Question

Our Oregon home is not a good candidate for solar. How can we make the house more energy efficient?

Asked by Brittany Sims, Portland, OR

My family's home is not a good candidate for solar, and we are good about conserving energy in our daily tasks inside the home. What's the next step to be more energy efficient?

Answer

Florian Speier

Answered by Florian Speier

San Francisco, CA

Zeitgeist Sustainable Residential Design

October 3, 2008

If your house is not a candidate for photovoltaic panels (solar panels that produce electricity), you can still look into other alternative sources of energy.

  • Solar hot water is often feasible where photovoltaic panels are not; Portland is rated as a good location with an estimated payback time of about eight years. Of course, this requires you to have a roof that is not shaded by trees or neighboring houses.
  • Unfortunately Portland is not windy enough for wind energy, but geothermal heat pumps are successful in Oregon and eligible for tax credits.

Whether or not one of these technologies works for you, I commend your desire to make yours an energy efficient home. As you know, lowering your usage is often cheaper and easier than producing energy. Improving your house and using the right sources of energy for the tasks at hand can greatly reduce your carbon footprint.

Seal your home

To reduce the energy usage of your home, you need to increase insulation and stop drafts. Have a professional come out to your house to evaluate your specific condition. If you go to the Energy Star website and click on "home energy audits," you can find a professional in your area or follow the instructions for a do-it-yourself audit.

Many homes can benefit from simple improvements. It is often complex and expensive to add insulation to the exterior walls, so start with the attic and crawlspace. Blowing cellulose insulation into the attic is an affordable and highly efficient way to reduce your home's energy consumption. Go for a high R-value here—at least the R-38 recommended for your area by the Department of Energy. Since the temperature difference between inside and outside is greatest in the roof area, improvements here translate into the biggest energy savings.

Next, tackle the crawlspace. You can either insulate the floor of the house from underneath with sprayfoam (which may not be the most eco-friendly product but does an exceptional job of insulating and sealing any cracks), or you can cover the crawlspace floor with a vapor barrier to keep the air dry and then limit crawlspace ventilation. The latter option is typically cheaper but less effective.

Next on the list are windows. In the Pacific Northwest, the most important factor for replacement windows is a low U-value. Nearly every window sold in the U.S. has a performance sticker from the National Fenestration Rating Council, as I explained in my advice to Jackie from Florida. In northern Oregon, where overheating from the sun is rare, the SHGC value is less important. The U-value, however, directly describes the heat loss to the outside during the cooler months, and lower is better. Look for a number below 0.35.

Use the right sources of energy for heating

Besides reducing heat losses, it is equally important to look at how you use energy in the house. The most important rule is never to use electricity to generate heat. Electricity is the most valuable and expensive form of energy, because the coal plants that produce much of it have an efficiency of only about 30%. A modern, gas-fired domestic water heater, for example, can achieve efficiencies of over 95%, so using gas to heat water is better for the environment by roughly a factor of three.

Have a look at how you produce hot water and heat in your house.

  • If you are already using gas, you might still be able to improve efficiency by sealing and insulating the ductwork or upgrading to newer appliances. An energy auditor can check your current appliances and give you detailed cost/benefit advice.
  • For hot water, you could use a very high efficiency water heater like the Polaris (around $3,000) that gets around 95% efficiency compared to around 70% on a standard Energy Star model, or you could switch to a tankless water heater from Bosch or Takagi (starting at around $600). The latter are not quite as efficient (around 75%), but they make up for most of that by eliminating the storage losses of a hot-water tank.
  • When choosing a forced-air gas furnace, look for high-efficiency Category IV condensing furnaces that are vastly more efficient than standard models. Most manufacturers offer them now.

Radiant-heat floors: combine efficiency and comfort

If you want to tackle a bigger project, consider this improvement that our firm is currently installing on a remodel and addition—hydronic radiant floor heat. Radiant heat is vastly more comfortable than forced air because the air gets less dry and your feet are never cold. It is also more efficient: the floor radiates heat directly to your body, so you require lower inside air temperatures to feel comfortable.

The retrofit is relatively simple. Warm-water lines are stapled under your house from the crawlspace and then insulated. A tankless water heater circulates warm water through these tubes.

In a so-called "open system" you turn a valve in summer and let all the cold water you use in the house run through these tubes first, giving you free cooling when the weather is hot.

The best part of all is the relatively low cost—the pre-assembled system for our 3,000-sq.-ft. project costs only about $6,000, shipped directly from the manufacturer. If you want a solar hot-water tie-in instead of using a water heater, that will cost around $5,000 extra. Some homeowners decide to install these themselves, or you can work with a local contractor.

Make sure all electrical appliances are efficient and Energy Star rated

Finally, make sure all electrical appliances are efficient and Energy Star rated, especially your fridge. And, of course, those compact fluorescent lightbulbs save 75% of the energy needed for lighting the home.

Tagged In: radiant heat, energy audit

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