Home Energy-Saving Systems


Even before the era of home energy audits, thrifty homeowners knew the value of caulking drafty window frames.
Even before the era of home energy audits, thrifty homeowners knew the value of caulking drafty window frames.
Harold M. Lambert/Lambert/Getty Images

When you work on your home to make it more energy efficient and less expensive to maintain, you should consider what safety measures need to be implemented as well.

Homes are made up of many different components that work together as a system. If you change one part of that system, the other parts are affected. Ultimately, you alter the way the home functions.

A previously unweatherized house typically has a leaky shell. Air from outside is free to infiltrate and exfiltrate through various uncaulked and unfilled cracks, gaps, and holes in the exterior. When you stop up those leaks, replace old windows, caulk, and fill, thus removing some of the pathways through which air formerly entered the house. From the standpoint of saving energy this is a good thing. The less air that leaves the house, the less heating and cooling need to be produced in order to replace it. But is there such a thing as a house that is too airtight?

The answer is that it really isn't possible to make a house too airtight. It is possible, however, to make it too poorly ventilated. Where is the dividing line? In this article, we'll discuss the equipment or techniques that can help you protect your home's air flow as you make it more energy efficient. We'll even review alternative energy sources to improve your home.

Potential Hazards of Weatherizing a ­Home

Systems in the house require a reliable influx of air to operate properly. Specifically, these are the items that burn fuel on site and then exhaust combustion byproducts outside through a vent or fluepipe, such as furnaces, boilers, water heaters, fireplaces, and gas clothes dryers. If a house is made relatively airtight and not enough combustion air is provided for these fuel-burners, problems can result.

­Here's an example: A furnace or boiler burns fuel in order to heat a house. The fuel (either gas or oil) requires mixing with air in order to combust properly. When the burner on a conventional furnace or boiler fires up, it draws air into a combustion chamber. The air mixes with the fuel, the mixture is burned up, and the exhaust gases are vented outside. Air rushing into the combustion chamber and then up the fluepipe has to come from somewhere. This air has to be replaced, or made up.

In poorly weatherized houses, this "make-up air" can enter through the variety of gaps in the building's exterior shell. Since it's easy for the air to enter this way, such gaps are referred to as "paths of least resistance." But what happens when you start to close these pathways? Where does make-up air come from then?

If you tighten up your home's exterior and do not make provisions to provide the fuel-burning equipment on site with a source of make-up air, the air may be drawn down different -- and less desirable -- pathways. One of these might be the water heater's fluepipe.

For example, a problem might arise when a water heater and furnace happen to operate at the same time. Both demand make-up air. If not enough air is freely available, the furnace can draw make-up air from the water heater's fluepipe. Should this occur, combustion by-products produced by the water heater are vented back down the fluepipe and into the house. This condition is called "backdrafting," and it has potentially dangerous consequences.

Combustion byproducts, such as those produced by fuel-burning water heaters, boilers, furnaces, fireplaces, and gas clothes dryers, contain carbon monoxide gas, a poison that is taken up by the body's red blood cells in place of oxygen. According to the Consumer Product Safety Commission (CPSC), approximately 125 people in the United States die every year of carbon-monoxide poisoning. Some of those deaths are attributed to backdrafting conditions from fuel-burning devices.

Backdrafting can also occur when exterior-vented fan devices operate. A kitchen range hood is a good example, as well as bathroom ventilation fans. Anything that pushes air out of the house reduces the air pressure inside, and make-up air has to come from somewhere in order to replace the air that is lost. The more airtight the house, the greater the potential for backdrafting.

The solution to backdrafting is to provide enough make-up air for fuel-burning equipment to operate correctly. Building codes require a make-up air inlet to be piped into the mechanical room in all new homes. Older homes, however, often lack such a pipe.

Therefore, you should consult your furnace or boiler service person before you do any tightening of your home's shell. It could be that your house already has a make-up-air pipe in place. If it doesn't, one can be easily added.

One more note about fuel-burning items in the home. If you opt to have a furnace or boiler replaced with a new, energy-efficient model, consider paying more for a high-efficiency sealed combustion unit. These systems draw combustion air directly from outside the house. This eliminates the need for a lot of make-up air, though you still might need some for a gas- or oil-fired water heater.

Carbon Monoxide Detectors

To alert you to the possibility that backdrafting or another problem is occurring, every house should have carbon-monoxide (CO) detectors installed. Smoke detectors are required in all homes, but in many parts of the country CO detectors are not. Costing as little as $40 or so, CO detectors can alert you to a potentially dangerous buildup of the colorless, odorless, and tasteless gas.

As described earlier, carbon monoxide found in the house environment can result from improperly burning and venting fuel-burning heating equipment like furnaces, boilers, space heaters, and fireplaces. It can also come from gas or oil water heaters, gas ranges, clothes dryers, and even from automobile exhaust that leaks or is drawn into the house from an attached garage.

The usual recommendation is that a CO detector be placed in or near the sleeping quarters in a house. That way even if you're asleep, the alarm will alert you when the detector picks up the presence of the gas in the house. It is a good idea to place a second detector in or near the mechanical room. Venting malfunction is most likely to occur in this area. Municipal fire departments often have programs that give smoke detectors away for free. Some are starting to do the same with CO detectors.

Other Airtightness Issues

Many people observe that after they have some types of energy upgrading done in their homes, conditions inside change markedly, especially during the winter. One common scenario is that after a homeowner has her or his old windows replaced with new ones, she or he will start noticing excess moisture inside the house -- notably condensation on cold mornings on the inside panes of the new window glass. What happened?

Old windows are usually not very airtight. They allow air to infiltrate the house and also to leave the house. This sets up an uncontrolled ventilation pattern that removes moisture from inside the house (in the form of water vapor) and imports dry air from outside. The result is dry air inside during most of the winter -- a common complaint from those who live in leaky older homes.

Once the old, leaky windows are replaced with airtight new ones, that indoor moisture no longer has a means of escape. It builds up to levels that can create condensation on cold surfaces. Since window glazing is usually the coldest surface in most houses, that's where the condensation shows up first. This is one of the most common complaints to window companies. Customers who thought having new windows installed would rid them of condensation on their windows sometimes find just the opposite to be the case: They're getting more condensation than ever.

The new windows are not at fault. There is simply too much humidity in the house. The solution is to reduce the humidity level inside. After that the condensation is reduced or disappears.

Homeowners who undertake comprehensive air sealing in their homes often find similar problems with moisture buildup. They've cut off the ventilation that diluted the humidity and brought in drier air from outside.

Similarly, an upgrade to sealed combustion furnaces and boilers can lead to issues with excess humidity. The problem lies in the fact that drier outdoor air that used to be drawn into the house by the combustion process in the old furnace is no longer streaming inside. That means the air inside the house is not being replaced with outdoor air. Humid air that was formerly diluted with the incoming drier air is now predominant and condensation difficulties can crop up.

In the next section, we'll review how to protect the air quality in your home.

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Protecting Air Quality

In the absence of sufficient air exchange with the outdoors, indoor air can start to suffer quality problems. Odors from cooking and pets, off-gassing from building materials and furnishings, radon gas, combustion byproducts from gas ranges, and other pollutants can accumulate. Studies reveal that, because we spend approximately 90 percent of our time indoors, exposure to these items can be dangerous -- especially for children, seniors, and those who suffer from cardiovascular or respiratory diseases. The solution is to increase ventilation in order to dilute and exhaust the problem air. Below are some guidelines on how to improve the air quality in your home.

Turn on the Fan

One good way to reduce humidity and air pollutants is to attack the problem of poor indoor air quality at the source. Because bathroom fans reduce the level of indoor humidity by venting water vapor to the outside, be sure to turn on the fan when you bathe or shower. Also, turn on the fan to a kitchen range hood while cooking to vent odors and humidity. This is especially important when you use a gas range or oven. Gas ranges produce combustion byproducts that collect in the house unless vented.

Some range hoods, however, remove only gaseous pollutants like combustion byproducts when they vent to the outside, and many range hoods do not even do that. Recirculating-type range hoods are somewhat effective at removing airborne grease, but they do not take combustion byproducts out of the air.

Whole House Solutions

Air filters, either stand-alone or furnace-mounted, can be helpful in straining dust and dead skin cells (from both humans and pets) from the air, but they are not effective at removing gas-type pollutants.

One of the best methods of reducing the level and impact of indoor air pollutants and excess humidity is to mix the indoor air with fresh, dry air from outside the house. But after you've just spent hours and dollars trying to increase the airtightness of your house in order to make it more energy-efficient, how do you increase the ventilation without reducing the effect of everything you've accomplished?

It's hard to make an older home so airtight that indoor air pollution becomes a major problem -- or at least one that can't be solved by taking one or two simple steps to alleviate the condition. Old houses just have too many places where air can leak out (and outdoor air can be drawn in). You'll never be able to find and plug them all. Newer homes are generally more airtight from the start.

If your house feels stale, stuffy, or excessively humid, simply opening a door or window for a few minutes each day will replace some of the bad air with good air.

Homeowners with children may find that this procedure takes place naturally, as incoming and outgoing traffic continually pumps air in and out of the house. If you need to resort to occasionally ventilating by opening doors and windows, the heat loss will be minimal if you don't leave them open for too long.

For homes with chronic indoor air quality problems that can't be eliminated or reduced by manual ventilation and removing the pollutants and humidity at the source, other means are available to introduce fresh air to your home with minimal heat loss. Heat recovery ventilators (HRVs) use fans to continually bring air in from outside the house. As incoming air enters the HRV, it passes through a heat exchanger that is kept warm by the indoor air exiting the other side. Because the two air streams never mix, the only thing transferred from the outgoing air stream to the incoming one is heat. And while there is not a 100-percent heat transfer, the exchange is efficient enough that the incoming fresh air can be quickly warmed by the home's heating system.

An HRV can be installed either as a stand-alone system or tied into forced-air furnace ducting. The fans, used to pull in and push out the air, are small, but they do use some electricity. Filters can be added to the installation in order to clean the incoming air before it enters the house. An HRV installed correctly should be virtually unnoticeable to the homeowner. There should be little or no noise and the mix of incoming air with the air already inside the house should not create drafts or cold spots. An HRV can also be shut off when it is not needed.

In the next section, learn about alternative energy sources to power your home and ease your utility bills.

Alternative Energy Sources

There is a growing movement in this country toward the exploration of sources of alternative energy -- solar heating, electrical generation, wind power, and hydro power. Alternative energy can eventually be valuable in reducing dependence on fossil fuels on both an individual and a national basis. How many options you can put into practice, however, depends on whether your home is located in an area with suitable conditions for alternative power generation. Below are some alternative energy sources to consider.

Electricity Blowing in the Wind

Large wind-powered generators are being built in many places throughout the country. Wind energy is also a potential source of power for individual homeowners. In order to produce electricity with a wind generator, however, there has to be a reliable source of wind to turn the blades of a turbine. You also need either storage for the power generated on site or a means to tap into the power grid. Connection to the grid ensures that that you can use some of the utility company's power when your wind generator is not producing. When the generator is producing excess power, it can be sold to the utility company. Investment in an individual wind turbine is expensive, even more so for onsite power storage with sufficient capacity to power an entire house.

Running Water

Individual hydro applications are very demanding in their site specifications, requiring a steady source of running water that falls a certain distance. The places where individual hydro power generation can work are few and far between, but in the right location the power is reliable and consistent.

Harnessing the Sun

Solar water and space heating, as well as electrical power generation, offer perhaps the most widespread applications. Many individual solar water heating systems are already in place in this country, and they provide free hot water either year-round or just during the sunnier months, depending on locale. Homeowners also engage the sun's help in heating indoor and outdoor swimming pools. If built with the sun in mind and oriented optimally, many home designs can be adapted to take advantage of passive solar heating -- or with solar avoidance as the primary focus in warmer climates.

Solar power generation has mainly been considered too expensive for anything but remote or portable applications, such as at cabins, on boats, or in recreational vehicles. However, the continual reduction in the price of solar panels and the introduction of new, more easily installed products may persuade more homeowners to look toward the sun as a competitive source of electrical power.

Storage and Buyback

One of the hurdles to the development of alternative sources of energy has been the issue of storage of generated power. In a home setting, large banks of storage batteries take up space and need to be maintained. Plus they need replacement when their capacity to store power has been exhausted.

But the willingness of utility companies to purchase power from individuals with excess power-generating capacity might spur further investment in alternative power systems. The ability to hook up to the grid to tap power when needed and to sell power back to the utility company when possible eliminates the necessity for on-site storage of power and its attendant space, maintenance, and cost problems. Utility companies also benefit from such arrangements. Any electricity they purchase from individuals is electricity they don't have to generate, which might give them the option to forestall building and maintaining additional power plants in the future.

Homeowners also can change the type of equipment they use to heat and cool their homes. Check out those options in the next section.

Alternative Heating and Cooling Equipment

There are ways to save energy in your home that require investments in auxiliary heating or cooling equipment. Some of those options are listed below.

Wood -- a Renewable Fuel

Wood, of course, has been used as a heating fuel for as long as people have been on the earth. In the overall span of that time, only relatively recently have people sought to increase the benefit of wood's heat-producing ability by containing the burning process inside a metal enclosure.

A variety of high-efficiency wood-burning stoves, fireplaces, and fireplace inserts are currently on the market.

Wood can be used as a primary heat source but more often plays a supplementary role to a central heating furnace or boiler. And while burning wood can reduce our dependence on oil or gas, the fact remains that wood has to come from somewhere. You have to purchase it or cut it, split it, stack it, and store it yourself. But for those with access to an inexpensive or free supply of wood, installing and using a wood-burning stove or insert can make a dramatic difference in your utility bill.

Fireplaces -- Not So Efficient

Burning wood in an older, conventional fireplace is not the best way to generate heat; the wood burns uncontrollably and inefficiently. In fact, 90 percent of the heat energy produced goes up the flue, along with a lot of dirty smoke. Worse, this type of fire gobbles up a huge amount of room air that is used to help combust the fuel and convey it up the chimney. That air is drawn into the house from many different places: It leaks through and around windows and doors, and cracks and gaps in the exterior siding and foundation. It is possible to sit in a room that has a roaring fire blazing in an open fireplace, yet still feel a cold draft of air at your back as air rushes toward the fire.

Glass doors on the front of an open fireplace help increase the efficiency, but there is still a lot of heat going up the flue that could better be used to heat the house.

Fireplace Inserts

A cast iron or steel fireplace insert mounted inside an open fireplace provides many of the benefits of a wood-burning stove. The metal radiates heat into the room, an adjustable opening on the front of the insert allows control of the air going into the firebox for more efficient burning, and many inserts are available with glass panels in the doors, which provide a view of the fire. Nearly any open fireplace can be retrofitted with an insert, and the difference in the heat produced is well worth the effort and expense.

Woodstoves

Cast-iron, steel, or stone woodstoves can be both beautiful and efficient. Like fireplace inserts, the metal radiates heat in all directions, the burning of the fire is controlled by regulating the flow of air into the firebox, and many stoves come with glass panels that allow the fire to be seen. A surround made of masonry material can soak up heat while the fire is burning and later radiate it into the house, acting as a heat-storage device.

A drawback to woodstoves is that they take up space in the home and might not be easily added to an existing home. A metal or masonry flue has to be provided for safe venting of the hot combustion gases, so a clear path from the stove to the roof has to be available. Additionally, as with any wood-burning device, hauling wood in and out during the heating season can be messy and might introduce insects into the home.

Stand-Alone Wood Furnaces

Exterior wood furnaces hit the market some years ago, and their popularity continues to rise. A stand-alone unit consists of a small building outside the house that contains a large wood-burning stove. The stove heats a jacket filled with water, which is then pumped into the house through a set of underground pipes. The pipes enter the house and travel to a conventional air handler inside a furnace.

Inside the furnace the water passes through a heat exchanger unit that acts and looks much like the radiator on the front of a car. Water flowing through the heat ex-changer gives up its heat to the air, pushed by the blower fan in the furnace. The heat is then distributed throughout the house through the existing ductwork.

The advantages to such systems are many. They require fueling only once or twice a day and burn large logs that don't require much splitting or cutting. The combustion process takes place safely outside the home. And the mess of hauling, splitting, and storing wood is all confined to the outdoors. The only thing that enters the house from the system is the hot water traveling through the piping. Provided with a source of wood for the winter, a homeowner could heat his or her entire home with such a system instead of just a room or two, as is typical with a woodstove or insert. If retrofitted to an existing HVAC system, the original gas or oil burner can be left in place, providing a convenient backup if, for instance, the occupants are away for several days.

Corn and Pellet Stoves

In areas where field corn, usually used to feed livestock, is available inexpensively, corn stoves are another heating alternative. Corn stoves have a hopper on top or on the side into which bags or bushels of loose corn are deposited. A thermostatically controlled auger shuffles kernels of the corn into a small firebox a few at a time. Inside the firebox a clean, intense fire combusts the corn, turning it into heat that is moved around the room by a small fan.

Homeowners with access to a small field and the means to plant and harvest their own corn or access to inexpensive corn purchased directly from a farmer or grain elevator can generate their own heat economically with a corn stove. Venting the stove can be accomplished via a small fluepipe that can either penetrate the roof or exit through a sidewall of the house. The latter feature can make the installation of a corn stove easier than a woodstove, in some cases.

Bags of corn can be stored in a compact space, can be hauled easily, and don't require any further processing -- unlike the cutting and splitting necessary with wood. Because corn contains oil and ethanol, both of which burn cleanly, only a small amount of ash develops in the firebox. Some corn stoves draw combustion air from outside the house, eliminating the need for make-up air that otherwise would be drawn inside through holes and gaps in the building's exterior shell.

Corn stoves require electricity to operate and thus cannot run during a power outage. However, some have provisions for a backup battery that allows the stove to function in emergencies.

Some corn stoves can also burn pellets -- compressed nuggets of sawmill waste. There are also pellet stoves available, designed only for that use. Corn cannot be burned in pellet stoves. Pellets are available in bags from farm and feed stores, as well as from places that sell wood and pellet stoves. Pellet and corn stoves are also available in fireplace insert configurations.

Masonry Heaters

Unlike open fireplaces, masonry heaters burn wood in an enclosed firebox. The combustion gases travel through a maze of masonry passages where they release their heat. After the fire burns out, heat continues to radiate from the masonry for hours. Masonry heaters are often large and expensive, and some of the ones made with polished soapstone are architectural marvels. Most masonry heaters are built into new homes since placing a foundation under one in an existing home can be problematic. Because of its size, a room or an entire area usually must be designed around a masonry heater.

While many woodstoves restrict the air intake in order to make wood burn longer, masonry heaters are made to accommodate short, hot fires. The heat extracted from the wood is then transferred to the masonry, which then releases that stored heat to the house after the fire goes out.

Swamp Coolers

What if someone offered you the opportunity to purchase a device that would function similarly to an air conditioner at about half the price of a conventional A/C system and would run on a fraction of the electricity? Such a product exists. It's called a "swamp cooler" or "evaporative cooler."

Swamp coolers are designed to be used only in areas where the air is relatively dry, because they add moisture to the air. But in suitable climates, swamp coolers can reduce cooling costs dramatically.

In addition to lower initial costs, swamp coolers operate on less than a quarter of the electricity required by a conventional air-conditioning system. And they run on only 120 volts as opposed to 240 volts, which can cut installation costs further by eliminating the necessity for additional wiring or a possible electrical service upgrade.

Swamp coolers operate by blowing air through wet pads. The air emerges as much as 20 degrees cooler after it passes through the unit. Because particles of air pollutants remain behind on the wet surface of the pads, swamp coolers provide some air filtration as well.

The air is blown into the house, slightly humidified. At least one window must be open when using a swamp cooler in order to allow the air to be blown inside to escape somewhere. There are some window-mounted swamp coolers available, but the usual installation is a whole-house system that can tie into existing or new ductwork. Water can be supplied manually to a holding tank or automatically via a hose or piped connection; consumption averages between about 2-15 gallons per day. Systems can use a thermostat for control purposes, and 2- or 3-stage or variable-speed fans provide precise management of the cool air input.

Maintenance consists of replacing the pads periodically and cleaning the unit. Pad longevity can be extended by ensuring the water sprayed on or dripped through the pads is of good quality. Hard-water minerals can build up on the pads and reduce their capacity for evaporation, thus diminishing the efficiency of the device.

When taking steps to make your home more energy efficient, it's also important to make sure you maintain good air flow and air quality. By following the guidelines in this article, you will keep your home safe, save considerable money, and, equally important, conserve energy for future generations.©Publications International, Ltd.