Future of building envelopes (façades) in Sri Lanka

Wednesday, 30 January 2019 00:13 -     - {{hitsCtrl.values.hits}}

A ‘façade’ is the external envelope or face of a building which includes pretty much everything above ground level on its external enclosure. These are commonly identified as curtain wall, aluminium or stone cladding, glazing, renders, masonry walls, windows, doors, balustrades, canopies and skylights, etc.

Façade engineering is an art and science which resolves the technical challenges in the process of delivering the architect’s intent on a building envelope. One of the common misconceptions in Sri Lanka is that the term ‘façade’ is being expressed to define curtain walls, cladding and glazing works only. Even some of the construction industry professionals failed to understand the difference between ‘façade engineering’ and ‘façade access engineering’. Façade access engineering may be considered as part of façade engineering, however its purpose is to provide access strategies for the erection, cleaning, maintenance and remediation of façades and these two should not be confused.

This article is written in an attempt to provide an overview of façade engineering, highlight the importance and the positive outcomes of employing a professionally qualified façade engineer in building construction projects in Sri Lanka and their recognition in the industry. 

The façade of a building is considered to be one of the major, most expensive and most important elements of a building project as it defines the identity or the aesthetic appeal, which can represent up to 35% of the construction cost and technically perform as a barrier between the interior (habitable) space and the external environment of the building. Due to the nature of being the environmental barrier which plays a major role in the energy efficiency, façades are expected to be the most onerous part compared to any other part in a building fabric. Historic evidence also suggests that the façades are the elements of buildings which are reported to have highest level of failures.

Until recently even in the developed countries, the design, fabrication and installation of façades have largely been a process established from the application of empirical techniques which is mainly driven by the façade contractor to deliver the architects intent with an involvement of a structural engineer occasionally in the process. This is still the case in Sri Lanka, with the exception of very few iconic projects. 

Relying mostly on façade contractors or material manufactures and suppliers is not the best approach. In countries like Sri Lanka where there are no façade specific tight guidelines enforced by the authorities, they may promote the materials/systems within their capacity or capability only rather than merit of a building or its users. However, façades have become more and more complicated even beyond the capabilities of architects, structural and mechanical engineers due to their complexity. 

With the implementation of new and more onerous regulations enforced by the authorities in the developed countries, the design of façades is now being considered as part of a holistic strategy. In particular, science needs to be carefully considered to deal with, resolving aesthetic, environmental and structural issues to achieve the effective enclosure of buildings. As a consequence, façade engineering has become a science in its own right. 

In order to carry out the design, manufacture and installation activities of façades in more comprehensive, more efficient and a more effective manner (in addition to a traditional architect, structural engineer or mechanical engineer) an involvement of a dedicated engineer with a particular set of skills and experience, who understands the behaviour of various types of façade is required. These skills typically include areas such as heat flow through 2D and 3D construction details, computations fluid dynamics (CFD), the characteristic/the behaviour of materials, manufacturing techniques /methodologies, structural analysis and logistics. 

Façade engineers usually come from architecture, civil/structural engineering or mechanical engineering (building physics) backgrounds. Due to the very limited involvement with façades in their original discipline they would normally require developing their skills and knowledge to be able to become a façade engineer. They may also require undertaking a recognised higher study or obtain membership with a qualifying body by proving their abilities to become a professionally qualified.    

Façade engineers generally consider aspects such as the design, certification, fabrication and installation of the building façades with regards to the performance of materials and systems being utilised as part of a building façade in terms of weather tightness, structural integrity, thermal performance, fire behaviour, acoustic performance, ventilation, shading, condensation, interface with the primary structure, comfort of the occupants and energy efficiency, durability, sustainability, natural light admittance, safety and serviceability, security, maintenance and buildability. This is a separate field beyond the capabilities of most façade contractors and material/system manufacturers.

The advice of façade engineers may be obtained on both construction of new buildings and refurbishment of existing buildings. Façade engineers who work as consultants may be involved in a project from the concept design stage until the completion, working alongside the architect, civil or structural engineer, mechanical or building services engineer and cost consultant (quantity surveyor) or involve in façade failure investigations to provide suggestions for remedial works. They are able to advise on a full range of façade systems, utilisable materials, performance requirements.

Recently, main/general contractors also appoint façade engineers to work on behalf of them as ‘façade package managers’, when more than one façade contractors involved in a project, in order to coordinate the technical aspects related to façades. More than one façade contractors may be employed in a project to build different types of façades (curtain walling, stone cladding, masonry, etc.) or more than one contractor with similar capacity may work on different buildings or phases of one high scale project.

Façade engineers may also work for façade contractors, material manufacturers, system suppliers and at educational institutions or laboratories (as researchers).

The first two categories as stated above are known as ‘generalist façade engineer’, whereas the latter category is known as ‘specialist façade engineer’. 

The outcomes of involving a façade engineer will result in performance lead specification and design, design excellence, delivery of facades that do what is intended of them, controlling risk, driving cost out, maintaining of continuity through the fabrication and installation stages, attention to quality as the design becomes a physical reality, verification of performance upon delivery and when the occupants take over the building and offer remedies when issues raises. 

Another common misconception is that the service of a façade engineer is not required for a small-scale building such as houses and dwellings, etc. but an involvement of a façade engineer from an early stage of any project would increase the probability of delivering an energy efficient cost-effective quality building envelope. 

Throughout the world there are many complex geometry building facades being built, utilising variety of innovative materials. However, only three European universities offer specialised master’s degree courses in the field of Façade Engineering/Façade Design, where generally the students are from the façade industry. As a result of these factors, the number of professionally qualified façade engineers is considerably lower than the requirement. 

The lack of a façade specific professional organisation as well as inadequate detailed technical information on façades (within the regulations in the United Kingdom) were realised by the professionals in the industry, which resulted the formation of ‘Centre for Window and Cladding Technology’ (CWCT) and ‘Society of Façade Engineering’ (SFE) in the United Kingdom. CWCT is contributing to the industry by producing guidelines and technical notes on various technical aspects of façades in addition to conducting trainings time to time. SFE is a professional body which works alongside Chartered Institute of Building Services Engineers (CIBSE), Royal Institute of British Architects (RIBA) and The Institution of Structural Engineers (IStructe) and recognises professionally qualified façade engineers in the industry. 

A brief web-based research suggests that the sole available document produced by an authority in Sri Lanka where reference of building façades is made is the ‘Code of practice for energy efficient buildings in Sri Lanka – 2008’ issued by ‘Sri Lanka Sustainable Energy Authority’. Section 4 ‘Building Envelop’ of this document consists of very generic and considerably minimal (over three pages long) information with regards to performance requirements of building façades. In an instance, a mistake with regards to the ‘air leakage’ limit was observed which is believed to be a typo error. The above document requires a detailed review and revisions to be made to suit the current requirements and good practice.

It may not be appropriate to entirely rely on British, American, Australian or any other standards and build façades in Sri Lanka, due to the variance of the topographical and environmental conditions of Sri Lanka compared to many other countries in the world. It is high time that the relevant authorities in the country consider producing a set of documents in which the minimum performance requirements and strict guidelines with regards to building façades in Sri Lanka are outlined, keeping the upcoming mega projects (consisting of high rise and complex geometry buildings) in mind. On the other hand, façade engineering profession needs to be professionalised and reliance on the skills and responsibilities of façade engineer to be increased. 

(The writer holds an MSc Façade Engineering, ASFE and is a Façade Engineer.)