Accurate energy accounting to assess and reduce whole building carbon footprint
Buildings emit substantial amounts of greenhouse gases.
The CO2 emissions from buildings in North America are substantial. In 2005, 39% of total North American CO2 emissions were attributed to buildings – more than from industry or transportation. However, this only reflects operational energy consumption. The embodied energy of building products and materials is not accounted for when assessing the overall “carbon footprint” of a building. Thus, the actual greenhouse gas emissions of buildings make up an even greater percentage of the overall total.
It is estimated that roughly 30% of the carbon emissions of a building over its lifetime are due to the embodied energy of the products used to construct that building. A true carbon emissions assessment of any building would take into account both operational performance energy and building product embodied energy.
As buildings become more energy-efficient by reducing operational energy demands, material optimization offers the greatest opportunity for innovation and greenhouse gas emissions reduction for the overall building.
Just as predicted energy consumption is quantified and assessed, so too can building materials and their associated embodied energy be modelled and measured.
Currently, no efficient means exists to evaluate environmental impact of materials during the design and planning process, when it can have the most influence on design decisions and building performance. http://choosetally.com/
Energy-reduction goals are often set at the initial stages of a building design. Energy models predict operational energy demand reduction due to the performance of the envelope, efficiencies in mechanical systems, and overall thermal performance of the building; however, such models exclude accounting for the embodied energy of those systems, and completely omit any embodied energy accounting for structural systems, finishes, or cladding materials.
To accurately predict environmental impact, product selection should be assessed not only on its thermal performance but also on greenhouse gas emissions produced throughout its life cycle. This type of assessment is complicated, challenging and does not always accurately account for externalities.
The innovative solution would provide a means to quickly and accurately assess parametric data. This data would reflect accurate building material, product and technology full life-cycle data on a comparable per unit basis. The output of the comparison would need to allow “best fit” decisions to be made within the initial phases of design. Finally, a technological solution would need to be able to accurately read and process information from 3D modelling software, such as Rhino or Revit.
A number of life cycles and companies have attempted to create such a tool. Google Flux was in the process of creating such a solution, but abandoned development. Two existing programmes offer promising solutions: Thornton Tomasetti’s Embodied Carbon and Energy Efficiency Tool (http://core.thorntontomasetti.com/embodied-carbon-efficiency-tool/) and Tally LCA App for Autodesk Revit by Kieran (http://choosetally.com/).
Thornton Tomasetti – an international Structural Engineering firm – developed parametric modeling tools that allow engineers to calculate structural member sizes. By incorporating embodied average energy/carbon coefficients from the Inventory of Carbon and Energy created by the University of Bath, engineers can now calculate the total embodied carbon and energy of the overall structural design. This data, coupled with the Thornton Tomasetti generative structural design suite of tools, allows for quick and accurate optimization of a structural design. Iterations of structural systems – building typologies, column grid layouts, and different combinations of structural materials – are generated within minutes. Time typically spent on design iterations is greatly reduced, allowing for comprehensive comparison and analysis in a very short timeframe.
Tally quantifies embodied energy along with other environmental impacts and emissions to land, air and water. It can be used for whole-building analysis or for comparative analyses of various design options, and can account for the diverse range of material classes defined in a BIM model, as well as materials that are not modelled explicitly.
Unlike other environmental assessment tools, which tend to export data to unwieldy spreadsheets, Tally allows users to produce data graphics that are readily comprehensible, transparent and customizable.
Clearly, embodied energy modelling would allow for quantifiable carbon assessment and reduction during design, ultimately lowering the carbon footprint of the built project. Likewise, it would incentivize the use and procurement of low embodied energy materials and minimize and/or increase efficient use of high energy options.
Quick and accurate modelling tools such as those mentioned above can allow for quantifiable embodied energy assessment and reduction during design, allowing for informed decision-making. While use of these tools can directly affect the design process, and thus impact the carbon footprint of a built project, their major impact would be the disruption of global manufacturing supply chains.
A clear, accurate accounting, coupled with the desire to decrease greenhouse gas emissions, would incentivize the use and procurement of low embodied energy materials; greater use would demonstrate increased demand, thus ideally resulting in manufacturers optimizing their own supply chains. The impact of this optimization on carbon reduction on a global scale represents the true potential of these tools.
The barriers to innovation – and the solutions
The typical design and construction schedule does not allow for lengthy, complex modelling and assessment.
Barriers to modelling embodied energy in buildings, and then using those results to inform design decisions, exist and will be challenging to overcome. The modelling tools mentioned here seem to address the problems with accurate accounting and the complexity of the calculations required, allowing for timely solutions to support expedient decision-making.
However, accurate data provided by manufacturers and suppliers of the products under consideration remains elusive. The result is that during the design phase, when decision-making would occur, only general assumptions about specific manufactured products can be considered.
Additionally, there are no existing financial incentives to use an embodied energy assessment methodology. In New York City, financial incentives for operational energy modelling (and associated reduction in estimated operational energy demand) exist; clearly outlined frameworks have been established, and NYSERDA (New York State Energy Research and Development Authority) handles their distribution. Likewise, demonstrating a specific reduction in predicted operational energy is required by building code, and for design review and ultimate permitting. None of the above exists for modelling, and then showing reduction in, the embodied energy of a building.
The way forward
Embodied energy reduction of products needs to be incentivized. It’s a lot of work measuring externalities that don’t translate into simple payback.
The UK construction industry is the largest consumer of natural resources in the country with over 400 million tonnes of material consumed each year (Davis Langdon LLP, 2009). This accounts for approximately 10% of total UK carbon emissions (ENVEST, 2010). – ice.org.uk
To reduce the greenhouse gas emissions from buildings, clear accounting for operational and embodied energy must occur. Although promising technological solutions exist to provide clear modelling during design, those models must be used, and product decisions must be made that result in lower overall embodied energy. Manufacturers must make clear and accurate data available in order to assess existing options. Finally, new products and materials produced from optimized manufacturing and a transparent supply chain must become more readily available.
Just as operational energy reduction and improvements are required by code and for building permitting, so too must embodied energy/carbon performance be required. According to the Institution of Civil Engineers in the UK:
In May 2016 the UK Green Construction Board launched a new specification to encourage a consistent industry approach to reducing carbon in infrastructure – a world first. PAS 2080:2016 Carbon management in infrastructure and its associated guidance document aim to bring a joined up approach to the way industry evaluates and manages whole life carbon emissions to deliver reduced carbon, reduced cost solutions.
Reduction in overall greenhouse gas emissions from buildings is imperative. Use of energy modelling tools that account for both operational and embodied energy consumption is necessary. Such tools exist; their effectiveness, however, is limited by a lack of data from manufacturers and suppliers. Additional incentives and/or regulations are therefore necessary to compel accurate and timely reporting of that data.