Nitin Bhatia is the Managing Director & Principal Consultant of FACET Façade Consultancy, a specialist façade consultancy practice executing projects across India, Middle East and Africa. Nitin has trained as an architect and has worked across disciplines including design, management, R&D and forensics and is currently working on several projects in India and overseas including super tall buildings such as the 117 oor World One Tower in Mumbai with an added experience in engineering, manufacture, installation, project management, procurement and testing of façades. Nitin Bhatia spoke eloquently on evaluation and selection of glazing systems for optimal performance of façades and fenestration.
WFM: Kindly brief on how the façade and fenestration designs could help building “net energy gainers” or “zeroenergy” buildings?
Nitin Bhatia (NB): Today’s façade is a result of the aspirations of the end consumer, buoyed by developers and designers. That said, due to sheer economics, such consumers are a tiny minority, hence projects propagating the growth and evolution of façades remain relatively few and far between. It is not that the technology of advanced/energy efficient façades does not exist today, but it is other considerations that do not promulgate its widespread utilisation.
An energy efficient façade is a costly proposition and is therefore dependent upon Brigade World Trade Cente, Bangalore the developer’s appetite to procure it. The costs involved include all or a combination of thermal isolation of the framing system, high performing glazing, shading systems, double skin, light shelves, photovoltaics, and finally orientation and geometry. If all these are considered and incorporated in the façade design the façade could contribute towards an energy efficient building and may perhaps be a net energy positive building when other factors are included.
With every passing year, costs for materials and technologies enabling “energy efficient facades” are reducing as a result of technological advancements, hardware and software development and ease of availability, as well as economies of scale, thereby making energy efficient façade components economically feasible to use.
WFM: What are the design factors which could optimise daylighting?
NB: There are many design factors that must be used to achieve the means to the end; most important of them would be the “logic” that ties them all. In all likelihood, no two projects would
have the same solution. Dissimilar geographies,
orientations, municipal guidelines, etc., shall require
Typically, the façade orientation, geometry, visible light transmittance, shading and light shelves should be considered when designing optimum daylighting. So, one has to ensure that natural light is allowed to reach the far interior of a room, yet not allow too much light to cause discomfort due to glare. At the same time, depending on the geographical location, solar light hitting the fenestration directly should be restricted to avoid heat accumulation in the room if be the case. Intelligent use of performance coatings, shading systems, etc., may be utilised to achieve this goal.
Unfortunately, the combination of all above has been considered on limited projects effectively leading to projects utilising expansive extents of blinds; this so largely due to the costs involved and in some cases capability limitation of developers and designers.
WFM: Improving the insulating value of window glazing has been the subject of research since the 1980s. Could you please tell us about the latest developments in this area?
NB: Insulation of a window can be done in many ways. Obvious methods are utilisation of high performance glazing and thermally broken framing systems. However, other methods such as exterior blinds / louvres, sun shades, etc., also contribute extensively to improve insulation performance of a window. Glass coating technologies (very high performing low e coatings) and fritting technologies play a great role today in achieving the objective.
WFM: How would U-value and highly insulating window technologies affect energy conservation?
NB: Shading coefficient (SC) is a measure of heat transfer due to direct solar radiation (direct sun light). U-value is a measure of heat transfer due to radiation from surrounding materials/local environment. Therefore, SC is a more critical value than U-Value of a fenestration. That said and depending upon the geography where the framing is to be installed, thermal conductivity analysis of the framing should be carried to out determine heat transmission through the system.
WFM: Please tell us briey on challenges involved in designing integrated façades for both energy conservation at the same time for optimal day-lighting?
NB: The biggest challenge when dealing with day lighting is to arrive at a balance between external reflectivity, light transmittance and distribution, and glare. Too much light leads to glare and too little leads to the requirement of artificial lighting. Add lower slab to slab height to this and you have a further restriction of reflective natural day lighting.
WFM: What are future Window & Façade technologies those could save signicant energy in buildings?
NB: Other than evolution of material technologies and economies of scale, parametric simulation softwares are and will play an exceedingly critical role in the future of façade design. All parameters can be modelled and designed for optimal orientation, geometry, shading, light shelving & day lighting, radiation & thermal insulation. In addition, and perhaps the most critical shall be the evolving discerning occupant; the ultimate driver of improvement in performance.