Monday, March 22, 2010
7 steps to a net-zero home — start with conservation
By Ann Robinson and Annie Schwemmer
One of our favorite home-improvement publications is Fine Homebuilding magazine, published by Taunton Press. It is the largest residential construction magazine with informative how-to articles written by the "guys who swing the hammers."
The April 2008 issue features excellent article by Betsy Pettit on "Remodeling for Energy Efficiency."
This article listed seven steps to net-zero energy use. Net-zero is a general term applied to a building that functions with zero net energy consumption and zero carbon emissions annually. This means that the building is sufficiently energy efficient to require a reduced amount of energy, and any energy it does use is produced on site without the need of power supplemented from the public grid.
What we like about this article is that its suggestions are laid out sequentially, leading to the net-zero goal. You may not get to all seven of them, but you would still proceed in the following order to get the "most bang" for your buck:
Step 1: Upgrade the mechanical systems. If you have an old boiler or furnace, get a new one. You can begin saving energy dollars right away. Newer units are far more efficient that those of even a decade ago; a 95 percent efficiency rate is not hard to achieve these days. Don't forget your water heater: Adding a solar water heater is a good option if you can afford it. (Note: If you proceed through the list and get past Item 5, your new system can be downsized. Therefore, before you take this step, you need to have a plan regarding how far you are going to take this quest for energy efficiency.)
Step 2: Bring the basement and crawlspace inside the house. Keeping your basement and crawl spaces warm and dry adds living and storage space to your home and wards off mold. Spray foam is a quick and effective way to change these areas into conditioned (cooled or heated) spaces, and this can also help seal any foundation leaks.
Step 3: Superinsulate and air-seal the roof. A poorly insulated house keeps it cold in the winter and warm in the summer — the opposite of your comfort goals. Using spray foam makes it possible to add insulation and to provide a barrier to air movement all in one step.
Step 4: Replace the windows. After you have sealed the bottom and the top of your house, you can turn your attention to the walls. Windows often leak both air and water into a home. Poor windows are like big holes in your walls. Windows with at least an Energy Star Rating will seal these holes.
Step 5: Insulate the walls. Filling empty walls with cellulose is an inexpensive way to warm up your house. This works on a wood framed house, though it takes an experienced contractor and checking with infrared cameras to make sure the job has been done correctly. A masonry home offers more of a challenge; filling the wall cavity is generally not possible. Other options include furring out the interior walls with new studs to hold new insulation, or — if you are doing some exterior upgrades to the house — you can add rigid insulation to the exterior of the house and cover it up with your new finishes.
Step 6: Buy Energy Star (or better) fixtures, appliances and lighting. After your heating/cooling loads and your water heating needs, your next largest energy items will be the fixtures, appliances and lighting. For example, a new Energy Star refrigerator will use about 15 percent less energy than a standard model, and a compact fluorescent bulb will save up to 30 percent over the older incandescent model.
Step 7: Add a renewable-energy source. Once you have reduced your energy consumption significantly, it becomes more reasonable to produce part or all of your energy demand with systems such as photovoltaics (solar), wind or water power.
Unless you have slashed your energy needs, the investment in renewable power sources will never pencil out. Conservation is still your best option for improving the world, along with your own budget. As always, we welcome your home architect design questions at firstname.lastname@example.org.