With growing concern over climate change and mounting interest in sustainable design, there’s been increased focus on net zero energy in the design and construction industries.
“We define net zero as a building, a community, a country or a planet that produces as much energy as it consumes on an annual basis using only renewable energy,” says William Maclay, author of The New Net Zero and President and founder of Maclay Architects.
And there are plenty of advantages to net zero, William adds. Such as:
1. Net zero buildings are now less expensive on a cash flow basis than fossil fuel buildings
2. Global climate change is making people aware that our buildings cannot just be less bad; they must not contribute to climate change at all
3. The technology and design strategy and technology is established and cost-effective today
4. Net zero buildings are healthier, more durable and more beautiful than fossil fuel buildings
5. The cost of solar photovoltaics (PV) and other renewable technologies has dropped drastically to the point where the financed cost to own and operate them is less than fossil fuels
William recently checked in to offer more of his insight on the advantages of sustainable design and how architects, designers and builders can implement it today. Here’s what he had to say:
How did you become so passionate about sustainable design?
In 1970, I went to a lecture on solar energy and decided that my life commitment was to create a renewably powered planet through architecture. In 1971, I and two others began constructing a solar- and wind-powered community similar to cohousing (which did not exist in the U.S. at that time).
From that time on, my career has focused on the design of healthy, renewably-powered buildings and communities. In 2005, Maclay Architects completed our first large renewably-powered office and manufacturing facility that is over 90 percent renewably powered. It is visited by thousands of people a year who are inspired to see that renewable energy can power larger buildings. We followed that project with net zero buildings, including the Putney School Fieldhouse and over 10 other net zero or near net zero projects. In 2010, we decided to share our knowledge on how to cost-effectively design and build net zero buildings through writing a book, which we completed in 2014. It is an in-depth book on net zero building design and construction, highlighting large and small buildings and construction details.
What areas of construction should designers, architects and builders focus on when building with net zero in mind?
1. Our book, The New Net Zero, identifies 12 steps (or core practices) for net zero design and construction. These include selecting an effective team; using integrated and collaborative design processes; minimizing energy loads; selecting appropriate mechanical and electrical systems; powering with PV; detailing and specifying products and procedures for net zero performance; and testing, monitoring and commissioning.
2. Energy use intensity (EUI) calculations should be discussed throughout goal setting, design and building monitoring. To meet net zero ready standards during design, the team must set EUI goals (we use 10-25 kBtus/sf-year site energy for typical residential, office and classroom buildings), perform energy modeling to ensure that the building design meets energy goals, inspect and test to meet those metrics during construction, and then monitor the first year energy consumption to ensure performance is consistent with the design goals.
3. The New Net Zero also discusses a financial analysis process that identifies increased capital and decreased operating costs for net zero buildings compared to a code building. The analysis determines first-year and long-term capital and operating costs so that building owners can determine if net zero improvements are justified financially.
4. There is more upfront cost and effort in the early stages of the design process, which can reduce effort and expense later.
5. Building science-based design and construction details is essential for net zero success.
How should net zero concepts be applied to new residential structures?
1. It’s important to discuss energy use intensity (EUI) calculations as outlined above.
2. Design a very energy-conserving envelope. In cold climates, roofs should be R60, walls R40, below-grade surfaces R20, and windows R5; and and air infiltration should be less than 0.1 cubic feet per minute per square foot of aboveground surface area based on blower door testing at 50 pascals (cfm50/sf).
3. Sun-tempered passive solar design strategies that is right-sized and not oversized for the building are important.
4. Air source heat pumps for heating and cooling, solar photovoltaics for powering homes, and high-efficiency appliances should also be used.
What about to existing houses?
1. All of the same processes/procedures as indicated above, although greater creativity, effort and likely expense are required to achieve goals.
2. Increased attention to building science.
3. Generating a strategic energy master plan so that implementation can occur incrementally over time, connected to changes in program requirements or maintenance.
4. Deciding whether to insulate on the inside or outside, depending on whether the interior or exterior is in worse condition and therefore more cost-effective to upgrade.
What are some of your favorite examples of net-zero projects? What can we learn from them?
BedZED: An early multifamily net zero building in England that demonstrated feasibility for other projects.
National Renewable Energy Lab: A large office complex that is net zero.
Putney School Fieldhouse: Our firm’s first institutional net zero project and one of the first national secondary school buildings that is net zero. It has documented net zero performance since 2009. This building utilizes air source heat pumps without any backup heating in a very cold climate.
Putney School Net Zero Campus Masterplan: A net zero energy campus masterplan to make a campus with over 40 buildings net zero over the next 20 years. This plan includes building-by-building energy analysis, recommendations, and cost information, and is a model net zero campus energy masterplan.
Bosarge Family Education Center – Coastal Maine Botanical Gardens: Net zero daylit space connected to the botanical gardens and outside classrooms, and the winner of the 2013 Northeast Sustainable Energy Association (NESEA) Net Zero Energy Building Award. This building used panelized construction by Bensonwood to reduce construction time and control construction costs.
Renewable NRG Net Zero Community: This 300,000 sf feasibility study documents positive cash flow for over 300,000 square feet of residential and commercial net zero buildings in Vermont.
How can architects and builders challenge preconceptions and/or assumptions of their clients to push for more sustainable design?
Common client misconceptions or challenges to sustainable design include that net zero is too expensive, it’s for single family homes but not for larger projects, or it’s too expensive for renovations. The process identified above demonstrates energy and financial performance on a building-by-building process so that building owners can determine whether net zero building meets their financial and environmental needs. When this process is used, it demonstrates that net zero buildings are often cash flow positive from day one.
Clients might also assume that net zero and sustainable buildings are not attractive; but today, most environmentally-focused buildings are healthy, attractive, and a prudent investment
What are some go-to resources for architects and designers who want to learn more about net zero building?
- Building Science Corporation
- Architecture 2030
- Center for Maximum Potential Building Systems
- Illuminating Engineering Society
- New Buildings Institute
- Living Futures Institute
- Center for Maximum Potential Building Systems
- Passive House Institute US
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