The use of glass for a building façade has long been a preferred cladding for designers as a way of opening up the space and bringing the exterior inside. Glazing helps provide the necessary daylight inside a building and brings the heat into the built form. It also adds to the aesthetics and helps reduce the maintenance costs. All buildings have elements such as doors, windows, and skylights where glass is used as infills with metal or UPVC profiles. Glass today has become a lot more specialised with enhanced technical and performance capabilities that require specialist knowledge. The performance of the glass affects the ingress of heat and light so it is important to use the correct glass for the building depending on the usage and energy efficiency required.
The glass comes in pure sheets which are called float glass as the process of manufacturing includes floating the molten glass on molten tin or similar materials. Float glass is a very basic component of glazing used in buildings. It can be used in the form of insulated glass or double glass units (DGUs). Double glass units are the common form of insulated glass where two glass panels are combined with an air gap to create a double glazed panel. Depending on the performance specified the glass processor builds the DGUs where individual float glass panels are toughened, coated, and tinted before being fused together. As general protocols, these are tested and the test reports are reviewed before the actual fabrication.
Architects will look at the light transmission and U-value as well as the shading coefficient as key basic performance factors. In this region, in particular, UV transmission and the light to solar is an important consideration to counteract the building’s solar heat gain. Reflectivity and the colour of the glass are purely aesthetic and will depend on the client’s brief. Light transmission is usually specified in percentages and indicates the amount of transparency of the glass. This value is decided depending on the building usage. A retail unit, for example, will require more transparency and so the figures are closer to 80-90%. For residential buildings where comfort and less glare are required, the value would be around 40-50% transmittance. The lower the transmittance the darker the glass appears.
The U-value is one of the main criteria which indicates the thermal performance of the glass. This is usually measured in w/m2 which is the amount of energy that will pass through a 1 m2 area of a substance for each degree of temperature difference from one side to the other. Generally, municipalities across the world stipulate this figure, which is an average of DGU and the profile system. In Dubai, the green building guidelines define this based on the surface area of the glass compared to the overall façade area.
The shading coefficient (SC) is a measure of the heat gain through the glass from solar radiation. Specifically, the SC is the ratio between the solar heat gain for a particular type of glass and that of double-strength clear glass. A lower shading coefficient indicates a lower solar heat gain. Architectural glass has come a long way in becoming one of the premier materials preferred by architects and designers and modern innovations have provided more options for designers allowing us to continue to meet the needs of building owners and developers today and in the future.
CASE 1: The Arcadia School Seconadary Campus, Dubai
Arcadia Secondary School, Dubai The project has high-performance glass with flexible design
High-performance glass is used in this project with flexible design. When modelling for the façade, we designed the glass to take into account the solar gain on the western and southern side of the building rather than simply using a generic glass cladding for the entire building.
Fact File Client: Arcadia Academy Location: Dubai Architects: Godwin Austen Johnson Materials: High-performance glazing Date of start and completion: July 2018 – July 2020
CASE 2: Office Project, Abu Dhabi
Ceramic fritted glass is used in this office project at Abu Dhabi
For this project, the ceramic fritted glass has been used which cuts the glare and adds to the overall solar heat gain criteria yet still maintains the transparency effect.
Fact File Project type: Office Materials: High-performance glazing with a ceramic fritting for skylights Architects: Godwin Austen Johnson Date of start and completion: Ongoing
CASE 3: Dubai Sports City Sports Academics
The façade Dubai Sports City was made up of high-performance glass, but to further offset the solar gains and cut off the glares
A large part of the façade design of the Dubai Sports City was made up of high-performance glass, but to further offset the solar gains and cut off the glares, we used glulam columns with aluminium aerofoils. Glulam is a sustainable material that helps reduce a building’s footprint by reducing energy usage.
Fact File Project type: Sports facility Client: Dubai Sports City Location: Dubai Architects: Godwin Austen Johnson Materials: High-performance glazing with aerofoil devices Date of start and completion: July 2006 – July 2008
CASE 4: Serenia Residences, The Palm Jumeirah, Dubai
The project has parallel opening windows
For this luxury residential project, the parallel opening windows were used that allows a better flow from all sides and, because they are parallel to the façade, attract less dust which eventually reduces the frequent use of BMUs.
Fact File Project type: Residential Client: Palma Holdings Location: Dubai Architects: Godwin Austen Johnson Materials: High-performance glazing with parallel opening windows Date of start and completion: July 2015 – July 2017
CASE 5: Dubai College Sports Aand Performing Arts Center, Dubai
The façade of Dubai College Sports and Performing Arts Centre has laminated frosted glazing
At the Dubai College, the laminated frosted glazing was used where the PVB interlayer is frosted which allows diffused light into the building but cuts out any glare. The high-performance DGUs helps in reducing energy usage and the client is less dependent on artificial lights during the day time.
The future of glazing is exciting. Smart façades and the use of integrated photovoltaic, where PV cells are an integral feature of general glazing and cladding materials, are certainly going to feature in the future of cladding here in the GCC over the next few years
PV cells incorporated and fused into the DGUs generate clean energy and still allow light through. These are multifunctional providing thermal and sound insulation ensuring filtering close to 99% of the UV radiations and absorbing 95% of the IR radiation. Smart glass is made up of electrically controlled glass panels where the opacity is controlled through an electrical current in the interlayer. By careful performance modelling, the right amount of opacity is introduced which can be connected to illumination sensors. The transparency is adjusted to let in the right amount of light energy from the outside. Analysis performed on some of our projects has shown that comparing the CAPEX with the OPEX of the glass against the use of automatic blinds the OPEX always wins over the CAPEX.
Fact File Project type: School Client: Dubai College Location: Dubai Architects: Godwin Austen Johnson Materials: Frosted PVB layer DGUs Date of start and completion: July 2019 – July 2020
Avinash Kumar began his career in 1998 as an architect in New Delhi, India. He holds a Bachelor of Architecture from the M.N.I.T Bhopal and a professional certificate in the environment and sustainable design from CEPT, India. During the five years of his professional tenure in India, Kumar was involved in several projects ranging from hospitality to education. He moved to Dubai to join GAJ as a senior architect in 2005 and continued to be involved in educational projects, most notably the Ladybird Early Learning Centre and the Arcadia Preparatory School, both in Dubai. He was also a key member of the team responsible for the Dubai Sports City, a multi-purpose venue that has successfully blended a comprehensive sports village with a host of international stadia, including the ICC headquarters, to create a unique lifestyle community.