New build vs Refurb – The Life Cycle answer

Building projects are often asked the question if knocking down that existing building is the best outcome for the project and the environment. For a recent Australian CBD Office project, Edge used Life Cycle Assessment (LCA) at concept stage (LCA Lite) to provide the answer in terms of environmental impacts for the local government planning authority. Using LCA as a planning tool gives designers and planners the power to make informed environmental decisions early in the design process. The results of the study are detailed below:

The question

Which has the lower environmental impact for a building project: Demolish and New build or Refurbish existing?

The study

Two comparable design scenarios were analysed via LCA over 15 year period, Demolish and New Build vs. Refurbish Existing. A summary of the two scenarios is detailed in the table below:

Note: There is a large list of other Project and LCA assumptions that cannot be communicated concisely in this blog. However the above assumptions cover the main items.

The end-of-life, life cycle stage (Module C1-4, in EN15879) was excluded for both scenarios as after 15 years both scenarios would still be operating.

Part of the sell to refurbish the building was delivering a high-level of building energy efficiency. Hence the Refurbish Existing scenario will achieved 5-star NABERS energy where the Demolish and New Build scenario represents a more standard practice approach to energy efficiency with 3-star NABERS energy.

The result

The LCA results were calculated for 7 different environmental indicators, but in this blog we will communicate the results in terms of carbon emissions (kg CO2-e) and cumulative reduction (a sum of the % reduction over all 7 environmental indicators, the same method used in the Green Star LCA credit) only for simplicity.

The results are as follows:

  • Carbon Emissions: The Refurb Existing scenario has 36% less carbon emissions than Demolish and New Build scenario. Estimated to save approx. 34,740,000 kg CO2-e over 15 years.
  • Social Cost of Carbon: The Refurb Existing scenario would save $2,057,000 in the social costs of carbon when compared to the Demolish and New Build scenario. Using the Social Cost of Carbon factor of $59.2/tonne CO2-e
  • Cumulative Reduction: The Refurb Existing scenario has a cumulative reduction of 231% when compared to the Demolish and New Build scenario. Across all 7 environmental indicators assessed.

Note: The above graph shows carbon emissions normalised per m2

From the above graph we can observe the following when comparing the Refurb Existing scenario to the Demolish and New Build scenario:

  • 49% reduction in embodied carbon emissions from materials (Product (A1-3) life cycle stage)
  • 51% reduction in construction carbon emissions (Construction A4-5)
  • 31% reduction in operational carbon emissions (Use – energy B6)

Summary

Over 15 years, Life cycle analysis shows that refurbishing an existing building and retaining the structure has a much lower environmental impact than demolishing and constructing a new building.

 

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