What Is Triple Net Zero? Triple Net Zero refers to achieving net zero energy, net zero water, and net zero waste. Here’s a quick exploration of each.
What Is Net Zero Energy?
To achieve net zero energy, a building must be able to produce as much energy as it uses per year.
How We Get There
The building must use the least amount of energy possible: with passive solar orientation of the building massing on the site, airtight building enclosure (envelope) with sufficient insulation and air and vapor barrier; and right-sized building systems.
High Performance Envelope
Studio G Architects ensure that the building is energy-efficient by limiting the amount of glass to what is needed to maximize interior daylighting and provide good views; we limit west-facing windows that deliver unwanted heat gain in the summer. We right-size exterior insulation based on careful energy modeling for the specific climate conditions. We utilize air-sealing details that help maintain building temperature: cool interior in the summer and warm interior in the winter.
Right Sized Systems
We work with our engineers to design the smallest heating, cooling, and ventilation systems that meet the building needs, to reduce the renewable energy needed to power the mechanical systems. We design high efficiency lighting and reduce ‘plug loads’ with energy efficient appliances and equipment.
Renewable Energy
Then we need renewable energy to satisfy the resulting energy demand: typically rooftop photovoltaic (PV) array that back feeds to the energy grid. With sufficient PVs, the building can generate more power than it needs on a sunny day and pull power from the grid at night and days with no sun. Over the course of a year, if the building generates as much energy as it uses, it is Net Zero Energy.
Another renewable energy source for projects, often called ‘geo-thermal,’ is actually a ground source heat pump system. With it, underground pipes carrying water or refrigerant are heated or cooled by the earth’s constant 60 degrees +/- temperature and delivered throughout the building for heating and cooling, depending on need. These are becoming more prevalent with increased public subsidies to lower the relatively high upfront costs. To achieve Net Zero Energy, a project needs PVs or another source of renewable energy to power the heat pumps as well as the rest of the electrical needs.
E+ Highland: Exceeding Net Zero Energy
Designed to achieve net positive energy, LEED Platinum, Phius, and ILFI Zero Energy Certification, E+ Highland will provide resilient, healthy, and affordable family housing.
Technical advancements to meet energy-positive and resiliency goals include airtight passive building techniques, optimizing window/wall ratio, and targeting a thermal-bridge-free enclosure. The hot water system uses CO2 refrigerant with zero Ozone Depletion Potential.
A high-efficiency rooftop PV wave rack system maximizes renewable energy. Residents will have minimal utility costs and maintain comfort for 5+ days during a power outage.
What Is Net Zero Water?
To achieve net zero water, all potable water used within a building must be returned to the aquifer below-ground. The goal is to reduce the amount of potable water used, maximize ‘alternative water’ collection, and return used water to the aquifer.
Types of Water
- Potable water – drinking water from a public source
- Grey water – non-potable water from sinks, showers, and washing machines
- Black water – sewer water from toilets
- ‘Alternative water’ – defined by the US Dept of Energy as “water sourced from sustainable supplies, serving to mitigate the reliance on fresh surface water and groundwater.” This includes collected rainwater.
How We Get There
Reduce Potable Water Use
The easiest water conservation strategy is utilization of low-flow toilets, faucets and showers. Another is collection of rainwater to be used for flushing toilets, which don’t need potable water. This requires a secondary indoor pipe system to carry rainwater to the toilets.
Recharge the Aquifer
Low-impact site development strategies can manage water on a site and help conserve and reuse the water: Pervious (porous) paving allows water to drain and recharge the aquifer. Bioswales and rain gardens can reduce water run-off and flooding, avoid underground structures and slowly release water back into the aquifer. Landscape irrigation doesn’t need potable water. Rainwater can be collected and stored for site irrigation that then re-charges the aquifer. Together these strategies can achieve net zero water.
Grey water and black water, once collected, are typically treated through a public sewer system or a site-specific septic system. The first does not recharge the aquifer because sewer treatment systems typically flow to the ocean or other large body of water. Septic systems do recharge the aquifer if they have a leaching field.
Developing Technologies
New technologies are being developed that will expand re-use of grey and black water. One example is the Living Machine, which the EPA defines as “an emerging wastewater treatment technology that utilizes a series of tanks, which support vegetation and a variety of other organisms.” The Living Machine uses some of the same processes as traditional treatment systems, but in a single building or site, the system can currently be cost-prohibitive. Other developing technologies that don’t rely on chemicals, such as UV sterilization and technologies using oxygen generators to disinfect and treat wastewater, are becoming more widespread.
Consider the Watershed
Studio G has determined that increasing flood risk due to a rapidly changing climate demands analysis of the watershed area around a project site to understand the potential impacts of existing bodies of water on our approach to site design.
Residences at Lawrence Hill: Returning Water to the Source
The Residences at Lawrence Hill in Wellfleet, MA, is a 46-unit multi-family housing project that incorporates efficient plumbing fixtures, native plantings, and low-impact site development.
Water will be returned to the aquifer through two systems – a local alternative wastewater treatment plant will treat grey and black water from these housing units and nearby school and public buildings before slowly releasing the treated water into the ground to recharge the aquifer. It also includes underground recharge basins to collect rainwater and return that to the aquifer over time.
The overall design will reduce potable water use, maximize alternative water collection, and return all used water to the ground, achieving Net Zero Water.
What is Net Zero Waste?
According to the EPA, “Achieving Net Zero Waste means reducing, reusing, and recovering waste streams to convert them to valuable resources with zero solid waste sent to landfills over the course of the year.”
For a new construction project, this starts with construction waste diversion strategies throughout the construction period, to divert construction debris and unused materials from landfills.
When planning a new building, the owner needs to develop its program for composting, material reuse, and recycling. In some municipalities, this is required. After conversation with our client, the design team needs to design space or spaces that support the efficient collection, separation, and storage of waste streams. Compost, trash, and recycling should have clearly marked receptacles. Studio G assists our clients in preparing the space, environmental graphics, and an educational program for building occupants on how to properly dispose of waste to ensure it is directed to the correct location.
Some building owners weigh waste bins (compost, recycling, trash) from building areas and report the totals on a large display screen in the lobby to develop friendly competition between ‘teams’ to reduce their weight in the “trash” category. This is especially useful in educational buildings.
Florence Roche Elementary School: Decreasing Waste
If you visit the Florence Roche Elementary School construction site in Groton, MA, you will see clearly marked dumpsters and receptacles for targeted material waste streams identified in the Construction Waste Management Plan. The plan includes a goal to divert at least 75% by weight of the total construction and demolition waste materials generated onsite, exceeding LEED v4.1 50% requirement.
To date, 79.47% of construction waste has been diverted from landfills and we’re excited to see where the project lands at the end of construction.
Educating Inhabitants about Triple Net Zero
Each building, whether a school, civic building, or housing, can educate occupants and inspire environmentally friendly practices. Informational displays can teach inhabitants about the high-performance and net zero design strategies implemented in the design and in the building operations, informing them about how they can positively contribute.
Studio G works with clients to develop graphics encouraging composting, recycling practices, and reducing water usage. For example, signage above sinks can inform people where the water they used to wash their hands will go and how it will be used. Display boards and monitors in common areas can show energy usage over the course of a day and week, and the weight of waste generated by type or building location. Friendly competitions can be developed to encourage good habits by residents. We see opportunities to get creative and inspire each person to contribute.
Triple Net Zero is Achievable Today
Achieving net zero energy, water, and waste is an ambitious goal but not one that is out of reach. We’re thrilled that more communities and clients are interested and driving toward these forward-looking practices. We’re excited by emerging technologies that will provide many more ways to design buildings that reduce negative environmental impacts and help us regenerate our communities. The more frequently architects and engineers employ new strategies in our practice, measure outcomes, and improve the strategies, the more we improve inhabitants’ lives, reduce operational costs, and preserve our planet.
