Net zero carbon buildings

Every building in the world — every home, office, school, factory— needs to be net zero carbon by 2050 to keep global temperatures below 2 degrees C. Estimates suggest that exceeding 2C  by 2030 at least $4 trillion in assets will be at risk and another 100 million people driven into poverty.

Cities account for more than 70 percent of global carbon dioxide (CO₂) emissions. About half of those emissions come from the energy consumed in buildings for lighting, electricity, heating and cooling. Moreover, cities in emerging economies will account for the majority of global growth in energy use through 2030.

This is far more challenging than greening electricity generation or even transportation. Few of the world’s estimated 1.7 billion buildings are net zero carbon today.  To change this a multi-partner global initiative called Zero Carbon Buildings for All, was launched at the 2019 UN Climate Action Summit in September 2019. Participating countries including Kenya, Turkey, the United Arab Emirates, and the United Kingdom have committed to national and local policies to make all new buildings net zero carbon by 2030, and existing buildings by 2050.

Last year the World Green Building Council (WorldGBC)  launched a similar effort called Net Zero Carbon Buildings Commitment for businesses, property developers, cities and regions with the same targets.

"Zero carbon buildings are at the heart of the solution set for the world to achieve the climate goals set at the Paris Accord," said Diane Hoskins, Co-CEO of Gensler, one the world’s largest architectural firms. Gensler is recommending all of their clients build or retrofit to meet net zero carbon standards. 

What is a net zero carbon building (ZCB)?

Net zero carbon building (ZCB) do not have any carbon emissions associated with their annual energy demand. This is achieved with high levels of energy efficiency and renewable energy generated either on site, solar panels on the roofs for example, or off-site from a wind farm or other source. This mean replacing gas for heating and cooking with electricity; Research shows that reducing energy demand in buildings represents the most cost-effective way to tackle climate change.  ZCBs can also have important co-benefits, like improving health and quality of life for residents and workers.

Deep Energy Efficiency Can Cut Energy Use 75%

The key to ZCB is what’s known is deep energy efficiency. This is a whole-building approach where design and architecture, construction materials including insulation and windows, heating, cooling, electricity and air exchange equipment are all integrated to reduce energy use 50 to 75 percent or even more.

A similar approach for existing buildings is called “deep energy retrofits”. In a residential home this kind of retrofit might include:

• super-insulating existing walls, floors, and attic space;
• replacing doors and windows with energy-efficient units;
• upgrades to high-efficiency HVAC (heating/cooling)
• high performance insulation in the foundation walls;
• effective air sealing and moisture control;
• energy efficient water heater, lighting, and appliances;

“We have the technology to make buildings net zero carbon but in most places regulations and or the business model are missing,” said Emma Stewart, Director of Urban Efficiency & Climate at the WRI Ross Center For Sustainable Cities. Building codes that aren’t supportive or utilities that don’t allow building generated electricity to be sold back to the grid are just two examples of the barriers Stewart said.

New York City’s iconic Empire State Building underwent a deep energy retrofit in 2009 and cut its energy use nearly 40 percent, saving $4.4 million a year in energy costs. Eight simple energy saving measures, carefully coordinated meant it only took three years to cover the retrofit costs.

However deep energy retrofits even on a much smaller scale can create cash flow challenges for the construction industry and some building owners. Governments at various levels can provide support through bridge loans or temporary subsidies suggests Stewart.

To have all buildings net zero by 2050 will require a massive increase in the number of renovations. Currently less than one percent of existing building stock undergo any type of renovation annually according to the Global Alliance for Buildings and Construction. This needs to increase to at least three percent per year to reach the 2050 goal.

“Buildings are the biggest overlooked climate problem,” said Stewart. “We need to use whole systems thinking and have everyone from mechanical engineers to architects to trades people and building occupants working together to figure this out.”