Near-Zero Energy Homes Are Great for Environmental Conservation
Based on results of a three-home experiment conducted by the Tennessee Valley Authority (TVA), a typical 2,400-square-foot, two-story home in an area that experiences significant summers and winters can require enough heating, cooling, and energy for other operations to run up utility bills of as much as $7 per day, or $4 per day, or $1 per day.
What makes the difference? In the TVA's experiment, and in real life houses across the country, the difference results primarily from differing levels of attention to energy efficiency.
While all three experimental houses are basically identical, one house was built with conventional heating, cooling, and energy systems. The second house was built the same as the first but then retrofitted at a cost of only about $9000 to be somewhat more energy efficient. The third house was built from the ground up with careful attention paid to energy efficiency.
This involved everything from using advanced building techniques which make the house relatively air-tight through adding extra insulation all the way to positioning all the heating and colling systems -- including the air ducts -- inside the thermal barrier that makes up the home's exterior "envelope."
While it's not always possible or cost-effective to retrofit a house to this extent, the TVA experiment is one more piece of evidence proving that energy costs can be significantly reduced just by paying attention to energy efficiency. And in most cases, the payback period for any required investment or extra expense is just a few years.
For example, the Empire State Building has reportedly been retrofitted with energy-efficient windows that will pay for themselves in about three years.
At least one California couple has remodeled their 1950s home to make it so energy efficient that a 2.7 kilowatt rooftop solar system is enough to meet all their electricity needs.
Many people argue that energy efficient buildings are prohibitively expensive, but Habitat for Humanity has reportedly built a "net zero energy" house near Denver for about $116 per square foot -- far less than the national average of about $200 per square foot.
Home builders are increasing their focus on energy efficiency in the new homes they offer, and frequently include not just solar systems and air-tight insulation, but well thought out design features that minimize the home's need for energy to heat and cool the interior. In fact, advanced homes can go beyond "energy neutral" (requiring zero external energy inputs during the year) to actually produce more energy then they use, allowing the owners to sell their excess energy into the grid and use the profits to offset other operating costs, such as taxes and maintenance.
It's a little known fact that homes and other buildings in the U.S. now generate nearly half of all U.S. carbon emissions, according to some experts. Increasing the energy efficient of the built-environment could therefore create a huge boost in environmental conservation.
Some movement toward energy efficiency is already in evidence. For example, building codes around the world are approaching the level where homes will be so well-insulated they will need almost no interior heating or cooling.Â Once the problem of heat-loss and heat-gain from the local environment is reduced or eliminated, a home needs only a small heating and cooling system to provide its inhabitants with comfortable indoor temperatures, year round.Â Reportedly, this will be the standard in the U.K. by 2016, in the European Union by 2018 and in California by 2020.
As energy prices continue to rise, energy efficiency will pay off bigger and bigger every year they are in place.
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Photo credit: Â Center for Neighborhood Technology