Home building used to be based on location, style and amenities. This was common with the McMansion-style" of building where very little thought was paid to energy-saving devices or environmentally-safe building materials. And now with energy prices climbing almost weekly these huge places are extremely costly to heat and leave a carbon footprint the size of a brontosaurus.

1. The Lot

The first thing that a homeowner should do is pick a lot that can allow a home to be built with a southern exposure - but not too much west because the summer sun will overdrive an air conditioning system. The energy-efficient homes are allowing as little northern exposure as possible even building into the side of a hill so that the northern wall has the least above-ground exposure. This lowers the profile to the north but allows the winter sun to add to the heating.

2. Building Structure

The way a home is constructed will determine how much heat loss there will be:

Wood Frame: The traditional wood-framed home is usually insulated with fiberglass batts which are subject to air channeling in from imperfections in the walls. This air can get into the home through outlets and other portals. This type of framing allows between R-12 and R-15 insulating value.

Insulated Concrete Forms: ICF's are a hollow foam block made from the same material as coffee cups. Reinforced with steel these blocks are filled with cement providing the whole shell of the home from foundation up to the gables. The walls are sealed from the elements and the foam provides almost an R-20 value for heat loss. In addiiton these homes are less prone to damage from high winds due to tornadoes and hurricanes.

Structural Insulated Panels (SIP): Resembling a a large "arctic ice cream bar" SIP's have a core of foam between 6" and 8" thick sandwiched by two oriented strand boards. These are made for wall and roofing units and have the strength of a wood-framed home with an amazing R-value because the walls are sealed. In addition, unlike wood-frame and ICF, SIP's go together quicker lowering labor costs.

Logs: A home built of logs doesn't have the R-value of the other structures but is a leader in "thermal mass." This means that logs can absorb heat from the sun or fireplace and store it it. When the room gets cooler heat is released from the logs lowering the heating bill.

Wood Frame with Foam Spray: A traditionally-built home can get as good or better insulation value as any other product with a polyurethane-based foam spray. This is applied between the studs and it expands to form a thick sealed base of foam which is leak-proof and waterproof.

3. Windows

Windows are probably the biggest area of energy loss in the home. By its very nature glass is a conductor of heat and 1 pane will equal only .9 R-value of heat loss protection. Even if the panes are doubled the resulting R-value with a 10mm air space creeps up to barely 2.04. This is because the air in the glass is subject to a convection current whereby the cold air on the bottom and the hot air on top move and this movement transfers the warm air outside.

If the windows are triple-glazed, low emissivity and argon gas-filled the R-value goes up to 4 or even 5 depending upon the materials on the frame. This is because the metallic coating on the glass reflects heat back into the home and the heavy argon gas cuts down on the convection movements between the window panes.

For air conditioning units the better windows have a "shading coefficient." In the summer west facing windows can not only let the sun's rays in but the panes can intensify the heat so placement of the windows is also crucial to the energy savings in the home. In addition the emissivity coatings provide a shading effect which deflect these rays preventing excess use of the air conditioner.

4. The Attic

It's no secret that heat rises. If you don't believe this just get on a step ladder and put a thermometer up near the ceiling. This is why it is important to insulate the attic to R-40. The U.S. Department of Energy recommends R50 for homes with electric baseboard heating. This can be accomplished with fiberglass batts, loose cellulose insulation or expanding polyurethane foam.

5. Passive Solar Water Heating

Another area of green home building is in water heating. By installing a solar-assist hot water system you can save hundreds of dollars every year in electrical bills. This system operates by a coolant solution (glycol) passing through a panel containing cylinders which heats the coolant with the sun's energy. This heated coolant is pumped into a heating coil in a tank beside a regular water heater. The heat is transferred to the water which is then pumped into the water tank. This elevates the temperature of the tank and either provides the house's hot water needs or, in the winter, supplements th regular water tank's energy needs. The pump is operated by a photovoltaic cell which provides the electicity.

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