Green homes across the USA
In Washington suburbs, most new houses qualify as McMansions, but not the “Erdhaus” — a small, super tight, Dwell-like home built of compressed earth bricks.
Its German name, meaning “earth house,” speaks to its unusual exterior building material. All 5,600 of its bricks were made from the dirt on the home’s narrow sliver of a lot in Falls Church, Va.
As regular Green Home readers know, I’m also building an energy-efficient home in the same town, less than a mile away, so I’ve visited Erdhaus a few times. Its owners, German-born Andreas Bentz and Mike Nichols, both very well versed in building green home , have been quite helpful in my own journey.
Why compressed earth? “I like the solidity of bricks. Mike liked the energy conservation aspect. It turned out to have both” says Bentz, an airline pilot who grew up in southwestern Bavaria and earned a Ph.D. in economics in England.
The result is an organic, minimalist yet striking gem of 1,460 square feet (not counting a full basement) that I’ve picked as “This Week’s Green House.” It uses rainwater collected in three large cisterns (a total of 4,200 gallons) to irrigate the landscaping and flush the toilets.
“It’s a simple system, but it works,” Bentz says about how the toilet tanks and outside hose bibs are plumbed on a separate water line. “It makes me feel good to flush rainwater down the toilet, instead of precious drinking water.”
The home, completed in February after a full year of construction, may be the most airtight home in Virginia. That’s what Chris Conway, a technical adviser for the Atlanta-based EarthCraft green-rating program, told the owners when he did the final blower door test.
“I called up my parents and said, ‘We’re 0.09,’ and they said, ‘Yeah, and…’” Bentz recalls with a laugh, adding his parents had no idea what he was talking about. Nor do most people. What does this mean?
The blower door test looks at how quickly a house “leaks” air, so the lower the number, the tighter the house. It does so by measuring air changes per hour, assuming the outside pressure is 50 Pascals higher than the inside one. If the home scores 1, that means its inside air is exchanged with the outside once an hour. EarthCraft requires its homes obtain 0.5 or lower ELR (envelope leakage ratio.)
The Erdhaus’ 0.09 means its inside air is completely exchanged with the outside every 11 hours or so. It uses mechanical ventilation to ensure the inside air remains healthy.
Bentz and Nichols acted as their own general contractors and did much of the finishing work themselves. They stained the concrete floors, painted, tiled and installed IKEA kitchen cabinetry, among other things. They blogged about their experience.
“The year it took to build the house was terrible,” Bentz told me last year. He did much of the cistern work himself, digging so much that he ended up with back pain.
“I would discourage anyone from acting as their own general contractor. There really is a steep learning curve,” Nichols says. “We probably didn’t save any money, because it took us longer.” He says they started with a construction manager, who overpromised and underdelivered, so they took over.
Yet they learned a lot. My builder Arjay West, who chairs a green building group for a local chapter of the National Association of Home Builders, toured their home with me this month. He said Bentz, who explained every operational detail, knows more about the field than most green builders.
Their home’s south-facing side has a wall of Weathershield Windows, which have a special Cardinal glass with a high solar heat gain coefficient (SHGC) so it can absorb the sun’s rays. “We wanted to heat with those windows,” Bentz says. They plan to put awnings over the windows, so they don’t overheat the interior in the summer. They have no air conditioning.
Since they made the compressed earth bricks themselves, Bentz says he doesn’t know the exact insulating value of the exterior walls, but he estimates their R value at 40 to 50. (The walls have 3 inches of styrofoam over the bricks.)
Their utility bills are low. The electric averages about $40 monthly, the gas about $20 monthly (except it jumps to about $100 in winter) and the water/sewer is only $20 per quarter.
Bentz said the home cost half what custom building typically runs in the Washington area, which often exceeds $200 per square foot.
“It was more than we expected, but it was worth every penny,” says Nichols, who works in the aviation trade industry.
Nichols says Bentz grew up green, composting since he was a small child. He says he was inspired to build a green home, partly by reading Dwell magazine as well as architect Sarah Susanka’s series of The Not So Big House books.
“That’s a big part of being green — not consuming more than you need,” Nichols says. Their house has two bedrooms and two bathrooms on its main level. There’s a den and third bathroom in the basement. The house is amazingly uncluttered.
“The absolute best thing about the house is how quiet and peaceful it is,” Nichols says. He’s enamored with their new town, including its farmers’ market and its proximity to both the Metro and bike trail. He says their neighbors and the folks at City Hall have been incredibly helpful. Here is info about Green Home in Florida.
