Global net zero buildings are already possible, finds new study

The study finds that the technology and skills already exist to achieve net- or nearly-zero energy building in nearly every part of the world - including both developed and developing countries - at costs in the range of those of traditional projects.

It is widely agreed that the sectors that can make the biggest difference to reducing carbon emissions include power, transport, and buildings. The building sector in particular is responsible for 39% of energy related greenhouse gas emissions globally, and embodied carbon in building materials could consume up to half of the remaining 1.5°C carbon budget.

Achieving net zero carbon emissions in the building sector is vital to achieving climate goals. Sustainable building and energy retrofits are also a source of jobs, and have been identified as a key part of climate-friendly economic recovery from COVID-19.

"With respect to climate change, the world has agreed to a target of 2°C, but we find ourselves on a pathway towards between 3 and 5°C. Buildings are at the core of meeting the world's quality of life ambitions and addressing climate change. Of all the options available to us, getting buildings right stands out in terms of timeframe, scale effect, and economics," says Scott Foster, Director, Sustainable Energy Division, United Nations Economic Commission for Europe.

He continues, "The UN developed our Framework Guidelines for Energy Efficiency Standards in Buildings as principles-based standards conceived to meet the challenges. To do so we followed a similar approach to this paper, incorporating climate science and industry advances to inform public policy. The alignment of the findings in this paper with the Framework Guidelines reflects the growing global consensus on sustainable buildings for all."

The study examines low and ultra-low energy buildings and visionary policies internationally, and finds that change can often be achieved quickly. For example, Brussels transformed their buildings from among the lowest performing to the highest performing in all of Europe in just seven years, using a combination of voluntary measures to support and encourage industry leaders to innovate and demonstrate what was possible prior to requiring that level of performance through regulation.

In addition, because project spend related to energy efficiency is low, the study finds that the cost of sustainable buildings can match or even be less than those constructed through traditional methods. For example, the City of Vancouver anticipated a modest increase in construction costs as a result of increased building code performance requirements but instead experienced a cost decrease of 1%.

"Buildings are often the largest consumer of energy and source of emission in cities, and frequently represent the lowest cost option for reducing emissions," says David Miller, Director, International Diplomacy at C40 Cities Climate Leadership Group and former Mayor of Toronto. "The findings in this important paper highlight the experience of leading cities in which committed leadership has overcome the challenges to enable better, more comfortable, healthy, affordable and sustainable homes and buildings for all."

While the study highlights the ease with which many cities have begun the transition to sustainable housing, challenges remain. The greatest technological difficulties are seen in high-rise commercial buildings in hot and humid climates and in retrofitted historic heritage buildings. Deep retrofits are also costly in the short term, and although they may cost less over time, innovative financing is often required upfront.

"The sustainable cooling of buildings is a major challenge," says Radhika Khosla, study co-author and Senior Researcher at the Smith School of Enterprise and the Environment, University of Oxford. "In a warming climate, building energy use will go up even if cooling is as efficient as possible. Rising affluence, space and comfort needs are set to dramatically increase energy demand - with corresponding increases in greenhouse gas emissions. However, there are solutions: for example, shading and wind-channelling designs to block the sun and allow for natural ventilation in high-rises."

According to the new research, the key to achieving net zero targets is the maximization of energy efficiency through building features, with remaining energy requirements generated from locally produced, renewable energy sources such as solar panels. The use of renewable materials, such as timber, can also help decrease CO2 emissions. Bio-based materials could represent a double win in construction: first, by replacing energy- and carbon-intensive materials such as cement, and second, by storing carbon temporarily.

Overall, the study highlights that the global outlook on sustainable housing is positive. China in particular is highlighted as the global leader in this space: facilitated by a clear efficiency standard, over 7 million square meters of ultra-low-energy buildings have been erected in the country in the past few years.

"Having buildings that achieve nearly zero energy is absolutely possible in the hot-humid climates of Asia, as more and more exemplary cases and key techniques are found," says Yvonne Chan, study co-author and Senior Programme Coordinator, Delta Electronics Foundation.

However, the authors caution that urgent action must be taken to make use of existing technologies and skills.

"Our research shows that net zero energy buildings and retrofits are feasible in every corner of the world, all climates and virtually every building type. Already a market reality in many locations, they're pivotal pillars of a climate neutral economy. However - given that our building stock takes many decades to turn over or be fully retrofitted - if we're to hit a zero-energy global building sector by mid-century this technology has to become the standard practice now," says Diana Urge-Vorsatz, study co-author and Director, Centre for Climate Change and Sustainable Energy Policy at the Central European University.

"Every single building, we build or retrofit that does not take full advantage of our net zero technology and know-how locks us into a warmer climate."