Sunset Roost is an off-grid, super insulated, passive solar designed, 1,860 square foot octagonal house. The structure is heated and energized by a unique synergistic system of renewable sources. The home sits atop a hill with expansive views to the southwest which present memorable sunsets year round (hence the name Sunset Roost.) Large windows provide significant solar gain and contain the relaxed homey interior environment while providing access to inspiring vistas. In many regards, this home defies labels and must be experienced to be truly appreciated or understood.
Space Heating: Passive Solar plus Masonry Heater
A large masonry heater (14 ft. tall) is the focal point of the aesthetics and the heat source for the house. The heater was custom built by Stonecastle Masonry with a core of firebrick faced with river rocks collected from around Alaska by the owners. The firebox includes a domestic hot water coil which has proven to be the perfect seasonal compliment to the lack of wintertime performance of the solar thermal panels on the roof. The house is also equipped with radiant floor heat energized by the renewable energy systems which will be described later. The owners choose to not utilize the floor system, but to heat exclusively with passive solar gain and the masonry heater because of the overall comfort, efficiency and versatility of the heater. Two cords of wood supplies all of the space heat and most of the domestic hot water for the entire winter. Passive solar gain has been the only source of heat from early March to the middle of October with the indoor temperature never falling below 68oF.
The masonry heater also includes a bake oven which can produce fine breads, pizzas and more in the winter, but is quite useless in the summer, unless you're interested in a sauna at the same time.
Finally, the size and weight of the heater contribute significantly to the thermal mass within the house. The positive effects of this are discussed below.
With snow still on the ground outside, the sun beams through the large living room window and provides the only heat necessary to maintain the interior temperature above 68 degrees throughout the day and night. All windows in the house are argon filled triple pane glass with fiberglass frames. The key to maximizing the use of the passive solar energy without overheating the house is the enormous amount of thermal mass contained within this structure.
River rocks were utilized to construct the base of the kitchen island as well as benches and planters in the great room. The ton of dirt in the planters also adds thermal mass. The back side of the masonry heater firebox aligns immediately adjacent to the master bath soaking tub. The tub is surrounded with river rock for additional thermal mass (photo below). Whenever there is a good fire in the heater, the soaking tub maintains a hundred-degree-plus water temperature indefinitely. This lends itself nicely to inexpensive marathon soaking sessions.
The concrete slab-on-grade floor is thick and well insulated underneath, and also contributes to the thermal mass. The collective effect of all of these sources of mass is to create a thermal flywheel that soaks up heat when it is available and returns it when needed. The enormous mass in Sunset Roost stores enough energy to stabilize the temperature for days, even when outside temperatures are well below freezing.
In summer when the sun is higher in the sky, the large eaves and one awning reduce the solar gain to manageable levels. Opening two windows for cross ventilation keeps the interior temperature at or below the outside air temperature.
In winter, the thermal mass functions with the same flywheel effect. The masonry heater soaks up the heat from the fire and gradually radiates the energy into the home over a 24 hour period. This completely eliminates the wide temperature fluctuations normally associated with wood heat. It also improves the burn efficiency of the wood by allowing higher burn temperatures, which produce cleaner and more complete combustion. This amounts to less wood consumed to produce the equivalent heat.
The kitchen and dining areas (below) incorporate river rocks for additional mass and to continue the natural Alaska theme throughout the great room. Straight lines, sharp corners, balanced symmetry and boxy shapes are not prominent in nature and were avoided throughout this home. The result is a natural flow and a comfortable relaxed atmosphere.
Efficient From Day One
To create the most sustainable structure possible, the design team considered efficiency in every aspect of the project, starting with the building footprint. The 2,100 sq. ft. figures above demonstrate how the perimeter of similar-sized structures change with respect to the shape. The closer to round that the shape becomes, there is less perimeter wall space exposed to the heat-draining elements. Circular structures are more costly to construct, and rectangles are much less efficient, so an octagon was chosen for Sunset Roost as a balance between ease of construction and an inherently efficient shape. Additionally, the octagon optimized the performance of the central masonry heater, and the curved south wall maximized the solar gain into the great room for passive heating. Small efficiency gains in each step of the design process ultimately added up to significant overall energy demand savings.
The home owner went through many back-of-the-napkin floor-plans before plan "D3b" (above) was chosen as the "final draft."
REINA's computer produced technical drawings and the 3D view above.
Potentially the most important step in creating a net zero structure is constructing a super-insulated air tight envelope. Sunset Roost incorporates the REMOTE wall system developed by the Cold Climate Housing Research Center specifically for extremely cold environments. A standard 2x6 frame wall provided the structural support and room for fiberglass insulation. The exterior surface of the OSB sheeting was covered with a 6-mil vapor barrier, with attention to sealing detail at all penetrations. Three layers of 3-inch thick EPS foam was added to the exterior and overlapped all window and door framing to eliminate thermal bridging. This style of construction made it easy to achieve a very air tight wall with a total R-value of 65.
Custom scissor-trusses free-spanned from exterior wall to exterior wall. This created an open cathedral ceiling inside and allowed enough attic space to blow in 25 inches of cellulose for an R85 roof.
Framing the house took place during the short days of early winter and the crew got to enjoy many sunsets. The above view of Denali (180 miles distant) is through the future dining room window.
Off Grid and Powered By Renewable Energy
Sunset Roost is totally off-grid and is powered by a synergistic system of renewable energies. The photo above shows the 160 sq. ft. of solar thermal panels mounted on the roof. An 80-foot tower supports the 3kW wind turbine southeast of the house. A 1620-watt solar PV array is pole mounted on the east side of the house, and the top shows just above the roof to the left of the thermal panels. A 6kW diesel generator automatically provides back-up electricity and recharges the batteries if the 2-days worth of stored battery power runs low.
This hybrid system has proven very effective. During 2011, the generator only turned on ten times the entire year. December was the most challenging month, as electric consumption skyrocketed with the holidays and children off school. This was combined with the shortest days of the year and almost no solar PV input, so the generator ended up running four times during December 2011. The annual summary shows the generator operated: once in January, twice in February, once in October, twice in November and four times in December.
To manage with small renewable systems, consumption was limited by installing only Energy Star appliances and efficient florescent and LED lighting, and eliminating as many phantom loads as possible.
During the sunnier months, the solar thermal panels on the roof heat the majority of the domestic hot water. Some days they produce more hot water than is needed and the extra heat is transferred to a huge, 12,000 gallon seasonal storage tank buried next to the house (tank photo below). Frequently, the electric systems produce more power than can be used or stored in the batteries. That extra power is used to heat domestic water, and then, through an exchanger, the heat is transferred to the seasonal storage tank. During the winter months, this stored energy can be utilized through an exchanger to heat domestic hot water or the radiant floor system.
Smooth surface floors were installed throughout the house for ease of cleaning and to benefit interior air quality. Cork was used in the two bedrooms; bamboo in the kitchen and dining room; and the remainder of the home is stained concrete. A river meanders from the front entry, down the hall, around an island and through the great room, with tributaries joining from the master bedroom and the guest bath. The river forms a soft boundary between the living room and the kitchen/dining area before exiting out the back door. A few rock accents were placed in strategic locations in the river to add character.
The staining process started with saw-cuts to define the river and physically separate the colors. The river was stained first, then covered with tape while the brown background was stained. The mottled colorization of the stain provides a natural tone that blends well with the other rock, plant and tree features.
Sunset Roost features many nature based design elements. The kitchen backsplash is a silhouette of the Alaska Range Mountains cut to scale. The photo below shows a portion of the backsplash, countertops and Alaskan birch cabinets, all made by Dreamworks Cabinetry, LLC. The custom rock drawer-pulls were crafted from rocks from the owners collection.
Select rocks were epoxied to furniture cap nuts to create individually unique drawer-pulls. The theme for the master bath cabinets (below) was heart-shaped rocks.
Sustainable In Many Ways
Long term sustainability and health were considered in many more aspects of this home. Dual flush toilets were installed to reduce water consumption. VOC free paints and adhesives were utilized to maintain air quality. The many indoor plants also contribute to air quality. Local building materials were utilized whenever practical to reduce the overall environmental footprint and to support the local economy.
The professional staff at Reina enjoys finding creative ways to construct homes that are not only energy efficient and healthy, but bring to life in physical structure the uniqueness of Alaskans and their interests. Reina makes dream homes a reality.
In closing, enjoy one more dreamy view from Sunset Roost...