Net Zero Energy: Making a Positive Impact
Twenty years ago, many people were not familiar with the term “sustainability.” Some had heard the word but didn’t know the real meaning. Now we know. “Sustainability” is a catch-all phrase that speaks to many facets of the work we must do to combat climate change.
“Net zero energy” is a new phrase that many people have heard but may not know what it means. Synonyms are “carbon neutral” or “zero energy building.” Net zero energy is a term that we will know well in the coming years. A simple definition of NZE is: “a building which offsets all energy used in the building with renewable energy created on site, calculated on an annual basis.” Buildings use energy. A lot of energy. Buildings use 40% of the primary energy in the U.S. (primary energy is the raw energy used to create electricity, gasoline or other refined energies that we use every day), and buildings use 80% of the electricity running through our power grid. As architects, developers, builders, business owners and building users, we have the potential to make a real difference in our nation’s energy usage. By creating NZE buildings ,we can have a positive impact.
Creating a NZE building is no small task, but through careful design we have the ability to do that today. Almost any building can be Net Zero Energy, and the cost need not exceed the cost of a typical well-constructed building.
How to Create a NZE Building
These four steps to design a NZE building can be implemented by any knowledgeable design professional:
1. Use nature. Design the building to use the sun for passive solar heating and daylighting, minimize unwanted solar heat gain during the summer, utilize cooling breezes or nighttime flushes, or other natural design techniques that will help the building perform better.
2. Seal the envelope. The “envelope” is the exterior walls and roof of the building. By using high levels of insulation and airtight construction, we can minimize the amount of heating and cooling that is lost through this envelope. That saves a lot of energy and reduces the size of mechanical systems.
3. Use efficient all-electric systems. Most of our buildings use natural gas to heat the building or to heat the water used in the building, but there are a variety of very efficient electric systems that are now available to replace those gas systems. Efficient systems will have a coefficient of performance of 3 or greater (a COP of 3+ means for every unit of electricity used, three units of hot air or hot water are created). We know we can’t produce natural gas on site, but we can produce electricity, therefore a true NZE building must be an all-electric building.
4. Photovoltaics create electricity on site. Photovoltaic panels create electricity from the sun. When we perform these first three steps well, then we can install PV panels on the building to offset the electricity used in the building. If we don’t have a well-insulated, well-sealed, all-electric building that uses the sun and breezes (those all-important first three steps), then we will never be able to install enough PV to offset the electric usage.
Electricity is the Key to Unlocking our NZE Future
There is a new wrinkle in these four steps. We must make the first three steps mandatory for every project, no matter what. But the truth is that the fourth step is optional – optional because our electricity grid is quickly becoming renewable itself. Xcel Energy plans to reduce carbon emissions by 80% by 2030 and be 100% carbon neutral by 2050. Poudre Valley REA (an electric utility in Northern Colorado) plans to be 100% renewable by 2030. This means that our electric grid is becoming a renewable source of power, and it is happening faster than anticipated. If our electric grid is 100% renewable but we are still using natural gas to heat our buildings, we are not taking full advantage of that renewable electric grid.
Is NZE really that easy? Yes! And no. On a high level, it is that easy. But there are an increasing number of products and systems to understand and integrate. Ground-source heat pumps, variable refrigerant flow, mini-splits, chilled beams, energy modeling, dew points, blower door tests, energy recovery ventilators, commissioning, life-cycle analysis and more must be understood and integrated by the design and construction team. But the technologies are available now. And they need not increase construction costs. Just as the electric automobile is the future and is available now, so the electric building is the future and is available now.
So, the next time you build a building, remodel a building, or even when you replace your HVAC system, water heater, or anything else that uses gas, consider the high-efficiency electric alternatives. NZE is the future. And the future is now.
Published in the September 2019 issue of Building Dialogue.