You will want to live in The ROSE Cottage, a net zero energy home built for a lifetime
Lloyd Alter is visited the Consumer Electronics Show in Las Vegas as a guest of Bosch, and is looking at how technology will change the way we live.
Harold Turner doesn't live in a house, it is a test bed. He calls it the Rose Cottage, which stands for
Renewable energy production
Owner (occupant) driven spatial design
Sustainable building practices
Energy efficient construction
At 3,370 square feet, I wouldn't call it a cottage either. The name doesn't do it justice; half the bed and breakfasts in England come up higher in search, when in fact it is a pretty extraordinary place, a demonstration of a new kind of building, the ROSE construction method.
The ROSE Construction Method™ (RCM) was developed to produce projects with a timeless architectural design, while incorporating standardized engineering protocols that result in cost effective and affordable zero net energy construction. What works “best” changes with geographic location, site constraints, budget, and evolving building technologies. By incorporating leading edge building products; state of the art building science practices; and creative architectural designs; each project is customized to meet the specific needs and desires of the owner. Unlike more radical design approaches to zero net energy homes, RCM homes are intended to fit within the architectural context of their surroundings, while still attaining the highest performance levels of energy efficiency, comfort, and health.
When I first saw that massive solar array built on to the garage, I thought this was going to be one of those all-gizmo-green net zero homes in the middle of nowhere. In fact, it is quite close to downtown Concord, New Hampshire, a 2.5 mile bike ride from Harold Turner's office. It is also very well insulated; Harold tells Bosch in an interview:
The shell of the building is largely airtight. Materials like cellulose fibers, mineral wool, and expanding polystyrene in the walls, roof, and subfloors, and insulated windows with double and triple glazing ensure that as little heat as possible escapes in winter and enters in summer.
It's not quite a Passivhaus, but walls are R-40, roof is R-60 and there's R-22 under the slab. There is also an interesting approach the careful placement and sizing to doors and windows in the house designed by Harold and architect David B. Hart of HL Turner Group, and described in the RCM website:
In order to meet the goal of zero net energy performance, careful selection and placement of window and door natural lighting was a paramount feature while still achieving high performance levels of envelope air leakage and thermal achievement. .... any type of exterior door was a significant drop-off in thermal performance, so it only made sense to use the doors (5 total) as daylighting features as well, which allowed a reduction in the total windows required for great natural light.
Heat is provided by two Bosch ground source heat pumps; one supplies hot water for the radiant floor heating system, the other tempers the air. Instead of using wells like many ground source heat pump system, this one uses a slinky setup of horizontal pipes that are laid in a sand bed under the slab. He's also got a Bosch Buderis solar thermal system tied in. I asked Harold about the point made by Martin Holladay about solar thermal systems, that they produce a lot of excess heat when you don't need it; Harold explained that excess heat from the hot water system is pumped into the ground bed, storing it for the shoulder seasons. It's not wasted. Tech details are available on this Bosch case study pdf.
power usage/Screen capture
The electricity for the house is provided by the 13.8 kW photovoltaic array. Nosy parkers can watch how much electricity Harold is producing and using at any time with the live feed
Solectria inverters are connected to the PV array, and then through a by-directional smart meter (net metering) to the utility grid. A bank of 16 DC, 60 amp-hour batteries are also connected to the PV system through two 3,600W DC Outback inverters and can supply up to 7,200W of back-up emergency power if the utility grid goes down. The system generated a total of 16,220 KWH during its first 12 months of operation.
There is also a serious heat recovery ventilator system that brings fresh air into the tightly sealed house.
The whole house is mechanically ventilated utilizing a Fantech SHR3005R dedicated air-to-air (92% efficient) heat recovery exchanger and a Fantech HEPA filter air supply system that provides fresh air throughout the house. In addition, only zero VOC paints (Glidden Professional) and cabinets (Executive Cabinetry) were used, helping to minimize or eliminate any toxic air pollutants inside the house.
For all of those people out there who think that environmentalism is a left wing plot, Harold notes that it actually is the opposite. He has put a lot of care into designing the house so that his family can stay there a long time, aging in place.
Creating a flexible design that can fit the needs of several types of multi-generational occupants is a perfect match to the investment in a zero net energy home that generates as much energy from renewable sources, as it uses. It’s not a political design solution, it’s a conservative solution of minimizing waste and maximizing efficiency. It’s not about the points, it’s about the performance. It’s also about the dignity of human life and the possibilities of growing old and dying in your own home.
It helps to keep things simple; " The mind is not always clear at 85, so heating, lighting and security controls need to be kept simple enough for the aged to operate without a caregiver or technician to undertake daily tasks." Although by the time Harold is 85 the house will probably be smart enough to take care of itself. And the mechanical room sure doesn't look simple!
The house is capable of withstanding the harshest winters and the hottest summers that northern New England can dish out. It has all the heating, cooling, lighting, and fresh air systems required to maintain a safe, comfortable, healthy, and efficient environment.
Lloyd Alter/CC BY 2.0
I usually complain about big houses in the country that are full of gizmo green, but meeting Harold at CES and talking about what he has done, you cannot help but come away impressed. He built this for a reasonable $ 175 per square foot, and tells Bosch:
I am particularly proud of the fact that we achieved our goal and managed to complete the building work in just over a year. The end result is a net-zero-energy house whose architecture fits in with the picturesque surroundings here on the banks of the lake, and which is also very comfortable inside. I’m also proud that we used mainly sustainable, long-lasting, and high quality materials, most of which were sourced locally.
It also isn't a one-off; it is a demonstration of principles and technologies that can be replicated for any RCM customer. I like their motto, too: It's not rocket science, it's building science.