Modest Size Design
The Octagon Atrium surround provides an architectural benefit to the quality of the home. Originally designed with a practical purpose in mind to follow the arc of the sun and acting as a passive solar heat generator, it also enhances the esthetic value and ambiance of the house. In addition to the compact design, the house has an expansive and multi dimensional feel to it, because of the cathedral ceiling and the connection to the outdoors provided by the huge open glass doors into the atrium.

The octagon consists of three levels. The basement which has above it the main floor containing the living room and kitchen and then the upper floor, which provides one bedroom and a full bath and the cathedral space to the living room. Around this octagon hub are single story spaces (wings), containing the back and front entries, a laundry room, two bedrooms, a dining room, a full bath, a powder room and the atrium.

Orientation for Use of Renewable Energy
The site chosen offers ample opportunity to take advantage of the elements including solar, wind and rainfall. The passive solar design takes advantage of the sun's heat, which is absorbed and held by thermal mass in the home. The design emphasizes features that allow for the control or management of the heat. An active air circulation system (see Indoor Air Quality) distributes air to northern areas of the house, and strategically placed doors allow the homeowner to shut off or welcome incoming heat.

The attached atrium was constructed in the shape of a semi-circle from east across the south to the west. This allows the sun to heat the thermal mass, placed throughout the house, all day long. Thermal mass includes 3-inch dense stained concrete floors which act as heat sinks (heat storage). There are also three eighty gallon warm water storage tanks located in the atrium and a Finish style masonry wood stove in the center of the octagon shaped portion of the building that act as heat sinks. A stone wall and brick walk in the atrium will continue to give off heat during the night to keep the atrium above freezing throughout the winter.

The release of that captured heat is controlled by two sets of walls. The exterior walls are double-paned with the required U-Value or insulation to prevent the heat from escaping. The interior walls of the atrium have 8 foot high doors that open wide to distribute or dispose of the heat in a controlled way. The living room and atrium exchange heat when doors are opened between them, or if closed, the heat is restricted to the outer atrium.

Orientation and design for daylighting
The southern exposure is enhanced by strategic door and window placement designed to maximize natural daylight in the home.

Window Sizing, Location and Shading
This is a passive solar design, with a wall of mostly glass along the South-East, South, and South-West walls. Overhangs on the southern wall offer shading in summer months.

Foundation
The basement of the octagon was created with Insulated concrete forms which offer high insulation values.

Windows
The windows are Energy Star certified.

Exterior Wall Finishes
The home was finished with a Fiber cement board siding and synthetic plaster exterior. Both are durable and low maintenance products.

Roof
A steel roof with recycled content and a lifetime warranty was installed. The roof has special gutters for collection of snow for domestic water use.

Ventilation Design (related to climate conditions)
The design of the home and the ample thermal mass support ventilation and passive cooling. A waterfall feature in the atrium helps with cooling through evaporation, which is the same principle as a swamp cooler, but without the added electrical energy input. A system which distributes and balances the warm or cool air flow throughout the home works on the principle that warm air becomes trapped in the cathedral ceiling. Air ducts are located between the ceiling and north facing rooms without passive solar advantage. An inline ventilator is used to push the warm air through the ducts into these rooms or to circulate the air to areas for ventilation.

Building Envelope
A tight and well insulated building envelope supports all other portions of the home's design. The octagon portion of the house has a basement, without windows, which also acts as a thermal heat/cool sink. It is surrounded by dirt and does not have an exterior wall any closer to the elements then 8.5 feet. The basement walls are concrete poured in foam block forms (Insulated concrete forms) that provide a total of 5 inch of foam insulation. The basement floor has not been insulated, since it is 9 feet below grade; the constant temperature of the earth assists in keeping the basement warm/cool.

The octagon roof is 16 inches thick and contains non-formaldehyde 13-inch fiberglass batts. In the loft bedroom and bathroom the ceilings are flat with 16 inches of blown-in insulation.

The single story portions of the home have double walls which consist of two separate 2x4 walls, with a 5 inch space between them to create a 12 inch wall from face of stud to face of stud. These wall cavities are filled with fiberglass or cellulose insulation.

Half inch sheathing covers the exterior, then two inches of rigid insulation and a thin layer of synthetic plaster finish. All inside surfaces of the exterior walls have a vapor barrier under 0.5 inch of drywall.

A crawl space is located under the west wing. The front entry and laundry room have foam block concrete walls.

A four foot wide by two inch thick Styrofoam sheet was installed three feet below finished grade and horizontally around the entire perimeter of the building to increase the thermal influence of the solar heated home.

Mechanical Systems
A two kilowatt wind turbine and 5 kilowatt solar photovoltaic system provide electricity for the home's equipment and appliances. The electrical system is supported by a massive battery bank and inverters to supply 110 power throughout the home.

Active solar heated water is used for three different jobs in this home: (1) to provide domestic warm water, (2) to provide additional floor heat and (3) to melt snow and ice in the rainwater collecting gutters when required. Heat is generated by two evacuated tube warm water making panels on the roof. This technology is fairly new, but has been around long enough to prove especially effective in colder climates. The absence of air between an outer glass tube and an inner copper tube containing acetone creates conductive isolation between the cold winter air and the acetone inside the copper tubes. The acetone inside the tubes boils due to the sun's radiation. The heat generated during this process is transported to three eighty-gallon tanks when the panels are warmer than the tanks. The three well insulated tanks hold the heat. An active solar system distributes and circulates heat to the right places by using controls and pumps.

Floor heat is generated by a system of embedded hydronic (water filled) heat pipes in the concrete floor. The sun transfers heat to the concrete slabs directly and a circulating pump distributes the heat throughout the home. The heat warms the concrete in other portions of the home and releases it slowly and evenly. When the slabs cool down too much, a thermostat will call for additional (solar collected) heat stored in the tanks, to be circulated. When the tanks are not warm enough to provide the heat needed, a Buderus evaporating boiler will provide supplemental heated water.

To vary the temperature between rooms, separate zones can be established by installing valves so that the flow of warm water (and heat to the room) can be reduced or increased.

Wrapped around the octagon basement is 2.5 inch x 300 feet of poly pipe, which emits excess heat from the solar hot water panel to the soil underneath the one story crawlspace during the warm summer month. This excess heat slowly finds its way into the structure above, during the colder months, helping to passively keep the house at a more even temperature year around.

A Finish style masonry wood stove acts as thermal mass for the passive solar home as well as provides backup heat. Grid connected electrical power and a buried propane tank offer backup fuels. The solar processes are staged to use fossil fuel only as a last resort.

Water Heating
Domestic hot water is generated by the solar evacuated tubes described above. When there is not enough heat in the tanks a Buderus evaporating gas boiler will make up the difference. For example, when the sun brings the water in the tanks up to 100 degrees Fahrenheit and the homeowner wants a 120 degree shower, the evaporating boiler heats the water an additional 20 degrees.

Appliances
The Buderus gas boiler is an Energy Star certified product and rated at 98 percent efficient.

Report performance data if available
The R-value of walls is R-45 and ceiling is R-52. The basement walls achieve an R-value of 32.

This household of five have average monthly electric bills of $14.00 and fill the 400 gallon propane tank (for stove, dryer and boiler) once per year.

Other
The greenhouse (atrium) that surrounds the living space is critical to the passive solar design of this home. The greenhouse is a point of passive solar intake, contains some of the thermal mass, and offers domestic warm water heat reclamation through its greywater circulation system. It also offers air filtration, grey water filtration, year round plant growing capabilities, and aesthetic beauty.

Greywater Collection and Reuse
A greywater system provides water for flushing toilets. Greywater, or wastewater generated from domestic activities such as dish washing, laundry and bathing, is recycled through the atrium planter. The water nourishes plants and finally flushes toilets.

Since one of the goals of the system is to water plants and an overall goal for the home's design is to reduce impacts upon natural systems, the homeowners use biodegradable soaps and shampoos.

Rainwater collection and reuse
Rainwater catchment provides all domestic water with the use of an innovative roof/gutter design. The gutter is designed for snow collection and contains a solar driven hydronic heat system to melt the snow and ice, which is collected in below grade tanks. The 10,000 gallon tanks are integrated into the passive cooling design and serve as firefighting first response.

To prevent large debris and insects from entering the tanks, a screen was installed and sand and rock placed in the gutter and over the downspouts, as a first line of defense.

The tanks contain a low-level float and a motorized valve, which will tell a back-up well to place gallons of water into the tank if needed.

A four-stage whole house drinking water filtration system ensures safe drinking water. More detail on this system is available here.

Water Efficient Appliances, Equipment and Fixtures
A continuous domestic warm water recirculation loop provides instant warm water at each fixture reducing wasted water waiting for the warm to arrive. Dual flush toilets reduce water used for small flushes.