by: Dennis E. Hayes, Designer

The home of the future is about to become available to home buyers and builders. Five western states have pyramid homes now that have proven themselves to be more energy efficient than any other home when comparing actual energy use records.  Energy costs for 20 years have proven pyramid homes are using less than a third and sometimes as low as one-fourth the energy of similar sized conventional homes.  The use of SIPs (structural insulating panels) to replace conventionally framed exterior walls (roof) promises to greatly increase that efficiency.

What does this comparison of energy efficiency mean to a home buyer? A recent local radio ad promotes PGE’s new "Earth Advantaged" homes with claims of 15% better efficiency than comparable code compliance homes in the Portland area. Soon, home buyers, will be able to see a solar pyramid home that will rewrite the record book when it comes to claims such as this and hopefully a new and higher energy standard will emerge to spur competition.

The single biggest factor responsible for superior energy efficiency in a pyramid home is its compact shape. Shape makes all the difference in the world. Of all possible geometric forms the pyramid has the least amount of exposed exterior surface area per square foot of heated or conditioned floor space. Heat loss (or gain) is a direct mathematical function of surface area.

A common term used in construction today is "R" value when talking about insulation in the roof or walls. This is a very misleading term and I suggest with good evidence that it not be used. It is supposed to indicate the relative energy efficiency of a material in stopping the flow of heat through a wall or roof. The coefficient of heat loss (which is a small decimal point number describing the heat flow in BTU’s per hour per inch of thickness) is the "U" factor and the reciprocal of that decimal number (or 1 divided by the U factor) is called the "R" factor (which is a whole number). The larger the "R" value the better the home’s efficiency, right? Not exactly! Insulation’s "R" value is only one small part of the formula used in calculating a building’s total heat loss. A claim of any percentage amount of comparative energy efficiency is misleading as well. A humorous but true old adage says that "figures can lie and liars can figure" should suffice to remind us to examine the whole picture when it comes to claims of energy efficiency. A truer statement proving energy efficiency is the actual energy bill history paid by the homeowner.

For example, a 2,850 square foot, all-electric pyramid home in Boise, Idaho has official records kept by Idaho Power for over twenty years. The owner burns about two cords of firewood per winter in his Vermont Casting™ catalytic converter wood stove and has enjoyed an average energy cost of less than $600 per year since building the home in 1982. The home has no solar hot water system, no solar electric (PV) system, just passive solar gain through Velux™ roof windows and an energy conscious homeowner living in the home. The highest compliment paid by the owner has been that it is a "zero maintenance" home. His total energy cost per square foot is 21¢ per year, or 1 3/4¢ per square foot per month. Those are the numbers that really count. An analogy in the automobile industry would be to say that "this vehicle gets 15% better gas mileage than a comparable sized auto".... we all can measure "miles per gallon" and judge for ourselves the relative efficiency of the vehicle.

A building’s exterior surface area measured in square feet "multiplied" times the material’s "U" factor and the design temperature difference between the interior and exterior surfaces will yield an overall heat loss in BTU’s per hour. A perfect vacuum in the exterior shell would lose zero BTU’s. A building that leaks air like a sieve through all the joints would lose all it’s heat energy in a short time. The point is that the shape of the building and the air tightness are much more important to energy efficiency than simply the "R" rating of the insulation.

The above mentioned pyramid home in Boise has R19 fiberglass batt insulation in its 2X6 frame exterior walls and roof. There is also 1" foil faced foam sheathing on the interior surface as a vapor barrier that has an R7 rating. Joints in the sheet rock were sealed to reduce air leakage. The maximum R value is R26 for this pyramid. The home was built on an acre of ground with a well and septic system for a total cost of $57,500 and was financed by HUD in a loan program called EX-TECH 233. Energy records have been maintained by Idaho Power and the home owner since it was built as part of HUD’s loan requirements.

A simple box shaped home has 20% more exterior surface area required to cover the same amount of floor space (as compared to a pyramid having the same floor area) which logically results in that much more heat loss per square foot of usable floor area. But here again the shape becomes an even more important factor to determine energy efficiency. Since hot air rises and will migrate immediately to the highest points in a room of any shape or configuration, the pyramid’s simple geometry has that warm air automatically concentrated in a single area at the apex. The sloping exterior walls provide a natural migration path of warm air into a convenient location at the apex where the entire building's air return register is placed. Recycling the air down through filters to be reused (where it can be felt) accounts for a large savings in heating bills. A BTU has often been discribed as the amount of heat released by burning a common wood kitchen match. If a home loses 30,000 BTUH’s per hour in the winter, that’s a lot of kitchen matches. Now, if we can capture and reuse a lot of that heat we’ve already paid for once, well, you get the picture. 

Most of the heat energy that has moved past our sensory detection ability (the first five or six feet of air space above the floor) has migrated up to the concentrating apex region of the pyramid where it is recaptured and returned through the air handler's filter system down to the plenum supply floor space, to be recirculated and reused again and again. Because of the pyramid home’s air tightness, an air to air heat exchanger provides constant fresh air without opening windows and losing all the heat. The sealed and insulated floor space is an insulated supply air plenum under the entire main floor. The floor is warmed by direct radiation contact with the warm air and select locations have adjustable supply air registers to provide spot warmth. There are no separate supply air ducts in the floor space to lose heat to a cold crawl space that has been vented to outside air temperatures. Since the space is continually conditioned by the air handler and is sealed, it is as dry and clean as the interior of your home. 

In the summer, the heat is naturally exhausted off the apex of the pyramid like a chimney by simply opening windows at the apex and on the shady side of the lower level to encourage an upward flow of air. This chimney effect provides for a natural breeze and cooling effect throughout the interior of the home.  Velux™ windows, which can be computer controlled to electrically open and close on temperature settings, act like air scoops and tend to capture the slightest breeze due to their awning style design.

Pyramid homes in Southern Idaho’s semiarid sage brush desert and in Arizona’s Sonoran desert have been kept entirely comfortable using nothing more than ground mounted evaporative coolers blowing into the Plenwood floor space. A natural cooling effect is created by using the pyramid’s natural chimney effect to move cool air in low, while exhausting hot air off the apex. Evaporative coolers require a dry climate to be effective, of course, as they lose their cooling ability in areas of high relative humidity.

Another extremely important feature of the pyramid home is its material use efficiency. There is virtually no waste pile created at the completion of erecting the shell. It’s an unfortunate reality that a lot of the conventional home you buy ends up in the landfill. Combining new renewable resource efficient building materials like SIPs and engineered wood products to minimize the reliance on large wood members in the building’s structural shell reduces the quantity of wood (in board foot measure) to as little as 10% that of a conventional wood frame home. Put another way, a builder can build eight to ten pyramid homes with the same amount of lumber used today in a single wood framed home. The logical result of this efficiency is the protection of our old growth forests.

Having used products like I-joists and laminated veneer lumber , I am convinced that the replacement of standard dimensional lumber framing with SIPs is a major breakthrough for the home building industry. In a short period of time, builders will learn that it is the "only way to go" when considering their next home building project. The faster and more efficient construction technologies afforded by leading SIP manufacturers will pave the way for conventional home builders to greatly increase their standards of energy efficiency. By actual use, SIPs built homes have proven themselves to be 57% more energy efficient than stick frame versions. When SIPs solar pyramid homes become available, a new era of building alternatives will evolve. No longer can we afford to squander precious natural resources and without question we should realize that ENERGY EFFICIENCY will become a paramount factor in resale value and appraised valuations. The new SIPs solar pyramid home is a logical evolutionary step forward and is a direct example of thinking outside the box when shape makes all the difference in the world.