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The carbon footprintAs the market for sustainable design and construction evolves, more rigorous methods have emerged to define what constitutes a sustainable, green, or environmentally-friendly building or building product.  In our view, carbon is the most rigorous and measurable method of assessing environmental footprint.  Carbon is a short form for carbon dioxide (CO2), the most ubiquitous greenhouse gas (GHG).  Included in a building’s carbon footprint are the following:

  • 85% of the GHG emissions occur during a building’s operational life, mostly from energy consumption.  GHG’s are generated through a number of sources, mostly fuel combustion whether gasoline/diesel for transportation, natural gas for heating and fossil fuels combusted for energy production.  Refrigerants used in building air conditioning systems are also strong GHGs that contribute to a building’s operational carbon footprint.
  • 15% of a building’s carbon footprint is embodied carbon, eg GHG’s emitted to construct the building.

The Greenhouse Gas Protocol (GHG Protocol) is the most widely used international accounting framework for quantifying GHG emissions.  Embodied carbon is calculated using Life Cycle Assessment (LCA), which not only calculates the GHG’s  generated in buildings or their materials but also air/water pollution and embodied energy.  In North America, the most common software tools for assessing lifecycle impacts are:Athena Institute

1. Athena Institute’s Impact Estimator for Buildings and a simplified version called EcoCalculator.  The Impact Estimator is used to evaluate the environmental footprint of assemblies or complete structures.  The EcoCalculator is a free tool that provides instant LCA results for hundreds of common building assemblies.

BEESlogo 2. TheBEES® (Building for Environmental and Economic Sustainability).  BEES software is product-oriented, containing data for nearly 200 products (generic and manufacturer brands) such as wall insulation, siding and sheathing.  BEES combines environmental measures with life-cycle costing to provide a final rating.

Both the Athena and BEES tools are especially useful early in the design process, allowing designers to experiment with different material choices to reduce the overall environmental impact and achieve the most effective combinations.

Going for Net-Zero Carbon…

Net-Zero Carbon, or carbon neutrality, refers to neutral (meaning zero) net total carbon release.  This term is usually applied to the operational carbon footprint of a building.  The key to approaching carbon neutrality in a cost-effective manner is, to begin with deep carbon reduction through energy efficiency.   Remaining energy consumption is then sourced, wherever possible, from renewable energy sources.  This can be done directly by generating power from a renewable source like solar photovoltaics, or by selecting an approved green energy provider, like Bullfrog Power.  To achieve complete operational carbon neutrality may require offsetting the remaining emissions by planting new trees or purchasing carbon offsets.   A carbon offset is an emission reduction credit from another organization’s project that results in reduced greenhouse gas in the atmosphere than would otherwise occur.

Applying this to buildings, we can recommend to our clients the following path to net-zero Carbon:

  • For new buildings, focus on
    • the building size,
    • use,
    • orientation,
    • material selection,
    • envelope construction (thermal, moisture, air),
    • mechanical systems, and
    • integration of landscaping.
  • For renovations, focus on
    • the material selection for the renovation
    • “building systems” considerations (e.g., upgraded envelopes, mechanical systems, and integration of landscaping)

    Climate Change & Greenhouse Gas (GHG) services can also be provided:

    • Carbon reduction strategy
    • GHG verification and GHG emissions reduction.
    • GHG Accounting (carbon footprinting) and Verification using ISO 14064/65 and guidelines through the Greenhouse Gas Management Institute
    • Life Cycle Analysis (LCA).