Hildebrand/Kennedy Cabin
Egrets’ Cove Community § Big Hill, Kentucky
www.egretscove.org
Size ‑ 20' X 24' (480 square feet) with 12' X 32' (384 square feet) screened porch
Cost ‑ c. $18 ‑ 19,000 in materials, and backhoe work
Space Heating in Winter ‑ Passive solar with wood stove back up. 68 square feet of windows facing due south. Vermont Casting Aspen (very low emissions) woodstove.
Insulation – 16 inches (R‑ 50) blown cellulose in ceiling (raised heel trusses to accommodate depth of insulation near the walls) c. R‑ 26 in walls and floor (combined fiberglass and foam core aluminum). Insulated reflective night curtain over 6' X 6' window. Plumbing and electrical lines are all run on the inside of the house rather than within the walls to prevent heat leaks where outlet boxes, drain lines, etc. replace insulation in walls. Seven of the cabin's eight windows are R‑9 heat mirror windows that greatly reduce heat loss.
Ventilation ‑ c. 3 square foot low vent on west with same size vent high on east wall. Door left open to screen porch in summer.
Cooling in summer ‑ Overhang on south wall is calculated to allow low angle winter sun to enter but to block out high angle summer sun. Roof is white enameled steel instead of traditional dark colored asphalt shingles to reflect, rather than absorb summer heat. Reflective aluminum stapled to the bottom of rafters further prevents summer heat from entering house, as does the extra ceiling insulation. Large screened porch on north side of cabin is valuable inexpensive living space in warm half of the year.
Water ‑ Water is collected from north side of house and porch roof (c. 780 square feet) for domestic use. This is roughly 23,000 gallons per year or over 60 gallons per day on average. Far more that we require. The water is held in a 1000 gallon recyclable polyethylene cistern. Limestone in the cistern reduces the acidity of the rain. A Shur ‑Flo low energy
(0.9 amp) pump delivers the water on demand. Drinking water is filtered by gravity through a Katadyn Swiss ceramic and silver filter. It cost about $200 and silently filters out all common pathogens, purifying about 3 gallons of water a day. Filter cartridges typically need replacement after 15,000 gallons. It doesn't remove aromatic hydrocarbons and other chemical contaminates that may be more of a problem on water collected from more urban areas. Water off the south roof is collected and used for irrigating food and ornamental crops.
Water heating ‑ A 60 gallon double tank solar batch heater provides hot water through 3 seasons. It has a hinged panel that reflects addition solar energy onto the water tanks during the day and insulates them at night. In winter we use a 5 gallon tank on our wood stove. We are experimenting with an ultra low water use shower using 1-2 gallons of solar heated water under relatively high pressure.
Lighting ‑ High windows on the south, east and west walls provide daylighting throughout the cabin. 26 watt compact fluorescent bulbs provide light at night. Light colored walls, floor and ceiling maximize available light.
Composting Toilet ‑ A composting toilet on our porch replaces a relatively wasteful water flush toilet. It has two 50 cubic foot chambers that we switch every 18 months. This gives the first chamber a year and a half to break down any pathogens through aerobic bacterial composting. The south wall of the compost chambers is painted flat black to absorb sunlight an increase the temperature (composting is much more efficient at higher temperatures). A supply of fresh air to insure aerobic composting is drawn in through low vents as the sun heats the air in the black vent pipe behind clear glazing. Sawdust, chopped leaves or other mulch materials are added to control moisture and to maintain a good ratio of carbon to nitrogen so that anaerobic bacteria, that make foul odors and break down pathogens much more slowly, don't take over.
Use of Space – Curtains rather than doors and hallways are used to separate rooms, which creates more useable space and allows better airflow and lighting. 9 foot high ceilings reduce the claustrophobic feel common to many small houses.
A Solar Perspective
Sunshine is the energy source that powers and organizes life on Earth. Oil, natural gas and coal are fossil energy sources, in the sense that they are solar energy that was captured by plants long ago. Since they are being burned at a very fast rate and new oil, natural gas and coal is forming at an extremely slow rate, they can’t be considered as a sustainable source of energy. Other than the small potential of nuclear energy, we are left with sunshine as the source of sustainable energy.
How much sunshine? Approximately 4 billion calories worth of sunshine falls on an acre of land each year in Kentucky, ½ of that in 100 days of summer. Roughly twice as much per acre falls on tropical land. This is the basic energy budget for a sustainable society.
How is that solar energy currently used? About ½ is expended evaporating water. This provides us in central Kentucky with an average of 48” or about 13 million gallons of water falling as rain on that acre each year. About 1.6% of the solar energy reaching the ground (64,000,000 calories) is captured by green leaves through the process of photosynthesis. This is where all of the food for us as well as the many other creatures who share the land with us comes from. People eat something like 1500-2000 pounds of food a year (75% of it is water). It is also where the wood for lumber, paper, and firewood come from. Using solar energy to make biomass (food and fiber) requires topsoil and water. In the US about 6 pounds of topsoil is eroded for every pound of food eaten. Producing a significant part of our transportation fuel from corn-based ethanol would dramatically increase the speed of soil erosion. Reducing soil erosion and using food and trees more frugally and efficiently would go a long way towards creating a sustainable solar based society.
Capturing solar energy to heat water is relatively cheap and simple. The payback period for solar water heaters is quite short. Passive solar heat in winter is another relatively cheap and easy way to utilize solar energy. South facing windows will capture more heat than they lose in winter. Sealing air cracks and insulating well will hold the solar heat in our houses longer and reduce the amount of other energy we need to use to stay warm.
Photovoltaic electricity (electricity created directly when sunlight hits a solar electric panel) is currently quite expensive. The cost of supplying it is dropping and will likely continue to drop as the demand increases and the technology matures. Because solar electric energy is quite expensive, it encourages the use of energy efficient appliances, such as compact fluorescent light bulbs that use about 1/3 the energy of conventional incandescent bulbs. Expensive energy also encourages thrifty habits like turning off lights when not in the room. Cheap energy doesn’t help anything in the long term.
Moving towards a sustainable energy system means:
- accepting the days of cheap fossil energy are soon to be gone.
- making more efficient use of food and trees
- not washing away the topsoil that enables plants to capture sunshine
- installing solar water heaters
- trying to maximize south facing windows, and insulating homes well
- experimenting with solar energy, focusing on inexpensive simple uses that could
possibly be employed by people with very low incomes (under $2 a day).