SEVEN STEPS TO NET ZERO ENERGY USE
After you get past item 5, the house will be efficient enough to downsize the mechanical equipment, which you replaced in step 1. If you’re planning to go at least through step 5, keep that in mind before buying a new HVAC unit.
1. Upgrade the mechanical systems
An old furnace is often the worst energy user in an old house. A new furnace can save energy dollars right away. Replacing window air conditioners with a central system also can save energy right away, as long as the ductwork has been placed in the conditioned space. Solar water heating is a good option to add here if you can afford it.
2. Bring the basement and crawlspace inside the house
Warm, dry basements and crawlspaces can extend living and storage space. Wet basements are the source of high humidity levels and discomfort in the summertime in old houses. They also can be the source of mold growth that gets distributed around the house. Spray foam is a fast, effective way to bring these areas into the conditioned space while sealing the leaks between foundation and floor framing.
3. Super-insulate and air-seal the roof If air leaks in at the bottom of the house, it leaks out at the top, which makes a house cold and drafty in winter. A poorly insulated roof also can make a house hot in summer. Air-sealing is a by-product of good insulating, so it’s really a one-step process. Using spray foam under a roof also can eliminate the need for roof venting, which is tricky in complicated roofs.
4. Replace the windows
With the bottom and top of the house sealed and insulated, the next opportunity is the walls. And old windows are like big holes in the walls. Old windows often leak both air and water into the house while functioning poorly. They might not open and close properly, and can be obscured with storm windows and screens that diminish the amount of light that can enter. Properly installed, Energy Star (or better) windows seal the holes in the walls to keep out water and weather extremes.
5. Insulate the walls
Filling empty wall cavities with cellulose is a cheap, easy, effective way to warm up an old house. Blowing cellulose into existing wall cavities is an art, to be sure, but there are many contractors who have been doing it for years. In fact, there are now inexpensive ways to check with infrared cameras to make sure that all voids have been filled without disturbing the existing plaster or sheathing on outside walls. Because siding or shingles on old houses might also have worn out, we take the opportunity to install foam sheathing on the outside of the house before re-siding.
6. Buy Energy Star (or better) fixtures, appliances, and lighting once you have reduced your space conditioning and water-heating loads, the lighting, appliance, and plug load will be your next big energy item. A new Energy Star refrigerator will use 15% less energy than a standard model. Replacing old light fixtures with pin-based compact fluorescent fixtures ensures your electric bill will stay lower (up to 30%).
7. Add a renewable-energy source
Once your energy consumption has been reduced significantly, it becomes reasonable to produce your own energy with systems such as photovoltaics, wind power, or hydro, if you happen to have a stream nearby. Until you slash the energy usage, though, it’s not worth the investment in renewable power sources. Conservation is still the cheapest game in town.
David Knowles, Owner/Project Manager