissivity coatings reduces heat transfer, while dynamic glazing that adjusts the tint based on sunlight intensity enhances energy efficiency.

Ar. Bhole adds that the inclusion of automated shading systems like louvres or blinds, coupled with strategic window placement, optimises cross ventilation and daylighting. These operable windows ensure effective control over natural light and ventilation, reducing the dependency on artificial lighting and HVAC systems, and contributing to overall sustainability.

Big glass windows allow more natural light, heating & ventilation, points out Ar. Sumesh Sivasankar. If the windows are big, they allow more sunlight and thus effectively warms a room during the colder months in cold countries and hence it is advisable to have big windows. But we should also understand that some of these big windows are not outfitted to open. However, many large windows are designed to allow them to be opened to permit fresh air into the room.

According to Ar. Sriram, no material is universally sustainable. Every material offers certain advantages at a certain cost. The strategic use of the material leads to sustainability. Glass maximises views and daylight at the cost of increased heat gain and glare. The negatives can be mitigated by using the correct specification glass, at the appropriate orientation, facing necessary views, and shaded externally (if necessary) with fins, fabric or other alternates.

KEY POINTS TO CONSIDER WHILE SELECTING GLASS FOR FAÇADES AND FENESTRATIONS:

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  High-performance glass: Employing energy-efficient glass with low emissivity coatings enhances insulation, curbing heating and cooling loads effectively.

• Insulated glazing units (IGUs): Double or triple glazing, supplemented with argon or krypton gas fillings between panes, boosts thermal performance and minimises air leakage.
• Solar shading devices: External shading elements like louvres help mitigate solar heat gain while preserving natural light levels.
• Thermal breaks and frames: Opting for frames with thermal breaks minimises thermal bridging, enhancing energy efficiency between indoor and outdoor environments.
• Natural ventilation: Designing windows for cross-ventilation fosters passive cooling, reducing reliance on mechanical HVAC systems and enhancing indoor air quality.
• Integrated building design: Considering building orientation, site conditions, and climate optimises daylighting and diminishes energy consumption throughout the building lifecycle.
• Life cycle assessment (LCA): Conducting a thorough analysis of materials and construction methods identifies opportunities to reduce embodied energy and minimise environmental impact from production to disposal.

(Er. Rohit Rajpoot, Assistant Manager-Façade, Group-108)

IMPROVING ENERGY PERFORMANCE OF BUILDINGS THROUGH PROPER FAÇADE AND FENESTRATION DESIGNS

Façade and fenestration design is pivotal in enhancing building energy performance. Incorporating high-performance insulation in walls and roofs effectively reduces heat transfer, advises Ar. Vivek Bhole. Airtight construction minimises air leakage, contributing to improved thermal efficiency. Strategically placed windows for natural ventilation reduce cooling needs while daylighting optimises with skylights, and light shelves. Reflective surfaces significantly reduce the reliance on artificial lighting. Building orientation plays a crucial role in minimising solar heat gain and maximising beneficial daylighting, ultimately contributing to the building’s energy efficiency.

Energy performance can be significantly improved by focusing on the thermal envelope of the building, notes Ar. Kembhavi. Employing high-performance insulation, minimising thermal bridging, and utilising efficient fenestration systems are essential. Furthermore, integrating renewable energy sources like solar panels into the façade design can further reduce energy consumption.

Doing a sun/wind study of the building can provide us with a lot of inputs to better design the fenestrations, adds Ar. Rao. A lot of times, the façade is designed based on a particular preconceived notion, results in bad energy performance.

Improving a building’s energy performance via proper façade and fenestration designs involves key strategies. Optimal insulation using high-performance materials minimises heat transfer. Energy-efficient glazing, such as double or triple-glazed windows with low-emissivity coatings, reduces heat loss and solar heat gain while maximising natural light. External shading devices like overhangs mitigate solar heat gain while maintaining daylighting. Thermal mass materials stabilise indoor temperatures. Ensuring air tightness around windows minimises leakage. Natural ventilation systems and operable windows enhance airflow and reduce mechanical cooling needs. Proper building orientation maximises passive solar heating in winter and minimises heat gain in summer. By integrating these principles, buildings achieve enhanced energy efficiency, reduced costs, and improved occupant comfort while minimising environmental impact, advices Er. Rohit Rajpoot.

According to Sivasankar, the following three points we can improve the energy efficiency/performance of any building:

• Areas covering the U-value of the glass to protect the building from heat transfer.
• Solar power gain coefficient to increase the energy performance and Light transmission that in-takes the amount of light passing into the building.

Façade design can directly save energy in three ways, ratifies Ar. Sriram. One, the façade can be designed to minimise heat gain in hot weather and minimise heat loss in cold weather, thereby reducing HVAC energy load. HVAC is the highest energy load in a commercial building. Two, Façade can maximise daylighting, reducing the energy consumption of artificial lighting. Three, the façade can maximise cross ventilation in relevant spaces, thereby reducing the spaces or hours of air-conditioning, while improving health.

PASSIVE/ACTIVE WAYS TO ENSURE THERMAL COMFORT

Thermal comfort can be achieved through natural ventilation and optimising natural light.

Achieving thermal comfort through natural ventilation involves strategic placement of openings to facilitate cross-ventilation and utilising building form to encourage airflow, observes Kembhavi. Optimising natural light involves maximising daylight penetration while minimising glare and solar heat gain through the use of daylighting strategies such as light shelves and skylights.

According to Ar. Rao, one of the most effective passive ways to ensure thermal comfort is to be able to manage the prevailing wind direction to pass through the building and have large overhangs to cut direct heat from the openings. This has resulted in a certain style of architecture which has been prevalent in the tropical areas of the world. An active way to ensure thermal comfort would be to design the fenestrations based on studies and introduce some sort of mechanism that allows for dynamic façades like the Foundation Cartier Building in Paris or the Louvre, Abu Dhabi designed by Jean Nouvel, adds Ar. Rao.

Ar. Bhole also agrees that passive cooling methods, such as cross ventilation, evaporative cooling, and vegetation shading, effectively reduce reliance on air conditioning. Natural daylighting is optimised through windows, light shelves, and skylights, providing ample natural light and reducing the need for artificial lighting. In instances where passive strategies are insufficient, active control systems, including energy-efficient fans and radiant heating/ cooling, provide additional comfort while maintaining energy efficiency, he adds.

Sumesh Sivasankar too agrees that natural ventilation is a passive cooling strategy that consists of using natural forces, such as wind and buoyancy to drive cool outdoor air through a space. In short, any design element or technology used to lower a building’s temperature without the use of electricity or natural gas is referred to as passive cooling.

These are strategies that include daylighting, natural ventilation, and solar energy. Er. Rohit Rajpoot, Assistant Manager- Façade, Group-108: Talking about passive and active methods ensure thermal comfort and optimise natural light in a space, Er. Rohit Rajpoot lists down a few passive methods and active methods:

Passive Methods:

• Natural ventilation: Designing buildings with operable windows, vents, and cross-ventilation channels promotes airflow, reducing reliance on mechanical systems and enhancing indoor air quality.
• Building orientation: Orienting buildings to capture prevailing winds and maximise natural ventilation while minimising solar heat gain helps regulate indoor temperatures.
• Shading devices: Installing external shading elements like overhangs, louvres, or awnings mitigates direct sunlight penetration, reducing solar heat gain and glare while maintaining daylighting.

Active methods:

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  Mechanical ventilation: Utilising energy-efficient mechanical ventilation systems with heat recovery capabilities enhances indoor air quality and thermal comfort, especially in enclosed spaces.

• Dynamic shading systems: Implementing automated shading systems that adjust in response to solar angles and daylight levels optimise natural light while minimising heat gain and glare.
• Daylight harvesting: Installing sensors and controls to adjust artificial lighting levels based on natural light availability maximises energy efficiency and occupant comfort.

By integrating passive & active strategies, spaces can achieve optimal thermal comfort and natural light utilisation, contributing to enhanced occupant well-being and energy efficiency.

Ar. Sriram Further adds that there are an array of passive strategies such as cross ventilation, stack ventilation, evaporative cooling, tower cooling, etc., to aid thermal comfort, and strategies such as light shelves, reflective surfaces, ceiling cut-outs, strategic courtyards, controlling building depth, etc. to maximise daylighting. In active methods, energy-rated conditioning systems, adaptive cooling, climate-controlled regions, advanced sensors and optimisation, etc. are available for thermal comfort. Active strategies such as controllable kinetic façades, and sensory controls, maximise natural light.

LATEST FAÇADE & FENESTRATION TECHNOLOGIES TO BUILD BETTER

Some of the latest technologies include dynamic glazing systems that adjust tint levels based on external conditions, transparent photovoltaic glass for energy generation, and smart façade systems equipped with sensors and actuators for real-time response to environmental changes, states Ar. Kembhavi.

With the technologies and computational software available today, a lot of designers are moving towards intelligent façades, which can react based on environmental conditions. If it’s a cloudy day, the fenestrations would open up to bring in more natural light, and vice versa, notes Ar. Shridhar Rao.

The energy needed to move these mechanisms is self-generated by the building. For all the energy spent during the construction of the building, it is now possible to generate energy from the operation of the buildings and utilise it for its functioning.

The forefront of façade technologies encompasses dynamic solutions, says Ar, Bhole. Kinetic façades respond to environmental conditions, optimising both energy performance and occupant comfort. Building-integrated photovoltaics (BIPV) generate clean energy directly on the façade, contributing to sustainable power sources. Biomimetic materials, inspired by nature, offer solutions like self-cleaning surfaces and heat-regulating properties. Smart glass technologies, such as electrochromic glass, adjust transparency based on lighting conditions, providing privacy and glare control. These innovations collectively redefine the standards for efficient and environmentally conscious building design.

According to Er. Rohit Rajpoot, the following technologies will help build sustainably:

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  Dynamic glass: Dynamic glass technology enables windows to tint automatically in response to sunlight, reducing solar heat gain while preserving natural light and views.

• Smart shading systems: Equipped with sensors, smart shading systems adjust in real-time to optimise daylight levels, minimise glare, and regulate interior temperatures, improving comfort and energy efficiency.
• Integrated photovoltaics (BIPV): BIPV systems seamlessly integrate solar panels into façade elements, generating renewable energy and providing thermal insulation.
• Double-skin façades: Double-skin façade systems incorporate an outer layer to buffer against external conditions, enhancing insulation and acoustic performance.
• Nano-coatings and self-cleaning materials: Advanced nano-coatings applied to glass surfaces repel dirt and water, reducing maintenance and enhancing aesthetics.
• Prefabricated façade systems: Prefabricated systems streamline construction, reduce waste, and improve quality control.

These technologies collectively offer higher energy efficiency, comfort, and sustainability, meeting the evolving demands of modern architecture and environmental responsibility.

Talking about the future materials, Ar. Sriram says that fabric façade is a simple and cost-efficient technology that is suitable for Indian conditions. It can transform cost-efficient structures such as MLCP, warehouses, back-end offices, etc. They are simple to execute, fast to construct, easy to quality control, and aesthetically pleasing. Their fire rating is getting better with time. In fenestration, concealed aluminium frame is a technology that changing the way buildings are planned. Green spaces beside villas have increased due to the availability of sleeker aluminium sections.

The future of façade is changing based on the technologies that are coming up. As sustainability and user experience become more important in architecture, façades will only continue to play a vital role in creating visually striking and energy-efficient buildings. According to Sumesh Sivasankar, biophilic façades, smart façades, parametric façades, kinetic façades, 3D façades, and zero- carbon façades are just a few examples that are shaping up and changing the future of façade architecture.

FUTURE FAÇADES, 50 YEARS FROM NOW

Looking ahead to the 2070s, Ar. Kembhavi envisions façades that are highly responsive and adaptive, capable of self-regulating to optimise energy performance and occupant comfort. This may involve the widespread integration of nanotechnology for self-cleaning and self-repairing surfaces, as well as advanced biomimetic designs inspired by natural systems. Additionally, he foresees the increased use of sustainable materials and the seamless integration of building-integrated renewable energy systems, transforming façades into active contributors to environmental sustainability.

Buildings will be valued based on their lifetime energy utilisation. Energy generation shall be pertinent in terms of making decisions about façades. Designers would be able to analyse their building designs during their conception to be able to make informed decisions, envisages Ar. Shridhar Rao.

Envisioning façades in the 2070s involves a paradigm shift towards fully integrated, self-sustaining building envelopes, forecasts Ar. Bhole. Bio-integrated façades could feature living walls, algae panels, or vertical farms, seamlessly blending nature with architecture. Adaptive materials might exhibit self-repairing capabilities, generate energy, and respond to environmental cues in real-time, optimising both performance and comfort. Advanced digital integration could result in interactive façades that not only display information but respond to user input, generating art or music, predicts Ar. Bhole. This visionary approach anticipates a future where sustainability, innovation, and aesthetic evolution converge to redefine the built environment.

Er. Rohit Rajpoot envisions smart and responsive future façades with the following features:

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  Advanced sensors and artificial intelligence enable façades to dynamically adjust to environmental conditions, optimizing energy efficiency and occupant comfort in real-time.

• Biophilic design integration: Living elements such as green walls and biophilic materials enhance indoor air quality, connect occupants with nature, and promote well-being.
• Nanotechnology and self-healing materials: Façade materials with self-healing properties repair damage autonomously, prolonging lifespan and reducing maintenance costs.
• Energy harvesting surfaces: Integrated photovoltaic and piezoelectric technologies harvest solar and kinetic energy, contributing to building sustainability and powering integrated systems.
• Interactive and transparent interfaces: Transparent surfaces enable augmented reality experiences, adaptive shading, and personalised environmental controls, transforming façades into dynamic interfaces.
• Modular and adaptive construction: 3D printing and robotics facilitate rapid assembly and customisation of façade components, promoting sustainable and flexible building design.
• Carbon-negative materials: Carbon-negative façade materials mitigate environmental impact and reduce carbon emissions, aligning with sustainability goals.

There are two schools of future prediction in architecture, says Ar. Sriram. The ‘Utopian school’ imagines 2070 buildings with reflective glass volumes in all geometric shapes. Glass can be engineered to control its thermal, and lighting properties, through electric and magnetic signals, and LED Screens all over façades.

The second is the ‘Sustainability school’ that imagines 2070 buildings as green vertical gardens as built façade. Concrete walls with automated sensory windows, but covered by greenery and shaded by solar panels. This focuses on healthy living and biophilic design. Ar. Sriram believes that the future is somewhere between the two versions of imagination.

Sumesh Sivasankar mentions that the façade will see a drastic change in the design and in the material used to manufacture it. It will be more focused on energy efficiency in the built environment where technology like sensor networks and building management systems track all sorts of data and will be integrated to enhance the lifecycle of the building with the Internet of things (IoT) that may interact with behavior of the public.

CONCLUSION

Building façades and fenestrations are very important contributors to the comfort parameters & attractiveness of any building. They are the key elements of a building in achieving the dual role of comfort and attractiveness. The concept of sustainability has surfaced to become a guiding paradigm in creating the evolution of the built environment in meeting the needs of humans in the present. Diverse professionals have sought different ways of meeting this paradigm shift in the built environment by developing design concepts, elements and materials that will ensure the achievement of sustainability. The cover story emphasises the guidelines for designing a sustainable building façade and fenestration to ensure the comfort of occupants as well as to meet the aesthetic requirements. A sustainable façade design should be a climatic-based approach.

This dictates the material, building orientation and fenestration requirements of the building. Designers can leverage on these elements to accentuate the fenestration and ensure harmonising it with a good understanding of the local climate of the building location. Furthermore, material specification by designers based on the understanding of the immediate and current global climate change is crucial as this will determine the final comfort of occupants, reduced energy consumption and also visual sustainability of the building typology.