Solar Home Plans

 RETROFIT CONSTRUCTION 

After a house is built there is only so much that can be done to take advantage of the sun's energy. This VERTICAL GLAZED TWO STORY SUNROOM is located in Keeseville, NY where temperatures often plummet below -20F during the month of January. The one-inch thermo pane windows face southwest. Perhaps if they faced due south the heat gain during the winter months would be a bit better, but due south is not always an option. Some people prefer the simplicity of vertical glazing. Heat losses are less than tilted glazing losses.    During the cold, short, days of winter between the hours of 12 noon and 3PM the sun room becomes cozy enough to provide a nice playroom for the children, but heat losses from the sunroom are excessive after sunset. This simple passive solar addition brings a little light and warmth into an otherwise bleak environment. Unfortunately only a small fraction of the home heating needs are met with this vertical glazing system. If a fan were used to pump some of the solar heat into the house during the day the situation could be improved, but even with a fan to improve heat collection this would not be considered a solar home.

PASSIVE SOLAR HOMES

Passive solar homes like this one are popular in the Southwest where there is a plentiful supply of sunlight. Hot air is allowed to flow freely through the house during the day where the heat is stored inside massive adobe walls that moderate temperature swings.. The heated air is prevented from escaping through the greenhouse glazing with simple flaps that close when heat is no longer available. Thermal shades can be used on the upper thermo pane windows to retain heat that might otherwise be lost.

Passive heating systems like this have the advantage of not depending on mechanical devices, but in cold climates heat must be stored for longer periods of time inside well insulated chambers. This is why active heat transfer systems have become more popular in cold climates. 

Locally available materials like adobe bricks from the desert floor and Vegas from a pine forest are used in the construction of passive solar heated homes in the Southwest. I know this for a fact because I built a few when I lived in New Mexico. 

ACTIVE SOLAR HOMES use conventional electricity to run fans and pumps that transport heat. Some people argue that active systems are counterproductive because they waste fossil fuel to collect solar energy, however others argue that a penny spent to harvest a dollars worth of heat is money well spent. Money has always been an important concern for folks who invest in solar applications, however money is not the only concern. Appearance is also important. Does form follow function or does function follow form? From my conversations and observations I have concluded they are both important. Good housing designs emerge where form and function meet.  Futuristic housing should not only look good to the eye but I believe it should be beneficial to the spirit and the environment. Hexagonal housing, I believe, captures the spirit of the 21^st Century. Examine some of these designs and tell me what you think:

HEX-A-FRAME  is a conceptual model of a cold climate hexagonal house joined to a square house. The side of the square house would measure 16 feet, as would the side of the hexagonal attachment. The diameter of the hexagonal section would be 32 feet. The total living space of a house like this would be about 1500 square feet not counting the 250 sq foot workshop, the 250 square foot loft solar greenhouse, the 150 square foot gym and the 1000 cubic foot heat storage vault. The solar collectors would cover a surface area of 250 square feet. A wood-burning stove would supply heat not supplied by the sun.

The Hex-3 is made from three hexagonal units topped with interlocking cube octahedron roofs. Two 250 sq. ft. collector arrays are mounted on the outside hexagonal units. The interior unit could be a second floor greenhouse or a photovoltaic array. The Hex3 measures 80 feet by 40 feet with a height of 33 feet. The living is easy inside this house with a living space surface area of 6,500 sq. ft. Notice that all the roof surfaces could not possibly all face due south. Still 80 % or more of the sun’s energy would be available to an arrangement like this.  

My father often reminded me that my main problem in life was my need to start on the top. Dad said, “If you start on the top there will only be one way for you to go, son.” That’s OK I’ll deal with the foundation later, Dad, but first I’d like to focus on a steep roof design that will facilitate flush mounting 16 solar collectors capable of harvesting enough heat to get us through a New England winter.  Conservation and storage of heat make solar thermal systems possible, but where is all this heat coming from.

To maximize heat gain the solar collection area should be perpendicular to the angle of the sun. Since the earth wobbles on its orbit with a tilt angle of 23.5 degrees it is impossible to have the roof tilted at the best angle every day of the year unless the collectors are moveable. You might think that 41 degrees would be an ideal roof angle for Long Island since half the year’s perpendicular solar radiation would be less than 41 degrees and the other half would be more than and this would be a good first guess, but taking into consideration that more heat is needed in winter than summer a pitch angle closer to 50⁰ would be more beneficial.

A minimum of R19 for outside walls and R30 in the roof is recommended. Be sure to provide some ventilation above the insulation between the 2X12 roof rafters and remember hot air tends to collect in the high places of the house. Don’t skimp on insulation especially in these high areas of high heat losses. The money you spend on insulation will more than pay for itself in a short time.

This energy independent house is designed to make good use of construction materials and maximize living space. Notice the third floor could easily be used as an attic. The floor under the roof should be insulated like you would any attic floor in case you decide not to heat this area at times of the year when it becomes impractical. As a matter of fact you may decide not to insulate the roof ceiling. If you neglect this chore the third floor becomes an official attic and you avoid paying living space taxes for this space.

Polystyrene foam insulation on the outside of the basement walls can keep your basement dry and provide a great heat sink. The footings and walls should be insulated with 4” closed cell foam. These sheets of insulation should be covered with chicken wire and plastered with cement on top half to prevent vermin degradation. Insulating the basement walls on the outside also provides an excellent base for the construction of the heat storage vault.

 

GRAVEL & SAND Gravel and sand are not normally thought of as insulating materials, but they are. A foot of gravel followed by six inches of sand provides drainage. Water and wet soil conduct heat. Well-drained gravel and sand are both good insulators. A dry gravel and sand sub floor will insulate the basement from a cold ground and allow walls of the basement and heat storage vault to store additional heat. 

Heat Storage systems moderate temperature swings and allow heat to be distributed when it's needed most.  The more tolerance a person has for temperature fluctuation the less important heat storage becomes.  A person with a comfort range between 72 F and 68 F will need more heat storage than someone who can tolerate temperature swings between 60 F and 80 F. A well-insulated, preheated 80-gallon water tank could be used to assist a domestic hot water system, however a much larger heat storage vault would be needed to supply all the heat and hot water needs of our 4,000 sq. ft. house. 

What are people saying about these books?