Opinion Piece by Simon Sturgis
Glass facades – An obsolete typology
Glass facades for buildings have been a staple of commercial architecture since the 1950s, and the advent of two New York buildings in particular: the Seagram Building, designed by Mies Van de Rohe, and the United Nations Secretariat Building, designed by Oscar Niemeyer and Le Corbusier.
Both buildings offered a post-war vision of shiny modernity and the latter, completed in 1952, was the first example of a fully glazed, curtain-walled building using the then recent innovation of air conditioning. In the 1950s, energy was cheap, and there was no thought of a climate crisis.
The architectural and sculptural appeal of all-glass facades combined with the speed and economy of construction has remained irresistible to architects and developers, the benefits of great views and an abundance of natural light have also made them attractive to occupiers and therefore easy to let. This combination of these factors has proved enduring for the past 70 years.
Despite that history, the case for all-glass facades now needs to be re-examined for two vital reasons: resource efficiency and climate change. In practice, these two are connected, as increasing the efficiency with which resources are used reduces carbon emissions.
The most obvious source of carbon emissions for an all-glass building is the energy used in the cooling required to mitigate the heat gain from the façade, which is typically double-glazed. The greater the proportion of glass in a facade, the greater the load on the air-conditioning and the greater the carbon emissions.
The second and less obvious source of carbon emissions related to such a facade is the material-related emissions associated with sourcing, manufacture, transport, construction, maintenance and disposal, which are known as embodied emissions.
The requirement to reduce air-conditioning load while keeping an all-glass facade means that sophisticated glazing measures have to be found, and this usually means a triple-glazed facade with a large gap between the outer pane and double-glazed inner panes to accommodate electrically operated blinds.
The external and internal layers of glass are also usually laminated for safety reasons, all of which means five layers of glass are set in a deep aluminium framing system. This type of system has a high embodied carbon cost.
An additional problem is that laminated glass and double-glazed units typically have warranties of 25 years, and even if they continue to perform beyond this time, the units still tend to need replacing every 30–40 years.
Typically, replacing all the glazing leads directly to replacement of the whole system, and these systems can be difficult to recycle effectively. This therefore represents ongoing carbon and financial costs over the life cycle of an all-glass façade. Typically, the cycles over which such entire facade replacement takes place are not synchronised with the expected lease cycles either.
So, whether it from the perspective of day-to-day energy use or construction and maintenance, all-glass buildings are problematic in terms of both carbon emissions and resource efficiency. Far better from all perspectives is a facade where most of the surface area has a life expectancy of 80-100 years, and no more than 40 per cent comprises smaller, simpler double-glazed units that can be replaced when required. Such replacements are cheaper, generate less embodied carbon and are potentially less disruptive over the commercial life of the building.
Does any of this matter, however, if the rent is justifying the additional costs of a 30–40-year facade replacement cycle and demand is sufficient?
There are two areas that will make an increasing difference to investors, owners and occupiers, the first of which being regulation. In the UK for instance, the new Greater London Authorities London Plan will be requiring whole life carbon emission assessments for all referable schemes, and many glass buildings are of a size that are automatically referable. The requirement for whole life carbon assessments is spreading across an increasing number of local authorities which will also put increasing pressure on non-referable schemes to be fully carbon efficient.
Over the next ten years or so, this requirement is likely to tighten up further in response to the UK government policy for zero carbon by 2050. Today’s all-glass buildings will likely fail to meet more stringent future environmental regulations, and this will become an issue when the facades need replacing. Such replacements will almost certainly not be like for like which suggests that designing an all glass façade today is inviting early obsolescence.
The second key issue is the investment and insurance risks inherent in climate change, and the likely impact of these on occupier sentiment. There are several international organisations that are advising investors and insurers on the implications of climate change, including the Financial Stability Board’s Task Force for Climate-related Financial Disclosures (TCFD), the World Business Council for Sustainable Development, and the Principles for Responsible Investment – Real Estate (PRI).
All of these make clear links between investment and climate change.
For example, the PRI states: ‘As part of wider efforts to implement the Paris Agreement, every real-estate asset owner, investor and stakeholder must now recognise they have a clear fiduciary duty to understand and actively manage environmental, social and governance [factors] and climate-related risks as a routine component of their business thinking, practices and management processes’.
The TCFD meanwhile says recommendations in its 2017 report ‘will ensure that the effects of climate change become routinely considered in business and investment decisions’. During 2021 the Bank of England, which already stress-tests financial institutions for financial resilience, will be including climatic risk in such testing as well. All these measures will help put climate change at the centre of financial decision-making and have a direct impact on real estate.
All-glass buildings responsible for significant carbon emissions will therefore be increasingly problematic, both from a regulatory and an investment perspective. Tenants will become concerned about occupying buildings that are not perceived to be “zero carbon”, and this can only have a negative impact on the value of all-glass buildings which therefore could also potentially become commercially obsolete.
Simon Sturgis is the founder of Targeting Zero