A Quiet Word, Sir.
Leading façade specialists were asked by Architect’s Datafile Magazine what they would like architects and specifiers to know. Read the account from Wintech Group MD Chris Macey.
On keeping the weather out:
When windows and façades were first made they were made by craftsmen; they were hand built products that took the benefit of empirical techniques and experience to deliver their weather performance. The quality of materials used at the time to create weatherproof integrity was not great. They were usually natural materials like timber or stone and oil based putties. So if they wanted to make something that was consistently waterproof they had to do it on the basis of shape and design rather than performance specific sealing materials. Tiled roofs are a good example of this philosophy; there are no sealants in a tiled roof.
Modern product design and application is straying from this time established principal with façades becoming ever more reliant on material performance such as sealants and gaskets being used to keep the weather out.
Modern materials, technologies and designs are therefore becoming more reliant on the performance of materials. In order to work effectively in the field, these depend upon the quality of the workmanship; the environment at the time of application; the way in which they are installed; the quality with which they are installed and the quality of the material and its application. With all these variables there is plenty of opportunity for something to go wrong.
For example, craftsmen throughout the ages knew that thresholds on doors had to have a certain height to keep the weather under storm conditions; the height of a weather bar across a door threshold is generally about 20mm as this was the height which delivered a reasonably consistent performance when gaskets were not available. Now we are seeing more designs that rely on compression gaskets and seals. If these fail for one of the reasons mentioned before there is a potentiality for failure.
It is therefore important from Wintech’s perspective to have designs which have a degree of redundancy and which primarily deliver their performance on the design or shape rather than materials so that you are not reliant on one component’s material performance in application.
To a certain extent, the now widespread use of pressure-drained and equalized systems addresses this issue and takes the benefit of level of inherent redundancy. If the external gaskets on the products fail and don’t work properly, the system itself is drained and ventilated and remains water proof.
We do however need to ensure that these principals are also engaged in the application of products to a particular application, in other words these principals must also apply to the construction interfaces.
On the environmental performance challenge:
The increasing emphasis on energy conservation means that we really have to change the way we go about design and specification of building façades.
Traditionally, the design process has required architects to receive advice from the service and structural engineers to tell them what they need in terms of environmental and structural performance to create their buildings. These performance constraints then naturally find their way into the eventual façade specification for the building envelope. This has been done historically by these engineers defining the figures needed to generally achieve a level of environmental performance that satisfies minimum statutory requirements.
However, increasingly now we are finding there is a significant gap in performance between the required levels of façade needed for energy conservation as dictated by the services engineering team to achieve statutory compliance and what can actually be delivered by the architectural design.
In my opinion, architects will therefore need to consider a slightly more holistic approach to the initial design process, taking expert advice to better appreciate the constraints that energy conservation might have on their design and to better understand how energy conservation is needed to inform the materiality, function and form of a design. For instance, this reduced carbon usage and regulatory pressure has started to impose restrictions on the amount of transparent area you might reasonably achieve on residential buildings if the effects of solar overheating and U values are taken seriously.
I guess you might expect me to say this but on modern buildings that are truly carbon efficient there is an urgent need for skilled façade engineers to be involved in the early iterative design process with the other members of the team so that these things don’t become a problem at some point in the future at the delivery stage.
Wintech has had projects recently where the U values and G values are so depressed to achieve compliance and where there are certain architectural features which have meant the specified performance requirements can’t be achieved. As a result something has had to give; these are less than ideal circumstances under which to be introduced to a major project.
So far, it has been possible to massage the façade design and performance figures in a way as to prevent a difficulty. However, I can foresee that shortly – especially when the new regulation requirements start to come to the fore – we will be seeing buildings with designs that can’t be built as designed and still achieve their target carbon performance without appropriate professional façade engineering support.
Readthe article in Architect’s Datafile.
Building images: 62 Buckingham Gate