Living in a net-zero home is often a luxury for those who can afford solar panels, state-of-the-art HVAC and other innovations and renovations.

But lower-income people are those who could benefit most from energy cost savings, and those who suffer most from extreme climate. Milwaukee is trying to address this disconnect by building net-zero homes for low-income buyers in partnership with Habitat for Humanity, a marquee project of the city’s 2023 Climate and Equity Plan.

In September, the U.S. Department of Energy announced a $3.4 million grant that will go toward Milwaukee’s construction of 35 homes on vacant lots in disadvantaged neighborhoods and the opening of a factory to make wall panels for net-zero manufactured homes.

City leaders have found the undertaking more challenging than expected, especially on the factory front. But they hope overcoming roadblocks will help create a new local and regional market for energy-efficient, affordable prefabricated homes, while also training a new generation of architects in the sector through partnership with the University of Wisconsin-Milwaukee School of Architecture and Urban Planning.

“It remains an ambitious project,” said Milwaukee environmental sustainability director Erick Shambarger. “We’re trying to support equity, climate, new technology, manufacturing. It takes some time, but we’re excited about it and looking forward to making it a success.”

Panelized, prefabricated homes can be built relatively cheaply, but making them highly energy efficient is a different story. A handful of small companies nationwide make the wall panels used in such construction to highly energy-efficient standards, but transporting the panels is expensive and creates greenhouse gas emissions. 

The city sought a local manufacturer, but an initial request for proposals yielded no viable candidates. Now the city and UWM professors are working with the Rocky Mountain Institute to convince a qualified company to open a site in Milwaukee to make energy-efficient panelized home components at commercial scale, for both the city and private customers.

“It’s such a great fit for Milwaukee,” said Lucas Toffoli, a principal in RMI’s carbon-free buildings program. “It’s a city that has a very strong blue-collar tradition, so the idea of bringing back some manufacturing, and leveling up the home-building capacity of the city feels very congruent with the spirit of Milwaukee.”

And panelized homes could be a cornerstone of affordable, energy-efficient housing nationwide if the sector was better organized and incentivized, RMI argues — a goal that Milwaukee could help further. 

“Local action always drives a message in a way that federal action doesn’t,” Toffoli said. “It will be even more important under the incoming presidential administration and Congress. Having this project getting started at the local level in an important Midwestern city is a way to help ensure that progress continues at some level, even if it’s less of a priority at the federal level.” 

Panel problems

Habitat for Humanity builds its own panels in its Milwaukee warehouse, and is working on an energy-efficient panelized design that it hope will yield the first net-zero affordable homes in 2025. Milwaukee has yet to select a developer for the DOE-funded program, but Milwaukee Habitat was a partner in the DOE grant and CEO Brian Sonderman said the organization is hopeful it will be chosen during an RFP process.

Single-family homes are typically “stick built” from the ground up, with 2×4 or similar boards forming a skeleton and then, one by one, walls. Panelized homes involve walls transported intact to the site. 

Milwaukee Habitat for Humanity often uses a hybrid method wherein walls are “stick built” laying on their side in the Habitat warehouse, and then brought to the site where volunteers help assemble the new house.

There are various other methods of making panels that don’t involve lumber, UWM Associate Professor Alexander Timmer explained, and making these models highly energy efficient is still an emerging and decentralized field.

“It’s the chicken-or-the-egg problem in some sense,” Timmer said, since component manufacturers don’t know if there’s a market for energy-efficient panelized homes, and developers don’t build the homes because few component suppliers exist.

Wall panels can involve two sheets of plywood with insulation in between, or a steel interior surrounded by rigid insulation, among other models.

“With 2x4s, any small crew can build a home,” said Timmer. “With panelized, you need a factory, specialized tools, specialized knowledge. The hope is we are graduating architects into the market who know these technologies and techniques, and can design them to high energy efficiency standards. The city needs architects and builders who want to do these things and feel comfortable doing them.”

Toffoli touted the benefits of net-zero homes beyond the carbon emissions and utility bill savings.

“There’s less draftiness, greater comfort throughout the whole home,” said Toffoli. “In addition to making the heater run less to warm the air, there’s a big comfort benefit and acoustic benefit,” with little noise or pollutants filtering into the well-sealed home.

“In the middle of a severe Wisconsin winter storm, [if] power goes out for everyone, you have a home that can basically ride through harsh conditions passively much better,” Toffoli added. 

Toffoli said examples in Pennsylvania and Massachusetts show panelized, highly energy-efficient homes can be built at costs not much greater than standard market panelized homes. A different design, including thinner studs and more insulation, means less heat or cold is transported from the outside in. Insulation and highly efficient windows cost more than market rate, but smaller appliances can be used because of the efficiency, helping to mitigate the cost increase. 

He said mass production of net-zero panelized homes is much more efficient and cost-effective than stick-built energy-efficient homes. 

“You don’t need to, every time, find a contractor who understands the proper sequence of control layers for a very high-performance wall,” Toffoli said. “It’s been done in part in a factory where they’re plugging and chugging on a design that’s been validated and repeated.”

The DOE grant includes $1 million for Milwaukee to incentivize construction of the panel factory, $40,000 each toward 25 homes, plus funds for administration and other costs. Shambarger said $40,000 per home will cover the construction cost difference between an affordable home that merely complies with building codes, and one that is net-zero – meeting federal standards with a highly efficient envelope, an electric heat pump and solar panels.

Shambarger noted that the city funding and business will not be enough to motivate a company to build a new factory in Milwaukee.  

“Any company is going to have to have a customer base” beyond the city orders, Shambarger said. “We’ll have to make sure other housing developers like the product that companies have, that it’s cost effective. One of the things we learned the first time around is most of the developers really didn’t understand how to do net-zero energy. We want to make sure the product we select fits within Milwaukee neighborhoods, will work in our climate, has buy-in from the community.”

Local jobs would be created by the factory, which is slated to be in Century City, the neighborhood with the most vacant manufacturing space.

“Overall with the climate and equity plan, we are trying to create good-paying jobs that people want,” Shambarger said. “That often means the trades. One of the things attractive about building housing components in a factory is it offers steady year-round employment, rather than having to go on unemployment for the winter,” as many building tradespeople do.

Creating Habitat

Sonderman said that in the past, Milwaukee Habitat has put solar on some homes, but little else specifically to lower energy costs.

“Clearly if there was a really substantial market for developers who were interested and willing to do this work, the reality is Habitat wouldn’t be the first call,” he said. “It’s something new. One of the things we’re looking forward to is sharing with our Habitat network in the state and other developers and builders, so we build some confidence this can be done efficiently and cost-effectively.”

Net-zero homes are not only a way to fight climate change, but an environmental and economic justice issue in predominantly Black neighborhoods scarred by redlining and disinvestment, where the majority of residents are renters, Sonderman added.

“Even for the individuals who don’t live in that home but live in the neighborhood, it breathes hope, it says that our neighborhood is being invested in,” Sonderman said. “That matters deeply for the residents of Lindsay Heights, Harambee, Midtown and elsewhere. To take a project like this and see it come to fruition has tremendous ripple effect in a positive way.”

Several other Habitat chapters nationwide are building net-zero homes, including in Colorado, Illinois and Oregon.

Milwaukee Habitat is planning to build 34 homes in 2025 and up to 60 homes annually by 2028. Sonderman said they will make as many as possible net-zero.

“We’re not in a capacity to be the full-scale factory [Shambarger] was envisioning,” he said. “But we believe we’ll be able to supply the walls we need to build dozens and dozens of net-zero homes in the future.”

Milwaukee plans to build net-zero modular homes for lower-income residents — but it’s not easy is an article from Energy News Network, a nonprofit news service covering the clean energy transition. If you would like to support us please make a donation.