Experts offer five best practices for building net-zero-ready homes.
If a builder wants to achieve the big goal of building and selling zero-energy-ready homes, it may pay to think small.
“Getting to net zero is not a single big move,” says Wayne Williams, AIA, of Workshop: Architecture, who designed the four-home pocket neighborhood of net-zero NextGen Homes in Chattanooga, Tenn. “It’s capturing a series of small advantages every step of the way.”
Known as zero-energy-ready or net-zero homes, these houses are a step beyond the federal government’s Energy Star certification. They’re highly energy efficient, achieving the equivalent of HERS rating in the 50s and below, depending on the climate and square footage; meet indoor air quality standards; and adhere to building science principles.
Lastly, these houses must either have photovoltaic panels or be “renewable ready” so that they can potentially generate as much energy as they use.
It sounds complicated, but according to Williams and net-zero builders, those “small advantages” can be found in a variety of areas, from site planning to vendor selection. Carefully add them all up, and you have the makings of success in a small, but growing, market.
According to the Net Zero Energy Coalition, the number of residential net-zero projects jumped 100% between 2015 and 2017, reaching 12,000 in the U.S. and Canada. Some of the motivation may be regulatory, as states and localities explore zero energy codes in their quest to cut carbon emissions.
Regardless of the reasons, builders are taking notice. In 2017, 29% of builders said they had built a zero-energy home within the past two years, according to research by Dodge Data and Analytics, and 44% expected to do so in the coming two years.
For some, zero energy already has become a steady source of business, even with limited marketing. “Mostly buyers find me,” admits Anthony Aebi of Zero Net Now, who is currently developing a 25-lot development of net-zero homes priced starting in the $500s to the $700s in New Paltz, N.Y.
— Wayne Williams, AIA, Workshop: Architecture
In Denver, Thrive Home Builders expects to close 185 homes this year, all of them zero-energy ready. “It’s been a journey for us,” says Bill Rectanus, vice-president of operations for the Colorado-based builder.
5 Best Practices for Building Net-Zero Homes
When it comes to building zero-energy-ready homes, experienced builders and architects urge newcomers to start with the basics.
1. Pay attention to your land plan and homesites
Whether you are building a single home or a neighborhood, careful siting allows you to leverage a home’s sun exposure and perhaps even increase the density of the development.
“Through design, you can yield a few more lots and lower your land cost per lot,” says Williams. “It frees up a little bit of capital to get a better quality window or door, because you can’t fix those later.”
2. Skip the trendy products in favor of quality construction techniques
“We could build our energy-efficient homes with materials from Home Depot,” says Rectanus. His counterparts agree: “If I was speaking to a group of builders and architects, I would say you just have to understand what you’re doing,” says Stephan Kamrass, principal of Sareth Builders in Westlake, Ohio. “You can use the same materials … you just have to think of the whole house as a system and understand how the materials interact with each other.”
“It’s not about the bells and whistles,” Williams says. “It’s about building science.”
At Sareth Builders, every zero-energy-ready home starts with a tight building envelope. “My houses are literally airtight. It’s like living in a Tupperware container,” says Kamrass, who builds homes ranging from 1,800 square feet to 13,000 square feet. He uses advanced framing techniques, which reduce lumber and labor costs while upping energy efficiency, and raised-heel roof trusses, which leave more room for insulation.
When it comes to windows, Kamrass typically chooses double-pane units. “My dream is to have triple-pane windows in every house, but they are expensive and heavy. A good double-hung Energy Star window with air sealing is generally good enough.”
Williams pays close attention to areas where the foundation meets the walls, and the walls connect to the roof. “Any time you have a change in plane like horizontal to vertical or a change in materials, there’s a potential pathway for moisture,” he says.
3. Prepare the house for future renewables
“We preplumb the house with conduits in the attic and prepare the electric panel so that when homeowners are ready to make the investment in photovoltaics, the house is ready” and solar installers won’t need to penetrate the building envelope, Kamrass explains.
Once a zero-energy-ready home is built and properly sealed, builders must find the most energy-efficient HVAC for their climate and market. In New York, Aebi opts for geothermal heating and cooling systems for his homes, with heat recovery ventilators. In Colorado, Thrive’s all-electric approach for its Vitality series led the builder to Mitsubishi’s electric heat pump.
That product helps builders like Thrive get homes net-zero-ready in two important ways, according to Chad Gillespie, senior manager performance construction at Mitsubishi Electric. “Our systems are generally more energy efficient than traditional systems, and we can help builders get ductwork in conditioned space,” with smaller systems that can squeeze into tight spots within the building envelope, such as closets.
4. Prioritize air quality
Prioritize air quality, ideally meeting the EPA’s Indoor airPLUS standards to protect against mold, radon, and carbon monoxide and incorporate fresh air. One way to do this is through energy recovery ventilators, or ERVs, but those can be tricky, says Thrive’s Rectanus.
“We really believe in balanced ventilation, but the cost of ERVs can be really hard on a production builder’s budget,” says Rectanus. Thrive chose to install an integrated exhaust and supply fan system for fresh air in its Vitality series homes.
5. Talk with your trades so they know what they need to do
Talk with your trades so they know what they need to do to help you build these homes correctly and efficiently. “It really helps to sit down with vendors and know they are believers,” Rectanus says. “They’re proud of the homes they build.”
Selling Net Zero
If building zero-energy-ready homes requires concentration on the details, then marketing and selling them demands a big-picture focus. “We’re not selling energy efficiency on the sales floor,” says Rectanus. “We’re selling the holistic brand of Thrive Homes.”
That means offering zero-energy homes as a standard package, not a luxury upgrade, where buyers must decide whether to spend their money on granite countertops or indoor air filtration. “We don’t put them in that position,” says Rectanus, whose two Vitality floor plans start in the high $600s and low $700s.
Neither does Kamrass. “I really target a small niche of people who want to build a beautiful home, but who also understand we’re building for comfort, sustainability, and durability.”