Cleaner, greener home heating options are abundant, but they’re not all equal. Compare the pros and cons before you decide which should heat your home.
MOTHER EARTH NEWS contributor Gary Reysa's Montana home has a shed (right) that collects and transfers heat to the house (left) through underground water pipes. The garage (middle) is heated by solar hot air collectors.
Heating our homes and businesses is expensive, and doing so is getting more costly each year. As costs rise and climate change complications increase, more and more of us are searching for cleaner, greener and more affordable home heating options. Fortunately, there are many. Choose carefully, however, as not all options are equal. Some greener home heating options rely on nonrenewable fuels, such as natural gas. Moreover, some are ideally suited for new construction while others work best for retrofitting existing buildings.
Before you start shopping for a home heating system, remember that significant gains in comfort and energy savings can be achieved quickly and inexpensively by making your home or business more energy-efficient. Doing so requires a series of relatively simple steps — most important, sealing leaks in the walls, ceilings and floors, and around doors and windows.
To get started, you can hire a professional energy auditor, who will give your home a complete energy physical examination. A home energy audit can also help you determine the exact costs and savings of upgrading your heating system to one of the available options described here. The cost of an energy audit will vary depending on where you live, but it can be $500 or more. (If that’s too expensive, you can do a free online energy survey or a DIY audit — for more information read Home Energy Audits: Measure Your Energy Costs and Add Up the Savings!.
One of the most valuable tests an energy auditor will perform is a blower door test, which determines how leaky your house is. The test will also help you identify where leaks are located so they can be sealed with caulk, liquid spray foam or weatherstripping, depending on their location.
After the building has been sealed up, it’s time to pile on the insulation. Significant energy savings call for generous amounts of insulation that exceed current code requirements. Like caulk and weatherstripping, insulation not only reduces energy bills in winter, it also reduces heat gain in the cooling season, helping you slash your fuel bills while keeping you and your family comfortable.
You can easily add insulation to most attics and under floors lying over unconditioned (not heated or cooled) spaces, such as crawl spaces. You can also easily add insulation to uninsulated walls. Beefing up existing wall insulation is more demanding than adding insulation to an attic, but it can be done. Consult an insulation expert to find out your choices. Also consider installing insulated window shades and using them diligently to stay warm in winter.
While efficiency measures may not be as exciting as a new solar heating system, they are the cheapest, fastest and most sustainable ways to save energy and create a warm home or business. They will not only save you money in fuel bills, but will also reduce the size — and thus the cost — of a new heating system.
After you’ve retrofitted your home for energy efficiency, it’s time to sort through your green heating options. One simple way to have a cleaner home heating system is to install a super-efficient boiler, gas furnace or oil furnace to replace your existing heater. Furnaces are equipped with a duct system that delivers heated air to each room. Boilers provide hot water in homes heated with hydronic heat (baseboard hot water or radiators) or radiant floor heat.
Fortunately, the efficiency of furnaces and boilers has increased dramatically in recent years, and installing a model in the 90 to 94 percent efficiency range is now possible — and can save you a lot of money. If your heater is more than 10 years old, you may save money by replacing it with a newer and much more efficient model.
One of the first features you should consider is direct venting. Direct-vent furnaces and boilers pipe in outside air to a sealed combustion chamber. (Older furnaces suck air from inside your home.) Direct venting offers two significant benefits: It dramatically reduces the potential for indoor air pollution, and it reduces cold air leakage into a home during winter.
You should also select a heater with an electronic ignition instead of a pilot light; the former is considerably more efficient. Be on the lookout for other energy features, including more efficient heat exchangers and condensers. Both will save you money and reduce fuel use and pollution.
Although more efficient furnaces and boilers burn fossil fuels — natural gas, propane or fuel oil — they use less fuel than their predecessors and thus produce much less air pollution. They also tie into existing delivery systems, making installation in an existing home less costly than other options discussed here.
Wood is a renewable resource that’s widely available. Even in cities and towns, homeowners can find loads of combustible material such as tree trimmings and scrap wood. This wood can be used in woodstoves, which are made from welded steel or cast iron. Some woodstoves are double-walled. They often come with a fan that circulates air from around the stove into the room, which is a feature that helps improve their efficiency.
Modern woodstoves are much more efficient and produce much less pollution than their predecessors. The fuel is also abundant, renewable (if trees are planted to replace those that are cut down) and fairly inexpensive, but bear in mind that woodstoves are the most polluting of all renewable energy heaters.
Woodstoves also require a considerable amount of work, especially if you fell your own trees, cut and split the wood, stack it, then haul it into the house. Moreover, a woodstove will need to be cleaned weekly to remove ash. Woodstoves are also the most dangerous of all renewable energy technologies. They can cause burns and house fires if the flue pipe isn’t cleaned regularly or the stove isn’t installed properly.
Another major shortcoming of woodstoves is that they zone heat. That is, they primarily heat the rooms in which they are located. The air in back bedrooms and upstairs rooms may remain cold.
When shopping for a woodstove, look for the most efficient and cleanest-burning model. You may need a permit to install a woodstove, and you also may need to hire a professional. If you install your own, be sure to follow code requirements and manufacturer suggestions very carefully.
Some woodstoves come equipped with a catalytic converter that burns unburned liquids and gases that are released from burning wood. These hydrocarbons contain a considerable amount of energy, so burning them can significantly boost the efficiency of a woodstove. Combustion of gases in the catalytic burner also reduces creosote buildup and the risk of fire. Catalytic converters may require frequent replacement, so check with a woodstove dealer before you invest in this option.
Other woodstoves contain baffles instead of a catalytic converter. Baffles, which are located above the combustion chamber, direct the unburned gases and liquids back over the fire where they can burn. This design helps wring more Btu out of wood and also helps reduce creosote buildup.
To provide more uniform house heat, consider installing a wood-burning furnace that also burns some other fuel — such as natural gas — to provide heat when you’re not home and can’t tend to the fire. Wood furnaces typically distribute heat through a duct system, such as those found in homes heated by forced-air furnaces.
Though outdoor wood furnaces are not as efficient as an indoor stove, many people install them to reduce the risk of a house fire and eliminate the hassle and mess of hauling wood into a home and removing ashes. Outdoor furnaces generate hot water that circulates underground to your home. The hot water circulates through a heat exchanger in the duct system near an existing furnace, from which it is distributed through your home.
One of the most efficient — and least environmentally damaging — home heating options is a heat pump. They come in two varieties: air-source and ground-source.
Air-source heat pumps draw heat out of the atmosphere (even on cold days), concentrate the heat using refrigeration technology, and then distribute the heat through the house, usually through a duct system or through pipes.
Ground-source heat pumps, also known as geothermal systems, concentrate heat from the earth via pipes buried roughly 6 to 8 feet beneath the surface or in vertically drilled wells that typically run a couple of hundred feet deep.
Heat pumps are powered by electricity, but because they extract free heat directly from the air or ground, they are extremely efficient. As a general rule, for every Btu of electrical energy consumed by an air-source heat pump, you’ll get about 3 Btu of heat. For ground-source systems, the ratio is about 1 to 4.
What’s more, heat pumps can be run in reverse, which cools buildings. That is, in summer, these systems extract heat from buildings and dump it into the environment. Ground-source systems can also be equipped with water heaters, so a large portion of one’s domestic hot water can be acquired using heat from the ground.
Heat pumps burn no fossil fuel, although the electricity that powers them may be generated from coal, natural gas or even nuclear power plants. Because no fuel is burned inside your home, these systems do not create indoor air pollution or cause house fires. While both types of heat pumps are suitable for new and existing buildings, air-source heat pumps are far easier — and less expensive — to install in an existing home.
One common type of air-source heat pump that provides heating and cooling is known as a “mini-split,” so named because it contains a central outdoor unit and one or more indoor units that provide hot or cold air, depending on the season. These units are relatively easy and inexpensive to install. They do not require ductwork.
Ground-source systems cost more than conventional heating and cooling systems because of the need to excavate or drill for pipes. They are considerably more efficient than air-source options, however, and can thus be more economical in the long run.
One of the easiest and most cost-effective means of heating a home is a solar hot air system, which is typically used as a supplemental heat source. Solar hot air systems consist of collectors that are often mounted on south-facing walls of homes. In winter, the low-angled sun shines on the collectors and heats them. If the temperature inside the unit reaches 110 degrees Fahrenheit, a small fan kicks on. It draws cool air from the room into and through the collector, where the air is heated and then pumped back into the house. A single hot air collector heats 500 square feet, give or take a little, depending on the amount of sunlight available during winter and the efficiency of the building.
Solar hot air collectors are efficient and fairly inexpensive. Provided you have good carpentry skills and knowledge of home construction, they’re relatively easy to install. You can even build them yourself — read Build a Simple Solar Heater. Check for electrical lines and plumbing in walls before you begin, or hire a professional installer.
Collectors can be mounted on new or existing homes. Solar hot air systems are low-maintenance and long-lasting. They also offer a respectable return on investment, making them one of the most cost-effective green home heating options. Before you purchase a system, however, check with a local installer to determine the size of the system you’ll need, the expected heat output and the economics. One model from Your Solar Home is equipped with a small solar module that produces electricity to power a home with solar-heated air. Other manufacturers’ systems require grid power, though their power consumption is quite small. Solar hot air collectors, if certified by the Solar Rating and Certification Corporation (SRCC), qualify for a 30 percent federal tax credit.
Solar hot water systems are commonly referred to as solar thermal systems. They consist of solar collectors that are typically mounted on the roof of a house, a storage tank (usually located in the basement or a utility room), and pipes that connect the two. Pumps circulate a heat transfer fluid — either water or nontoxic antifreeze (propylene glycol) — through the solar collectors, where it is heated by the sun in the collectors. It is then pumped back to the storage tank, where a heat exchanger transfers the solar heat the collectors have gained to water in a different storage tank. Hot water is drawn from this tank for use in the house.
By adding more solar collectors and installing a larger storage tank, these reliable, cost-effective systems can be used to heat homes. Solar thermal systems can tie into new or existing radiant floor, baseboard hot water or forced-air systems, although special high-temperature collectors, known as evacuated tube collectors, usually must be used to generate higher-temperature water for radiant floor heating.
Solar thermal home heating systems work well in many climates, are quiet and do not contribute to indoor air pollution. They can be installed on new or existing homes and require little electricity to operate their pumps and electronic controls. Many qualified installers can be found in major cities and towns. You can also take solar heating installation into your own hands — see Solar Heating Plan for Any Home.
Although these systems qualify for federal tax credits and sometimes state or local incentives, they do tend to be pricey. Analyze the cost effectiveness carefully.
One of the main drawbacks of solar thermal heating systems is that they produce excess hot water during the sunniest time of the year. Some homeowners divert this heat to pipes buried in the ground alongside the house. Others dump excess heat in a sand pit far from the house. Be careful about installing a system like this in an area with short winters, because if you end up dumping or diverting extra heat, it won’t be a very good investment.
One of the most economical ways to heat a new home is to use passive solar. Passive solar heats homes and businesses without mechanical devices, such as pumps, motors or fans. It requires no pipes and no electricity — just clean, low-angled winter sun that streams through south-facing windows and warms a home gently during winter months. Interior thermal mass, usually concrete floors, earthen plaster or brick walls, absorb heat during the day and release it at night, keeping a home at a comfortable temperature at all times.
Passive solar design should be air-tight and well-insulated. It employs special low-e (low-emittance) windows that retain hard-earned solar heat during winter and repel heat from the outside in summer. Overhangs protect the glass from the sun during summer, which also helps keep buildings cool. (See Passive Solar Design: Creating Sun-Inspired Homes.)
Passive solar homes can supply 50 to 80 percent of a home’s annual heating costs — even more in sunnier locations. It is ideal for new homes, and should be designed into a home from the very beginning. If incorporated, it will save homeowners tens of thousands of dollars over their lifetimes.
Passive solar requires few, if any, additional costs. At the most, expect to pay only 3 percent more in additional costs to build a passive solar home, which is a reasonable price for a lifetime of free heating and cooling.
Although passive solar is inexpensive to incorporate, offers a high return on your investment, and is clean and reliable, adding passive solar to existing homes is much more challenging. One option is to build an attached sun space, such as a solar greenhouse or a sunroom addition. (See Plan the Perfect Sunroom Addition.) Another is to add windows to the south side of an existing home, which opens it up for solar gain.
You’ll find that heating your home efficiently and in a more environmentally sound manner is worth the effort. With so many home heating options, your biggest challenge will be selecting the one you like best. In doing so, you’re helping to combat the costly effects of climate change and create a cleaner, more sustainable future.
Dan Chiras is the author of 30 books and the director of The Evergreen Institute in Gerald, Mo., where he teaches classes on renewable energy and green building.
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