Keeping It Neutral–On Carbon

Both embodied carbon and operational carbon need to be addressed
[ Page 3 of 5 ]  previous page Page 1 Page 2 Page 3 Page 4 Page 5 next page
Sponsored by Propane Education and Research Council (PERC) and Sloan
By Peter J. Arsenault, FAIA, NCARB, LEED AP
You are not currently logged in to your CE Center account. Log in to view and complete the quiz questions that are embedded in this article.

U.S. fuel processors are making renewable propane today, and the push for cleaner liquid fuels such as sustainable aviation fuel and renewable diesel fuel will lead to a sharp increase in renewable propane production. By 2050, renewable propane could meet half the world’s demand for propane, according to the World LP Gas Association. All of these efforts can help contribute to a more carbon-neutral world.

Bryan Cordill is the Director of Residential Business Development at the Propane Education and Research Council (PERC). He observes that "Propane is clean today, and cleaner tomorrow with the advancement of renewable propane." These latest developments certainly hold promise for hybrid solutions and fully carbon-neutral solutions in the near future.


With an understanding of the embodied carbon that comes from the production of materials, products, and burning of fuels, we turn our attention to the carbon produced by building operations. Not surprisingly, this topic has received considerable research and attention over the past decade or more as evidenced in the newly released (anticipated October 2023) ANSI/ASHRAE Standard 228-2023 titled “Standard Method of Evaluating Zero Net Energy and Zero Net Carbon Building Performance.” This document is a standard for evaluating whether a building or group of buildings meets the definition of "zero net energy" or "zero net carbon.” The standard includes a calculation for annual averages to determine if the source energy or carbon flows coming to a building are less than or equal to outward flows during operation. The standard covers existing buildings, new buildings, and groups of buildings. Those seeking to achieve net zero buildings would do well to consult this new resource.

Photo courtesy of Sloan

Specifying sustainable commercial restroom products helps to reduce water usage, which in turn helps to reduce carbon emissions from the energy needed to move and treat water.

Photo courtesy of Sloan

The ability of restroom fixtures to conserve water being delivered and being sent to wastewater treatment directly impacts the amount of energy and carbon emissions that come about as a result of their use.


When looking to address zero net energy or zero net carbon operational solutions, it is common to look at high-intensity energy-consuming equipment in a building and assume they are the only place to focus. While that is an important aspect that should be explored and addressed in building design, there is another area that deserves attention too, namely the amount of potable water usage in a building. As LEED and other green building standards have identified, potable water is a precious resource in and of itself that should be conserved and used properly. But equally significant is the fact that water in buildings requires significant amounts of energy first to extract and treat it for drinking, then for transporting it through a geographic area, and for delivering it to buildings. Equally important, we do well to recognize that a great deal of that water is never consumed for drinking. Rather it is used for washing, flushing, or other reasons and sent down a drain where more significant amounts of energy are then needed to treat the wastewater and its contents. This is particularly true in restroom fixtures in buildings with high usage such as schools, transportation centers, entertainment facilities, restaurants, and hospitality settings, among others. We have noted already that specifying such products that have lower embodied energy and carbon is important, but there are additional considerations as well.

The first characteristic to look for is the ability to reduce water use in restrooms by selecting products that operate well with lower water volume requirements. For toilets and flush valves, that means selecting well-designed products that operate at or below code and industry standards for water conservation. Doing so means less wastewater is produced requiring less energy, and fewer carbon emissions, to treat it.

Handwashing is another area of high energy and water usage in many buildings. The high volume of traffic in commercial restrooms is one factor, but another potential factor is the improper use of the faucets—sometimes a faucet may be turned on and left running, resulting in significant waste. Selecting sensor-operated fixtures that are suited to the particular needs of a building can help in this regard. Working with manufacturers of restroom products dedicated to sustainability will not only help with embodied carbon but also with operational savings through lower water use and the resulting lower carbon emissions.

Paul Sambanis is the Vice President of Sustainability with Sloan. He has heard comments from some design professionals that they think the options are unattractive if the focus is on sustainability or carbon neutrality. He retorts that “While sustainable product offerings may have been limited or budget-restrictive in the past, that is no longer the case. Manufacturers have stepped up and currently offer a much broader and wider range of options that meet water-conserving, energy-conserving, and carbon-neutral goals for all types of building projects.”

The ability to back up the claims of such performance usually comes from third-party verification and demonstrated compliance with relevant standards. In this case, there are a number of such standards that help identify preferred products. The first is the U.S. Environmental Protection Agency (EPA) WaterSense program. This initiative encourages water efficiency by labeling products and services that meet the EPA's criteria for efficiency and performance. WaterSense-labeled products are certified to use at least 20 percent less water, save energy, and perform as well as or better than regular models. The program's goal is to protect the future of the U.S. water supply. WaterSense-labeled products include toilets, flush valves, showerheads, and faucets.

There are also products that meet the requirements of the Living Building Challenge and the WELL Standard. In these cases, they may not only show superior water conservation capabilities, but also contribute to safer, healthier, and cleaner indoor environments.


A carbon-neutral or zero-carbon building doesn’t mean zero energy─all buildings will continue to need energy to operate. The goal is to provide that energy without producing carbon emissions to begin with or to offset grid emissions by returning an equivalent amount of carbon-free energy. Towards this end, there are two terms that are used to describe relevant design approaches for homes:

  • Zero Net Energy (ZNE) homes are defined as those that produce as much energy as they consume over the course of a year. ZNE homes are typically designed to be energy conserving and use renewable energy sources, such as solar panels, to offset their energy consumption. ZNE homes are also known as carbon-free homes when the energy they produce is carbon-free. ZNE homes are commonly designed to be heavily insulated, exceptionally well air sealed, use green construction technology, use sustainable products that reduce CO2 emissions and water use, and incorporate energy-efficient systems and appliances.
  • Zero Energy Ready (ZER) homes are built to be ready for an onsite energy generation system to be installed, even if it is not installed during construction or renovation of the home. ZER homes are also well designed and built with energy conservation measures so they can offset most or all of their annual energy consumption with an on-site renewable energy system. These homes are airtight, well-insulated, and energy efficient. With the energy-producing system installed, they can then produce as much renewable energy as they consume over the course of a year, leaving the occupants with a net zero energy bill.

Photo courtesy of PERC

Zero Net Energy (ZNE) and Zero Energy Ready (ZER) homes are designed to use renewable energy or alternative fuels to produce as much carbon free energy as the building uses.


[ Page 3 of 5 ]  previous page Page 1 Page 2 Page 3 Page 4 Page 5 next page
Originally published in Architectural Record
Originally published in November 2023


Keeping It Neutral–On Carbon
Buyer's Guide
Sloan® Smart Systems SC Argus Pro
Sloan’s IoT solution, SC Argus Pro, consists of smart products, data bridges, and the cloud-based SC Argus Pro software. The smart system allows you to monitor and maintain products remotely, reduce water usage and improve sustainability, and create a healthier, more hygienic environment.