Energy Efficiency and Comfort
You want your new house to be more energy efficient. Do you ante up for the more expensive, more efficient gas furnace because it is used eight months of the year? Maybe not. You really need to look at your overall energy strategy as the furnace is really just one component of it. For example, how is air going to be exchanged throughout the home? How many air returns will be installed? We recommend that you review this plan with the designer of the heating system. Ask them to explain the system to you and what can be done for energy efficiency and a higher air quality. If you have allergies, ask about a media filter or electronic air filter for the system. Ask about insulation. Insulation upgrades are easy to do in the planning stages and upgrading areas such as the attic can even happening in the latter stages of construction
In some areas it’s a common practice to route the air back to the heating or cooling unit through wall cavities between wood studs and the space between floor joists. Sending all the conditioned air through ducts and sealing them with mastic (a gray, goopy glue) or foil tape is the obvious first step. Duct tape, as it turns out, is ideal for the quick fix or the emergency repair, but lousy when used for its stated purpose — sealing ducts. Tests at the Lawrence Berkeley National Laboratory in Berkeley, Calif., have shown that it falls off ducts as it ages. In this case, the air leaking from the ducts will find its way back into the living areas above, but the rooms that are farthest from the furnace may be uncomfortable. Sealing and insulating the ducts, which is not commonly done when they are in a basement, will help insure that the air is more evenly distributed. Some builder will only have one or two air returns for a 2,200 sq. ft. home. This will leave pockets of stale air or hot spots in many rooms. Exchanging the air throughout the home will make for great comfort and better air quality.
Moving on from the ducts, there’s the outside air coming into the house through the walls. This also affects energy consumption. When there’s sloppy construction and air infiltration is excessive, it causes the furnace or air conditioning to run unnecessarily, which runs up the utility bills. All those points of entry need to be plugged up. Heat can also pass through the window itself, making a house colder in winter and hotter in summer; getting the right window — a dual paned one with a low emissive coating — will help to staunch this flow. Sealing all the gaps is best done when the home is framed and ready for insulation. The insulation people and take expanding foam and seal all the needed areas before they get covered with insulation.
When you address all the other things in your new house that will affect how much energy is needed to heat and cool it and finally get back to the furnace, you should be pleasantly surprised. In all likelihood you will be able to purchase less expensive models that would ordinarily be installed in a smaller house because you’ve reduced the heating and loads. When their new system is up and running after you move in, they’ll find that it is significantly less costly to operate. You will also notice that it delivers a noticeably higher level of comfort than their old one did because the heating is more evenly distributed through the house.
Such a comprehensive and systematic approach to heating and cooling has been advocated for at least 20 years by building science engineers, but it has finally captured the imagination and attention of home builders through the Department of Energy’s Building American program.
Started in 1996, this program has two ambitious goals: 1) devise strategies that will make new houses 30 to 50 per cent more energy efficient than conventionally built ones, and 2) accomplish this through a series of tradeoffs and substitutions so that the dollars saved by some of the changes will cover the added cost of others.
In the past, energy efficiency has been a hard sell to both builders and buyers because it nearly always made the houses more costly to build and buy. Few people got very excited about a more efficient furnace, for example, and buying one usually only made financial sense if the buyers planned to be in the house five to ten years, long enough to exceed the “payback period,” the length of time required for the savings on the utility bills to equal the extra money spent the furnace. And the immediate tangible benefits — a much greater level of comfort because the house was evenly heated and cooled were often unrealized because the rest of the heating and cooling system was unchanged. With the Building America approach, however, buyers pay a minimal amount extra to get energy efficiencies and get greater comfort and savings from day one. It is a win-win for everyone.
Another federal program that also promotes energy efficiency in new houses is the Energy Star Homes program, which is jointly sponsored by the Department of Energy and the Environmental Protection Agency. Many of the participating builders in these two programs are small, but some divisions of the larger, national firms including Centex, Brookfield, Beazer and Ryan are also involved. If you don’t find a participating builder in the area where you want to build, you can still ask any builder that you are considering about duct sealing, duct location, windows, air infiltration, and insulation. When trying to make a house more energy efficient, sealing the ducts, locating them so that less energy is lost to the great outdoors, buying good windows, and plugging up the air leaks will make a huge difference. To locate a builder who participates in the Building America Program, check its Web site: www.buildingamerica.gov.
How Much Insulation Does My Home Need?
For new construction or home additions, R-11 to R-28 insulation is recommended for exterior walls depending on location (see map below). To meet this recommendation, most homes and additions constructed with 2 in. x 4 in. walls require a combination of wall cavity insulation, such as batts and insulating sheathing or rigid foam boards. If you live in an area with an insulation recommendation that is greater than R-20, you may want to consider building with 2 in. x 6 in. framing instead of 2 in. x 4 in. framing to allow room for thicker wall cavity insulation—R-19 to R-21.
Today, new products are on the market that provide both insulation and structural support and should be considered for new home construction or additions. Structural insulated panels, known as SIPS, and masonry products like insulating concrete forms are among these. Some homebuilders are even using an old technique borrowed from the pioneers, building walls using straw bales. Check the Consumer’s Guide for more information on structural insulation. Radiant barriers (in hot climates), reflective insulation, and foundation insulation should all be considered for new home construction. Check with your contractor for more information about these options.
For insulation recommendations tailored to your home, visit the DOE Zip Code Insulation Calculator.