Many states have enacted an energy conservation construction code to supplement their building codes. The purpose of the energy conservation code is to provide a construction standard that will minimize energy consumption in a building while maintaining the necessary comfort factors. The conservation code applies to new construction, renovations, and additions to buildings. The code is not retroactive and therefore does not apply to buildings constructed prior to its enactment. You can check with the local building department to determine whether there is an energy conservation construction code in your state and if so, whether it was in effect prior to the construction of the house you are planning to buy.
If you are considering the purchase of an existing building, there is a high probability that the house is not as energy efficient as it could be. Although the energy-deficient items are usually found during a prepurchase home inspection, they are often not upgraded until the buyer takes possession of the house. Consequently, after you move into the house, you should perform an energy audit to bring back into focus those items that are needed for conservation improvements.
Having an energy-efficient house is not only good citizenship; it is also good for your pocketbook, resulting in reduced utility bills. The actual dollar savings will of course depend on the gas, oil, and electricity rates in your area; the climate; and the extent to which your house is already energy efficient. You can often determine the projected savings and payback period for the costs involved in making your home energy efficient by contacting your local utility company. For a nominal fee, many utility companies will analyze your energy-conserving improvements, taking into account current and projected energy costs, and will estimate your dollar savings per year.
An energy audit is an inspection of the house to determine the extent of deficiencies that result in energy being wasted. The decision whether to upgrade deficiencies is usually based on economics. Are the dollars spent in making energy-conservation improvements a wise investment? Will the improvements save you enough money on heating and cooling to pay for themselves? For most homes, the answer is yes, especially with ever-increasing costs for fuel.
One cause for wasted energy in a house, especially an older one, is the lack of adequate insulation. Insulation is a basic energy saver and should be used in all houses regardless of location. In colder climates, it reduces heat loss and thereby reduces fuel costs. In warmer climates, the insulation reduces heat gain and consequently reduces cooling costs (electricity is used for running most residential air-conditioning units). During your energy audit, you should determine whether your house is adequately insulated.
Insulation is available in a variety of forms and materials. The three most common forms are flexible insulation, loose-fill insulation, and rigid insulation. Flexible insulation is manufactured in two types, batts and blankets. Both are made of fibrous materials such as glass fibers, rock wool, wood fibers, or cotton. Organic fibers are treated chemically to make them resistant to fire and decay. Batts are precut in 4or 8-foot lengths and are available in thicknesses between 2 and 6 inches. Blankets are furnished in continuous rolls and are available in thicknesses between 11⁄2 and 3 inches. Both batts and blankets are manufactured in 15- and 23-inch widths so that they can be readily used in homes that have been constructed with joist and stud spacing of 16 or 24 inches.
Loose-fill insulation is generally made from rock wool, glass fibers, vermiculite, pearlite, cellulose, granulated cork, shredded redwood bark, sawdust, or wood shavings. It is normally supplied in bags or bales and can be poured, blown, or placed by hand. Loose-fill insulation is suited for use in the sidewalls of homes that were not insulated during construction or between the floor joists of unheated attics. However, if there is no floor covering, it is not recommended for use between the floor joists when an attic fan could blow the loose material around.
Rigid insulation is generally made from extruded polystyrene, polystyrene bead board, urethane, fiberglass, or wood fiberboard. It is often used to insulate masonry walls and comes in widths of 24 and 48 inches. Most rigid insulation boards are not fire resistant and should be covered with at least 1⁄2-inch gypsum wallboard to ensure fire safety. Rigid insulation boards are also used as backer boards for aluminum and vinyl exterior siding.
Another type of insulation that was popular in the late 1970s was foamed-in-place insulation. It was made from urea formaldehyde. In many homes, the foam ingredients were improperly mixed and installed. This resulted in excessive formaldehyde vapor being released into the house, causing adverse health effects. Urea formaldehyde foam insulation (UFFI) is no longer being installed; however, many homes have UFFI in their walls. This is no longer considered a problem. See “Formaldehyde” in chapter 20.
One measure of the effectiveness of insulation is its resistance to heat flow, the R-number. The higher the R-number, the greater the resistance to winter heat loss or summer heat gain. Table 19-1 shows typical R-numbers for various types and thicknesses of insulation.
R-numbers are additive. You can add an insulation rated R-11 to one that is rated R-19 to achieve a resistance value of R-30. The thermal resistance of an area covered with loose-fill or flexible insulation can change over the years. The insulation value depends not only on the material but also on the amount of trapped air contained within the material. If the loose fill is disturbed or the flexible insulation crushed (because of items being stored on top of it), it will no longer be as thick as when it was installed. Consequently, its effective R-number will be reduced. To determine the current R-number of the insulation in your home, you should measure its thickness.
The insulation recommended for your house can be determined from the map in FIG. 19-1. You might be surprised to learn how much insulation is recommended. The R-numbers, however, are based on current and projected fuel costs. If your house is already insulated, once you determine the amount of existing insulation, you can add the difference. Remember, the R-numbers are additive. In some homes, it might not be economically justifiable to increase the insulation to the recommended value.
In determining whether your house is adequately insulated, you should check the exterior walls and the ceilings and floors that face unheated areas, such as the attic and crawl space. (See FIG. 19-2.) In unfinished areas where the insulation is exposed (often in the floor of an attic or ceiling of a crawl space), the thickness can easily be measured. If the attic floor is covered, you can pry up one board and look for insulation. Determining the amount of insulation in a finished exterior wall is more difficult. However, you can make a quick determination whether the wall is inadequately insulated or has no insulation by feeling the inside surface during the heating season. If the wall feels cold to the touch, insulation is needed.
Sometimes you can determine the amount of insulation by removing the cover to a light switch and peering into the wall space, using a flashlight. Caution should be observed, since the switch is electrically hot. Because of the small amount of open space between the wall and switch box, this method is usually not effective. Also, it is possible that the electrician who installed the wiring might have pulled the insulation away from the switch and outlet boxes to facilitate installation. In this case, you might think that there is no insulation in the wall. The only way to determine positively how much insulation there is in a finished exterior wall is to make a small hole in the wall (in a nonobvious location such as a closet) and measure it. The hole can then be patched.
While you are determining the amount of insulation, you should also determine whether there is a vapor barrier associated with Many insulation materials are produced with a the insulation. A vapor barrier is a thin sheet vapor barrier applied on one side. If the insula-material such as polyethylene film, aluminum tion does not have a vapor barrier, a separate foil, or an asphalt-impregnated kraft paper one can be installed. The purpose of a vapor through which water vapor cannot readily pass. barrier is to prevent moisture problems in exterior walls and ceilings, and floors that face unheated areas, due to condensation of water vapor (normal in a house) that passes through those surfaces. To be effective, the vapor barrier must be facing the heated room rather than the cool, unheated area. (See FIG. 19-3.)
Fig. 19-1. Recommended R-numbers for insulation in ceilings, floors, and walls. U.S. Department of Energy