The buzzword in custom home building these days is "green." With the price of heating fuels pushing the $150 a barrel mark the efficiency of the modern home is being rethought and redesigned. This includes expending energy to maintain sir conditioning and central HVAC systems.

In addition North Carolina is now enforcing the IRC and IBC codes requiring a wind-borne debris region extending 1500 feet inland from the Atlantic Ocean. Home within this are have to install shutters or special laminate glass with withstand airborne objects in hurricane-force (120 mph +) winds. In addition coastal homes will have to withstand wave damage.

Given the fact that the price of energy and the elements have had an effect on the way commercial buildings are designed it is only logical that residences follow suit, even those dwellings miles away from the ocean. The old wood frame, gable-ended two-story homes are just not cutting it in an area where the elements sometimes dictate the structural integrity.

Concrete-Based Structures

Since the days of the pioneers stick-built homes have been the overwhelming residence of choice for home builders. Estimates today still put wood building starts at 85 percent of the market share. Wood used to be cheap and easy to work but with the spike in transportation fuel prices wood will no longer have this advantage. In addition to its poor performance in heavy winds and its vulnerability to fire and insects, wood is beginning to lose its edge everywhere in the country.

During the past 10 years home builders have been choosing concrete as the structural walls for their home. This includes concrete masonry block, ICFs (insulating concrete forms) and removable forming systems (called "cast-in-place"). Another design is precast/prestressed slab wall system which is raised on site. These are an effective and quick way to get the building up but are used more for commercial aspects.

Cast-In-Place Concrete

This method involves building forms and having the concrete poured on site. The forms are temporary and usually made of wood, but the new forming systems are lightweight aluminum. The insulating is done during this process. Rigid foam insulation is either placed inside or between the forms, depending on what style the contractor uses. When the trucks arrive the concrete is poured on either side of or between the foam. For reinforcement steel rebar is inserted beforehand. As with any concrete pour when the cement has cured the forms are removed and re-used.

Concrete Blocks

In days gone by these were the vanguard of commercial building and for residential basements. Today there are many types of concrete block systems that offer insulating options:

Interior Insulated Block: This is the most common system as the interior is framed and insulated. However this puts the thermal mass qualities of the concrete on the wrong side for realizing its benefit.

Exterior Insulated Block: Because it features placing rigid foam insulation on the outside block walls this product is the most energy efficient of the systems. The process makes for a seamless surface that can be increased in insulation value by just choosing a thicker product. Since the thermal mass of the cement is on the inside the temperature is moderated.

Cavity Insulated Block: Traditionally, builders filled the cavities of block with vermiculite insulation but now they use rigid foam, loose insulation fill or expanding sprayed foam." Thermal bridging," the process of heat escaping through conduction because of the materilas, negated a lot of the properties of this type of insulating block but new webbing materials have cut this down so that the benefits of the thermal mass can be achieved on the inside walls.

Pre-Insulated Block: These are regular blocks which come from the manufacturer with foam cores. Thermal bridging used to be a problem but the newer models have thermal breaks. Mortarless Insulated Block: These blocks are first dry-stacked and then foam inserts are put into the block cavities. However, a coat of cement is applied inside and out which makes the wall seamless. In addition the wall is now ready to be surfaced with traditional materials.

Insulated Concrete Forms (ICF)

ICF's are a stay-in-place rigid foam (coffee cup foam) block system with a cavity in the middle where concrete is poured. Reinforcing rods are added for strength and when the cement dries there is a solid wall systen which is insulated on both sides of the wall. The blocks go together much like a child's building blocks to form an interlocking system. Special webbed spacers 16" apart allow interior and exterior materials to be applied. These foam blocks typically are 8 inches x 16 inches or 16 inches x 4 feet. The interlocking edges aid assembly.

Because the foam is on both sides of the wall the R-value is higher than the traditional stick-built home. What would make ICF more efficient would be if there was a way to scrape the foam off the inside wall so that the home owner could take advantage of the thermal mass of the concrete for both heating and cooling.

Whatever product is chosen there are things they all have in common:

• They are great structures against high winds, flying debris and wave action
• High fire rating
• Insect proof
• Waterproof

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