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Ways to Improve Home Energy Efficiency
Ways to Improve Home Energy Efficiency
Homeowners who are serious about improving energy efficiency know there are numerous options available to them, many of which are simple enough for anyone to implement. Whether it's adding insulation, setting back the thermostat in the winter, installing compact fluorescent lamps, sealing air leaks in the building envelope, wrapping hot water pipes, turning down the temperature on the water heater or similar activities, these proactive measures can result in a significant reduction in energy use and help trim home energy bills.
We've addressed all these recommendations, and more, in past issues of this magazine, so when we started putting together this article for our annual home energy issue, we went looking for the next steps - those options that go beyond simple activities, into more complex projects with long-term benefits. We identified seven innovative solutions that we believe fit the bill admirably.
Once you've taken the initial steps described above, you can begin to make these more significant upgrades to your existing or new home. Consider this the advanced course in home energy efficiency.
Keep in mind that this is by far not an exhaustive list, but it is an indication that the business of improving home energy efficiency has expanded, and now encompasses a growing range of opportunities available to those homeowners ready to take the next step in reducing energy consumption.
1. Solar Hot Water Systems
Providing some or all of a home's hot water, residential active solar hot water systems are easy retrofits. Basically a pre-heating system for the hot water heater, a typical system consists of roof-mounted flat plate solar collector panels, piping, a thermostat controller, pumps and, in closed loop systems, a heat exchanger. Ideally, the collectors face south, tilted at an angle optimized for the geographic region and in line of unimpeded sunshine most of the day.
Open loop systems, popular in the south, heat the water directly, with the energy collection loop open to the rest of the hot water system. When not circulating, the water drains down into the storage tank. There's no anti-freeze in the system.
Closed loop systems, popular in northern climates, have non-toxic antifreeze in the water to keep it flowing in subfreezing temperatures. The solar exchange fluid is kept separate from the potable water.
Many systems can provide about 70 percent of a home's hot water requirements. Generally, a small family would use two 4-by-8-foot flat plate solar collectors and an 80-gallon storage tank; a larger family would add one or two more collectors and use a 120-gallon tank.
The Revolution Solar Hot Water System from Chico, Calif.-based Fafco is a drain-back system that works with electric and natural gas water heaters. It operates automatically, turning on when solar energy is available and shutting off at other times.
The closed-loop Dawn Solar System features a concealed, rather than exposed, collection system hidden beneath roof tiles. On sunny days in northern climates, it provides all or almost all of the hot water needed in summer and late spring/early autumn months, and less in winter. On sunny days in southern climates, the system can provide most of the hot water for a family of five.
2. Radiant Roof Barriers
Suitable for just about any new house or addition, radiant roof barriers offer a straightforward way to reduce solar heat gain in the attic during the summer and heat loss through the attic in the winter. The effective component is a layer of aluminum that reflects radiant heat. Radiant roof barriers are available in rolls that unfurl and attach to the roof sheathing in the attic or as an integrated component of roof sheathing.
While the primary benefit of radiant roof barriers is in reducing air-conditioning loads on hot days, when installed in a cold climate a radiant roof barrier can also reduce winter heating loads. The high reflectivity of the aluminum helps block interior heat from escaping out through the roof deck in cold weather.
Some radiant roof barriers are available ready for installation as the roofing support itself, nailed directly to the top of the rafters. LP TechShield radiant barrier roof sheathing, for example, is regular 4-by-8-foot oriented strand board (OSB) with a thin, durable sheet of aluminum laminated to the smooth side of the OSB panel. According to the manufacturer, it can reduce attic temperatures by as much as 30 degrees in the summer and reduce monthly cooling bills by as much as 20 percent.
The barrier, available in five thicknesses, installs with the aluminum layer face down. LP TechShield radiant barrier roofing panels also incorporate small incisions that enable the release of moisture, minimizing moisture build-up.
According to an energy analysis by EarthCraft House Program, an Atlanta-based greenbuilding program, LP TechShield radiant barrier minimized peak cooling demand by 14.7 percent and 18.8 percent in two different model homes with well-sealed duct systems and building envelopes, low-e windows and R-30 insulated ceilings. The reduction in peak cooling enabled the homebuilder to reduce the size of heating and air-conditioning units by 10 to 15 percent. Homeowners benefit from reduced cooling bills, increased comfort and potentially increased resale value. For more information: 888-820-0325 or http://www.lpcorp.com/techshield.
3. Energy Management Systems
Coming soon to your neighborhood (maybe) - a plug-and-play energy management system from the local utility that can help conserve energy use and provide backup power to critical household circuits for 8 to 10 hours.
The system, called GridPoint Connect, from Washington, D.C.-based GridPoint, integrates with a home's renewable energy source, such as a solar collector, and ties to the home's main electrical panel. It then manages or "balances" energy, sending power to the home when needed and selling excess power to the utility. Its components include software, which manages and reports on energy use, an onboard network computer to run the software, and hardware such as storage batteries, a battery charger and an inverter to convert DC power to household AC power.
The system provides homeowners, who pay a modest fee for its use, with detailed information about the amount of energy produced, used or sold to the utility. It also can analyze a utility rate schedule, compare that to the homeowner's current and historical energy consumption patterns, and help the homeowner determine the most cost-effective time to run appliances or turn off high-consumption appliances. It also can estimate the hours of backup power available in the event of an outage.
GridPoint Connect is a good alternative to backup generators, particularly in areas where towns or homeowner associations disallow home generators. Furthermore, unlike generators, which take a few moments to ramp up, GridPoint Connect's batteries kick in immediately when the power supply is interrupted, providing 1- to 1.5-kilowatts per hour of battery backup power.
4. Combined Heat and Power Systems
How's this for the height of efficiency - heat your home and generate electricity to power it simultaneously with the same system. The process, referred to as cogeneration, is possible with a micro-CHP (combined heat and power) hot water or hot air heating system.
While cogeneration has been popular for many years in commercial properties and residences in Europe and Japan, it has only recently become available for home use in the United States. Cogeneration units generally can supply most of the electric power needed for an average home.
In a micro-CHP, an internal combustion liquid-cooled engine that runs on natural gas or propane produces electrical power. During the engine's operation, heat is recovered from the cooling, lubrication and exhaust systems via a heat exchanger and is used to heat the home. The engine is housed in an acoustically treated cabinet, typically located in a basement or utility room.
A micro-CHP system is an easy retrofit but must be done by factory installers to an existing heating system or as a new heating system in a new home. In states where net metering is available (13 and counting), the homeowner can sell surplus electricity back to the utility, generally earning credit at the full retail rate or, in a couple of states, at a slightly lower price.
The Ecopower Micro-CHP system from Marathon Engine Systems, based in East Troy, Wisc., works with baseboard or radiant heat systems. It produces 42,000 BTUs of heat per hour and 4.7 kilowatts of electric power per hour, which is enough to support a home of about 3,000 to 3,500 square feet, with some excess to sell back to the utility.
The Freewatt Micro-CHP Home Heating and Power System, from Medfield, Mass.-based Climate Energy, pairs its own Energy Star high-efficiency heating system, either for warm air or hydronic heating, with a new generator from Honda. The unit produces 12,000 BTUs per hour of heat and about 1.2 kilowatts per hour of electricity. At times of peak demand for heat, the engine's heat output is supplemented by operation of the furnace or boiler. For more information: Marathon Engine: 262-642-6436 or http://www.marathonengine.com ; Climate Energy: 508-359-4500 or http://www.climate-energy.com .
5. Smart Ductwork
Ducts for air conditioning and forced air heating systems are typically installed in unheated attics, basements or crawl spaces, where there are few obstacles to work around. Though expedient for the builder because it keeps first costs down, that is not an energy-efficient installation. According to the Environmental Protection Agency, residential duct systems located in unconditioned spaces can lose as much as 20 to 30 percent of the energy in the air they distribute, much of that from leakage because of improperly sealed or insulated ductwork.
However, homeowners and builders can increase heating and cooling equipment efficiency by installing ductwork in conditioned spaces (i.e. insulated spaces) rather than in the usual unconditioned spaces. This type of installation - dubbed "smart ductwork" - eliminates much of that loss because any leakage is into space a homeowner is trying to heat or cool anyway.
Some ducts can be easily located in existing soffits. Others may require chases or bulkheads along walls, ceiling plenums in hallways, or open-web trusses or wooden I-beams within floors in multiple-story homes. Another plus: a duct system within conditioned space can be smaller than a duct system within unconditioned space, making it easier to fit within wall cavities and between floors.
Though ducts installed in conditioned spaces usually do not need anywhere near the amount of insulation around them as ducts in unconditioned spaces, the EPA does recommend at least minimal insulation (with a value of R-2 to R-4), especially in hot and humid areas to prevent condensation from forming on outside cold surfaces. In addition, all ducts in conditioned spaces should be properly sealed to ensure optimal performance and to maintain good interior air quality.
Though installation costs for smart ductwork can be slightly higher than a typical install, payback will come with reduced energy consumption over time. Because the concept is relatively new, try to use a heating and air-conditioning contractor who is already familiar with the practice. For more information: http://www.toolbase.org/pdf/techinv/ductsinconditionedspace_techspec.pdf.
6. High Thermal Mass Walls
Building a new home or addition with above-grade and below-grade high thermal mass walls can result in high energy efficiency from foundation and basement on up. High thermal mass walls are constructed of materials, such as concrete, that conduct heat slowly, keeping the interior cool longer in hot weather and warm longer in cool weather.
The overall R-value of a wall assembly with high thermal mass is much greater than what can be estimated by traditional-material R-value calculation of the separate layers because of the way the resulting wall behaves in place. For example, high thermal mass walls made of concrete and rigid foam insulation feature two layers of concrete between which is sandwiched a layer of extruded polystyrene or polyisocyanurate insulation. This type of wall minimizes the flow of heat into or out of a home during the day.
High thermal mass walls are especially effective in areas with large temperature swings between daytime and nighttime, since the walls can offset heating and air conditioning loads to a time when electricity is less expensive. The walls meet Energy Star criteria by providing higher R-values than wood-framed walls, enabling the home to stay cooler in summer and warmer in winter. In addition, with the increased energy efficiency of high thermal mass walls, the size of the home's HVAC system can often be reduced.
Concrete high thermal mass walls can be poured in place or pre-cast offsite and delivered to the home site as blocks, which are then lifted into place by a crane. If poured in place, the amount of insulation can be customized for the specific location and climate.
On the interior of the home, high thermal mass walls can take drywall finishing, like any conventionally built wall, and on the exterior almost any type of cladding, including brick, stone and stucco.
Also worth noting: Concrete walls are excellent sound insulators, keeping a home quieter inside (or outside) than a traditional wood-framed house. They also provide much better termite and moisture resistance. For more information: http://www.concretethinker.com/Papers.aspx?Docid=35.
HVAC Energy Efficiency
With HVAC energy efficiency, all areas that help control the comfort level of your home are involved. The average home and business spends 35% to 40% of their energy bills on the inside environment in which people occupy. As a fixed cost, its reduction was first seen as a money saving venture.
Today people are more aware of the environment around us and conservation is becoming a way of life. To reduce our dependency on foreign energy sources and improve the environment, the use of more efficient systems in our homes and business is seen as a smart move.
The manufacturing of the units that are being produced today are meeting the needs of this requirement of being more fuel efficiency from the units just a few years ago. The federal government has set a new level of standards for energy efficiency in every type of HVAC component. This includes the humidifiers, AC units, fans and furnaces.
To make it easier for the American consumer to compare these units they have been labeled as Energy Star units. Not only is the energy efficiency of these units stated on them, but this also means they qualify for a tax break from the US Government.
For a manufacturer to place the Energy Star label on their products, it has to be certified that it meets the requirements that are set.
The energy efficiency of the units being produced has increased but energy efficiency has not stopped there. The utilization of new technologies has also assisted in this overall effect to save on a home owner’s energy bill. This has come with the continuing development of the heat pump systems.The heat pumps can supply both heating and cooling in homes for a more efficient use of the energy that is being used.
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