Sustainable Structures

Our blog often features talk about sustainability, a buzz word that crops up in our daily lives now more than ever before. Tomorrow is World Environment Day and a moment for us all to reflect on the future of our planet and how we can ‘do our bit’ to protect it. Sustainable building design could be seen as the remit solely of the architect, but structural engineers are key decision makers too.

The choice of materials used in construction have great bearing on the sustainability of a building. ‘Embodied energy’ is the term used to describe the energy which is used in the extraction, refining, manufacturing and transportation of building materials and if the carbon footprint of these processes can be reduced then that is a tick in the “eco” box. The production of cement for concrete, for example, is one of the largest sources of greenhouse gas emissions in the construction industry, so if a type of concrete that uses less energy in its production can be used, or even better, a complete alternative, then this is a huge plus.

Mindful structural design can have a far reaching effect. At the start of a project the engineer will consider how the building will live into the future; longevity, often incorporating flexible use and re-purposing, is the ultimate aim. ‘Designing for deconstruction’ is the catchy phrase I have picked up in my research – this asks the question of how the building will end its useful life. If it can be taken apart and re-used or recycled then this is a far better outcome than demolition into a pile of rubble. Achieving this goal seems apparently simple, for instance, using bolts to attach components rather than welding them. A clever engineer with an eye on the future will design with ‘whole life costs’ in mind, rather than short term solutions, for instance, with a foundation just strong enough for its purpose rather than one that is higher strength than is required – this will lessen the impact of the energy needed to break or crush it at the end of its life.

We all know how important it is to insulate our homes to prevent heat loss, and clever design will avoid what is known as a ‘thermal bridge’ where heat can escape. Structural Insulated Panels (SIPs) are a relatively new creation where walls are constructed with three layers – two boards with insulation in between. These can be used with any external cladding and provide great insulation with little or no thermal bridging. They are also very quick to erect, so are a win-win.

Close collaboration within the construction team is key to the end result of a more sustainable building, for instance with the maximisation of daylighting, the use of low energy heating such as a ground source heat pump or the integration of rain or grey water harvesting. Top this with a green roof and we would see a fine example of how architect and structural engineer can work together to produce sustainability balanced with functionality.