The Greenest Building
Quantifying the Environmental Value of Building Reuse
Executive
Summary
Until
now, little has been known about the climate change reductions that might be
offered by reusing and retrofitting existing buildings rather than demolishing
and replacing them with new construction. This groundbreaking study concludes
that building reuse almost always offers environmental savings over demolition
and new construction. Moreover, it can take between 10 and 80 years for a new,
energy-efficient building to overcome, through more efficient operations, the
negative climate change impacts that were created during the construction
process. However, care must be taken in the selection of construction materials
in order to minimize environmental impacts; the benefits of reuse can be
reduced or negated based on the type and quantity of materials selected for a
reuse project. This research provides the most comprehensive analysis to date of the
potential environmental impact reductions associated with building reuse. Each
year, approximately 1 billion square feet of buildings are demolished and
replaced with new construction.
This research provides the most comprehensive analysis to date of the potential environmental impact reductions associated with building reuse. Utilizing a Life Cycle Analysis (LCA) methodology, the study compares the relative environmental impacts of building reuse and renovation versus new construction over the course of a 75-year life span. LCA is an internationally recognized approach to evaluating the potential environmental and human health impacts associated with products and services throughout their respective life cycles.This study examines indicators within four environmental impact categories, including climate change, human health, ecosystem quality, and resource depletion. It tests six different building typologies, including a single-family home, multifamily building, commercial office, urban village mixed-use building, elementary school, and warehouse conversion. The study evaluates these building types across four U.S. cities, each representing a different climate zone, i.e., Portland, Phoenix, Chicago, and Atlanta. A summary of life cycle environmental impacts of building reuse, expressed as a percentage of new construction impacts, is shown in the following figure (Summary of Results).
Key
Findings and Analysis
Building
reuse almost always yields fewer environmental impacts than new construction
when comparing buildings of similar size and function. The range of
environmental savings from building reuse varies widely, based on building
type, location, and assumed level of energy efficiency. Savings from reuse are
between 4 and 46 percent over new construction when comparing buildings with
the same energy performance level. The warehouse-to-multifamily conversion –
one of the six typologies selected for study – is an exception: it generates a
1 to 6 percent greater environmental impact relative to new construction in the
ecosystem quality and human health impact categories, respectively. This is due
to a combination of factors, including the amount and type of materials used in
this project.
Conclusions
For
those concerned with climate change and other environmental impacts, reusing an
existing building and upgrading it to maximum efficiency is almost always the
best option regardless of building type and climate. Most climate scientists
agree that action in the immediate time frame is crucial to stave off
the worst impacts of climate change. Reusing existing buildings can offer
an important means of avoiding unnecessary carbon outlays and help communities
achieve their carbon reduction goals in the near term.
This
report sets the stage for further research that could augment and refine the
findings presented here. Study results are functions of the specific buildings
chosen for each scenario and the particular type and quantity of materials used
in construction and rehabilitation. Great care was taken to select scenarios
that would be representative of typical building reuse or conversion projects.
However, environmental impacts will differ for building conversions that use
different types and amounts of materials. Others are encouraged to repeat this
research using additional building case studies; replicating this analysis will
enhance our collective understanding of the range of impact differences
that can be expected between new construction and building reuse projects.
This
study introduces important questions about how different assumptions related to
energy efficiency affect key findings. In particular, further research is
needed to clarify how impacts are altered if a new or existing building can be
brought to a net-zero level using various technologies, including renewable
energy.
