“Climate change is running faster than we are — and we are running out of time.” That is the stark conclusion of the long-awaited Intergovernmental Panel on Climate Change (IPCC) special report on global warming.

“Pledges from the world's governments to reduce greenhouse gases, made in Paris in 2015, aren't enough to keep global warming from rising more than 1.5 degrees Celsius,” says the report, which is focused on highlighting the significant difference in impact on life between a 1.5 and 2 degree increase in global temperatures. Despite essentially sounding the climate alarm, the report manages to remain optimistic about our ability to limit warming, but only with a major, immediate and global response.

The report suggests that the 1.5-degree Celsius goal would require a 40-50% reduction in emissions by 2030. Then, by 2050, it would require a carbon-neutral world, one with no net additional greenhouse gases in the atmosphere, by 2050. Consider that global emissions are currently still rising and you realize that we’re going to have to have to make some drastic changes to avoid catastrophe.

“Limiting warming to 1.5 C is possible within the laws of chemistry and physics...but doing so would require unprecedented changes,” comments Jim Skea, one of the authors of the report. “The world has to collectively move now in order to make it happen.”

If we have any chance to achieve these goals huge pressure will have to be placed on the world’s biggest emitters of CO2 and the largest energy consumers – in both those categories we find the building sector. The global buildings sector is responsible for 30% of final energy consumption and more than 55% of global electricity demand. The buildings and buildings construction sectors combined are responsible for 36% of global final energy consumption and nearly 40% of total direct and indirect CO2 emissions, according to the International Energy Agency (IEA).

Zero energy buildings (ZEBs) - buildings that generate more energy than they consume when production and consumption are averaged over the course of a year - are possible and provide the juicy low-hanging-fruit for reduction of energy consumption. However, failures in building codes are holding back the mass adoption of these potentially world-saving structures, concludes a new report by the American Council for an Energy Efficient Economy.

The paper, ‘Pathways to Zero Energy Buildings through Building Codes’, provides a roadmap to triggering mass adoption of ZEBs, not only through updating residential and commercial codes but also through stretch codes and voluntary programs. It highlights barriers to widespread implementation of ZEB codes and offers detailed recommendations to help policymakers and other stakeholders overcome those barriers.

“Zero energy buildings (ZEBs) produce at least as much energy as they consume,” clarifies the report. “Whereas only a few thousand ZEBs have been constructed in the United States and Canada until now, it may be possible to improve building energy codes to the point where all new buildings are zero energy by 2030,” it states ambitiously, but only if coding barriers can be overcome.

ZEBs are built to the most stringent energy efficiency performance levels to minimize energy consumption while staying cost effective. The remaining load is typically met with onsite renewable energy, primarily solar photovoltaic rooftop panels. Cities, states, code organizations, and other groups have pledged commitment to zero energy buildings by setting goals for achieving ZEBs by a certain date. 2017 research by Edminster and Sankaran shows only 500 commercial and 3,000 single-family residential ZEB projects in the United States and Canada, a tiny fraction of building stock.

Building energy codes can be divided into two primary frameworks, prescriptive and performance. Prescriptive codes assign specific minimum criteria that must be met when constructing a building. Designers often complain that prescriptive codes limit their creativity. Performance codes provide a designer with greater flexibility by setting a minimum energy performance targets. After meeting certain mandatory requirements, the building architects and engineers can decide the best way to meet the targets. Both offer opportunities to improve energy efficiency on a path toward zero energy buildings but neither specifies how, creating a problem.

“One barrier to zero energy building codes is that some casual observers have the perception
that zero energy buildings require only the addition of solar energy. They believe that
energy efficiency upgrades like better insulation or high-efficiency HVAC equipment are unnecessary,” suggests the report while demonstrating the economic benefit of efficiency over generation. “The best design practice is still to reduce building loads with energy-efficient measures first, and then use solar to meet the remaining loads.”

“Another potential barrier is a debate over onsite solar versus community solar. Although
many organizations may agree with the general idea of achieving zero energy new building
construction, they may disagree about the best way to achieve it,” explains the report. “Some groups contend that building codes can, and should, consistently be improved until we achieve the goal of ZEBs at the individual building level. Others argue that we should instead focus efforts on community renewable energy because installing onsite renewable energy on every building is not cost effective or practical.”

Both individual and community generation are positive and significant steps towards our climate change targets, inevitably both will be needed to make every building a ZEB. However, because community-scale renewable energy is outside the scope of building energy codes, other policies would be required to coordinate building energy efficiency, onsite PV, and community systems, each adding substantial complexity to an already complex issue. In addition, the community-scale argument focuses primarily on economics and less on consumer preference. If someone wants their own rooftop PV, to share community solar, or both, they should be able to have it. ZEB building codes should be able to unify these options for simplicity.

Another potential barrier outlined in the report is a culture of resistance to energy code improvements. ASHRAE - Standard 90.1 is the US national commercial building model energy code - has committed to making net-zero energy projects financially viable by 2030. “This has helped create a culture that seeks regular efficiency improvements each code cycle,” the report says.

The International Energy Conservation Code (IECC), which serves as the US national residential building model energy code, however, has not set such a goal. Their process is driven by a broad combination of stakeholders with differing views and objectives. In the IECC, passing minor efficiency gains, like improved floor insulation requirements or fenestration U-factor requirements, has proved challenging in recent years because of this fractured stakeholder group.

“Some push for efficiency in the code, while others push back on energy efficiency changes that have a cost, even if proven to be cost effective. These conflicting interests have gridlocked the residential IECC code the past two cycles (2015 and 2018) and resulted in little to no energy efficiency progress in the IECC for six years,” explains the report. “A fundamental shift in either the stated goals of the ICC or the composition of the committees will be necessary to advance the IECC toward zero energy.”

It is essential for the ICC to develop “big, bold goals to achieve zero energy buildings by 2030,” recommends the report, stating that “it would help justify the continual improvement in efficiency of the code.”

The researchers concede that finding the best structure for these codes will require more research and must retain the flexibility to adapt to changes in the energy landscape. However, they insist that the lessons are ready to be learned so changes can be made - pointing to the success of regional codes and building energy standards like California’s zero energy building code and PHIUS+ that offer roadmaps to their own evolution.

“Advocates and policymakers should start considering incremental energy code changes now so that progress can continue,” concludes the report. “Energy advocates at the national level should continue to submit and defend proposals that move the codes closer to zero energy. Policymakers at the local level should start evaluating the best method to achieve zero energy through their building codes. Developing voluntary programs and zero energy stretch codes now can be important initial steps toward transitioning to a minimum ZEB code in the future.”