Getting the Number to Zero:

To this point in the discussion, the issue of designing a low to zero carbon building has been treated holistically and from the perspective of basic principles. Where these are the essential starting point for the carbon neutral design process, “zero carbon” mandates a numerical assessment and validation of the realized design. Zero Carbon requires designers to numerically validate the effectiveness of their approaches.

Where does Building Associated Carbon Come From?

There is carbon associated with all aspects of a building. Of primary importance is the carbon connected to operational energy. In both developed and developing countries, most of the energy sources used to heat, cool and light buildings are currently using fossil fuels. The burning of fossil fuels connected with operating buildings is responsible for approximately 70 to 80% of the CO2 footprint of the building. The 2030 Challenge is aimed at reducing the CO2 levels that are the result of burning fossil fuels to zero by the year 2030.

According to the Carbon Accounting Protocal that was developed by Professor Michael Utzinger to design the Aldo Leopold Legacy Center to zero carbon, this is termed Scope 1 and Scope 2 Carbon. Scope 1 Carbon is the result of Direct Emissions - arising from fuel combusion for heating and cooling (stationary combustion) as well as fuel used for organization vehicles. Scope 2 Carbon relates to Indirect Emissions, typically the result of electricity generation. Scope 2 carbon is more difficult to assess in instances where there is a lack of certainty as to the type of generation for the electricity used in the building.

Building materials contain embodied energy and there is carbon associated with the embodied energy of building materials. Embodied energy is the energy required to extract, manufacture and supply the material to the point of use (i.e. the energy to actually construct the building). Embodied energy is extremely complicated to calculate as the issues surrounding manufacturing vary from place to place. Materials themselves are able to make differing contributions to the overall energy efficiency of a building, particularly where impact/energy reduction is the primary goal of designing for carbon neutrality. This is most clear when comparing materials on the basis of either their ability to retain heat (act as thermal mass) or resist heat flow (act as insulation). The increased embodied energy of a material such as concrete may be warranted due to its ability to store heat (free passive solar heat!). Likewise, certain materials provide greater insulation when measured on a per/thickness basis, and may be the only suitable type of insulation given the potential in the region for mold or wetness.

Carbon is created by the people and their activities, including transportation to and from work, business travel and other organizational activities. This is refered to as Scope 3 Indirect Emissions (organizational activities). The travel distance to the building factors in heavily to this aspect of carbon, as well as the means of transportation. This focus aligns with several LEED® credits in the Sustainable Sites category. The assessment of Scope 3 carbon can be done using Personal Carbon Footprint calculators.

Site disturbance during construction releases carbon into the atmosphere. The more the site can be left alone, and the construction/excavation impacts minimized, the less CO2 is released. The eventual landscape treatment, choice of planting and materials can begin to sequester carbon for the life of the project. Hence landscape + site straddle the line between offending and assisting in balancing the carbon equation.

Renewables and On-Site Generation of non CO2 emitting energy is needed to balance all of the CO2 produced by all of the other impact and CO2 generation mechanisms.

Types of Tools:

There are various means by which this can be done, as well as relative scales of the problem that might be examined that range from personal carbon footprinting to site impact to the actual carbon costs of the building’s operational systems.

CARBON FOOTPRINT CALCULATORS are available online to look at your personal carbon emissions. Carbon footprinting is to be differentiated from Eco-footprint calculators that measure one’s consumption in terms of the number of planets required to satisfy the consumption of transportation, housing and goods. While not directly related to the specific development of an architectural project, these types of calculators can assist in getting a feel for the numeric relationship between lifestyle, consumption patterns and carbon. They can also be useful for projects that wish to extend their carbon analysis to include the transportation components of the occupants, as the transportation value can be isolated within most of these online calculators.

CARBON ESTIMATORS are available online to begin to assess the impact of buildings, in general terms and due to the 'act' of construction. The impact analysis carried out through www.buildcarbonneutral.org provides a more general figure as relates to project inputs specifying the building size (total square feet, stories above and below ground), the primary structural system above ground (wood, steel, concrete or mixed), and site conditions (eco region, existing landscape, proposed landscape, amount of landscape disturbed and amount of landscape installed). This is a free calculator, simple to use and therefore of great benefit at the outset of a project.

CARBON CALCULATORS provide more detailed feedback on both operating energy and embodied energy.

Operating Energy: Some operating energy calculators are available for purchase that will work with BIM systems and provide a fairly accurate feedback mechanism. The Green Building Studio suite, recently purchased by Autodesk, integrates detailed energy calculations into CAD inputs for a project. It is able to provide very detailed feedback and allows for benchmarking against base cases while improvements are worked through the digital model.

Embodied Energy: The Athena Institute offers a free Eco-Calculator, which includes carbon numbers for limited building sizes and regional locations, a purchasable Impact Estimator that includes Global Warming potential for a project, in addition to now offering Carbon Footprint Consulting services. Carbon can be calculated by other methods that are more detailed and more project specific.

The increased awareness of the carbon related issues surrounding the built environment are likely to result in an increase in the range of products available to assist practitioners with these potentially complex calculations. Whether looking at the operating energy use alone, or including the materials, construction, site disturbance and functional use of the building, all calculations need to examine the holistic aspects of the project in order to achieve a balance between carbon costs and the ability of the project to sequester carbon.

Calculating the Energy and Daylight Effectiveness of a Project:

There are tools to assist in design, early calculations and more detailed calculations that need to be used prior to the eventual detailed calculation of the carbon of a project. The design process for Carbon Neutrality requires as its springpoint that designers Reduce the Impact of the building. This means reducing the energy required to heat, cool and light the building. There are numerous software engines available to assist with this first step - sometimes before looking more specifically at the carbon numbers.

For a complete overview of existing tools, software and their use in carbon calcuation and the teaching curriculum