Visitors walking past the small, tidy lawn outside Brent and Wendy Mathers’ neo-modern Park Hill home have no idea that under the grass, two vertical pipes stretch 250 feet into the ground to heat and cool the house.
And most of them would be surprised to learn that the roof hosts 500 square feet of solar panels that help make the Mathers’ home even more energy-efficient.
“It’s intentionally disguised to keep it from being seen from the street,” said Brent, an architect and woodworker who designed some of the furniture in the home, which is among those featured on the Park Hill Home Tour on Sept. 28.
Brent and Wendy, who also is an architect, designed the house at 2334 Grape St. to visually suggest the unpretentious dimensions of other houses on the block. Most of those are older brick homes, one or two stories high, places that would fit comfortably inside a suburban McMansion.
But few of those neighboring houses come close to the energy-efficiency of the Mathers’ home, which they built last year after acquiring the lot in 2011. Only a carriage house, leased to renters, stood on the property. When it was listed for sale, the Mathers snapped it up.
“We got a good deal, because prices were still depressed, and it’s a nice, wide lot with good solar exposure,” Brent said.
Green demolition
After stripping the carriage-house appliances and fixtures, which they donated to Habitat for Humanity, they demolished the structure, along with a 40-foot spruce and a couple of aspen. They saved the usable wood for a friend who, like Brent, is a woodworker.
Then they designed their home. They knew they wanted geothermal heating and solar energy, and hired Dan Schmied of Sensible Heating And Cooling.
After the house was framed, with a roof and most of the wiring and plumbing in place, Schmied brought in a well-digging professional to drill the two 250-foot holes. Apart from their dramatic vertical depth, the holes are surprisingly small — only about five and a half inches in diameter. The pipes are even smaller, less than two inches in diameter and made of high-quality plastic.
The pipes circulate a solution that’s 80 percent water and 20 percent ethanol (the ethanol prevents it from freezing). The fluid enters one pipe leading from the house, descends into the earth, then is pumped up through the other side of the pipe.
Because the ground temperature is typically 52 degrees, heat transfers to and from the fluid as it circulates. In the summer, the excess heat is pumped away from the house and released into the earth. In the winter, the ground’s heat is pumped into the house. Because the heat is being moved, not produced, the system is dramatically more efficient than conventional heating, ventilation and air conditioning systems.
The result: Between the geothermal heat, the vast solar panel, the energy-efficient windows and doors and the extra insulation in the roof and exterior walls, the Mathers’ home is so tight that they use a heat-recovery ventilator to keep the air fresh.
Spare, clean design
The rest of the house also reflects their energy consciousness. The toilets are low-flow. The refrigerator uses a water-purifying filter, so the water doesn’t taste like stale ice cubes. Most of the materials used are wood, glass and other substances that don’t off-gas, meaning they don’t release harmful chemical compounds that can cause health problems.
The dark wood floors are walnut. So are most of the cabinets in the kitchen and bathrooms.
“We really like walnut,” said Wendy, who buys walnut-based cat litter for the Mathers’ three cats.
“Everything in the house had to respond to the walnut floors and cabinets, and we like materials in their raw state.”
So the soft white and turquoise backsplash in the kitchen is made from untinted Lucian glass tile from Ann Sacks. The gas fireplace’s concrete surround is light gray. The long, zebrawood dining table, which Brent made, is covered only with a clear, protective finish.
Twelve-foot-wide insulated glass sliding doors in the living room roll open in good weather to expand the living space onto a deck with a fountain. Rain chains direct water from the roof to the garden.
Before and during the 10 months of construction, the Mathers collected images of functional design that they especially liked. Japanese and Italian spaces influenced their decision to create a spare, neo-modern open floor plan on the 2,000-square-foot first floor.
The basement, also 2,000 square feet, is more traditional, with a living area, a woodshop, a sauna, a guest bedroom and bathroom, plus a laundry room with stacked appliances and a clothing chute that descends from the master bedroom.
“It’s all technology that was invented a long time ago, and we’re using it to create a house that generated its own energy,” Brent said. “The payback with geothermal energy is even better than solar.”
“We wanted the whole house to be sustainable, an invitation to indoor/outdoor living,” Wendy said.
Long-term choices
While geothermal energy is the least-expensive way to heat and cool a home and its water, the initial cost is at least 15 to 20 percent higher than a conventional heating and cooling system.
However, homeowners can file for a 30 percent tax credit, and Xcel Energy offers a rebate of $300 per ton in the heating and cooling unit. (A typical residential system is based on a 6-ton unit, with a potential rebate of $1,800.)
So, with energy bills pretty low on their list of worries, the Mathers take advantage of every opportunity to slide open the huge glass doors, enjoying their tidy back yard. A Buddha statue sits on the stump of the spruce that had to be taken down, surrounded by a thicket of bamboo shoots.
“We’re committed to being here for a while,” Wendy said. “We didn’t design the house for an exit strategy. But it turned out to be a good place for an empty nester, and the entrances are wide enough for wheelchairs if you want to age in place.”
Claire Martin: 303-954-1477, cmartin@denverpost.com or twitter.com/byclairemartin
Park Hill home tour
When: 11 a.m. to 5 p.m. Sept. 28.
Tickets: $15 in advance, $20 on the day of the event.
Proceeds benefit the Greater Park Hill Community, a nonprofit that supports neighborhood programs.
