Fenestration Forum: June 2012
By Brian Burton
Advances in adaptive facades
By Brian Burton
Virtually every component contained within modern building enclosures,
including fenestration elements, is being revisited by manufacturers,
designers and owners in ongoing efforts to reduce operating costs,
increase energy efficiency and improve the level of occupant comfort.
Virtually every component contained within modern building enclosures, including fenestration elements, is being revisited by manufacturers, designers and owners in ongoing efforts to reduce operating costs, increase energy efficiency and improve the level of occupant comfort. These efforts have been intensified over recent years partly as a result of the rapid increase in energy costs and the gradual recognition that the annual solar energy received on the building envelope surfaces is very close to being equal to the energy needed to operate the building. This is true in all four Canadian climate zones. In theory at least, with improved techniques and technologies used to capture and then use this energy, we should be able to design buildings that are energy self-sufficient. As a result, architects and building engineers are working hard to develop so-called “adaptive” or “responsive” building envelope systems.
These adaptive systems have the potential to use more of this available energy for heating, ventilation, cooling, lighting and electricity supply. One example of such an adaptive building envelope is a double facade that incorporates natural ventilation systems. The curtain wall system comprises an outer skin of glass and an inner wall constructed as a curtain wall that together provide a full-function wall. Prototypes of adaptive facade systems have been developed to act as modular systems that combine six primary principles applied in various combinations: decentralization of ventilation systems, incorporation of flush-integrated opening elements, automated daylighting control systems, high-performance UV protection, solar energy production using modern thin-film technology, and modular, or moveable, interior insulated panels to minimize heat loss or gain.
Currently there are three technologies that make the necessary high level of light control possible: liquid crystal, electrochromic and suspended particle device. These smart glass technologies enable control of the light that is transmitted into the building from 100 per cent transmittance down to near zero. This has a direct bearing on the temperature and heat buildup inside the built environment and consequently on heating and cooling bills.
Adaptive systems are moving away from the centrally controlled HVAC systems we have been accustomed to installing in the past to create systems that are more localized. Instead of controlling heat loss and gain by moving warm air around the interior of the building using a central system, which is not really that efficient, the concept involves creating a system where at least some of these functions work together to adapt locally to exterior and interior environmental conditions. The concept actually involves giving each area of the building what amounts to its own independent HVAC system instead of a one-size-fits-all approach. The idea does present challenges not only because of the complexities involved but also because of the need to consider and balance moisture transport and movement within the system, which is considered one of the primary concerns in the industry. If these types of systems are effectively introduced and proven they could offer designers more flexibility and have considerable potential when it comes to reducing energy costs and improving building performance.
We also know that improving comfort levels and effectively controlling daylighting are important factors that affect occupant productivity in commercial buildings. Typically the financial impact regarding improved productivity is underestimated. In fact a one per cent improvement can offset a company’s entire energy costs. Occupants usually insist on some form of override for daylighting controls, and the number-one complaint regarding these systems involves the inability to modify daylighting controls to meet specific needs.
When it comes to assessing adaptive facades we still need to be able to reliably predict the thermal and optical performance of components and systems. We also have to consider the impact of increased cooling loads and cooling energy use for larger buildings and the potential for increased visual discomfort from sun penetration for people working at computer systems in daylighted offices. It is very likely we will continue to see innovations of this nature as building professionals continue their efforts to focus on sustainability.
Brian Burton is the author of Building Science Forum and is serving
on CSA’s Fenestration Installation Technician Certification Committee.
Brian is a research and development specialist for Exp (The new identity
of Trow Associates). He can be reached at firstname.lastname@example.org or
through www.exp.com .