The idea that achieving a low carbon, sustainable building requires additional spend is very last decade.
The wish to meet BREEAM standards used to lead to the design of expensive bolt-ons, like additional photovoltaic panels or biomass, just to get those precious credits. But the construction industry has changed. Sustainable, low carbon design solutions are being incorporated in the early stages and, as a result, needn’t cost the earth.
It’s important to focus on fully understanding operational and embodied carbon, not on meeting ‘tick box’ credits. A modern low carbon building consists of two main parts:
- Low embodied carbon
- Low operational carbon.
Between them, there is also an often unspoken common denominator which Bryden Wood have explored. Put simply: if we build less, we emit less carbon.
Low embodied carbon and the future of sustainable design
It’s generally understood that changing material specification can help reduce embodied carbon and create a more sustainable design and build process. What is often not mentioned is that we can also achieve reduced embodied carbon and capital cost through optimisation and reducing the volume of building, and the earlier this is considered the bigger the carbon savings.
Bryden Wood have demonstrated that through optimising architectural layouts, we can produce higher net to gross ratio space. We do this by enhancing circulation and ancillary spaces and providing more useful, flexible space. With the reduction in internal floor area, there is less space to be conditioned with expensive MEP systems, less structure and less external envelope. This sustainable design process is incredibly effective.
Lean design encourages optimised material usage within the building. This might be improving the optimisation factor of steel, reducing the thickness of concrete slabs, or balancing insulation thicknesses of walls, floors and roofs with operational energy savings. A reduced quantity of building materials reduces a building’s weight. This in turn reduces the load on the foundations, allowing a further reduction in materials used in the substructure. Lean design places a renewed emphasis on optimum sizing, without unnecessary redundancies or capacities. This is an important component of sustainable architectural design.
Using fewer materials overall means less embodied carbon in the extraction of raw materials and their fabrication into building products. There is also a direct correlation with producing less waste both in the fabrication process and on site, meaning that low carbon design also saves precious materials. With the use of Building Information Modelling (BIM), we can know the exact quantities of materials required, which limits over-ordering to site, and aids sustainable construction. Using a DfMA strategy allows for deployment of resources and materials to be carefully pre-planned, making it even easier to monitor and limit over-spend.
When you need fewer materials, there is less to be transported to site, meaning fewer transport movements, lower emissions and a reduction in local air pollution. There can also be less packaging used. (And in the future we should all be striving for packaging to be reusable, eliminating waste from packaging altogether).
A further benefit of reduced quantities and transportation of building materials is lowering the capital cost. We can achieve this through the reduction of raw materials, excavation and construction works, but also through shortened construction programme, which limits overhead and prelim costs, as well as creating a path towards more sustainable construction.
Low operational carbon
Alongside developing the architectural design to reduce the overall building volume, we should adopt passive design measures, such as considering building orientation, using optimised facades to balance winter heat loss and summer heat gain, enhancing daylight and using natural or mixed mode ventilation. These sustainable building measures will reduce the MEP plant loads so that plant takes less space; reducing the building volume further. It will also result in reduced energy consumption in use, as well as reducing the capital cost of MEP systems.
To make sure we use the most appropriate passive sustainable design measures, we test them for optimum results using computer simulations. This means we know far more about how a building is due to operate than we ever have before. We can fine tune the building to make it run as efficiently as possible before it is even built, making further energy cost savings.
Sustainable design and build for the circular economy
We shouldn’t stop at lowering embodied and operational carbon when creating low carbon, sustainable buildings. A building’s impact starts before the building exists and carries on past the end of its useful life, as part of the circular economy. We can demonstrate that early sustainable impact can have an exponentially positive impact on carbon savings and the creation of our sustainable future.
Second-hand, locally sourced materials can influence design. This might be re-using existing raised flooring, using demolition crush material for a piling mat, or re-using existing steel columns. A pre-demolition audit of an existing building highlights reusable and recyclable materials. Where materials can be reused, these should be considered for reuse on the same or a local site, thereby reducing material miles and facilitating a more sustainable construction process
Although the circular economy market is in its infancy, by considering material reuse during the earliest design stages we can help build that marketplace. In time, this market will help to further reduce material costs.
Following through the circular economy idea to the end of a building’s life, simple design choices allow new materials to be reused at that stage. Using reversable joints for steelwork connections so that beams and columns can be disassembled in their primary form, allows them to be re-used rather than be melted down and recycled as a raw material. Intumescent paint has to be manually chipped off steelwork before it can be recycled or reused, so choosing to use boarding for fire protection is a better sustainable design choice. These decisions have little cost impact when they are integrated into the building’s design, but can help create – and sustain – the circular economy.
Extending a building’s life, or giving it a second life through refurbishment, reduces the need to use yet more building materials for its replacement. Designing adaptable buildings enables the function to change depending on its users’ needs. If COVID has taught us anything, it’s that workplaces and homes both need to be flexible to account for changing work patterns. It’s a balancing act to make sure a building can be adaptable without over-designing the structure, architecture and MEP. But when we build smarter we can do this. Repeatable building modules which can be switched in and out depending on requirements, such as glazing vs solid cladding modules, or heating vs heating and cooling fan coil unit modules, are simple features which may prevent a building from being torn down mid-way through its life expectancy. Through a small number of new parts, the building has a whole new lifespan, limiting its embodied carbon when compared with the alternative of a new build.
Building less volume reduces costs, embodied carbon and operational carbon. And with more thought to whole life performance, low carbon, sustainable buildings can keep delivering benefits even after their lifetimes. Truly a win-win scenario.