Introduction

The Athena Impact Estimator is a whole building, life cycle based environmental assessment tool that lets building designers, product specifiers and policy analysts compare the relative environmental effects or trade-offs across alternative building design solutions at the conceptual design stage. Some of the Impact Estimator’s specific features include:

• the ability to model the building’s complete structure and envelope (claddings, insulation, gypsum wall board, and roofing and window systems – over 1200 possible assembly combinations) over the expected life of a building;
• the ability to model maintenance and replacement life cycle effects based on building type, location and a user defined expected life for the building;
• a regionally sensitive calculator to convert operating energy to primary energy and emissions to allow users to compare embodied and operating energy environmental effects over the building’s life (requires a separate estimate of operating energy as an input);
• an "end-of-life" module, which simulates demolition energy and final disposition of the materials incorporated in a building;
• a context sensitive help facility in place of a users’ manual; and,
• the capability to model both Canadian and US regional locations.

Impact Estimator results are presented in various ways and levels of detail to meet the needs of different types of users. A researcher wanting detail can see the results by specific energy forms or waste substances, by life cycle stage and by assembly type. An architect may only be interested in tabular or graphical displays of LCA measures or characterisations by building assembly and for the total design. The Impact Estimator also allows the user to make direct comparisons among alternative designs on an absolute basis, on a per unit area basis or on a relative basis where one design is selected as the baseline project.

In North America, the Athena Impact Estimator for Buildings is the only software tool that evaluates whole buildings and assemblies based on internationally recognized life cycle assessment (LCA) methodology.

Using the Estimator, architects, engineers and others can easily assess and compare the environmental implications of industrial, institutional, commercial and residential designs–both for new buildings and major renovations. Where relevant, the software also distinguishes between owner–occupied and rental facilities.

The Estimator puts the environment on equal footing with other more traditional design criteria at the conceptual stage of a project. It incorporates Athena’s own widely–acclaimed building material life cycle inventory databases as well as those contained in the US LCI database (www.nrel.gov/lci). It is capable of simulating over 1,200 different assembly combinations and is applicable to 95% of the building stock in North America.

With the addition of Los Angeles and Seattle in version 4.1, seismic effects have been added to the structural calculations for projects in Los Angeles, Seattle and Vancouver. In version 5.0 (2014), Portland Oregon was added as a location and has the same seismic effects added as Seattle and Vancouver.

 

The Estimator takes into account the environmental impacts of:

• Material manufacturing, including resource extraction and recycled content
• Related transportation
• On-site construction
• Regional variation in energy use, transportation and other factors
• Building type and assumed lifespan
• Maintenance, repair and replacement effects
• Demolition and end-of-life disposition
• Operating energy emissions and pre-combustion effects

Although the Estimator doesn’t include an operating energy simulation capability, it does allow users to enter the results of a simulation in order to compute the fuel cycle burdens and factor them into the overall results.

 

A Special Note about the "End of Life" (Demolition) Module

The "End of Life" module simulates demolition energy and final disposition of the materials incorporated in a building. The whole area of solid waste is in flux. Until a consensus within North America is reached in the area of solid waste, the Impact Estimator for Buildings will continue to calculate the materials and energy consumed during the "End of Life" life cycle stage but will not determine the physical amount of material that actually goes to landfill.

Structural materials have a demolition energy per physical unit of material associated with them. All materials have a percentage that goes to landfill associated with them. The location (city) has an average distance to landfill associated with it. These values are used in conjunction with the amount of material in the building at the end of life to calculate the following:

1. the material and energy used to demolish all structural material
2. the physical amount of material that is destined for landfill. Note that this is not reported as land emission at this time pending a North American consensus as mentioned above.
3. the material and energy used to transport to landfill the material that is destined for landfill. Note that all remaining material is assumed at this time to remain on site, again pending a North American consensus.

 

Complex Results in a User-friendly Format

Although LCA is a complex process, the Estimator has been designed for ease of use.

The first step is to enter required information such as geographic location (the system allows users to select from specific Canadian and US regions as well as a US national average), expected building life and occupancy⁄type, and, if desired, optional information such as annual operating energy by fuel type.

Pre–set dialog boxes prompt users to describe the different assemblies–by requesting the geometry, live load of a floor assembly and envelope attributes, for example–that together form a conceptual building design. The Estimator then instantly provides cradle–to–grave implications in terms of:

 

Simplified Tracking

As design data is entered for each assembly, the software builds a “tree” so that each individual assembly can be identified and viewed easily. The tree can also display, in value or percentage terms, the impact of each assembly in terms of a selected measure such as global warming potential. This allows users to track affects of each assembly as it’s added, or to quickly pinpoint which one is causing a particular environmental effect.

 

Detailed LCA Results

Results from an individual design can be seen in summary tables and graphs by assembly group and life cycle stage. Detailed tables and graphs show individual energy use by type or form of energy and emissions by individual substance for both the assembly group and life cycle stage breakouts.

 

Make Flexible Comparison of Alternate Building Designs

Accommodating up to five comparisons at once, the Estimator allows users to change the design, substitute materials, and make side–by–side comparisons for any one or all of the environmental impact indicators. Or compare the new building design to one you did last year. You can also compare similar projects with different floor areas on a unit floor area basis. The Estimator can perform as many as five project comparisons at a time.