What is a Whole Building Life Cycle Assessment?

A Whole Building Life Cycle Assessment (WBLCA) is fundamentally the same concept as a regular life cycle assessment, but on an entire building instead of a singular product or material. WBLCA is a methodology used to quantify the environmental impacts of a building during the entirety of its life, from its construction to occupancy to its eventual demolition. Buildings are of particular interest because of their longevity, many times spanning decades or even centuries.

A true WBLCA assesses impacts from the extraction of the raw materials to make the products in the building (Module A1) thru to hopefully reuse/recovery of building materials for their next use (Module D). In between the first and last stage, the WBLCA calculates the impacts associated with product manufacturing, the construction of the building, the use phase and refurbishment of the building, and finally the demolition process. The graphic below does a great job at illustrating the individual modules associated with a WBLCA.

Source: New Buildings Institute

The WBLCA process involves data collection, software modeling, and then analysis of the assessment impacts.

WBLCA requires an extensive amount of input data from the materials and fuels used in construction, to the estimated energy consumption of the building once occupied. This can be accomplished thru a somewhat similar methodology to the product/process level LCA via collection of primary data from the bill of materials, specifications of a building, and Building Information Modeling (BIM). Ideally, the building products selected for use have their own environmental product declarations (EPDs) or LCAs that detail their individual impact on a functional unit basis. These impacts are then scaled up based on the quantity or weight of the material or product you have utilized in the building. EPDs and LCAs constitute primary data, which is the most preferred type of data in any type of life cycle analysis. If the specific building products don’t have EPDs or LCA data available, there are widely used general data sets or even industry-wide EPDs which can help give a representative environmental impact for use in the model.

In addition to materials and products, a WBLCA assesses impacts from construction activities and building functions. Practitioners gather data from the contractors and construction teams on any fuel that they utilized on-site for construction. To evaluate use phase environmental impacts, energy and water use data is requested if the building has been occupied, along with any refurbishment, repair, or replacement activities. If the building has not yet been in use, a good estimate can be gathered from energy modeling programs. Finally, to assess end of life, the assessor utilized any demolition or recycling/recovery/reuse information from the building material EPDs or LCAs and/or any plans that the building owner or operator has at that time. This “cradle to grave” approach provides a complete and full understanding of the impact of a buildings’ environmental impacts across its life span.

Unfortunately, most WBLCAs in the industry today only calculate a small piece of a whole building’s impacts. Typically, this includes the calculation of the impacts from the structural material selected for a building and sometimes the building’s envelope. In certain global rating systems, additional points are awarded towards your buildings’ ratings if you conduct a comparison between the potential products for your structural and envelope material and the material did use. The greater the environmental impact reduction between the theoretical material and the material actually used in construction, the more points. Several issues exist with this approach. The primary problem is that the theoretical material chosen as your ‘base model’ could be some of the worst material and would most likely not be chosen by the project in the first place. Therefore, by using a misleading base material, you get a false sense of the actual reduction in environmental impact that your material selection actually has. Much of the time this method of ‘WBLCA’ is employed following material selection, so it is an exercise in point chasing, as opposed to what could be an incredibly useful tool in understanding the interplay between embodied and operation carbon (link to that article we’ve written for Kingspan site).

There are multiple pay tools in the marketplace that can assist in a WBLCA, but there are also some free tools which can approximate a WBLCA. Athena’s Impact Estimator for Buildings (https://www.athenasmi.org/our-software-data/impact-estimator/) is applicable for new construction, renovations and additions in all North America building types. It provides a cradle-to-grave life cycle inventory profile. There is also tallyCAT (https://www.buildingtransparency.org/tally/tallycat/), which is a Revit plug-in that supports the export of material quantities from Revit to the Embodied Carbon Calculator (https://buildingtransparency.org/ec3) and allows the synchronization between them. This allows for updated embodied carbon data to be filled into the design models.

So why do a WBLCA? There are certain building codes that now have a WBLCA as a path to meeting certain criteria, listing certain building materials that need to be in WBLCA calculation. A limited scope, this path doesn’t consider the interplay with the building’s use phase and how material selection can impact this longevity of a building’s life. However, these beginning steps are at least exposing the building community at large to parts of what could truly be WBLCA and the value these assessments hold.