With the launch of Architecture 2030 and other similar initiatives, the building sector has been tasked with achieving carbon neutral buildings—a tremendous challenge made more difficult by the fact that no proven tools currently exist to track the progress of carbon reduction.

To resolve this dilemma, the Green Building Initiative (GBI) is working to revise its Green Globes environmental assessment and rating system so the energy section uses CO₂ as the basis for its calculations instead of the current kBtu/sf/yr of energy consumed. The revisions are being undertaken by a technical committee (of which I am a member) as part of the process to establish Green Globes as an official standard recognized by the American National Standards Institute (ANSI), and the first ANSI standard for commercial green building.

The proposed standard is similar to the United Kingdom’s L2A Standard, which requires new buildings to model their energy performance based on a set of prescriptive criteria, and then multiply the building’s fuel mix by a CO₂ emissions factor to determine the CO₂ target. This process is repeated for the proposed building and, if the proposed building’s CO₂ level is below the target, the building meets the standard.

Green Globes will go beyond minimum performance requirements and allow buildings to achieve several levels of environmental performance. This is in keeping with the current Green Globes system, which has been operating successfully in Canada for more than a decade and in the U.S. since 2004.

Fig. 1: Typical Target Finder Input Screen – normalizes CBECS data to location, space type, occupancy density, internal load and hours of use.

The proposed energy section has some similarities to ASHRAE Standard 90.1, though it differs in several fundamental ways. For example, the Green Globes standard does not have any mandatory provisions except that all buildings must meet local energy code, which will likely be Standard 90.1. Points within the proposed standard are achieved only by going beyond code, which can be accomplished either by using the prescriptive or performance approach. The prescriptive approach gives points for meeting incrementally higher levels of component efficiencies, while the performance approach gives points as a function of how much better the proposed building performs versus an industry benchmark, such as the U.S. Department of Energy’s Commercial Building Energy Consumptive Survey (CBECS) database. Widely considered to be the most comprehensive source for building energy benchmarking available, CBECS is used by the ENERGY STAR Target Finder program, which is incorporated within Green Globes.

The Green Globes standard will generate the benchmark through Target Finder, which has the ability to normalize the CBECS data to location, space type, occupancy density, internal load and hours of use. Users need only multiply the Target Finder output by a CO₂ equivalent (CO₂e) emissions factor and model the proposed building. The proposed standard will start awarding points to buildings that achieve a 50 percent CO₂e reduction from the average CBECS’s building for that location.

Going a step further, the material section within the proposed standard also includes a life cycle assessment (LCA) calculator that has CO₂e as one of its outputs. Thus both embedded and operational CO₂e can be calculated, providing an opportunity for an analysis of a whole building carbon footprint. Once a building has a year of measured operational data, it can also migrate to Green Globes for Continual Improvement of Existing Buildings, which will use the same CO₂e procedure outlined here. As envisioned by the technical committee, the result will be a seamless passing of data between embedded and operational CO₂e from the time a building is constructed to the end of its life.

Fig. 2: Typical Target Finder Output Screen – generates a Site Energy Use Intensity (EUI) and typical fuel mixes which are then multiplied by the CO2e emission factors in order to determine a building’s CO2e target.