A call for carbon-neutral construction

Concrete requirements and target values

The building sector can and must take a leading role if the world is to fulfil the Paris agreement. An international group of scientists and engineers including myself recently adopted the Graz Declaration (see box), which calls for determined action to reduce GHG emissions in the construction sector.

One goal is to introduce GHG budgets (comparable to a cost framework) that would be compatible with CO2 reduction targets advocated by the international scientific community1. These targets and budgets need to be scalable (for construction products, buildings, building portfolios and cities) and have clearly defined timeframes in order to deliver net-zero GHG emission levels by or before the middle of this century.

In order to be effective, such targets and budgets must be enshrined in legislation and standards. Requirements need to be framed in terms of performance, and they must ensure that no technologies receive special preference.

It is urgent that the initial construction phase itself receives particular attention, due to its disproportionately large impact: often more than half of the emissions created over the total lifetime of the building are released during its construction.

The current Swiss label for reduced GHG emissions in buildings, the 2000 Watt Society2, averages emissions across the lifetime of a building. This is misleading, because it underestimates the peak of emissions at the time of construction. The risk of a “lock in” situation is real if we think we are building a carbon efficient building when, in fact, we are just increasing the initial problem by releasing a large quantity of CO2 in the atmosphere.

The technology is there

New public buildings or those given public resources must set an example and target net-zero emissions, which is already feasible today: Researchers and industry in Switzerland have developed very low-emission concrete structures3. Carbon-negative insulation materials are already available on the market4. But what we still need is a fundamental change of mind-set.

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Author: Shirley