CHAPTER 5
Home Is Where the Heat Is
What's the use of a fine house if you haven't
got a tolerable planet to put it on?
—Henry David Thoreau
Americans emit more carbon dioxide into the atmosphere by heating and cooling their homes than by any other single activity besides driving their cars. All told, residential heating and cooling systems in the United States emit about 500 million tons of carbon dioxide into the atmosphere each year. That's equivalent to the emissions of more than 100 midsized coal-fired plants.
All these emissions from heating and cooling also cost a lot. Most American households have annual energy costs of roughly $2,200, half of which goes toward heating and cooling. It is not uncommon, especially in colder climates, for the heating bill to make up two-thirds of a household's total energy expenditures. And many homeowners, especially those in larger, older houses, greatly exceed the national average, which includes condos, apartments, and other small dwellings.
The good news is, no matter where you live or what size home or apartment you have, you can reduce your emissions from heating and cooling and save money at the same time. A number of easy steps can pay quick dividends, lowering emissions and costs. And beyond these initial steps, various kinds of retrofitting can reduce heating and cooling emissions even more, making it possible to achieve a good portion of our suggested 20 percent reduction in your overall emissions in this category alone.
Figure 5.1 Emissions from Heating and Cooling
Household energy use accounts for roughly one-third of your total carbon dioxide emissions, and, on average, more than half of household emissions derive from heating and cooling. Source: UCS modeling.
In chapter 4, our first recommendation, given that most Americans are very dependent on their automobiles, was to purchase a more energy-efficient car. When it comes to heating and cooling, however, the same logic does not apply. It may well be time to replace your aging furnace or central air-conditioning system with a more efficient model. But most American homes are so leaky and energy inefficient that you can begin by taking some simple steps to address that issue. They won't cost a lot and will reduce your emissions right away.
The key is that it's not just a furnace or an air-conditioning system that keeps you and your family at a comfortable temperature; it's the whole house. In cold weather, a house functions as a building-sized blanket, offering insulation from the freezing temperatures outside. In hot weather, a home shields you from the worst of the heat and humidity outside.
The benefit of considering your whole house as an energy system is that we have long known that by building homes in smart ways and with enough insulation, we can greatly reduce heating and cooling costs. Homes that prove this have been built for many decades. Engineers at the Massachusetts Institute of Technology constructed a number of demonstration homes in the 1950s—more than a half century ago—that showed indisputably that solar energy alone could provide the bulk of a home's space-heating and water-heating needs, even in the Northeast, with its often cold temperatures and cloudy days.
The oil crisis of the 1970s spurred much more innovation in efficient building techniques. Among the projects undertaken were many varieties of so-called passive solar houses—well-insulated homes that used no solar photovoltaic panels but rather captured the sun's energy by means of the house's orientation, insulation, and window placement. In the early 1980s, a federal government study closely monitored the energy usage in some 70 passive solar homes that had recently been built. The study confirmed that heating these houses cost an average of 70 percent less than heating comparable conventionally designed homes. In 1979, an enterprising contractor named Eugene Leger built a nonsolar, conventional-looking home in East Pepperell, Massachusetts, using large amounts of insulation to save on heating costs. Leger's “superinsulated” home deservedly garnered a lot of attention for its annual natural gas heating bill of just $50 (about $160 in today's dollars).
Since those early successes, much more progress has been made in the United States and around the world in energy-efficient building techniques.
Take, for instance, the “tale of two houses” built in Lakeland, Florida, in 1998—one of scores of similar efforts around the country. To evaluate the potential of the latest green building techniques at the time, the Florida Solar Energy Center, a research institute of the University of Central Florida, built two homes side by side. Each was constructed by the same builder with the same floor plan and the same basic amenities, including air-conditioning. One of the homes, however, was the builder's standard model, while the other made use of energy-efficient materials and design. The energy-efficient house included more wall insulation, a white roof, a solar water heating system, a high-efficiency heat pump for heating and cooling, and a 4-kilowatt photovoltaic system, among other features. When the homes were completed and occupied, energy usage at each was monitored closely. After a year, the energy-efficient home's consumption from the electric grid was found to be 92 percent lower than that of the conventional house next door. Although the efficiency and solar features added substantially to the construction cost, the experiment demonstrated the potential to radically reduce home energy usage with today's technology.
UCS Climate Team FAST FACT
We already have the technology we need to dramatically reduce emissions from heating and cooling in most residential and commercial buildings in the United States. If we committed ourselves to this task on a national scale, we could ultimately eliminate roughly 1 billion tons of carbon dioxide emissions into the atmosphere-enough to close roughly 215 polluting coal-fired plants.
As these examples show, we have the technology we need right now to sharply reduce costs and emissions from heating and cooling in most residential and commercial buildings in the country. If we committed ourselves to the endeavor on a national scale, we could eliminate upward of 1 billion tons of carbon dioxide emissions into the atmosphere per year, which would allow us to shutter roughly 215 average-sized coal power plants altogether. Best of all, we would sacrifice nothing in the way of comfort; we could live and work in the same places we do now and be every bit as warm in the winter and cool in the summer.
Right now, in every part of the United States, from Maine to southern California, people are building new homes and retrofitting old ones to use little or no fossil fuel for heating and cooling. These “deep-energy-reduction” and “zero-net-energy” homes establish a new standard and an exciting goal that we can all move toward. Of course, they entail some substantial upfront expenditures. But the benefits are real and enticing: these buildings will virtually eliminate almost all heating and cooling costs—and emissions—from now on. Period.
Investing in Energy Efficiency
The potential of deep-energy-reduction houses provides a helpful yardstick to measure the changes each of us could make in our own homes. We conventionally talk about the “payback period,” the length of time it will take for the savings from improvements in energy efficiency to cover the upfront cost. This technique is helpful for prioritizing particular improvements. But a better way to think about these projects is as an investment, pure and simple. After all, the improvements do more than simply recoup the initial costs; most continue to pay dividends in energy savings for as long as you own your home and even make your home more valuable and desirable when it comes time to sell.
Few of us can choose to drive our heating and cooling costs to zero all at once. But no matter what our personal circumstances are, each of us can take steps toward energy efficiency that will make a big difference. If you have any doubts about that, just ask Anthony Malkin. He oversaw a retrofit job, completed in 2010, that reduced his utility bill by nearly 40 percent.
In Malkin's case, though, that 40 percent reduction resulted in a yearly savings of $4.4 million in energy costs. That's because the building he retrofitted was the Empire State Building in New York City.
By employing up-to-date, energy-efficient materials and design, Malkin (whose firm manages the Empire State Building for a holding company) was able to adapt a 1930s energy hog of a skyscraper into one that ranks among the top 10 percent of all buildings in the nation for energy efficiency. And through this single effort, the Empire State Building's annual emissions of carbon dioxide will be reduced by more than 100,000 tons.
Granted, with some 2.7 million square feet of space, the building Malkin oversees is a bit bigger than your home. But the principles are exactly the same. Malkin's retrofit included installing heat reflectors behind the building's radiators and replacing windows (some 6,500 of them). He invested $18 million in energy efficiency. But not only will his investment be repaid in energy savings in the first four years, it will continue yielding significant economic and environmental dividends for decades to come.
UCS Climate Team FAST FACT
A 2010 retrofit of the Empire State Building in New York City, including replacement of the building's 6,500 windows, resulted in a 40 percent reduction in energy usage, saving $4.4 million-and 105,000 tons of carbon dioxide emissions-annually. The job will recoup its costs in just four years and continue to pay dividends in energy and emissions savings for decades to come.
To understand the power of Malkin's investment, look at it from a 10-year perspective. Even if energy costs stay flat (a highly unlikely assumption), Malkin will have turned his $18 million investment into $44 million worth of energy savings a decade from now—$44 million he would otherwise have had to spend. From that perspective, Malkin earned an annual return on his investment of more than 9 percent, or nearly $12 million more than he would have made from a 10-year bond yielding a 6 percent annual return. Plus, he modernized his building, making it even more attractive to tenants. Malkin understands all this, of course. He says he is happy for the environmental benefit, but he emphasizes that the changes made sense on purely economic grounds. As he put it, “It would have been bad business not to do this.”
What You Can Do
Starting right now, you can make changes large and small to lower your carbon emissions from heating and cooling. The job begins by assessing your home heating and cooling systems and gauging their current level of energy efficiency.
Step one is to amass some basic information, starting with your utility bills and basic information about your home. What kind of fuel do you use to heat and cool your home? How much do you spend each year? Is your home insulated? Are your home's heating and cooling units efficient and up-to-date? The answers to these kinds of basic questions will start you on the path to energy savings.
To a large extent, the answers to basic questions about the way each of us heats and cools our home depend in part on where we live. While natural gas is the most commonly used fuel for heating nationwide, there are significant regional variations. In the South, for instance, electricity is used for nearly all cooling and for heating in 44 percent of homes. Home heating oil is hardly used at all except in the Northeast, where it is used in some 36 percent of homes. Interestingly, though, despite the regional differences in types of fuel, households in each part of the country spend (very roughly) the same amount for heating and cooling.
Figure 5.2 Household Heating Systems in the United States, by Type
Natural gas is the most common fuel for heating homes in the United States, but different regions of the country have widely different profiles. The “other” category includes homes heated with wood, propane, and renewable sources such as geothermal heat pumps and solar energy.
Source: Adapted from U.S. Department of Energy, EIA.
Natural gas, the most commonly used fuel for furnaces, boilers, and water heaters, has generally lower carbon dioxide emissions than other heating fuels. When it comes to electricity, however, emissions vary tremendously, depending on whether the electricity is produced by burning coal (which emits the most carbon), oil, or natural gas. Electricity produced from renewable energy sources, of course, has the lowest emissions. We'll look more closely at electricity in the next chapter, including ways to buy green energy.
The next step is to assess your home's energy efficiency. The best way to do this is by arranging for a professional home energy audit, which can provide specific information about where the house is losing its heated or cooled air and what are the cheapest and easiest efficiency projects you might undertake. A professional energy audit can often be done free of charge or at a greatly reduced rate through your utility company or state energy office. If a free energy audit is not available, try the federal government's locator tool for energy-efficient builders in your area, most of whom could conduct an audit. Listings are available at www.energystar.gov.
There are also ways to get a sense of your home's energy efficiency on your own. One crude method is to tally up your energy bills for the past 12 months and divide by the square footage of livable space in your house (excluding your unfinished basement or attic). If you find that you—re spending anywhere near $1 per square foot on total household energy, very likely you can do a lot to increase your energy efficiency. Some of the most efficient homes today have annual rates closer to 10 cents per square foot. Of course, fuel costs vary enough that you should not rely on this method as anything more than a very rough gauge.
More precise assessment methods can be found online. One offered by Efficiency Vermont, a Vermont-based energy efficiency agency, for instance, follows much the same method as outlined above but with a downloadable worksheet that helps convert your utility bills to compute how many Btu (British thermal units) your house uses per square foot.
A website with a notably different approach was developed at the Lawrence Berkeley National Laboratory in conjunction with the U.S. Department of Energy. This website (http://hes.lbl.gov/consumer) walks you through a series of questions about your home's location and age, the kinds of windows and insulation it has, and so on. On the basis of the information you provide, the online calculator estimates how much you spend on energy and also how much you could save from energy efficiency improvements. This more sophisticated approach is helpful if you have accurate information about your house, but if you don't, you can still get a reasonable estimate of your home's efficiency from one of the simpler tools listed above.
Having good information about your home's efficiency will help you decide how to reduce your heating and cooling emissions. The best ways to do this will depend on many factors, including the age of the house, the amount of insulation it has, and the age of the heating and cooling units. If you rent your living space, your choices for improvements will be more limited; after all, you—re not going to replace your landlord's furnace to lower your heating bills. Still, there are a number of improvements that may be worth making, especially if you are paying the utility bills and care about lowering your emissions.
Broadly speaking, there are three overlapping strategies you can employ:
- Changing your heating and cooling practices
- Reducing heating and cooling losses by tightening up and insulating your house
- Upgrading your heating and cooling systems
We will consider these strategies separately to highlight some of the specific reductions each one can offer.
Upgrade Your Thermostat—and Your Thinking
Let's start by addressing your heating and cooling habits. Do your thermostat settings accurately reflect the way you use your home? Are you needlessly heating or cooling the house while you are away or asleep? A programmable thermostat will allow you to set the temperature in your home to reflect your needs throughout the week, and installing one is very easy—you can probably do it yourself. This is one of the least expensive and most cost-effective steps you can take to lower your carbon emissions.
According to the latest available figures, only about one-third of the homes in the United States have programmable thermostats; if you don't have one, we urge you to make this modest investment, even if you rent your apartment but pay for utilities. Some of the latest models are Wi-Fi enabled, allowing you to control your home's heating and cooling from your laptop or smartphone; one new model from a California-based startup called Nest Labs even includes sensors to tell when you are in the house and claims to automatically learn your habits and adjust accordingly.
For many years, books and websites on energy efficiency have touted programmable thermostats as a way to save 15 percent on home heating bills. But those savings can be realized only if occupants actually use the device to lower the heat (or reduce the cooling) while they sleep or are away from home. It sounds obvious, of course, but the data indicate that a significant portion of people who have programmable thermostats don't take full advantage of their potential.
A much-discussed study in 1999 surveyed heating and thermostat use by residents of some 300 single-family homes in Wisconsin. While roughly one-third of the homes surveyed had programmable thermostats, study participants who did have them reported hardly any energy savings from them. Why? Follow-up interviews determined that many of those who had the devices weren't programming them to substantially lower the temperature at night, and fewer still were using them to lower the temperature while they were away during the day.
More recently, research by the U.S. Environmental Protection Agency (EPA) has found that even though roughly half of all American homes are empty during the day, nearly 60 percent of residents report leaving the heat or the air-conditioning on while they are away during working hours, and only 46 percent report adjusting their thermostats for the hours when they sleep.
Some people mistakenly believe that heating their house at a constant temperature around the clock takes the same amount of energy as bringing the temperature back to a comfortable point after the thermostat has been adjusted. For virtually all types of heating and cooling and all housing types, that is emphatically not the case. All you'll do by running the furnace or air conditioner while you are away is heat or cool the furniture. Your pets won't mind slightly cooler or warmer temperatures either.
Many people who leave their heating system or air conditioner at a constant setting would probably reconsider their habits if they realized how much money they could save. As a rough rule of thumb, each degree Fahrenheit that one adjusts a thermostat downward (for heating) or upward (for cooling) yields a 1 percent saving in heating or cooling costs over a seven- to eight-hour period, with a comparable reduction in carbon emissions.
During winter, in other words, if you lower the thermostat from 68 degrees Fahrenheit (a comfortable temperature during the hours when you are using your home) to 60 degrees for seven hours during the night and for the eight hours you are away during the day, you will lower your heating bill and heating-related emissions by about 15 percent. Considering that the average American spends about $1,100 on heating annually, this simple action can save you $180 this year alone while reducing your carbon emissions by more than half a ton. (If you have a big home in a northern state, you could save considerably more.) Best of all, you'll be every bit as warm as usual during the waking hours you spend at home.
A similar rationale applies for cooling. A setting of 78 degrees Fahrenheit is optimal during the hours you are occupying your home, and the EPA recommends settings of 85 degrees when you are away during the day and 82 degrees (or higher) during the night.
So, if you don't have a programmable thermostat, perhaps this analysis will encourage you to purchase one right away. Do it to lower your emissions, or do it because it will pay for itself within a few months and continue to save you money for years to come. And if you are one of the millions of Americans who have a programmable thermostat but have never bothered to set it correctly, now is a perfect time to do so. If you aren't sure how, you can find step-by-step directions on the Internet for almost every model. If you—re reading this book at home, seize the moment right now: head over to your thermostat and program it to work to its maximum potential. If it is already programmed, try adjusting it by a few more degrees for additional reductions in your carbon emissions. You can use the money you'll save to give yourself a reward. Or, better yet, invest the money in additional energy efficiency improvements to drive down your emissions even further.
UCS Climate Team FAST FACT
You can save 15 percent or more on your heating and cooling costs and lower your carbon emissions by more than half a ton annually just by using a programmable thermostat to adjust your home's temperature during the night and while you are away at work during the day.
While we're on the topic of heating and cooling habits, we should mention that another good way to reduce heating and cooling emissions is to heat or cool only the part of the house that you are using. It doesn't make much sense to heat or cool rarely used guest rooms and storage spaces. This “heat only what you use” attitude is widespread in many other parts of the world. In Japan, for instance, even affluent households heat only the main living area. In the bedrooms, small space heaters are turned on only when needed. This practice is one of the reasons Japan's per capita carbon dioxide emissions are half those of the United States.
If you heat with radiators, shut them off in rooms that aren't being used. Small electric space heaters are a good way to heat little-used rooms; just be sure to use them judiciously and to buy a model that automatically shuts off if it tips over, to avoid a fire hazard. Similarly, a room air conditioner can be turned on to cool an unused room only when guests arrive. Depending on the type of heating system you have, it might be worth retrofitting to create separate zones with their own thermostats so you don't have to heat the whole house when you are using only part of it. Ask your plumber or energy auditor if this is feasible in your home.
Tighten Your Home: a.k.a. Don't Heat (or Cool) the Neighborhood
Now that you've adjusted your thermostat, it's time to take the next step: eliminating the air leaks in your home. Doing this is easier—and more effective—than it sounds.
Hot air leaking out of our homes in winter and coming in during summer wastes more energy than most of us would ever imagine. Even in reasonably tight homes, air leaks may account for 15 to 25 percent of the heat our furnaces generate in winter or that our homes gain in summer. If you pay $1,100 a year to heat and cool your home, you might be wasting as much as $275 annually. Do you really want to use that much energy to heat and cool your neighborhood? You wouldn't try to hold water in a leaky bucket, and you wouldn't keep trying to blow up a balloon with holes in it. But that's exactly what each of us does when we pump heated or cooled air into a leaky house.
By one estimate, an average unweatherized house in the United States loses as much air as it would if a good-sized window were left open year-round. Another estimate, by the American Council for an Energy-Efficient Economy, puts a dollar value on all this lost energy, estimating that each year in the United States about $13 billion worth of energy in the form of heated or cooled air escapes through holes and cracks in residential buildings.
Depending on how your home is constructed, you may be able to quickly reduce your carbon emissions and save money simply by caulking, sealing, and weatherstripping all seams, cracks, and openings to the outside. In fact, dollar for dollar, plugging these leaks is likely to be one of the most cost-effective energy-saving measures you can take.
Many home improvement books and websites offer detailed tips on how to seal a home, but the following chart shows where the leaks come from in most homes.
As you can see from the chart, air finds many places to escape. A lot of hot air leaves a house through the attic, especially if it's uninsulated. Ducts can be big culprits, as can the gaps where plumbing pipes come up from an unheated basement. And if your home has a fireplace, your chimney can suck vast amounts of heated or cooled air straight up to the outside, especially if the damper is left open or doesn't close snugly. (See the box for ways to make a fireplace tighter.)
UCS Climate Team FAST FACT
Some $13 billion worth of energy in the form of heated or cooled air escapes through holes and cracks in residential buildings, according to one reputable estimate. Put another way, as much as one-quarter of the carbon dioxide emissions from heating and cooling your home are caused by your furnace or air conditioner working extra hard to heat or cool your neighborhood.
Figure 5.3. Where Air Escapes from Your Home
Shown here are the greatest sources of air leaks in the average home. A major source, in homes with fireplaces, is an improperly damped chimney.
Source: EERE, 2009.
A good professional energy audit will show exactly where your home is leaking air. Auditors often use an infrared detector to see where heat losses are occurring. Also common is a test aptly known as a blower door test, in which a strong fan is sealed into a doorway to pull air out of your house. This depressurizes the space inside, causing outside air to flow in through all the cracks and crevices. The energy auditor can then tell where the leaks are by feeling for air flow with her hand or by using a “smoke pencil,” which visually shows air currents. Then she can advise you on which home sealing jobs will be most cost-effective to do first.
ASK THE EXPERTS
Does My Fireplace Contribute to Global Warming?
Yes, but perhaps not in the way you think. Burning wood creates higher direct carbon emissions than any of the major fossil fuels, but its overall carbon profile depends on the sustainability of the wood sourcing.
Even without considering the carbon equation of the actual wood burning, the traditional fireplace is a global warming problem because it loses more heat from your home than it creates. According to the U.S. Department of Energy, a blazing fire can send 24,000 cubic feet of air per hour up the chimney, along with about 90 percent of the heat produced by the fire and some of the heat produced by your furnace. And most fireplaces are a big source of air leaks when they're not in use.
Luckily, if you love the cozy feel of a fire, there are several good ways to increase your home's energy efficiency and reduce the pollution created by traditional wood fires. One option is to fit a woodstove (or gas stove) insert into your existing fireplace. These units usually have a tempered glass front so you can see the fire burn. But unlike a traditional open fire, they actually heat your home. And because they burn so much hotter, they create far less air pollution. If you don't want to purchase an insert, you can still reduce your carbon footprint for relatively little cost by installing tempered glass doors in front of your fireplace and making sure to keep them (and the flue) firmly shut when the fireplace is not in use. Or, if you use your fireplace rarely or not at all, you can put inflatable inserts into the chimney to seal air leaks.
If you are a do-it-yourself type, basic weatherizing is pretty easy. You can do your own low-tech test for air leaks by carefully walking around inside your home on a windy day; some efficiency manuals suggest holding a lit incense stick as you go, paying special attention to windows, doors, electrical boxes and outlets, plumbing fixtures, ceiling light fixtures, attic hatches, and other locations where there may be an air path to the outside. Wherever the smoke stream indicates a draft, you have found an air leak that can be caulked, sealed, or weatherstripped.
One dedicated homeowner in Montana named Gary Reysa closely documented his efforts in 2010 to cut his carbon emissions and overall home energy use in half. Sealing air leaks was one of Reysa's first priorities. In an online account of his efforts, he reports that he spent a total of about $50 on tubes of good-quality caulking and cans of polyurethane foam; he then spent about eight hours one weekend sealing air leaks. His onetime effort (augmented perhaps by his subsequently increased attention to energy efficiency) lowered his heating bill for the year by more than $150. If energy prices rise by 5 percent a year (a steep increase but not an unreasonable assumption), Reysa's investment will save him nearly $1,900 over 10 years and, he estimates, will reduce his carbon emissions by roughly 5 tons over the same period. Not bad for a single $50 weekend project.
There are many other strategies to increase your home's energy efficiency, and there are numerous books, articles, and websites that offer advice. We offer here some of the most important steps that have proven effective.
One of the cheapest and easiest strategies for cold climates is to add reflective barriers or insulation behind the radiators in your home, especially those that stand against outside walls. You can find reflective insulation in most home improvement stores. Or you can make barriers from any material that reflects heat: sheets of metal, even pieces of cardboard covered with aluminum foil. Installing reflective barriers was a key component of the Empire State Building retrofit job, and it can be part of your strategy at home as well.
Insulating your home is one of the cheapest and best ways to reduce your heating and cooling emissions. A home energy audit can provide professional advice tailored to your individual needs. If your walls are not insulated, an auditor might advise you to hire a contractor to blow loose cellulose or fiberglass insulation into them. Insulating the basement is a very good idea as well. These approaches are relatively inexpensive, recoup their costs quickly, and increase the comfort of your home immediately.
Even if your home is already insulated, you can probably save money and energy by adding more. One easy project is to add additional insulation to an unfinished attic. Given that rolls of fiberglass insulation cost around $20 each, the job should pay for itself in energy savings within a few seasons. In fact, according to the federal government's Energy Star program, if every American household added insulation to the attic, the nation could save more than $1.8 billion in annual energy costs and keep more than 12 million tons of carbon dioxide out of the atmosphere each year, the equivalent of emissions from some 2 million cars.
UCS Climate Team FAST FACT
According to data collected by the federal Energy Star program, if every American household added insulation to the attic, we would save more than $1.8 billion in annual energy costs and prevent nearly 12 million tons of heat-trapping emissions, equivalent to the emissions from 2 million cars.
In warm climates, you can get a relatively quick return on your investment by turning your roof into a “cool roof,” using materials or coatings that reflect the sun's energy away from the surface. While traditional roofs absorb as much as 95 percent of the sun's energy, cool roofs reflect up to 90 percent. That means they can lower the roof's surface temperature by as much as 100 degrees Fahrenheit, which reduces the heat transferred into the building below. This can be especially helpful in buildings that are not well insulated. The materials for flat or low-slope roofs are mainly bright white, but other cool-roof colors are becoming available as well. Cool roofs can be applied in a variety of ways, depending on your existing roofing material, either on top of your existing roof or as a low-profile coating that is brushed or sprayed on.
According to studies at the Lawrence Berkeley National Laboratory, switching to a cool roof can reduce the energy needed to cool your home by as much as 20 percent. A 1,000-square-foot cool roof could reduce your carbon dioxide emissions by half a ton per year, especially in a sunny, warm climate. In fact, as U.S. Secretary of Energy Steven Chu, a Nobel laureate, noted in 2010, “Cool roofs are one of the quickest and lowest-cost ways we can reduce our global carbon emissions.”
Moving up the ladder in terms of upfront costs, replacing single-paned windows and older frames with double- or triple-paned windows and insulated frames can be a good investment. There is little question about their energy savings. One study found that replacing single-paned windows with double-paned windows and insulated frames could reduce heating costs by 36 percent in a Boston winter and lower cooling costs by 32 percent in a Phoenix summer. New energy-efficient windows are quite expensive, but their so-called low-e coatings (which reduce radiant heat transfer) help keep you warmer in winter and cooler in summer, and energy savings should repay your investment in 5 to 10 years. Lower-cost options include applying sheets of clear plastic tightly over the inside of old windows, hanging insulated curtains or shades, and adding or replacing storm windows.
Upgrade Your Heating (and Cooling) Equipment
Once you have curbed the worst excesses of your heating and cooling habits and taken some modest steps to improve your home's energy efficiency, you may want to consider replacing your air conditioner, water heater, furnace, or boiler with a newer, more efficient model. These changes involve fairly substantial upfront costs, but the energy-efficient replacements will reduce your emissions right away and eventually save you money. Plus, you may well be eligible for tax credits or local utility rebates that can help recoup your out-of-pocket expenses more quickly.
The most important guideline for buying any major heating or cooling equipment is to consider not just the price tag but also the lifetime operating costs: despite their higher purchase price, the most efficient units are almost always more economical in energy costs down the line. It may take a number of years to recoup your initial investment, but in conjunction with better insulation, air sealing, and thermostat settings, today's most efficient equipment can help you cut the energy you use for heating and cooling in half, with a comparable reduction in your emissions.
COOLING
Overall, air conditioners may be the best candidates for replacement because they have become much more efficient over the past 15 years. Top-rated models are now up to 50 percent more efficient than even the current average. Especially if you now have an older, inefficient model, you may be able to replace it with a unit that cools your home using far less energy and with substantially fewer emissions, making the higher price tag worth it. Even an air conditioner with the minimum efficiency allowed by federal energy regulations can reduce your cooling costs and emissions by 20 percent over an older model. Check for a model's efficiency rating, called a SEER rating (seasonal energy efficiency ratio): the higher the number, the more efficient the unit.
UCS Climate Team FAST FACT
Air conditioners have become much more efficient over the past 15 years. Top-rated models now boast efficiency levels up to 50 percent higher than the current average.
If you are ready to replace your air-conditioning unit, you should also consider the even deeper reductions in emissions you could achieve from cheaper, lower-energy cooling choices such as ceiling fans, a whole-house exhaust fan, or, in drier climates, an evaporative cooler (often called a swamp cooler). Even if you still need air-conditioning, these options can greatly reduce the energy you use by allowing you to buy a smaller air conditioner and run it less often. In addition, passive solar solutions, such as planting trees or bushes and installing awnings or shades to keep out the summer sun, can be attractive and cost-effective ways to reduce your need for air-conditioning.
FURNACES AND BOILERS
You should think about replacing your furnace or boiler if it is more than 20 years old, if it has a continuously burning pilot light rather than electronic ignition, if it isn't heating your home comfortably in the winter, or if your heating bills seem particularly high. The kind of heating system you now have—whether forced hot air, hot-water radiators, steam heat, or something else—will most likely constrain your replacement choices. Unless you are undertaking a major remodeling, it is rarely cost-effective to change your entire heating system. Still, replacing your furnace or boiler will give you an opportunity to significantly reduce your emissions and cut your costs in the long run, especially in a relatively energy-efficient house.
Every model of furnace or boiler sold in the United States is given an AFUE (annual fuel utilization efficiency) rating that tells you how much of the unit's energy is converted to heat. (Water heaters have AFUE ratings, too.) The ratings also tell you the projected dollar savings per $100 of your present fuel bills. For example, let's say your current furnace's AFUE rating is 65 percent and you plan to install a high-efficiency natural gas system with a 90 percent AFUE rating. According to the rating data, your projected savings will be $27 per $100. If your annual fuel bill is near the norm of $1,100, then your total yearly savings in energy costs should be about $27 × 11 = $297.
That's a lot of savings each year. And even though a new furnace or boiler will not be cheap, and it will very likely take 10 years or more to recoup the initial purchase and installation costs, you will reduce your heating-related carbon emissions by 25 percent right away. According to the federal government, if just 10 percent of U.S. households replaced their old heating and cooling equipment with properly sized and installed Energy Star–qualified models, they could prevent the emission of some 7 million tons of carbon dioxide per year, equivalent to taking some 1.2 million cars off the road.
WATER HEATERS
Water heaters are responsible for about 15 percent of your home energy usage and emissions. Like air conditioners, they have benefited from successive waves of government requirements for greater efficiency; the most advanced models today are a lot more efficient than their predecessors. If it is time to replace your water heater, look at a range of options, including the highly efficient tankless (or on-demand) water heaters, which quickly heat water as needed rather than keeping it constantly hot in a tank; water heaters that use efficient air-source heat pump technology; and solar water heaters, which can be expensive to install but heat your water with zero carbon emissions and zero fuel costs. All of these options can be more expensive to install than a conventional water heater, but you will have the satisfaction of knowing you—re helping combat global warming, and your investment will be paid back over time.
If you have an older water heater and can't replace it now, you could add a layer of insulation to reduce energy loss. (Newer water heaters have plenty of insulation built in.) In addition, setting the water temperature somewhat lower will save money and energy and can reduce the risk of scalding as well as avoid mineral buildup and corrosion in your heater and pipes. An ideal temperature is 120 degrees Fahrenheit: that's the temperature threshold needed to prevent the growth of bacteria in your hot-water system.
HEAT PUMPS
If you are building a new home or retrofitting an existing energy system, heat pumps are an innovative and energy-efficient technology for both heating and cooling. Like a refrigerator or an air conditioner, a heat pump sends coolant around a loop that goes through two regions of different temperature. The coolant absorbs heat in one region (inside your house, for example) and releases it in the other region (outside). Heat pumps can be set up to reverse direction so that they provide both summer cooling and winter heating.
Heat pumps come in two types.
Air-source heat pumps rely on the difference in temperature between indoor air and outside air. Though relatively inexpensive, they are less efficient when the outdoor temperature drops to freezing or below, so they work best in regions that have moderate winters. These days, more and more central air-conditioning systems include heat pumps.
Geothermal or ground-source heat pumps draw heat from the ground or groundwater beneath a building. They are fairly expensive to install because the piping has to be sunk into the ground, but they use 30 to 45 percent less energy than typical new heating and cooling systems. In the United States, the use of geothermal heat pumps has increased dramatically over the past decade, with more than 100,000 systems installed in each of the past several years.
According to the U.S. Department of Energy, geothermal heat pumps can save a typical home hundreds of dollars in energy costs each year, with the system typically paying for itself in 8 to 12 years. Furthermore, recent policies offer strong incentives for homeowners to install these systems. The Emergency Economic Stabilization Act of 2008 included an eight-year extension (through 2016) of a 30 percent tax credit, with no upper limit, to all homeowners who install Energy Star–certified geothermal heat pumps. Such tax credits and other incentives can reduce the payback period for many homeowners to five years or less, making this efficient technology an increasingly attractive choice for heating and cooling buildings.
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How Do Geothermal Heat Pumps Work?
Geothermal heat pumps (also known as ground-source heat pumps) draw heat from the ground or groundwater beneath a building. About eight feet below the surface, the earth stays about 50 degrees Fahrenheit year-round-cooler than the outdoor air in summer and warmer than outdoors in winter. In a geothermal system, either air or liquid antifreeze is circulated through a loop of pipes buried underground that travels up into the building. In summer, the system carries heat from the building into the ground. In winter, it does the opposite, taking advantage of the earth's natural warmth. In regions with temperature extremes, such as the northern United States, geothermal heat pumps are fast gaining in popularity because they are so energy efficient and environmentally clean.
COGENERATION
Among the other heating and cooling possibilities available to homeowners is cogeneration, in which waste heat from a power plant provides space heating or water heating to nearby buildings—a system sometimes known as “district heating.” Such systems, widely used in Europe, can offer substantial energy savings and emission reductions. In the United States, many large institutions, such as universities, operate cogeneration systems, with steam tunnels heating multiple buildings. But now micro-cogeneration systems (also known as micro-combined heat and power systems) are applying the same principle on a household scale, gaining increased efficiency by converting fuel (normally natural gas) into both electricity and heat in a single process on-site in the basement of a home or an apartment building. Japan and some European countries are well ahead of the United States in introducing these systems, but they are becoming more widely available in the U.S. market. Because they capture waste heat and normally generate electricity from natural gas, they are of greatest value in cold areas where electricity is expensive and natural gas prices are low. As the cost of micro-cogeneration comes down in the future, these systems will become increasingly attractive.
While the wide array of heating and cooling options may seem overwhelming, making changes in this sector can achieve deep reductions in your carbon footprint with little alteration in your lifestyle. Eventually, burning huge amounts of fossil fuel to heat and cool our homes will quite likely come to be seen as one of our nation's most wasteful habits, akin to burning dollar bills in the fireplace to keep warm. Every step we take toward making our homes more energy efficient is another dollar saved from this wasteful practice—another dollar that we will never again have to pay to a utility company or to a foreign country for fossil fuel. More important, every step toward smarter energy design permanently eliminates a major source of carbon emissions without requiring us to curtail our usual activities. Seen from that perspective, the move toward energy efficiency and renewable power in our homes seems more enticing than ever.
Going Deep: Approaching Zero
If you are interested in making deep energy retrofits to your home, bear in mind that the upfront costs will be substantial. With that said, virtually any home can be retrofitted to lower heating and cooling costs almost to zero. A growing number of contractors across the country are offering such services and gaining expertise in achieving deep reductions more cost-effectively.
In warm and cold climates alike, the principle of deep energy reduction is the same: the house must be well insulated and sealed very tightly. In colder climates, the most cost-effective way to do this is to wrap a layer of rigid insulation around the outside of the house, essentially encasing it in a new shell. The advantage of this method is that the inside of the home remains largely untouched, retaining its existing character and finish detail.
The emergence of such deep-energy-reduction building techniques makes this a very exciting and dynamic time for those who want to reduce their carbon emissions and fight global warming. In almost every community around the country, homes and commercial buildings are being designed and built with impressively reduced energy needs.
In one dramatic example, the Cleveland Museum of Natural History in 2011 underwrote the construction of a so-called passive home, based on a building technique known as Passivhaus, pioneered in Germany. This attractive, conventional-looking home has triple-paned windows and walls more than 1 foot thick. Built to strict specifications, the house operates much like a Thermos bottle to insulate it in winter from the freezing temperatures outside. Instead of a furnace, the house needs only two ductless air-source heat pumps (one on each floor), which together consume only as much electricity as two hair dryers. Built in a prominent location downtown on the grounds of the museum, next to the botanical garden, the house was built originally as an exhibit that could be closely inspected inside and out by thousands of visitors. At the end of the special exhibit, the house was moved to a neighborhood a half mile away and sold as a private home.
Along with this exciting example of deep-energy-reduction building, a wealth of other energy-efficient projects and retrofits are being undertaken around the country. For instance, the Southwest Minnesota Housing Partnership renovated 60 dilapidated apartments in Worthington, a rural community in the southwestern part of the state, turning them into energy-efficient, affordable housing. The project, called Viking Terrace, drew on municipal and federal funding as well as low-income housing tax credits to incorporate many energy-saving features into the complex, including a high-efficiency geothermal heating and cooling system that is expected to pay for itself through energy savings in just a decade.
Projects such as Viking Terrace are still far from the norm, however, and require more time and research than projects using conventional construction techniques. On average, many builders say costs for green building now run 5 to 10 percent above conventional techniques. But as green materials and energy-efficient methods become more widespread and as energy prices rise, such projects will be more and more cost-effective.
A wealth of information about green buildings is available from the U.S. Green Building Council, online at www.usgbc.org. The EPA also offers a primer about green building techniques at www.epa.gov, and lists of local contractors who specialize in energy-efficient building can be found online, including a listing at www.greenbuilding.com. For people who want to reduce their global warming emissions and are able to take advantage of emerging green building techniques, this is an excellent time to get started.
Getting to 20
As we have discussed, almost everyone—homeowners and renters alike—can achieve significant reductions in their emissions from home heating and cooling. At the top of the list, two very inexpensive strategies can achieve immediate results. For about $50 you can buy and install a programmable thermostat. And for as little as $15 to $20 you can buy caulking, weatherstripping, or shrink-to-fit plastic to seal air leaks and leaky doors and windows. Homeowners can drive down emissions much further by adding insulation and upgrading to more efficient (or renewable-powered) heating and cooling equipment. All these techniques can help you make substantial progress toward the goal of reducing emissions by 20 percent over the coming year; some of them will most likely be included as we each find our preferred path to meeting that goal.