Heating Systems, the Energy Efficient Way
Basking in the sun and beyond
A cat lying in a sunny window knows how to get warm. So do you when you open the drapes on the sunny side of the house on a cold day. Dozens of simple actions like that can lower your heating bill, regardless of the type of heating system you now have. When it comes time to think about a new system, however, the choices become more complicated. You need to consider the differences between furnaces that heat air and furnaces that boil water. Or maybe a wall heater, heat pump, wood stove, or radiant system makes sense for your climate. And if you’re building a new house or doing major remodeling, don’t miss the chance to capture more (free!) solar energy.
Once you’ve installed an energy efficient heating system–and sized it correctly–the energy savings can be significant. Heating is one of the largest home energy expenses, averaging around $900 a year nationwide. In 2008 the cost of heating oil reached $4.50 a gallon, meaning that in some colder regions, where houses may use 600 to 1,000 gallons in the winter, heating costs rose to as high as $4,500 a year. Even in warm places, such as California, the average cost is $720 a year–and can be much higher depending on the house and its residents’ comfort levels.
For your home
- Don’t overheat. For most people, 68°F is a comfortable temperature.
- Automate efficiency. Turn the thermostat down to 55°F before you go to bed and when you’re away from home or asleep. If you have trouble remembering, you can use a programmable thermostat to automate the process. Typically, you can save about 2% on heating energy for each degree that you lower the thermostat for eight hours. Turning down the thermostat from 70° to 55° for eight hours can cut heating costs as much as 30%. Contrary to popular belief, it does not take more energy to bring a house back to the desired temperature than to maintain it at that temperature.
- Weatherize. Don’t lose the heat you’d paid for due to poor seals around doors and windows, other air leaks, and lack of insulation. Also, consider whether it might pay to upgrade your windows.
- Insulate yourself and your family. The most basic source of comfort is dressing warmly in winter. The layered look is not only fashionable, it’s strategic.
- Don’t heat unoccupied rooms. Turn down the thermostats, or close the registers and shut the doors to rooms not in use.
- Remove air conditioning units. If you have room air conditioners, either take them out in the winter or cover them well. They tend to be poor insulators.
For your heater
- Tune it or ruin it. Oil-fired systems should be cleaned and adjusted by a qualified professional every year; gas-fired systems every two years; and heat pumps every two or three years–or sooner if your winter use of gas or oil has increased substantially. Regular maintenance not only cuts energy and repair costs, but adds to the lifetime of the system. It also reduces the amount of carbon dioxide, carbon monoxide, particulate matter, and other pollutants released. Some additional maintenance chores that you can do yourself include:
- If you have a forced-air furnace, change the filter once a month and clean the blower at least once a year.
- If you have a hot water system, bleed radiators or baseboard heaters at least once a year.
- Do a furnace fan check. If you’re getting a lot of cold air out of the warm-air registers after the furnace turns off, call a furnace technician to check the fan-delay setting.
- Use reflectors. If you have radiators, put reflective foil behind them to reflect heat back into a room.
- Remove barriers. Keep furniture and other objects away from registers, radiators, or any heat source.
- Go modern. If your heating system is more than 20 years old, replace it with something more efficient. Also consider a replacement if you have an old coal-fired unit that was switched to oil or gas or an old gas furnace that doesn’t have electronic ignition. These older furnaces have efficiencies as low as 55% to 65%. The lowest efficiencies of today’s forced-air and boiler furnaces are 78% and 80% respectively.
When shopping, look for
Two of the most common types of heating systems are 1) furnaces that heat up air and force it through ducts and into rooms through registers and 2) furnaces that heat up water (boilers) and send it through pipes to radiators in rooms. These furnaces may be powered by oil, natural gas, or propane gas. Some that burned coal but were converted to oil or gas are still in operation. Here’s what to look for:
- A right-size system. The square footage of your house is not the only important factor. Have a competent contractor thoroughly evaluate your needs, also taking into account the floor plan, windows, shading, quality of insulation, air sealing, and windows.
- 90% efficiency, or better. Gas and oil furnaces are rated by their Annual Fuel Utilization Efficiency, or AFUE, which is the amount of usable heat the furnace produces divided by the amount of energy that goes into producing it. Forced-air furnaces made today are required by law to achieve an efficiency of 78% and boilers 80%. Your most energy-efficient choice would be a forced-air furnace or boiler rated at 90% or better. If you move from a furnace efficiency of, say, 55% to 90%, you could reduce your heating bill by anywhere from $200 to over $1,000 annually, depending on your climate, house size, and the type of fuel you use. Look for the government’s Energy Star labels on furnaces and boilers that are 5% to 15% more efficient than required by law. Click here for more information about how to calculate the energy savings you’d realize from a new system.
- A variable-speed motor. In addition to the energy used to heat up the air or water, electricity powers fans and pumps water in boilers. Units with “variable-speed” motors are usually more efficient than those with ordinary motors.
- A smart boiler. If you have a boiler, you can adjust it to a lower temperature when the weather outside is warmer. The control is usually located in a metal box connected to the boiler. If you can’t locate it, ask a heating company for help. Ask a technician about the feasibility of automatic “aquastat” controls that adjust the heat in the boiler for the most efficient match with the outside air temperature. This can cut energy use 5% to 10% on warmer days.
Here are the pros and cons of some other systems you might want to consider:
Wall heaters. Another option for heating a room or even a small house is a wall heater. Simpler than central heating systems, wall heaters do not require pipes or ducts, because heat flows from them directly into a room. They can easily be installed on an outside wall, where fumes are vented out and air for combustion is brought in. The most efficient models are not as efficient as the most efficient furnaces, but they do reach 75% to 80% efficiency, and are much cheaper than furnaces or boilers.
Electric furnaces and boilers. In general using electricity for your heating consumes more total energy and is more expensive than other options. It’s easy to understand why when you think about the energy losses at the power plant and in transmission lines. Depending on local rates, the cost of electric heating can be double that of natural gas and is higher than oil. If you generate your own electricity from solar panels on your roof, however, the equation changes.
Heat Pumps. Also called heat exchangers, these devices combine heating and cooling into one function. “Air-source” heat pumps are most cost- and energy-efficient in warm climates that need a lot of air conditioning and little heating. (They use a lot of energy when it gets very cold.) “Ground-source” heat pumps can work well in larger homes that need a lot of heating and cooling in equal measure. Neither system makes sense in homes where little or no air conditioning is needed. For more information on this option, see our heat pump article.
Electric baseboards and space heaters. While cost of electricity is higher than the alternatives, the upfront cost of some types of electrical heating equipment is low. Baseboard electric heaters, for example, cost only a fraction of a new boiler, furnace, or heat pump–even when they require installation of their own electrical circuits. That could be a decided advantage for those who cannot afford a large cash outlay for a heating system.
Radiant systems. Some heating systems use electrical heating cables or tubing that contains water heated by a boiler. In new construction these cables or tubes are usually embedded in a concrete, tile, or a specially designed wood floor. (Carpet floors do not work as well because they insulate, keeping some heat out of the room.) Radiant systems can provide a greater level of comfort at a lower thermostat setting because heat, which naturally travels upward, is widely dispersed throughout the room rather than concentrated near a radiator or register. Wall panels can also be used.
Two other advantages of radiant systems:
- They can bring differing amounts of heat to different rooms.
- Those that use water (“hydronic systems”) can also be used for air conditioning in the summer for cooling.
Depending on your situation, installing some radiant systems can be costly. While a conventional forced-air furnace would typically cost $2,000 to $7,000, a radiant system would run $9,000 to $22,500, with adapting the system to an existing home at the higher end. Putting a hydronic radiant system under an existing concrete floor involves putting a new layer of flooring over the slab. With a wood floor, it requires installation from below. Because of the high cost of electricity, electric radiant systems are typically installed in smaller spaces. A professionally installed electric system in a bathroom, for example, might run $400 to $700.
Solar heating. As long as you have a sunny climate and a side of the house that faces no more than 30 degrees from direct south, you can enjoy large amounts of free heat from the sun in winter. If you invest in solar collectors, you can also use sunny areas of the yard or on the roof to tap this resource. The strategies in existing homes include
- adding efficient south-facing windows. Generally, the area of the windows should be about 7% of the home’s floor area for maximum efficiency.
- using flooring materials near windows that absorb and store solar heat, such as dark-colored concrete or tile. Alternatively you can capture solar heat in south-facing windows with a “trombe” wall made of dark-colored concrete set behind glass. At night, insulating shutters or drapes can help retain the heat.
- building an overhang or add an awning on the south side of your house that minimizes direct sunlight in the summer, when the sun is high in the sky, and maximizes it in winter, when the sun is closer to the horizon. Planting a leafy tree also does the trick. In the summer, the leaves will block the sun but in the winter, the sunlight will enter your home.
- adding solar collectors on your roof or in your yard. These devices collect heat from the sun in pipes filled with either air or a mixture of antifreeze and water, which is brought into the house with fans or pumps. Depending on design and location, such collectors can provide up to 70% of a home’s heating. Their cost can range from $100 for a do-it-yourself air heater for one room to $25,000 to $100,000 or more for contractor-installed solar collectors for the whole house.
An efficient heating system keeps your home comfortable and your air clean.
…to your wallet
Sensible management and maintenance of your heating system can lower your energy bills significantly for a minimal investment. New high-efficiency models can save you hundreds of dollars every year.
…for the planet
The less energy we use in our homes, the lower our emissions of global warming gases and other pollutants.
Supersizing. Millions of homes have larger heating systems than they actually need, and these misfits can be costly upfront and long-term.
- Ask about rebates. Check www.dsire.org for state, local, utility, and federal rebates and other incentives for energy efficient heating systems.
- Installation of heating systems is definitely not a do-it-yourself project for most homeowners It requires the skills and experience of a professional contractor. For general advice on what questions to ask contractors and other tradespeople, see our “What to Ask Your Contractor”article. Some other tips for dealing with heating contractors:
- Don’t hire a company over the phone that won’t send a technician to your home for an on-site review.
- Don’t use any company that tries to sell older equipment or seems to be dumping equipment by offering big discounts.
- Ask the contractor to estimate the annual energy costs for the equipment they are proposing.
- Ask for a bid in writing that specifies the equipment to be installed, the work to be done, and the total price, including labor costs.
- Get more than one bid, and don’t jump at the lowest price. Better contractors may charge more, but if they do a better job with a better system, you will save in the long run. Be wary of ultra-low bids, especially if they omit routine services and warranties, or even worse, seem to be an attempt to dump inferior or outmoded equipment.
- Ask if your contractor uses the Manual J® residential load calculation procedure, which includes measures of your home’s insulation, air leakage, building layout, window type, number, and location, shade, and the condition of duct systems-as well as the efficiency rating of the equipment itself. This is the best way to figure out the proper size of your system.