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Sudhakar uPVC Windows and Doors

Glass & Glazing Technologies Increasing Efficiency of Building Systems


One of the most prominent trends in the last few years in real estate has been the usage of glass façades. Most of the iconic buildings in Indian metros today are elegant corporate houses with glass façades. Today, glass façades have become an industry with several companies offering a plethora of choices in everything from supplying different glass to customisation, cleaning and maintenance. The reason for architects’ and developers’ preference for glass is because it reduces the weight on the foundation and hence makes the building lighter as compared to constructing walls.

Structurally glazed façade systems create greater transparency than traditional captured systems. There are fewer visual interruptions due to the use of less metal on the glass façades, creating a seamless, continuous transparent look, merging the interiors with the exterior. Since there is little to no exposed exterior metal, there is also less thermal bridging with structural glazing, saving on energy consumption costs. Moreover, glass makes the area look far more spacious, wider and creates a sense of a ‘feel-good’ factor with big windows and brightness.

This story discusses types of architectural glass and their use on modern façades and fenestration; the functional, structural and energetic aspects of glass façades; the structural safety of glass; selection of glass for façades considering energy, thermal and acoustics-related parameters; fire-safety norms to be followed while designing and mounting glass façades; effective façade maintenance and the future of glass façades and fenestration.

Architectural Glass

Architectural glass is used copiously in modern building façades nowadays due to its properties as a building material along with its aesthetic qualities. It offers lightness to the structure along with natural light and surrounding views to its inhabitants. Also, it offers a swift construction of the façade with standard and repetitive glass modules. These qualities coupled with sustainable aspects of different glass that have been engineered by material scientists for specific performance standards, describes Ar. Gaurav Goel, Founder, Parametric Curiosity.

AR. Gaurav Goel Founder, Parametric curiosity | Sangram Singh Assistant General Manager, GSC Glass Pvt. Ltd | Binoy Kumar Das Managing Director, Façade Concept Design Group AR. Gaurav Goel Founder, Parametric Curiosity | Sangram Singh Assistant General Manager, GSC Glass Pvt. Ltd | Binoy Kumar Das Managing Director, Façade Concept Design Group

Architectural glass is classified based on manufacturing process and techniques, says Sangram Singh, General Manager, GSC Glass Ltd. Nowadays almost 100% of the glass is manufactured using the float glass manufacturing technique invented by Sir Pilkington in the 1950s. The float glass manufactured with this process has excellent optical properties and thus most suitable for architectural applications.

Binoy Kumar Das, Managing Director, Façade Concept Design Group stresses on the importance of glass selection, since it plays an important role for aesthetics and performance with internal and external reflection control. The architectural glass used as a building material, mainly provide aesthetic, technical and energy saving properties like solar control, thermal insulation, or both in modern façade and fenestration, agrees Rajiv Balaggan, Sales Head – Architectural Glass India, Pilkington Glass India Pvt. Ltd. The use of architectural glass defers from project to project and places to places. Depending on the requirements, appropriate energy saving glass/glass units can be suggested/proposed, adds Balaggan.

Rajiv Balaggan Sales Head - Architectural Glass India, Pilkington Glass India Pvt Ltd | Amrit Raj Thakur Dy. Manager, Central Procurement, Lodha Group | Madan Mohan Joshi D.G.M. – Projects, Lotus Greens Developers Ltd Rajiv Balaggan Sales Head – Architectural Glass India, Pilkington Glass India Pvt Ltd | Amrit Raj Thakur Dy. Manager, Central Procurement, Lodha Group | Madan Mohan Joshi D.G.M. – Projects, Lotus Greens Developers Ltd

Amrit Raj Thakur, Dy. Manager, Central Procurement, Lodha Group too agrees that glass, as a versatile building material, enables the efforts of the architects due to its transparency. Though it is transparent, it can support structures due to the development of glass strengthening procedures.

Types Of Architectural Glass

Corporate Building Ahmedabad, Blocher Partners India
Corporate Building Ahmedabad, Blocher Partners India

There are different types of glass available in the market and the selection of glass for the projects are based on energy studies. Glass with low external reflection is used to avoid maximum reflectivity on the outside façade which can affect the nearby building.

Glass with low internal reflection help to avoid the mirror effect from inside of a building at night, maximum visibility and light transmission. It also controls solar heat gain. Looking into these parameters, the selection of glass should be done as per sun path analysis and thermal comfort studies. Different types of glass, including low-E coated glass like double silver glass, triple silver glass, etc., can be used in the façade. Das explains the importance of performance studies, which are very much necessary before selection of glass. Glass selection should allow maximum daylight to come inside the building to reduce artificial light inside, but control solar heat gain, says Das.

To improve the energy performance of the façade, an additional coating is applied to the glass, either online called hard coating or offline called soft coated glass. “On one side hard-coated glass balances the equation between cost and energy performance, on the other side soft coated glass strikes balance between energy performance and light transmission”, adds Singh. Primarily two types of coatings are used:

1. Solar control coating, to cut down the solar gains inside the building

2. Low E coating to cut down the heat gain /loss due to non-solar heat.

Various other processing like heat treatment, insulation and lamination are used to meet the safety and energy requirements. In addition to these processes, ceramic fritting, frosting /acid etching, etc., are used for decorative as well as energy-saving purpose, explains Singh.

Due to innovations in manufacturing, glass is no longer a flat sheet material, explains Ar. Goel. Today, architects and façade engineers can manipulate glass for double curvature or bending to achieve complex forms of building geometry. Therefore, architectural glass in modern façades are flourishing as an adaptable material to deliver innumerable possibilities. There is an intriguing future ahead filled with constant innovation and research in modern glass façades.

Types of Architectural Glass used in Modern Façades & Fenestration:

Trump Tower by Lodha Group
Trump Tower by Lodha Group

• Clear glass
• Sun control glass
• Ceramic printed glass
• Digitally printed glass
• Electrochromic glass/Translucent glass
• Annealed glass
• Fully-tempered glass (toughened glass)
• Laminated Glass
• Insulating glass
• Tinted glass
• Self-cleaning glass
• Fire-rated glass (protective glass)
• Low E-coated glass
• Frosted glass
• Embossed glass
• Sandblasted glass

(Inputs from Madan Mohan Joshi, D.G.M. – Projects, Lotus Greens Developers Ltd. & Amrit Raj Thakur, Dy. Manager, Central Procurement, Lodha Group)

The Functional, Structural And Efficiency Aspects Of Glass Facades

While designing the glass façade, there are three most important parameters to consider, explains Singh. They are:

1. Functional fitness
2. Structural safety
3. Energy efficiency.

According to Madan Mohan Joshi, D.G.M.–Projects, Lotus Greens Developers Ltd., the glass façades are designed for following functional, structural and energetic aspects: energy efficiency/thermal performance, visual light transmission (VLT), safety, appearance and fire safety.

Functional Aspects

Architect Hartmut Wurster from Blocher Partners India
AR. Hartmut Wurster Architect and Head, Blocher Partners India

Explaining the function of glazing, Ar. Hartmut Wurster, Architect/Head, Blocher Partners India points out that glazing creates view relations between inside and outside of a building, which is important for orientation in buildings and to increase the aesthetic quality of a room in terms of creation of depth due to sun and shadow casting. Glazing provides daylight that can be established with a manmade lighting system only with effort. And daylight is a source of health for human bodies.

Functional fitness is the function of various parameters like size/weight of the glass, handling/ manufacturing capabilities, constructability, daylighting, placement of mullion/ transoms/openings, etc. The façade should be able to accommodate designed built of tolerances without affecting the form and function of the façade, says Singh. This part is looked upon while assessing the structural integrity of the façade – Will the façade be able to resist the designed wind load, accommodate thermal movement without putting undue stress on the joinery or glass, and accommodate building movement.

According to Das, building physics like sun path, daylight, shadow with thermal analysis are very much important analysis’ to be carried out by façade engineers while selecting a type of glass in façade. These studies also help to design air conditioning calculations properly when the overall thermal transmission values are provided by the façade engineer. This helps a lot to optimise and save overall cost while selecting the product, also overall maintenance, and to reduce operational cost.

Structural Aspects

JSW HQ1 - Glass Facade
JSW HQ1, Image courtesy – Pilkington Glass India

It is necessary to design the façade to be structurally fit and tolerant to all other loadings which can be encountered during the service life of façade like live load, maintenance loading (BMU), etc., points out Singh. According to Wurster, the glass itself can’t be used as a load bearing building material. With regulation in the area, it can take its loads without supporting structures (structural glazing). Otherwise, there is always an opening of whatever dimension in building structure required and the glazing itself needs structural support in a frame fitting into the PR system. So from that point of view, there is already complexity shown, because there are different crafts involved that need to work together coordinated. Structural analysis like wind load studies can decide the thickness of glass, whether used as single glass and double glass unit into façade, says Das.

Colombo City Centre Project, Sri Lanka
Colombo city center project in Colombo, Sri Lanka: FCD in collaboration with Globeclad, part of Mulk Hold, UAE carried out design and built for façade where FCD designed the façade. Sanken Construction is the main Design and Built Contractor. Architect – AEDAS, Singapore

The wind tunnel report can give accurate results and based on wind load parameters, the glass can be designed accordingly. If there are no wind tunnel reports, then wind simulation and wind load calculation can be done, which is followed by most of the current cases and the glass thickness can be decided. Identifying wind load KPA can be done considering the surface condition and corner conditions, including zoning can optimise the glass thickness and also aluminium profile, adds Das.

Energy-Efficiency Aspects

Nowadays energy performance of the façade is a key factor while designing the façade, as energy saving is the need of the hour. There are various techniques used to make the façade energy efficient, explains Singh. It starts from selecting the right orientation of the building, designing various architectural elements like sun breaker, louver, ceramic fritting, etc. This ensures the solar gain into the building is restricted at the design level itself for cooling dominated climates. The use of solar control and Low E coating is very popular in designing energy-efficient façades.

Altamount by Lodha Group
Altamount by Lodha Group

Apart from providing various choices and a fascinating look, a glass façade and fenestration provide energy efficiency while significantly reducing the cost of the building, says Balaggan. It helps to obtain natural light and transparency to the architects and clients and controls heat energy as well. There are now multi-functional façades that provide a variety of functions such as maintenance, heating and cooling. The façade engineering helps resolve aesthetic, environmental and structural issues to achieve the required results.

With today’s window and shopfront systems, any energetic standards can be resolved. More often the glassed openings work with better thermic insulation than wall parts and the built-in condition, observes Wurster. So sometimes specialists are required to check the overall package in openings in the façades to avoid different conditions which can lead to condensation. In shopfront situations and areas with bigger scale openings, the thermic loads need to be reviewed for overheating in hot summer conditions.

This can be done with a thermic simulation software by a specialist to avoid non-agreeable inside temperatures. Then measurements to reduce thermic loads should be taken. With thermic simulation, you already know about the inside room condition in the design development stage, so an integrated and coordinated shading system can be placed or special glazing can be used, elucidates Wurster.

Ichitan Tower Bangkok
Ichitan Tower Bangkok, Image courtesy – Façade Concept Design Group

Designing & Installing Double Skin Facades

The double skin façade is an envelope construction made of two transparent skins that are separated by an air corridor. The glass skins can be of single or double glazed units, depending on the requirement. For such buildings, external environment like wind velocity and direction is very important to know. The concept of double skin façades is not new, and there is a growing tendency by architects and engineers to use them. Since the function of this façade type is not yet completely investigated, in the existing literature, one can find reports that prioritise the main goals of this system in different ways.

According to Sangram Singh, the double-skin façade is a European architectural trend driven mostly by:

The aesthetic desire for an all-glass façade that leads to increased transparency

The practical need for improved indoor environment

The need for improving the acoustics in buildings located in noise polluted areas

The reduction of energy use during the occupation stage of a building

Double Skin Facades

Mario Schmidt Managing Director, Lingel Windows and Doors Technologies
Mario Schmidt Managing Director, Lingel Windows and Doors Technologies

Double skin façades are a very good alternative considering that there will be a significant gap between both glazings. This area is ventilated so that the heat created by the first glazing can move towards the top, and from the bottom cooler air can enter to assure a natural ventilation without electrical fans. The cost of double skin façade is higher due to the 2 glazing systems which need to be installed. Moreover, some of the areas of the building are getting reduced due to the space between the two glazing systems.

Heat EffectPresuming that the future demand will be for net zero building, and cost of electricity is going to increase, the main criteria for reducing the maintenance cost of buildings will be through a drastic reduction in electricity usage. Here it is important to create general awareness among the buyers and the users of commercial properties where curtain walls are widely used. Only when their demands are raised for limiting the maintenance cost, especially the electricity cost to x amount per square feet, the challenge on the developer as well as our industry will start to create environment-friendly glazing systems.

Since the concept of double skin façades is complicated and its use and function affects different parameters of the building (that often may interact with each other, i.e. daylight, natural ventilation, indoor air quality, acoustics, thermal and visual comfort, energy use, environmental profile, etc.), the literature studied is from different fields. It is also important to mention that, in this first step, it was considered important to present the function and the impacts of the mentioned system from a different point of view, says Singh

Residential House Glass Facade Design Residence of Deepak Kansal and Amandeep Kansal, a Lingel Project

Complex façades are not easy to design from a construction point of view, states Wurster. In these cases, a specialist façade consultant should be involved in the planning process and in the design development stage to work on the best solution for a building proposal. For instance, for double layer glassed façade, ventilation, aspects like the chimney effect should be considered to avoid overheating.

Many things must be known/ kept in mind while designing and installing different types of glass façades. These are mainly – safety, wind pressure, sustainability, energy consumption, use of natural light, glare, reflection, sound insulation, etc. The orientation of the building and its surroundings are very important to know as this will help take a call on many important factors. Building analysis is very much essential while selecting glass façade systems, including the analysis is sun path, daylight, shadow and thermal comfort studies, and wind analysis. These analysis results also help to design cost-effective façades. These studies can also help to design the double-skin façades if it is required for functional purposes.

Factors to Consider while Designing Glass Façades

Lotus ISLE - Sector 98, Noida, Lotus Greens Developers Ltd.
Lotus ISLE – Sector 98, Noida, Lotus Greens Developers Ltd.

The designer should always keep a few important factors in mind while designing glass façades, such as:

i. Prefabricated façade systems – Design façade system as a product which should consider factory oriented with best quality check and for easy installation at the site – for example, unitised façade which is the best example as façade system which can be installed using the quality checked product at the factory. It is easy to install and no external scaffolding is required to install a glass façade. The installation can be done from the inside of the building. The glass façade installation can go simultaneously with construction. The total project timeline can be reduced and it caters to overall saving on the project.

ii. Availability of local materials – While designing, one should keep in mind the availability of the local product in the region so while designing, always recommend keeping in mind the local constructability factor.

Impact Of Glass Facades On Internal Environment

Glazing plays a significant role in interior comfort levels, says Balaggan. Glass is used on doors, windows, walls, and skylights/ roofs and even used as a partition. Depending on the design concept, designers decide as to which glass to go with. Ventilation and insulation are other areas in which glass plays an important role. One of the great benefits of glass in design is that it offers a chance to invite the outside world in.

Glass helps in optimising light transmission and in Improving the acoustic and thermal performance of glass façades & fenestration. Let’s know how it happens:

1. Optimising Light transmission

Indirect heating of the glass
Indirect heating of the glass, Image courtesy – Lingel

It is important to know the orientation of the building while selecting proper architectural glass for façade and fenestration, says Balaggan The other factors to know are the surroundings of the building, shading devices and whether the project required green building certification if any. The selection of appropriate glass for glass façade and fenestration is based on several factors like optimum light transmission (good enough to avoid using artificial light in the day time), glass reflection values, direct heat value (SHGC or G value) and indirect heat value (U-value). The required data may vary from project to project, place to place and glass selection is done as per the requirement.

The thermal performance of the glass façade & fenestration can be achieved by IGU’s (Insulated Glazing Units). It can be further improved by using Low E glass in SGU (Single Glazing Unit) or DGU (Double Glazing Unit). It all depends on the requirement. The thermal performance of the glass unit is denoted by U-value. Lower the U-value better would be the thermal performance of the glass unit, observes Balaggan.

According to Wurster, the quality of inside space is regulated by the availability of daylight and the room climate. There are parameters like the U factor of the window to fulfill, which combines glass and frame. But if the U parameter for the frame is very bad, you can still meet the U factor with a better U for glazing.

And if there are joints to wall openings, the window part is not even relative to the climate in the room. An architect has to think about details and should try to resolve these connecting issues to openings. The highest insulation standard for one part could create problems on a weaker part with condensation. It is useful to implement a special expert planner to simulate the parts working together in different environmental conditions to create the optimum outcome, advises Wurster.

One will have to strike a correct balance among visible light transmission (VLT) which ensures sufficient daylighting and control glare into the building, energy performance by evaluating solar factor (SF) and U-value of the façade, points out Singh. Another important parameter is noise reduction, which can be achieved with acoustic glass. It is important to adhere to serviceability limits to ensure that the occupant always feels safe inside the building. One may have to do energy & daylighting simulations to correctly understand the design parameters in terms of VLT, SF & U-value.

A part of the reflection provided by the state-of-the-art highperformance glass might reduce the direct heating, but still, the indirect heating of the glass due to the hot temperature is creating a huge energy loss to all buildings in hot countries facing the west or the south direction of the building. According to Das, proper glass selection can give maximum comfort to the end-user. Refer to the table below.

2. Improving the Acoustic and Thermal Performance of Glass Façades & Fenestration

Acoustic lamination
Acoustic lamination

The acoustic and thermal performance of the glass façades could be improved by using high performance smart glass in place of normal glass observes Joshi. These high-performance glass are energy efficient, having a good visual light transmission (VLT) and nice in appearance also. In all hot (tropical) countries, buildings are challenged by the negative impact created by unwanted heat. With the increased glass areas, the demand for cooling increases considerably, especially during the hot summers. The sunlight hits the glass with the energy impact of 1000W per square meter of glass area, explains Schmidt.

The acoustic performance of glass façades & fenestration can be improved by using thick glass, laminated glass, laminated IGU and double skin façade. It’s the thickness of the whole glass unit which provides acoustic values, higher the thickness, better the sound insulation, says Balaggan.

Normal lamination
Normal lamination (Images courtesy – Façade Concept Design Group)

According to Das, acoustic analysis very much important as the selection of glass whether single glass, double glass including façade system barrier design to achieve sound reduction. To understand acoustic performance, it is important to understand “Mass Law” and “Inverse-square Law”, says Singh.

Although “Inverse-square law” may not be very useful in urban settings due to limited space but Mass Law plays an important role. Apart from this, acoustic interlayers are available which helps in dampening of the noise. One will also have to understand the frequency range to correctly provide and acoustically efficient solution.

The higher the STC rating (Sound Transmission Class), the abler the material is to resist the transmission of sound, points out Thakur. For example, if an 80 dB sound on one side of a wall/floor/ ceiling is reduced to 50 dB on the other side, that partition is said to have an STC of 30 dB. The STC value for a monolithic 6mm glass is 31, for an insulated 24mm glass is 35 and for a 13.52mm laminated glass is 39. Laminated glass also has superior sound insulation qualities in the higher frequency range where the noise from sources such as aircraft is a problem.

The G value (IR waves) and the U-value

The G value is a measure of how much solar heat (infrared radiation) is allowed in through a particular part of a building. The U-value is a measure of how much heat escapes via the windows, walls and roof.

The Performance of Solar Control Glass

The role of solar control glass towards achieving required energy transmittance, low emissivity coatings that improve thermal insulation. To achieve a lower U-value, we have to reduce conduction, convection and IR radiation.

The key parameters that describe the performance of solar control glass include.
1. Visible light transmission
2. Solar factor (SF)/Solar Heat Gain Coefficient
3. U-value, i.e. W/m2k
4. Selectively – Visible light/ total energy

Thus, the main goal of glass and glazing design should be to provide visual and thermal comfort to the occupants and thereby reducing the electricity cost for lighting and HVAC. When a building is in cooling mode, solar heat gains need to be minimised within the building space while optimising daylight and intake of outside air. Outside air could be introduced, particularly during the evening/night hours when the ambient temperature drops.

Marvel Artiza at Hubli by Blocher Partners India Architects Marvel Artiza at Hubli, Blocher Partners India

This strategy cools the thermal mass in the building during night hours and reduces the overall cooling load during the next day. On the other hand, if the building is in a heating mode, the envelope needs to be designed with appropriate glazing selection, coupled with shading strategy, to enhance solar heat gains during the daytime. Therefore, in practice, the architects and building designers need to integrate and balance these varying requirement considerations while designing an energy-efficient building. (Amrit Raj Thakur, Dy. Manager, Central Procurement, Lodha Group)

The Design considerations and methodologies based on NBC:

While selecting glass and glazing systems, following design considerations and methodologies based on NBC need to be followed to ensure the right use of glass and glazing systems.

1. General considerations- basic considerations must be given appropriate importance at the planning stage to achieve proper selection and design of glass in building façades. They are:
a. location
b. climatic zone
c. orientation
d. building details
e. natural ventilation

2. Considerations of safety and structural aspects – Considering all types of loads

3. Considerations for energy efficiency

4. Considerations for acoustical comfort

(Amrit Raj Thakur, Dy. Manager, Central Procurement, Lodha Group)

Glass Selection & Installation – Fire And Structural Safety

It is important to ensure that the serviceability and safety limit specified by “National Building Code” NBC 2017 is followed on a minimum basis.

1. Structural Safety of Glass:

A Residential Project by GSC Glass A Residential Project by GSC Glass

Load bearing capacity Schmidt explains, with the new National Building Code (NBC 2017) in place, where glass has been covered for the first time, it is clearly defined between safety and security areas. If the glazing unit starts from the bottom of the floor up till 900mm from the flooring, laminated safety glass is compulsory.

The thickness of the glass, as well as the thickness of the security PvB film, needs to be decided by the consultant as per law and latest stand of the technique, opines Schmidt. Talking about the safety aspects of glass façades, Schmidt says, “We need to reconsider the ongoing practice of making laminated toughened glass as the strength of the unit, which may fully collapse once the glass breaks. Here it is really important to use heat strengthened or annealed glass to assure the strength the moment the glass breaks.

As a thought from my end, all laminated glass used in curtain walls and even indoors and windows should be sealed all around like in structured glazing to assure the strength of the unit”. Glass is one of the hardest materials in the building industry, says Wurster, especially if it gets bent or takes shock forces from the side (in cross direction). In the built-in condition, to make sure to avoid forces like tension as impact, it is taken care of by fabrication elements. In case of breaking, there are safety regulations for glass in special conditions, like balustrades or overhead glazing. If glass breaks, it shall not break in shards, which is called in German “VSG” (A condition of 2 layers of toughened glass with metal foil between). In the usage of “VSG” when required you reduce the danger of shards.

Das recommends: The glass on the exterior should be laminated HS glass, if it is single glass to in use. Laminations like PVB layers or SGP films are used for structural safety, but normally the current industry practice is to go with tempered glass with DGU (Double Glazing Unit). The head soak treatment perverts it from spontaneous breakage. The laminated SGP film is strongly recommended for glass railing, canopy or any cantilever façades. Heat Strengthened (HS) glass has 2-times more strength than annealed glass. Tempered glass is 5-times stronger than annealed glass, adds Das.

Balaggan too recommends structurally safe glass, which is a laminated tempered glass, using high strength interlayer like Sentry, which provides high structural properties for applications like glass canopies, balustrades, fins, skylights and for security applications. He agrees that structurally safe glass has good load-bearing capacity compared to other façade materials. “Normally the glass is designed/selected based on wind loads. It has to be strong enough to withstand various loads like building loads, maintenance loads, self-load, load due to building movements, etc. There is a technical table which indicates the thumb rule guideline for selection of the glass,” he points out.

Mondeal Heights at Ahmedabad - A Glass Facade Project by Blocher Partners Architects
Mondeal Heights at Ahmedabad, Photo credits – Purnesh Dev Nikhanj for Blocher Partners

For creating more transparent buildings, it is necessary to design walls with small fixings, notes Thakur. By applying point fixing, it is necessary to use toughened glass, which can carry concentrated loading. Architects mostly suggest point fixing, which is applied in glass curtain walls. For large glass façades, there are some applications of glass in which the glass has to be jointed. Steel joints are widely used with the coupling of rubber or plastic elements to damp the stresses in the glass. When the glass is used as a principal load bearing structure, it is important to calculate the stresses at the hole. Some recent researches have shown that the edge stresses are higher than those in the middle of the pane. The design and detailing of the bearer connection, thus become a primary factor of the overall capacity of the structural system.

Apart from this, barrier loading is an important parameter to be checked upon when considering a full height façade, which is very common in today’s scenario, adds Sing. It is important to perform a complete risk assessment of the façade and very important to understand the post-breakage behaviour of the façade. One may also have to restrict the opening size to eliminate the possibility of somebody/something falling out of the opening. In some (very few) cases, one may also have to check the fire-resistance rating as required by the façade. With the advancement of the industry, now the glass is regarded as absolutely safe for use in façade, says Singh from GSC.

Various process like tempering, heat soaking, lamination, availability of multiple thicknesses makes the glass safe for almost all the area of usage in façade. Glass is lighter on building structure when compared with other façade material like masonry, stone, etc. and it is maintenance-free. Regular cleaning of the façade is still required to make the façade look spic and span. Glass is the first choice as façade material due to its transparency, which cannot be matched by any other façade material.

Glass and Its Applications

1. Annealed glass – It has a good surface flatness because it is not heat-treated and therefore not subject to distortion. On the downside, annealed glass breaks into sharp, dangerous shards.

2. Heat-strengthened glass – It has at least twice the strength and resistance to breakage from wind loads or thermal stresses compared to annealed glass.

3. Fully-tempered glass (Toughened glass) – provides at least four times the strength of annealed glass, which gives it superior resistance to glass breakage.

4. Laminated Glass – It involves sandwiching a transparent sheet of polymer, such as polyvinyl butyral, between two or more layers of flat glass using an adhesive. It can prevent the fall-out of dangerous glass shards following a fracture.

5. Insulating glass – It consists of two or more lites of glass separated by a hermetically sealed space for thermal insulation and condensation control. The airspace between the glass lites can be filled during the manufacturing process with either dry air or a low-conductivity gas, such as sulfur hexafluoride or argon. (Amrit Raj Thakur, Dy. Manager, Central Procurement, Lodha Group)

2. Fire Safety of Glass Facades

Residence of Golcha and Aarti, a Lingel project
Residence of Golcha and Aarti, a Lingel project

According to Wurster, the fire norms for opening parts depend in most cases on enclosing building parts. If there is an inquiry for a wall or slab part, there is also a requirement for the opening part. Which is determined by the duration of resistance against fire and classification the way they burn. While selecting glass façade and façade materials, says Das, the specification should follow façade norms/codes as per location or country wise. Normally glass façade should have a minimum 10% of window opening by providing openable windows for smoke ventilation and also should provide access to fireman to get inside the building if any fire occurs. Every glass façade should have floor to floor fire barrier with a minimum 2-hour fire rating. So all the products to be used as a fire barrier should be fire-rated, and wall cladding material to be used in the façade should have fire rate grades like A2, B1, B2, etc. Balaggan too agrees with these points.

According to Joshi, the following points should be kept in mind while selecting and designing the façade:

Sufficient openable windows (Almost 10% of the façade area on each floor) should be provided.

All the opening in the floor – i/c shafts, gaps between façade and structural slab, etc., should be sealed properly. Smoke seals need to be provided.

Concerning the new guidelines, the fire brigade has made it mandatory that every building with a glass façade must have openings (both ways openable, having “Emergency Exit” labels) on every floor, says Balaggan. The distance between the building structure and glass façade should not be more than 300 mm. Also, the smoke seals or barriers (made of non-combustible material) must be laid between the wall and the façade. As per the new guidelines, the glass façades that block escape areas like corridor, lifts & staircases should be synchronised with an opening mechanism and glass façade must be laminated. As per the NBC (National Building Code of India) 2016, all-glass walls should be able to resist fire for at least 2 hours, adds Balaggan.

When we talk about fire, points out Thakur, we have to factor in the radiant heat that fire generates. Radiant heat is invisible, extremely intense electromagnetic waves that travel at the speed of light. On striking an object, these waves are absorbed and their energy is converted into heat. Combustible objects like paper and wood auto-ignite due to the heat when they reach their flashpoint. While deciding on the ideal fire rated glazing product, it is important to decide what the design and safety needs are. We need to decide whether glazing requirement comes with only integrity or insulation or radiation control.

Simultaneously, we need to decide as to for what duration we need the fire resistance and whether the fire protection capability needs are from one side of the glazing (as in case of fire escape passages), or from both sides (as in case of internal partition between two sections in an office).

Effective Maintenance Of Glass Facades

Kishore Residence
Kishore Residence – outside view, a Lingel project

According to Wurster, during the planning process, façade maintenance is an aspect to consider and to provide a solution for. But there might not be a universal solution. For one project, the better option might be securants for façade climbing, for another installed façade elevator might be better. It depends on the geometry of the building. There are different types of building maintenance systems used in the glass façade but for tall building, large glass façade should recommend with BMU (Telescopic zip crane), says Das.

The BMU (building maintenance Unit) should be used for effective façade maintenance, advises Joshi. It has a track mounted machine at the top of the building and a trolley/ gondola attached to it for carrying the cleaning material and persons.

According to Thakur, the façade access systems should cover the maintenance requirements for the high rise building, making sure that it will reach all angles and difficult spots of the building. Safety and easy-to-use, handling is at the center of the approach. Every maintenance job must be carried out safely, providing maximum flexibility for maintenance workers.

Façade Maintenance Systems

Following are the types of façade maintenance systems –
Rope access
Building Maintenance Units (BMUs)
Elevated Work Platforms (EWPs)

Presently the safe and reliable building maintenance equipment available for façade maintenance of a tall building with a large glass façade is BMU, an automatic, remote or controlled mechanical vehicle with a cradle that can be suspended from the roof. This is also called Gondolas which is used worldwide for tall buildings with large façades. It comes in different sizes and shapes and suitable to conduct maintenance of the tall buildings. (Rajiv Balaggan, Sales Head – Architectural Glass India, Pilkington Glass India Pvt. Ltd)

Glass For Intelligent Building Envelope

Timesquare Glass Facade Design by Pilkington Glass India
Timesquare, Pilkington Glass India

Façade is the main constituent of building envelope and boundary between external and internal environment, which is crucial to energy consumption and comfort within buildings. Incorporating intelligence in their design is an effective way to achieve low energy consumption building. With the advancement in the glass technology, glass can help create an intelligent building envelope, says Balaggan.

Apart from using an already available wide range of solar control and thermally insulated glass, now there is a new glass product available which adapts to the changing incoming solar heat radiation conditions that change throughout the day and the season. The glass lightens and darkens by itself based on the amount of heat from the direct sunlight, explains Balaggan. It adjusts the level of solar control depending on the orientation of the building. Despite the automatic tinting, this technologically advanced glass enables you to enjoy a clear view of the outside environment throughout the day.

According to Schmidt, the new age architecture shows a combination of glass, balcony covers and vertical gardens to provide the best mix while allowing the maximum light to come in, at the same time avoiding the overheating of the building due to the glazing. Balconies, as well as vertical garden elements, prevent the direct sunlight hitting the glass, at the same time it creates a uniqueness to each building when all those three components are wisely mixed. In case the direct sun hit cannot be avoided, shading options like roller shutter or outdoor Venetian blinds provide shading as well as privacy and security. Here again, it is the architect or the façade consultant who has a wide range of unique products to play with to create an individual signature to every building.

Façade design should be able to adapt to the changing climatic conditions rather than shutting from climate, points out Das. Adaptive façade help to minimise the disadvantages so that high comfort can be achieved. This can be achieved by the right selection of façade systems and ventilation. It may include using a dynamic façade system and incorporating Solar PEV for electricity generation. In the future, intelligence façades could help to maintain optimum indoor conditions.

These days, architects are using a range of engineering and computational services to create intelligent glass building façades. Firstly, the parameters of the façade performance should be decided that would distinguish it as an intelligent one, says Ar. Goel. Eventually, computational tools can be used to optimise these parameters to achieve the desired goal for design performance.

For example, if a designer uses minimum solar insolation as a goal for the façade design, a parameter of incident solar insolation can be minimised using heuristic optimisation tools to produce several apt design options. These tools are provided with visual programming software for architects and allow them to explore design during the schematic design process itself. An example is Grasshopper 3D which provides optimisation tools such as Galapagos, Octopus or Wallacei that can be used in conjunction with Rhino 3D to achieve such design agendas.

While we all take for granted that buildings must be equipped with glass, its numerous benefits in buildings are mostly ignored, says Thakur. Beyond its critical role in terms of aesthetics, safety, durability, sound insulation, etc. glass is integral in designing truly sustainable and low energy buildings. Glass is a major contributor to energy-efficient buildings.

Glass Facades – A Symbol Of Modernism

Glass Facade Project by GSC Glass A Project by GSC Glass

Glass is one of the most remarkable building materials in the world today and glass is seen as a symbol of modernism in future architecture. Glass not only provides aesthetics but also plays a very important role in the energy efficiency of the building. Many of the industry’s leading architects and designers have used glass in their iconic buildings. Experimentation with glass in architectural design has crossed the conventional boundaries. Glass in current discourse has been used with research and knowledge acquired over a century, notes Ar. Goel.

Currently, glass façades can be designed with specific parameters and distinct manufacturing processes. This allows controlling its design and performance within the building. As glass façades have got technology-driven to achieve specific performance standards, it can be seen as an expression of modernism in this era of sustainable and engineered built environments.

Modern adaptive façades can significantly improve energy and thus cost efficiency of both new and refurbished buildings by responding to the changes in the outdoor conditions. Furthermore, they can provide a healthy and comfortable indoor environment to the building occupants, by adjusting the response to their needs. In the future, we will see multi-functional façades that provide a variety of functions such as heating and cooling.

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