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Welcome to the LifeCycleAnalysis_Toolkit wiki!

This page will provide an overview of LCA concepts and best practices.

THE BASICS

Life Cycle Assessment (LCA)
LCA is a methodology used to quantify environmental impacts of a product or process over its lifetime using biophysical indicators such as Global Warming Potential, Eutrophication Potential, Ozone Depletion Potential, Smog Formation Potential, Acidification Potential, etc.

Embodied Carbon
Embodied carbon is usually used as shorthand for the Global Warming Potential impacts associated with sourcing and extracting building materials, manufacturing, construction, demolition, maintenance and end-of-life processes

What units are used for embodied carbon?
Embodied carbon is used as shorthand for Global Warming Potential (GWP). GWP is measured in carbon dioxide equivalents (kgCO2e). This unit converts all emissions that contribute to global warming, such as CH4, into CO2e by multiplying by their relative strength in producing warming.

What is this LCA good for?
LCA is most useful for relative, rather than absolute, comparisons. Ideally the analysis can be used for comparing design options, making material selections, and setting design priorities.

What is biogenic carbon?
Biogenic carbon is the process of carbon sequestration that takes place during the growth phase of bio-based materials, and is usually assigned during the cradle-to-gate impacts. Some LCAs account for these processes, others do not. If carbon sequestration is accounted for, it is best practice to account for the amount of this carbon that is released at end-of-life.

How can we reduce the embodied impacts of buildings?

1. Reuse existing buildings (foundations, structural system)

2. Minimize new building area by optimizing program

3. Consider low carbon structural systems:

   • CLT as floor slabs
   • Glulam as beams, columns
   • Rammed earth or bio-based bricks instead of concrete
   • light guage metal instead of structural steel

4. Deploy lower-carbon materials:

   • increase fly ash or slag content in concrete
   • use FSC-certified wood
   • increase recycled/salvaged content
   • Optimize structural system (sizing of elements)
   • Minimize impact of specific products
   • compare product-specific EPDs

BEST PRACTICES

Functional Unit
The functional unit describes the unit of analysis of the assessment and the functional parameters held constant between options to ensure an apples-to-apples comparison. Describe whether the options are equivalent in relevant metrics like duration, fire-rating, structural, acoustic or thermal performance. For example, a comparison of enclosure systems should have an equivalent U-value.

System Boundary
Clearly define which industrial and natural processes are included and excluded in the study, usually referring to the lettered LCA stages shown in the below graphic.

Data Selection and Quality
Carefully consider the data source and quality. Country-specific data is preferred due to large international variation in electrical grid, manufacturing practices and fuel types.

Methodological Choices
Clearly state which environmental impact categories will be studied, and which methods of allocation were used for practices like recycling, by-products, waste or co-products, either by the modeller or data provider.