Deep retrofits: how repurposing old buildings can mitigate climate change

It will not be possible to meet global targets for reducing greenhouse gases if we only pay attention to new buildings. Firstly, more than 70% of buildings that exist today are expected to still be standing in 2050. Moreover, retrofitting an existing building can result in 50-75% less carbon than constructing the same building from scratch.

The Canada Green Building Council (CaGBC) estimates large building retrofits alone can reduce building sector emissions by up to 51%. Until recently buildings were declared net zero based on measuring operational carbon, which does not account for everything that went into the building’s construction.

Accordingly, the industry is developing better tools for measuring embodied carbon within existing structures, which includes the greenhouse gas emissions that arise from the manufacturing, transportation, installation, maintenance and disposal of building materials.

A deep retrofit is typically defined as a major renewal of an existing building, generating savings in energy and operating GHG emissions that exceed 30-50%. Deep retrofits also result in lower operating costs, improved thermal comfort and indoor environmental quality and raised asset value.

To demonstrate the potential energy savings and embodied carbon benefits of a deep retrofit, the Canadian Federal government undertook a significant pilot project with a 440,000 square foot office building from the 1950 in Toronto. The result: energy consumption was reduced by 69% and GHG emissions by more than 80%.

This project provides proof of concept that ageing office buildings can be retrofitted to be better than new, modelling replicable technologies such as ground source heat pumps, advanced heat recovery and rooftop solar photovoltaic panels. The existing concrete and steel structure, original to the 1950s construction, was reused in almost its entirety, which avoided almost 7,800 tonnes of embodied carbon emissions effectively locked into the existing materials.

Beyond carbon reduction, the project contributes to the health and wellbeing of occupants by pursuing the WELL building standard. The project also advances progressive standards for accessibility by supporting occupants with physical, sensory and cognitive disabilities.

Academic buildings are also ripe targets for deep retrofits. Most, if not all, universities have set ambitious sustainability goals and buildings are a major component of campus life. As they are renovated, they become teaching tools for innovative approaches to reducing emissions and demonstrate new technologies that advance the energy transition.

The deep retrofit of MacKimmie Complex, University of Calgary — a 380,000 square foot student-centred building – reduced energy consumption by 80% and achieved a zero carbon design certification from the CaGBC. The retrofit strategy enabled the reuse of 8,500 tonnes of sequestered carbon within the concrete structure itself. Operationally, the previous tower had an energy use intensity (EUI) of 500. While a conventional retrofit targets an EUI of 125-200, the MacKimmie Complex was pushed further to reach 75, an 85% reduction in EUI.

In addition to the economic return on investment, which has demonstrated a simple payback of 25 years on current utility costs alone, the university has taken advantage of the building as a teaching tool and opportunity for further research through the University’s ’Campus as a Learning Lab’ programme.

Museums went on a building spree in the early 21st century, often attributed to the Bilboa effect, which is in reference to Frank Gehry’s wildly successful Guggenheim museum in Spain. Some building budgets nearly toppled institutions. Now, with rising operating costs and tight capital budgets, deep retrofits can help relieve some of these financial burdens while improving museum spaces.

The Glenbow museum in Calgary, Canada, is currently undertaking a $205 million structural renovation that will completely open up and transform a cramped space that dates back to the 1970s by incorporating natural lighting and a street-facing entrance. The physical transformation through interior and exterior renovations aims to reveal Glenbow as a reimagined place for the community.

The overall cost of the renovated museum continues to be significantly lower compared to the costs associated with a new museum building. At this time, the Glenbow Revitalization anticipates roughly $450 per square foot compared to $1,000-$1,100 per square foot for a new build.

The revitalization of the museum also eliminated 56,000 tonnes of new carbon being produced over the lifespan of the building because operational carbon has been greatly reduced, also keeping 38,000 tonnes of concrete out of landfills as the building has not been demolished.

As a result of cost efficiencies and donor pride, the museum has been able to advance their mandate well beyond what had previously been possible by eliminating ticketing and making public access free in perpetuity.

Cities, builders and designers can give existing buildings a new life, helping us meet much needed climate-related targets while supporting the vitality of communities. To significantly scale these efforts, the following guidelines should be considered: