Purpose and Design Philosophy

The NCSU Solar House was built incorporating readily available solar and energy-efficient technologies to serve three primary purposes:

• To demonstrate how solar and energy-efficient technologies can be effectively incorporated into a solar house of traditional design typical of the region.
• To serve as an educational resource and laboratory for students, clubs, professional organizations, and the general public.
• To serve as a research laboratory for graduate students in engineering, architecture, interior design, and other related disciplines.

Key Features

1. A centrally located SUNSPACE collects, stores, and distributes solar heat for space heating.
2. Two THERMAL STORAGE WALLS collect, store, and transfer solar heat for space heating.
3. An Active SOLAR HOT WATER SYSTEM heats domestic hot water.
4. A PHOTOVOLTAIC SYSTEM (PV) generates 3.2 kilowatts of electricity.
5. SOLARTUBES provide natural daylighting
6. A WATER SOURCE, GEO-THERMAL HEAT PUMP coupled to a horizontal, closed-loop heat exchanger provides backup heating and cooling.
7. EARTH BERMING for first story north and west walls reduces winter heat loss and summer heat gain.
8. NATURAL ARCHITECTURAL devices provide summer shading on the south side of the house.
9. Numerous ENERGY-EFFICIENT FEATURES

Floor Plan

1st Floor Plan

2nd Floor Plan

House Data

• 1700 sq. ft. in living space, and 320 sq. ft. in sunspace and balcony
• 3 bedrooms, 2 baths, living/dining room combination, kitchen, den, utility room, sunspace, and balcony

Glazing

• 232 sq. ft. in sunspace
• 128 sq. ft. in Trombe wall
• 29 sq. ft. in direct gain windows

Living Room/Dining Room

• An open floor plan enhances the natural flow of heated air through the living space.
• Operable French doors to the sunspace can be used to control the flow of heat to living space.
• An open stairway in northwest corner completes the natural circulation of air between floors.
• 14-inch Natural Light Fixture reflects natural daylighting to living room.
• Fluorescent lights 75 percent less energy than incandescent bulbs.
• Small, north-facing windows lose less heat than large ones.
• Operable exterior insulating shutters can be closed during cold weather.
• Weather-stripping on the sunspace doors reduces infiltration.
• A pre-fab fireplace draws combustion air from the attic.

Kitchen

• A microwave is a very efficient way of cooking.
• A new high-efficiency refrigerator uses 515 kWh of electricity per year, a 28 percent reduction over the previous model.
• Roman shades are easy to use, provide excellent nighttime insulation, and reduce cooling in summer.
• Operable window controls heat flow from sunspace.

Master Bedroom Suite

• 10-inch natural light fixture provides cool daylight to dressing area.
• Double-pane windows lose less heat than single-pane windows.
• Pre-fab Plantation Shutters reduces heat gain in summer, and heat lose in winter.
• Casement windows seal tighter and have less infiltration than double-hung windows.
• Minimum east and west-facing windows reduce heat loss (i.e., windows have an R-value of 2, compared to a wall R-value of 19).
• Air movement from ceiling fan provides cooling effect in summer.
• Energy-efficient fluorescent bulbs come in many different sizes and shapes.
• A second sealing door above disappearing stairway reduces heat loss to attic.

Sunspace Balcony

• The sunspace is the primary source of heat for winter.
• The sunspace balcony is the focal point of the Solar House and provides an excellent view of the south lawn.
• The operable doors and windows on this level allow warm sunspace air to flow into the upper rooms – heating the entire second floor. As the warm air gives up its heat, it cools and falls down the northern stairwell, returning to the lower sunspace through the lower doors and windows where it is reheated – thus continuing the natural circulation cycle.
• The brick in the upper level of the sunspace serves as valuable form of thermal mass and helps to stabilize sunspace temperature variations.

Lower Level

• Operable French doors and a large window to the sunspace controls air flow between the sunspace and the living space.
• Spring bronze weather-stripping on interface of door reduces air leakage between the sunspace and the family room.
• Water-source, geo-thermal heat pump provides air conditioning and supplemental space heating.
• Energy-efficient fluorescent lights with electronic ballasts uses 75 percent less energy than incandescent bulbs.

Solar Water Heating System

• The solar water heating system will provide approximately 65 to 70 percent of hot water for a family of 3 or 4.
• Water is circulated through a 4 x 8 ft. solar collector mounted on the south roof of the Solar House.
• Drain-down solar water heating systems eliminate the need for antifreeze (water is drained down when the temperature of the water in the collector drops lower that what is in the storage tank).
• Circulation pump and controls are powered by a 10-watt PV module, which is mounted next to the water collector. System operates independently of grid electricity.

Utility Room

• Photovoltaic power center for roof-mounted panels provides interconnection to the utility power grid.
• PV Inverter converts DC Power, from PV system, to AC Power
• Eight 12-volt, 100 amp-hour batteries store PV generated electricity for evening and cloudy day use, as well as for emergency back-up power.
• Charge controller prevents excessive overcharging or discharging of the batteries.
• Circuit breakers are required by code to prevent injury and system failure.
• Data acquisition system collects data and displays current performance of the PV system.

Sunspace

• 3 square feet of thermal mass are required for each square foot of window glass to moderate temperature variations and store passive solar heat.
• Standard off-the-shelf components like brick, concrete block, stone or quarry tile can be used as thermal mass.
• An attractive, medium-to-dark surface is used to enhance the heat absorption of the thermal mass.
• Sunspace furnishings are carefully selected as not to shade the thermal mass from the sun.
• Operable windows and doors are used to isolate the sunspace from the conditioned space, in case extreme temperatures occur.
• Interface doors and windows (between the sunspace and conditioned space) are treated as exterior elements (i.e., fully weather-stripped).
• The sunspace is centrally located so that the living space wraps around the sunspace in a U-shaped design with every major room connected to the sunspace via a door or window.
• The sunspace serves as a heat distribution plenum, as well as an airlock during extreme months. A two-story sunspace promotes natural circulation of heat in the living space.

Exterior Features

• South-facing roof slope, equal to latitude (35 degrees for Raleigh), optimizes the annual solar collection of roof-mounted collectors.
• Natural architectural devices such as extended roof overhangs and trellises provide summer shading on the South side of the house.
• The south-facing roof area is used for PV modules, active solar collectors, and natural light reflecting fixtures.
• Limited East and West-facing windows reduce morning and evening heat gain in summer.
• Earth berming on North and West lower walls reduces heat loss in winter and heat gain in summer.
• Smaller windows on the North side of the house reduce heat loss. (Windows have only 11% of the insulating value of a standard wall.)
• Operable insulating shutters on North-facing windows reduce excessive heat loss in winter.

Landscaping and Shading

• Careful landscaping can reduce a home’s energy requirements every season of the year by blocking out the summer sun, encouraging warming solar radiation in winter, deflecting cold winter winds and channeling breezes for cooling in spring, summer and fall.
• A combination of trellis work and deciduous vines on the South side of the Solar House shades the patio and Trombe walls and adds a cooling effect to the sunspace in summer.
• Two walls on the lower lever (North and West) of the house are bermed (underground). A natural South-sloping lot made it possible.

Solar Powered Security Lights

• Solar powered, motion-sensing security lights are used on the exterior of the Solar House to deter trespassers at night. These systems are similar to conventional security lights except that they are powered by a photovoltaic cell. The cell charges the system’s battery during the day, and the battery powers the light at night. Each system’s battery is large enough to operate the lights for two weeks of normal operation without sunlight.
• These lights do not require any additional wiring, and can be mounted almost anywhere there is sufficient sunlight.

Trombe Walls at First Floor Bedrooms (for research & demonstration)

• Two 12-inch thick Trombe walls collect, store and transfer solar heat to the two bedrooms on the first floor. One brick, and one block.
• Vents in the East brick Trombe wall create a natural convection of heated air from the 4-inch air space between the exterior double-pane glazing and the wall, adding immediate heat to the room.
• Interior surfaces of Trombe walls should be left uncovered to promote radiant heat transfer.
• Windows in Trombe walls provide a visual connection to the outdoors, allowing natural lighting.