With the issues surrounding flammable materials, cladding and facades have generated much attention of late.
Beyond the immediate controversy, however, questions surround how façade design and specification are responding to modern building needs. These include safety but also extend to areas such as aesthetics, occupant wellbeing and thermal comfort.
To explore these issues, Sourceable spoke with Kieran Rice, Technical Director, Façade Practice, Lead ANZ at AECOM.
First, it is important to clarify the distinction between facades and cladding.
Traditionally thought of as simply a building’s external wall, façades represent the vertical portion of the building envelope. They can consist of cladding, windows, curtain wall systems or a combination of these.
Cladding, by contrast, represents only the opaque (non-window) portion of the façade and can feature materials such as precast concrete, aluminium composite panels or metal sheeting.
Whilst facades often include cladding, the concept of façade systems extends beyond cladding and represents the entire vertical portion of the building’s envelope.
Representing the barrier between a building’s interior and exterior, facades influence building performance in terms of heating and cooling, provision of natural light, acoustics and waterproofing. As the main part of the building which is outwardly visible, facades also define the building’s external expression and how it is perceived by those outside.
When choosing facades, Rice says three points are important.
First, the façade system must have a similar look and appearance to that originally shown by the architect and approved by the developer.
Second, there is performance. On this score, Rice says it is important to look both at the climate in which the building will sit and at its desired performance level. Where developers target Green Star certification, for instance, requirements in terms of thermal comfort and natural light will be more stringent compared with buildings where Green Star is not sought. To achieve this, designers need to specify the right types of glass and framing systems. External shading may also be needed.
Third, there is cost. In this area, Rice says decisions are impacted by other considerations such as desired aesthetics or levels of thermal performance. Whilst lower costs are desirable if other factors are held constant, developers may be willing to pay more where doing so can deliver either higher sale prices in the case of apartments or higher leasing prices for commercial buildings. These may be achievable where apartment buyers are willing to pay more for greater living comfort or where commercial tenants are willing to do likewise to create a workplace which is conducive to productivity and morale.
Developers, he said, usually base calculations on potential costs for facades on the type of clientele they are targeting and the amount of rent they expect that tenants will be willing to pay.
Whilst prices vary, Rice says that for apartments, you would generally look at a window/wall system in the ballpark of $750 to $800 per square meter (sqm). Commercial systems could range from $800 per sqm for a standard office in regional areas such as Ballarat up to a ballpark of $2,000 per sqm when targeting blue chip clients in central Sydney.
Asked about how cladding issues are affecting façade design strategies, Rice stresses that fire safety considerations are determined by fire engineers who look at safety for the entire building.
He says the fire safety of a wall system extends beyond specifying external cladding which is non-combustible and includes thinking about how cladding, insulation, framing, fire stops and other features operate together as a system.
On specific products, Rice says he would be surprised if flammable materials such as aluminium composite panels with a polyethylene core are still being used.
Beyond that, he says much of the broader response remains in flux and is yet to play out as the focus to-date has revolved around making existing buildings safe.
Over time, he says there may be guidelines or rules which specify that certain checks are needed or that certain products should not be used. (In NSW, some cladding products have already been banned.)
Beyond safety, Rice says façades will evolve in response to demands for greater energy performance. For commercial buildings, he points out that stringency requirements for energy efficiency under the National Construction Code will be tightened in NCC 2019 to the extent that buildings which are designed to minimum standards under NCC 2019 or later will need to consume 25 to 30 percent less energy compared with those built under earlier versions of the code. (For residential buildings, there is no tightening to stringency requirements in NCC 2019 but an increase in stringency is expected in NCC 2022.)
This, Rice says, will impact façade design going forward as stringency requirements increase over time. Even under the tighter requirements for commercial buildings under NCC 2019, for instance, it may be possible to avoid external shading for office buildings in Sydney yet still meet energy efficiency performance requirements. Nevertheless, some form of shading will almost certainly be needed under later versions of the Code as minimum energy performance requirements become more stringent still.
At a broader level, Rice talks of a global movement back toward buildings being designed for the specific climate in which they are located.
Prior to the 1940s, he said buildings were designed to suit the climate of the particular region in which they sat. That changed in the 1950s as mechanical heating and air-conditioning enabled similar types of buildings to be delivered throughout different climatic regions.
Nowadays, however, he says buildings should be constructed with the local climate in mind.
“I suspect that we are almost in a new period of architecture,” Rice said.
“In the 1930s and 40s, we were in a period based around passive heating and cooling. This was very climate focused. You would find that buildings were designed in the UK and they would be very different from the kind of building you would build in Greece or in Iran because the climate is different. In the UK, you would try to keep heat in. In Iraq, you designs buildings to keep heat out.
“In the 1940s and 50s, we ended up with machines that could heat and cool internal spaces through air conditioning and central heating. Then we entered a period where you could build any building anywhere. You could have exactly the same office building in Iran as in London – you just needed a bigger machine to heat or cool it.
“I think more and more, we will have to build our buildings with a sensibility to the local climate. Ultimately, maybe not next year, but as we move forward, we are going to find that the kind of building you will build in Sydney will be different from the one you build in Melbourne because the climate is different.”