Although they account for just 22% of all housing created in the United States, single-family custom homes are ideal projects to test green building strategies, said Scott Rodwin, founding principal of Rodwin Architecture and Skycastle Construction in Boulder.
“They’re an area where we as architects and engineers and designers and builders get to exert a level of control, and our clients get to give us permission to utilize all of our design, engineering and problem-solving skills, in a way that we don’t often get to on other types of projects,” he told attendees at Rocky Mountain Green in Denver on Thursday.
Because those types of homes are built for wealthier clients, builders don’t have the budget constraints they do on other projects, Rodwin said.
“Green generally costs more. It’s higher performance,” he said.
One of the easiest ways to bring clients’ expectations for the cost of a green home in line with reality is to make it smaller.
“Most of our clients over the years have wanted more house than they want to pay for,” he said. “One of the ways we can get people to be greener right off the bat is to say, ‘You can’t afford that much house. Let’s shrink it by 20%.'”
He highlighted three projects his firm has done that take green building to the extreme.
The Edge House
This project was completed for a family from Germany, where green building is much more entrenched than in the United States. The client was deeply committed to sustainable building and willing to pay whatever it took to build a cutting-edge home.
Many of the features of the home were innovative in the mid-2000s, but are standard now, Rodwin noted. In fact, the home achieved LEED Platinum certification when it was built, but wouldn’t have met that standard today, he said.
The home had a Western view so it could only support partial passive solar. Triple-paned double low-E windows helped limit how much the family needed to use the air conditioner.
There’s no way to build a net-zero single-family home without a ground source heat pump, Rodwin said. The problem with this project was that every hole they tried to drill filled in with gravel. The firm built a sleeve for the first 100 feet of the scree field, which allowed the driller to reach 250 for the geothermal wells.
The home was powered with 10kW of solar PV. Rodwin said that’s roughly what’s needed to offset 100% of energy for a home between 3,000 and 5,000 square feet. He noted that Xcel is often “the limiting factor” in how much renewable energy homes can support because “they only allow you to generate 120% of the anticipated energy on your house, and even to get to that, you have to do an energy model on your house; otherwise you have to use their standardized tables.”
Rodwin and his team employed central thermal mass to help control internal temperatures. A large skylight, typically discouraged for homes that use passive solar, helped light the center of the home. To control the temperature, the firm used an R-22 window filled with translucent aerogel insulation.
Other green features included:
- An extensive solar thermal system to heat water
- R-38 walls, R-65 roof, R-20 underslab, R-10 foundation and R-30 soffits with a 1-inch extruded polystyrene wrap
- ENERGY STAR appliances
- Compact florescent lighting, which was updated to LEDs once CFL fell out of fashion.
- Energy recovery ventilator. “When you seal up a house really tightly, you can build up toxicity inside the house so you have to introduce air mechanically,” Rodwin explained. ERVs also help decrease heat loss in the home.
- Hot water recirculation pumps
- Graywater system
- Subsurface irrigation for the 10-by-15 foot lawn
The advantage to custom homes, Rodwin said, “is that we know exactly how the homeowner is going to be using the house. … We’re able to tailor specific solutions” to them.
This project was for a family that wanted a “better-than-net-zero energy” house, and wanted to establish permaculture gardens on the property. The home was built in 2015 and achieved LEED Platinum certification.
The home was built with:
- A double wall with cellulose insulation and 1-inch XPS
- Passive solar, including on the chicken coop
- ENERGY STAR windows and appliances (and a clothesline instead of a drier)
- Insulated fiberglass doors
- A GSHP with Airtap water heater
- 10kw PV and all-electric power
- Insulated PEX tubing
- Compact water heating distances
- Diverting system to direct water from the roof into a garden or a rainwater harvesting system
- Beetle-kill soffits and trim. Rodwin warned that beetle-kill breaks down quickly in exterior applications, but is a beautiful, cheap material for interior finishes.
- Permeable hardscapes
It’s a regenerative home with a HERS rating of -8. “These clients, for the last four years, have received a check on average every month of $120 from Xcel. And they power both their cars off this house,” Rodwin said.
The firm’s newest project is 3,000 square feet and was docked 14 points for its size in LEED Gold certification, Rodwin said. Still, he and his team are “delighted” with the project.
The home was built with:
- Passive solar
- Spectrally selective glazing on windows
- Foam envelope
- ENERGY STAR appliances and ENERGY STAR-“tuned” windows
- All LED lighting
- Ground source heat pump
- Permeable surfaces
- No formaldehyde or carpet inside
- Partial living roof
Rodwin noted that in high-performance houses, it’s not uncommon for the homeowner to not “know how to drive” it, and they accidentally turn off the solar system or automatic lights.
“Going out and actually teaching our clients how to drive the vehicle, how to operate the house properly … is just as important as any other part of the design process,” Rodwin said. “Our services extend quite a bit beyond the normal design or construction of the house.”
“When we’re talking about new technologies, who can actually afford to take the risk to investigate those?” Rodwin said. Like snowshoers breaking the snow for someone behind them, wealthy clients and their builders make it easier for the green builders coming behind them who want to adopt sustainable materials and practices but don’t have the resources to experiment on their own.