Mitchell Dec, Energy Analyst, Glumac Energy Services

Recently there has been a great deal of buzz in the building industry about carbon footprints: What does it mean, how is it measured, and how do we reduce our own carbon footprint?

In response to the discussions, Architecture 2030, a group started by Edward Mazria in 2002, has crafted the 2010 Imperative and 2030 Challenge. Together, these two initiatives have created a benchmarking system for the architectural and engineering community to compare each building’s design against the carbon footprint of similar buildings.

A difficult task for a project is to determine the status of a design relative to the benchmark, and then to be certain that the building will perform as anticipated. This goal has added a new dimension to the opportunity of using energy analysis as a tool to predicting a building’s carbon footprint.

The carbon footprint analysis will also likely encourage a great deal of measurement and verification in order to determine the status of each building after construction. When a building is not performing, energy modeling and commissioning groups can work together to diagnose operation issues and to fix operational problems. This process will allow for the design team to validate that their practices are meeting the intent of their client’s goals.

Imperative by 2010 and Challenges through 2030

The 2010 Imperative and 2030 Challenge work together to provide a path for future projects to establish targets, and to validate whether a project meets its goal. This new way of gauging sustainability directly ties into projects that are already seeking a LEED^® rating. Additionally Mazria’s initiatives provide another way for the architectural and engineering community to verify that our design changes are truly benefiting sustainability goals.

Beginning in 2007, the 2010 Imperative calls upon the architectural and engineering community to design such that "the designs engage the environment in a way that dramatically reduces or eliminates the need for fossil fuel." In order to realize this goal, Mazria has called for changes in the academic design community, and for schools to incorporate goals toward becoming carbon-neutral campuses.

The 2030 Challenge uses the Commercial Buildings Energy Consumption Survey (CBECS) to benchmark energy use in kBtu per sf, and thus provides a generalized correlation to the reduction of each building’s carbon footprint. The 2030 Challenge establishes an immediate target for all new construction and major renovations to target an energy consumption reduction of 50% relative to the CBECS regional average for that building type. In 2010, the goal jumps to a 60% reduction target, and the target increases by 10% every 5 years. Therefore, by 2030 the target is a net-zero energy building.

Both the 2010 Imperative and 2030 Challenge place a cap on credit taken for purchasing green power and/or renewable energy credits. The cap is 20% of the targeted reduction. Therefore, if a current design has targeted a 50% reduction for 2007, only 20% of 50% (or 10% of the total CBECS regional average energy) can be claimed through purchasing green power. Due to this cap, the 2030 Challenge will greatly test our design practices, while encouraging new ideas relative to the standards often practiced.

Calculating True Carbon Emissions

Calculating the true carbon emissions of a specific project adds another dimension to understanding the 2030 Challenge and the goals of the initiative.

The single biggest variable in calculating the emissions of a building’s energy use is calculating the average CO₂ per kWh sold by the local utility. Every utility has a different purchased power mix, and the power mix typically changes from year to year.

Adding confusion to calculating an equivalent CO₂ per kWh is the difference between locally produced power, and the power provided to the end user. For example, many people in the Pacific Northwest have a misconception that the electricity used in the Pacific Northwest is "cleaner" than other regions. However, the truth is that the locally produced power emits fewer pounds of CO₂ per kWh, but the locally produced power does not offset all power used, especially in the major metropolitan cities. There are varied emissions due to the local utility power purchasing agreements.

A study by the Oregon Department of Energy (ODOE) determined the emissions of the electricity used by Oregon consumers. Table 1, below, captures the equivalent emissions for the consumer of the respective utility:

• Comparing just a couple of the utilities in Oregon provides one with a general understanding of how difficult it can be to determine the carbon footprint of a building. The emissions differ not only from state to state, but also from utility to utility. In this respect, the 2030 Challenge provides an easy to use approach for calculating the reduction in carbon emissions.
  
• Despite the bad press associated with natural gas and oil, the emissions associated with these resources are significantly less than the majority of electricity produced in the United States. For comparison, natural gas emits 11.6 lbs of CO₂ per therm (equivalent to 0.4 lbs of CO₂ per kWh) and oil emits 15.9 lbs of CO₂ per therm (equivalent to 0.55 lbs of CO₂ per kWh). Thus, one unit of natural gas energy emits about one-third the carbon of one unit of Portland General Electric’s (PGE) basic service option.

Going Further Than the 2030 Challenge

In order to accommodate our growing clients’ needs, the Glumac energy services team has coupled energy modeling for LEED^® and utility incentives, with carbon footprint analysis. However, Glumac has taken the analysis a step further to understand the emissions of the energy provided to the consumer. It is our mission to benchmark for both the 2030 Challenge, and for the true carbon emissions based on the electricity provider. The benchmarking for the 2030 Challenge is focused on net energy consumption, in kBtu per sf. Glumac's energy services team will stamp every report with a "Glumac Carbon Footprint" logo in order to document CO₂ reductions in a design.

The reason behind comparing the 2030 Challenge and the true carbon emissions is due to one imperfection in the 2030 Challenge. The 2030 Challenge assumes that a reduction in energy use results in a direct correlation to a reduction in CO₂ emissions. Table 2, below, is a prototype for a side-by-side comparison of LEED^®, the 2030 Challenge, and true CO₂ emissions.

In Table 2, Energy Efficiency Measures (EEMs) 6a and 6b describe two options for perimeter heating in a generic office using chilled beams. Option 6a uses electric baseboards, and Option 6b uses hydronic baseboards. While Option 6b benefits the true carbon footprint by emitting fewer pounds of CO₂, Option 6b uses less energy relative to the 2030 Challenge benchmarking.

The reason for the reverse correlation between the 2030 Challenge and the true carbon emissions is that the same amount of energy is needed in the space for heating needs. The electric heat is essentially 100% efficient, while the hydronic heat goes back to a condensing boiler that is on the order of 90% to 95% efficient. Therefore, there is a greater total energy input to the building when using hydronic heat. However, as noted above, the emissions of natural gas are on the order of one-third the emissions of Portland General Electric (PGE) per equivalent unit of energy, so a hydronic heating system results in less true carbon emissions.

This shows how there can be two analyses that can be contradictory to the design team’s goals. It is recommended that all projects that incorporate energy modeling use this tool in addition to assessing the carbon footprint. The energy model itself can provide a more refined carbon footprint analysis when compared to the benchmarking used for the 2030 Challenge. This verification can assist in validating that the design truly does reduce its emissions.