In simple terms, a net zero building annually produces more energy than it consumes using exclusively renewable energy. But, there is more to it.
There has been substantial debate regarding the meaning of “net zero” and the criteria a net zero project should meet. The discussion has grown fairly in-depth, typical for a new concept. However, we won’t be able to find an answer to achieving a net zero world unless everyone is on board with the standards that will make it possible.
A building’s energy performance is assessed using relative metrics, scored according to how much less energy it consumes compared to an existing building’s or code-compliant performance level. Therefore, someone may assert that a building is 2O% or 80% (Passive house levels) better than the code or the building before renovations.
While important, this does not provide much information about the whole picture.
Exploring & Defining Net Zero Buildings
The energy generated to power a building or project must originate from renewable sources according to any definition of “net zero.”
The requirements for where an energy-consuming building must get its energy from and whether or not a structure can use fossil fuels have yet to be declared net zero differ amongst definitions.
Several sustainable-building bodies have produced individual “net zero” definitions and criteria—however, most of these concern the structure’s performance and design. For example, according to some standards, all energy generated or used must originate on the building’s property or within its physical footprint.
Under other definitions, a building may use fossil fuels to power itself (for example, while using natural gas in the boiler to provide heating) as long as it generates an equal amount of energy from renewable sources to balance off its fossil fuel use.
There are still issues with how this offset is determined, such as whether or not one kBtu of power from the grid genuinely equals one kBtu of renewable energy generated on the premises.
Moreover, is electricity from different sources the same? Should the disparities between the production of power from renewable sources and fossil fuels be considered?
According to specific definitions, biomass might be regarded as a renewable energy source. However, while it is possible to develop carbon-neutral projects utilizing wood from the land, it is uncommon to have a steady supply of timber on-site.
How ASHRAE Defines Net Zero Buildings
American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is a global authority on energy and engineering, describes net zero as,
“a building which, on an annual basis, uses no more energy than is provided by the building’s on-site renewable energy sources.”¹
The European Council for an Energy Efficient Economy provides a similar definition,
“a net zero energy building is where, as a result of the very high level of energy efficiency of the building, the overall annual primary energy consumption is equal to or less than the energy production from renewable energy sources on site.”
According to these definitions, a building’s property significantly impacts whether or not it can attain net zero. For example, achieving net zero in a congested urban area is challenging but relatively simple on a wide-open rural property.
Other definitions consider off-property energy generation as a viable option for developing a net zero building to address these restrictions.
A more thorough definition that includes four significant characteristics for categorizing a net zero energy building (NZEB) depending on available energy sources is provided by the National Renewable Energy Laboratory (NREL).
They begin with a building that uses less energy, thanks to energy efficiency. Then, the objective is to use renewable energy produced on the building’s footprint to fulfill all of the building’s energy needs.
Additional energy production can be placed on the property if demand cannot be satisfied by renewable energy sources on the building footprint.
The third distinction permits using renewable energy sources, such as wood chips, to power systems related to the building’s electrical or hot/chilled water distribution when possibilities are scarce on the land.
This approach would also be relevant to net-metered, off-site renewable energy installations that were created especially for the project.
Finally, if the first three requirements cannot be satisfied, the last categorization is that renewable energy certificates may be bought from a specific provider.
The International Living Future Institute (ILFI), an organization that presently offers third-party certification of net zero energy projects, describes net zero as,
“one hundred percent of the building’s energy needs on a net annual basis must be supplied by on-site renewable energy.”
Although the criteria stipulate that there must be renewable energy on the site, there is flexibility to change these requirements and reach net zero through,
“the implementation of solutions beyond the individual project scale that maximize ecological benefit while maintaining self-sufficiency at the city block, neighborhood, or community scale.”
This approach seeks an elegant method to deal with property restrictions, and it is one that we support for developing a net-zero project that enables net metering and the installation of renewable energy sources in suitable places.
As long as the energy consumption is balanced by renewable output, these definitions for net zero buildings do not set a cap on energy use. However, some do promote energy conservation as the first step.
This implies that high energy-consuming buildings, whether new or old, may become net zero simply by incorporating a significant proportion of renewable energy.
The placement of renewable energy developed for a particular project must take into account a broader scale and context, focusing on how we utilize renewable energy and relate it to the energy load of our buildings.
Reducing The Energy Loads
Load reduction—lowering society’s overall energy consumption—is the first step toward a net zero society. We should concentrate on the energy performance of all new and existing buildings rather than just the net zero statistics.
This implies that we must first determine how much energy each structure uses.
This includes the use of:
- Increasing wall insulation
- Electric appliances like induction cooktops
- Heat pumps for hot water and heating and cooling
- Solar power
- Low-flow water fixtures
- High-performance windows
- Energy-efficient appliances (Energy Star rated)
- Efficient lighting (LED)
- Energy-efficient air ventilation for healthier indoor air quality
Defining a Broader Definition
We must redefine the ideal net zero building as a net zero project that extends beyond one building or property, anchoring its end goal in building performance and its contribution to a net zero community. And a net zero future to close this gap in current net zero thinking.
Put another way; we must adopt a new perspective when planning and constructing houses, workplaces, institutional buildings, industrial hubs, and other complexes.
It needs to limit the building’s energy demands. It makes no sense to deploy enormous renewable energy systems to power inefficient buildings.
We should aim for a balance of cost-effective improvements such as air-sealing, insulation, and renewables.
Final Thoughts (Net Zero Energy Buildings & Life)
So while the idea of net zero energy building is relatively straightforward, its verification may be difficult due to the diversity of energy sources that must account for both consumption and production and the potential sites for renewable energy sources.
Furthermore, nothing limits the notion of “net zero” to a single building, despite the possibility that it does so. The phrase can refer to a whole town, a state, a nation, the entire planet, an office complex, a residential neighborhood, a college campus, or even the world as a whole.
We must consider net zero waste, net zero water, net zero food, and other facets of a net zero society in addition to net zero buildings if we can live within our means.
References + Resources
1.) ASHRAE net zero definition link:
European Commission: Link
IEA: Net-Zero by 2050 – PDF
LIVING BUILDING CHALLENGETM 2.0 – PDF