Energy-Wise Landscape Design: A New Approach for your Home and Garden

By Sue Reed

An inspiring instructional handbook for transforming idealism into social change

The pursuit of freedom and justice is a timeless one, but new activists may not know where to begin, while more experienced ones often become jaded or fatigued. The task of constructing a new society, free from oppression and inequality, can be overwhelming. Tools for facilitating motivation, engagement, and communication can mean the difference between failure and success for activists and social movements.

Educating for Action collects the voices of activists whose combined experience in confronting injustice has generated a wealth of key insights for creating social change. This practical guide explores such topics as:

• Community activism and direct democracy
• Conflict negotiation, communication, and rhetoric
• Law, the educational system, and lifestyle activism
• Social media skills, conference planning, and online organizing

Written in an inspirational tone, Educating for Action consciously straddles the line between street activism and classroom instruction. Bridging the gap between these two worlds makes for an engaging and instructive manual for social justice, helping students, teachers, and larger activist communities turn their idealism into action.

Jason Del Gandio is a scholar-activist and assistant professor of rhetoric and public advocacy at Temple University. He is the author of Rhetoric for Radicals: A Handbook for 21st Century Activists .

Anthony J. Nocella II is a scholar-activist and senior fellow of the Dispute Resolution Institute at the Hamline Law School. He is a long-time anti-racism, youth justice, prison abolition, hip hop, animal, disability, and Earth liberation activist and has published over fifty scholarly articles and book chapters and sixteen books.

• Language: English
• Publisher: New Society Publishers
• Release date: Apr 1, 2010
• ISBN: 9781550924435

Sue Reed

Sue Reed is a registered Landscape Architect with thirty years' experience designing sustainable landscapes that are ecologically rich, energy efficient, and climate-responsive. Sue served for 14 years as adjunct faculty at the Conway School of Landscape Design and has led numerous workshops on the subject of ecological landscaping. Sue is the author of Energy-Wise Landscape Design, for which she also provided much of the photography.

Book preview

Introduction

IF SOMEONE TOLD YOU there was one single way you could:

• Save energy and money at the same time

• Heat and cool your house more efficiently and effectively

• Improve the beauty, utility and value of your property

• Get a big benefit from a small investment, and a solid return on investments you’ve already made

• While also incidentally contributing to a cleaner, healthier environment…

Would you be interested?

Have you been noticing your utility costs rising? Do you wish you could use less gas or electricity without changing your lifestyle or spending a lot of money? Do you want to stop feeling that little twinge of guilt each time you switch on a light or turn up the heat? Well, you’ve come to the right place.

This book shows how we can all save energy, simply by making small changes in the way we design and build our landscapes. The solutions presented here will work in every sort of landscape, whether large or small, hilly or flat, rural or urban. Many of them cost little to do, and some cost nothing at all. But every idea, action, design tip and suggestion in this book will help reduce the amount of energy — your own and the Earth’s — that’s spent on constructing and caring for our landscapes.

Lots of other books, magazines and websites explain how to improve the energy-efficiency of buildings. This is undoubtedly a good idea, but replacing windows, installing a new heating system or renovating a house may simply not be an option for many homeowners. Energy-wise Landscape Design presents hundreds of ways you can save energy, without touching your home or investing in new technologies (although the book does discuss some of those too).

This book explains two basic methods for saving energy. First we can arrange our gardens and grounds so they help keep our homes cool in summer and warm in winter. This is not to suggest that landscaping should entirely replace improving our houses. Rather, landscapes can be intentionally designed to help lessen extremes in outdoor temperature, thereby reducing our indoor heating or cooling needs. When we use plants and the landscape in this way, we also reap additional benefits: we don’t need to make complex decisions or gamble on new mechanical systems that may or may not work as planned, we make no big investment, and we avoid disturbing our living areas. Plus, any plants we use for this purpose generally get better with age rather than breaking down or becoming obsolete, as can happen with equipment.

The second way to save energy takes place in the landscapes themselves. This is the inevitable result of creating landscapes so they’re hardy, resilient, low-maintenance, self-sustaining, long-lasting and undemanding of outside resources. Imagine how much gas you’d save by mowing a smaller lawn or using your own fallen leaves for mulch instead of buying bagged and imported materials. Think about a landscape that’s designed to fit the land well and satisfy multiple needs, so that building it is easy and living in it is even easier. Consider the benefits of using materials efficiently and creating landscapes that endure for decades.

Taking any one of these actions will produce at least modest savings. But imagine the cumulative effect of taking many of these steps. As individuals we’d save serious money and use far less carbon-based fuel. And if a lot of us make just a few of the landscape choices suggested in this book, the energy savings across the country will be vast.

ORGANIZATION OF THE BOOK

This book is divided into seven sections:

• Sections I through IV present ideas for designing landscapes with energy in mind. Sections I and II focus on arranging the landscape to make houses more comfortable in summer and winter, while Sections III and IV provide design ideas for saving energy out in the landscape itself.

• Section V explains how to build and care for landscapes in the most energy-efficient ways.

• Section VI discusses methods for generating energy at the small scale of a home landscape.

• Section VII ends the book with a discussion of energy-efficient lighting.

Each chapter addresses a particular energy-saving goal and includes Actions that explain how to accomplish that goal. Numerous design and construction tips then provide tangible advice for implementing those actions in real-life situations.

THE BOOK’S CONTENT

This book presents ideas for conserving two kinds of energy. First it shows how to reduce operating energy — the energy used in our regular day-to-day functioning — that includes fuel for mowers and machinery, electricity for outdoor lights and watering systems and even the gasoline for our cars. Second, implementing the advice in this book will also reduce embedded energy — the energy used to manufacture and transport equipment and materials — that we consume in our landscapes without even realizing it.

Throughout the book, complex concepts and technical information are distilled down to their essence and explained in everyday language, so they can be easily understood. Specific numbers and formulas are rare. You don’t need to be a professional of any sort to follow the suggestions presented here. All the ideas are described in enough detail so they can be adapted to and applied in a variety of situations.

There are no exact recipes for success in this book. No numbered diagrams to copy and transfer into your own garden. No pretty pictures to imitate. No absolute best or perfect solutions. This is because all home landscapes are unique, no matter how similar they may appear at first glance. Even if two houses are nearly identical and sitting on adjoining twin lots, their landscapes will be different, simply because the larger world will affect them differently.

Shadows, breezes, soils and water patterns; the history and quality of construction; and most important, the lifestyle, family size and personal preferences of the people who live there: these and countless other factors determine how a landscape looks and functions. All situations call for their own unique solution, and all homeowners have their own dreams and notions of home. Any single landscape can be designed in dozens or even hundreds of different ways. This book is merely a guide to achieve any landscape design goal in a way that saves energy.

While the suggestions in this book can work in many different kinds of landscapes, some may be more well-suited to a particular landscape or region than others, or more appealing to some homeowners than others. Certain ideas may even appear to be mutually exclusive or contradictory. The point here is not to suggest you should implement every recommendation in this book. Rather, it’s to remind all of us to be thoughtful about the choices we make, to be aware of their costs and, whenever evaluating a possible action in our landscapes, to consider energy efficiency as an essential part of the equation.

Finally, in addition to helping any individual homeowner consume less energy, the suggestions in this book will also lighten this country’s need to import resources. And many of them will also help improve the health of the natural environment. The most important thing to keep in mind, though, is that these ideas will work for you whether or not you care about politics, the world economy, the environment or going green. This book assumes that saving energy, in itself, is a worthwhile goal.

SECTION I

Arranging the Landscape to Help Cool a House in Summer

THERE ARE MANY WAYS to cool a house. Before the current age of technology, people all over the world kept themselves comfortable, and protected themselves from the extremes of weather and climate, by working with nature. They shaped their homes and landscapes to minimize nature’s harshness and make the most of its beneficence.

However, around the middle of the twentieth century, we modern humans adopted a new comfort-enhancing process, one that has continued essentially unchanged since that time. In total innocence, and without any intent to do harm, we ignored basic, well-understood methods to prevent heat from accumulating in our houses. Instead we put our faith in strategies that would remove the heat after it had already accumulated.

This new approach was made possible by the extremely low cost of energy. In recent decades, it continued in our complete ignorance of the harm caused by producing and using large amounts of energy. And it continues today, even though energy has become extremely expensive, and we know without a doubt that burning fossil fuels damages the environment.

In response to the realities of today’s world, this section of the book explains several ways to keep ourselves comfortable by reducing the amount of heat our homes absorb in summer. Cooler houses are more comfortable, so they reduce our need for fans and air conditioning, potentially reducing a single home’s energy costs by hundreds of dollars each year.

In addition, when a house is cooled during the day, it releases less stored heat back out to the surrounding air at night. This reduces the heat island effect of warm air created around buildings, which might also indirectly help neighbors feel more comfortable and save energy themselves.

This section includes four chapters that show how to help cool buildings from the outside. Wherever you live, arranging the landscape to help cool your house will lower your fuel consumption, utility payments and CO2 emissions, while making your property more beautiful and increasing its real estate value. And it will make any house — whether it’s old and leaky or tight and well-insulated — more comfortable to live in.

The Heat Island Effect

The heat island effect occurs when solar heat radiated from pavement and buildings, combined with the exhaust from cars, factories and air conditioners, raises urban and suburban temperatures 2 to 10°F (1 to 6°C) higher than nearby rural areas. Elevated temperatures can impact communities by increasing peak energy demand, air-conditioning costs, air pollution levels, and heat-related illness and mortality.¹

Designing Structures for Passive Solar Cooling

All of the Actions and Design Tips in this section will be most effective if your house itself is also designed to help deflect the sun’s heat and make the most of cooling breezes. If you are planning to build a new home or renovate your existing home, keep in mind the following design principles for passive solar cooling.

South-facing walls should contain a large number of windows, for greatest solar gain in winter, but these windows should be protected from high-angle midday sun with overhangs, awnings or operable slatted shutters. Please note, this rule holds true only in the cold and temperate regions of the world. In hot regions, north-facing walls should have as many or more windows than south-facing walls, to enhance light and ventilation while reducing heat absorption.

East- and west-facing walls, which receive low-angle sunlight in morning and afternoon, should have few wi ndows. The best way to shade them is with plants.

Windows and vents should be opened to bring in outside air when temperatures are cool (night and early morning), then closed when outdoor temperatures rise. Note that in places where the outdoor air is very humid, or if temperatures don’t get much below 65°F at night, this passive ventilation may not have a significant effect.²

Other methods for ventilation include a solar (or thermal) chimney — avertical shaft, usually dark-colored — that protrudes well above the roof. This stack heats up during the day, creating a draft that pulls air upward, thus producing a breeze within the living space. Note, solar chimneys may also be used to ventilate just a single room, such as a composting toilet chamber, or for pulling air through a geo-thermal heat-exchange system. (See Chapter 20 for more detail about geothermal heating and cooling.) Another method is a whole-house fan, a unit that draws air through the entire house and pushes it out through a vent in the attic.

Low-emissivity (Low-E) window glass, which can prevent heat loss from the house in winter, can also prevent some of the sun’s heat from entering the house in summer. It’s important to select the right kind of Low-E coating to suit your prevailing conditions (is your house in a heating climate or a cooling climate?). Be sure to get complete information from your local supplier and avoid buying windows over the Internet or from distant suppliers who may not provide the most appropriate product.

Reflective and light-colored roofing can significantly reduce cooling costs, but the greatest gain from this action will be found in uninsulated or poorly insulated buildings.

The subject of passive solar design is vast and extensively explained in many books, magazines and websites. See Appendix C for a list of resources.

CHAPTER 1

The Sun and the Wind

THE FIRST TWO SECTIONS OF THIS BOOK show how thoughtful design of the landscape can reduce the energy needed to heat and cool a building. Essential to this effort is understanding nature’s processes. How do the sun and wind move, throughout the day and over the course of a year? How do they affect a building’s temperature and the comfort of the people inside? This chapter explains these basic physical realities, so the advice that follows will make sense and be easy to apply in a variety of situations.

For some of you, this information may be a review of concepts already fully known. For others, it may be mostly new knowledge, or perhaps a reminder about things learned long ago but now nearly forgotten. Whatever your background, this first chapter serves as a vital starting point for the rest of the book.

THE SUN

Civilizations throughout history have paid close attention to the sun’s movement across the sky. Ancient Egyptians built royal pyramids so that chambers deep inside would be briefly lit by a shaft of passing sunlight. Mayans oriented their ceremonial buildings to capture the sun’s rays at certain times of the year. Many early societies linked the sun to their religious beliefs, and used their familiarity with the sun’s place in the sky to guide the growing of food. For both of these purposes — the ceremonial and the agricultural — knowledge about the sun’s location throughout the year was central to early people’s survival.

Now, few among us depend on the sun for the basic necessities of life, and our Western religions pay it no attention at all. We modern humans have lost what used to be an intimate knowledge of the sun. This situation, however, may be about to change. As new technologies make it possible to create electricity affordably from solar energy, as government policies shift to emphasize and support renewable energy, and as we seek ways to reduce our own use of fossil fuels, many of us will become more attuned to the sun and its reliable path across the sky.

Let’s start at the beginning. Contrary to what people believed for thousands of years, and despite the very convincing illusion that the sun is moving while the Earth is standing still, our planet actually circles around the sun. Every year the Earth completes one entire orbit around the sun, and we all go along for the ride. The Earth’s orbit actually takes 365.25 days. To keep our calendars correct, every fourth year we add one day, February 29, and call that a leap year.

Fig. 1.1: We experience summer and winter because our planet’s axis is tilted relative to the direction of its orbit. If the earth’s axis were perpendicular to the its orbit, we’d have no seasons at all.

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As we make this trip, hours of daylight get shorter and longer, from winter to summer and back again. This happens because the Earth is slightly tilted; its north-south axis is not straight up and down relative to its path around the sun. Imagine a spinning top or gyroscope that’s leaning a bit sideways. This is what the Earth looks like as it circles the sun (the main difference being that our planet never falls over, because the spinning never slows down or stops, so far).

Because of this tilted axis, the northern and southern hemispheres (the top and bottom half) get exposed to the sun for different amounts of time, depending on the planet’s position in its orbit. In one part of the orbit, when the northern hemisphere is tilted toward the sun, we have summer in Seattle and Scranton while it’s winter in Australia. Six months later, when the planet has traveled around to the other side of its orbit and the northern hemisphere is tilted away from the sun, people in Chicago are shivering while in Sydney they’re sunbathing. In between these seasons, the northern and southern hemispheres trade spring and fall.

During this year of orbit, wherever we live, all of us are riding the Earth around its own daily rotation. We see the sun rise and set because we ourselves are in motion, while the sun is (essentially) standing still. It’s like taking a ride on a carousel as a child. Remember? Half the time you could see your mom, and then for a while you couldn’t, and then, aha there she was again!

The sun follows a set pattern throughout a year, appearing to rise earlier and set later as we approach the long days of summer, then reversing that process as we move into winter, when the sun rises late and sets early, and the days feel much too short. Then the cycle starts again. This pattern is consistent from year to year, and we clever humans have figured out how to predict exactly where the sun will be at any hour of any day, in any month or season of the year, anywhere we live.

We can, as a society, use this information to do many impressive things. We might power a space station, create electricity in solar thermal power plants or perhaps completely replace our need for fossil fuels. But this book offers a simpler message: we as individuals can use knowledge about the sun to make our living places as energy efficient as possible. To help you get started, the information below explains basic facts about the sun’s position in the sky.

The Sun’s Path Across the Sky

We all sense the sun’s changing patterns, whether or not we pay attention or know how to make sense of them. Are you awakened on a spring morning by the sun beaming into your bedroom, but by summer its rays at the same time of day are shining into a different room? When walking to work, do you see the sun between two familiar buildings and then realize, later in the year, that it’s not there anymore? Have you noticed traffic slowing down on one stretch of road as you drive home from work, because the sun is glaring off car windshields, but a few weeks later traffic flows freely during the same trip?

All day, all year, the sun is up there somewhere, but where, exactly? How can we know or measure its location when the sky contains no reference points? The answer is: we indicate the sun’s position in two dimensions, using the Earth itself as a reference. One dimension is the sun’s compass direction. The second is altitude, or the sun’s height above the horizon.

Yes Virginia, the Earth Is Round.

If you don’t quite believe that our planet is round, here are a few suggestions to help clarify the question:

• Watch a ship disappear over the horizon. If you can watch long enough, you’ll notice: it doesn’t fall off the edge, but rather it sinks gradually out of sight.

• Look at the shape of the shadow that’s cast on the moon during a lunar eclipse. It’s a curve. And the shadow is being cast by what?… the Earth!

• Take a trip on the next space shuttle and look back at where you came from.

Did You Know

If you’re standing near the North or South Pole, the ground beneath your feet is hardly spinning at all. But if you’re standing at the equator, you’re spinning faster than 1,000 miles per hour.

Direction

The sun rises in the east and sets in the west, right? It turns out that this familiar truism is actually true on only two days of the year: the vernal equinox and the autumnal equinox. During the rest of the year, the sun rises and sets just generally east and west.

Here’s what happens. On March 21, the vernal equinox, the sun rises and sets due east and west. After this moment, both sunrise and sunset shift toward the north until June 21, the summer solstice. This is the longest day of the year, when the sun rises as far to the north of east and sets as far to the north of west as it ever will. Then, as the Earth travels around toward the other side of the sun, sunrise and sunset shift gradually back toward the south (if you don’t remember why, see tilted axis discussion above). On September 21, the autumnal equinox, the sun again rises and sets due east and west. It then continues to shift further south until December 21, the winter solstice. On this, the shortest day of the year, sunrise and sunset are as far to the south as they will ever get. (Note: in some years, these dates may vary by one day in either direction.)

This general pattern holds true everywhere on the planet. At any given time of day, however, the exact position of the sun overhead depends on the geographic latitude of the viewer. People in Ecuador see the 9 AM sun shining from a dramatically different direction than a person in Alaska. (All of the suggestions in this book are based on a latitude of 40° north, which will be explained further in Chapter 2.)

Fig. 1.2: The position of the sun in the sky at various time of the year depends on the location from which it’s being seen. This diagram illustrates the sun’s direction as it’s experienced in temperate regions of the northern hemisphere.

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A couple of consistent facts help us understand how to design landscapes with the sun. The first is that, in the northern hemisphere, the sun at noon always shines from due south, and the sun never, at any time of day, shines from due north. The second important point to keep in mind is that, because the summer sun rises so far to the north of east and sets so far to the north of west, it takes a long time to get all the way across the sky, from one end of the day to the other. And in winter the reverse is true; because the sun’s starting and ending points are in the southeast and southwest, relatively close together, the sun spends a shorter amount of time in the sky overhead.

Altitude

The second measurement that tells us the location of the sun is its altitude, its height above the horizon. Sunrise happens when the sun first peaks over the horizon. From that point on, the sun’s altitude above the horizon increases until noon and then decreases until sunset. The shape of its arc across the sky depends entirely on the season: the summer sun sails high overhead; in spring and fall, its arc is a little lower than in summer; and in the depths of winter, the sun doesn’t get very high into the sky at all.

As with direction, the sun’s altitude also depends on the geographic location of the person looking at it or the landscape receiving its rays. Figure 1.3 depicts the sun’s path — both direction and altitude — at 40° north latitude.

Why do we need to know about the sun’s direction and altitude? The sun’s position in the sky affects our lives in many ways. For the purposes of this book, the two significant issues are the amount of heat we receive from the sun and the shape of shadows cast by objects that block the sun.

Knowing where the sun will be in relation to our homes and landscapes enables us to plan the location of trees, fences, shade structures and even the buildings themselves to help keep us comfortable throughout the year. Chapters 2 and 5 present several ways to apply this information, in summer and winter, at specific times of day. If you live at geographic latitude that’s very different from the 40° north used in this book, and you wish to figure out the sun’s exact position for yourself, Appendix A demonstrates how.

It’s especially important to understand the sun’s path at times of the year when outdoor temperatures rise or fall beyond our human comfort range. With this knowledge, we can take steps to work with the sun to help warm our living spaces in winter and cool them in the summer.

Our Human Comfort

All warm-blooded mammals, including humans, need to generate their own heat to stay alive. This is accomplished through the metabolism of food (via digestion). Some of the heat that we produce is used to perform vital tasks — circulation, respiration, metabolism, etc. — that keep our body functioning. At times, though, our bodies generate more heat than they need, and we have to shed this excess heat if we are to feel comfortable.

All mammals have a range of body temperatures within which they can survive and a narrower range of body temperature for optimal health. For survival, human body temperature must stay between about 77°F and 104°F. However, the normal temperature of a healthy human is quite narrow, between about 98°F and 100°F. Luckily for us, we have an amazing ability to regulate our core temperature so it stays in the normal range even when surrounding temperatures reach as low as about 60°F or as high as 150°F.¹

Most of us would not be able to live a normal life at those extremes of heat and cold. While temperature preferences vary greatly from person to person and from season to season, as a general rule we are most comfortable, and most able to shed excess body heat, when the air around us is between about 68°F and 82°F. So, apart from adjusting our home’s thermostat, how do we regulate our body temperature when the surrounding air is too hot or cold? The following discussion explains how.

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Fig. 1.3: Throughout the year, the sun rises and sets in different locations, and it also passes higher and lower across the sky. During the summer solstice, the midday sun is higher than at any other time; the midday sun on the winter solstice is lower than at any other time of year.

How Heat Is Transferred

Heat energy always moves from a warmer entity to a cooler one. This happens because the molecules in warm objects are vibrating faster than the molecules in cooler objects, and nature constantly works to even out this sort of difference, to establish a state of equilibrium. When a higher-energy molecule collides with a lower-energy molecule, a small amount of energy gets transferred from the warmer to the cooler one. The result is that warmer objects cool off a little bit (their molecules slow down) as they give their energy to colder things, whose bumped molecules then speed up and get warmer.

Fig. 1.4: Because radiant energy is transferred by infrared waves, it occurs without any direct contact between two objects.

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What Is a Molecule?

Molecules are the small particles that make up all matter, and they themselves consist of even smaller particles called atoms. A water molecule contains two hydrogen atoms and one oxygen atom (H2O). Oxygen is made of two oxygen atoms bonded together; adding a third oxygen atom creates a molecule of ozone. Molecules are held together by strong chemical/electrical bonds that may be broken under certain conditions.

The following methods of heat transfer — radiation, conduction, convection and change of phase — apply to living beings, including animals and plants, and to inanimate objects such as our house, car and water pipes. Whenever heat is lost or gained, from any sort of being, object or substance, more than one of these methods may be operating at the same time.

Radiation is the transfer of heat through the emission of infrared waves, which can pass equally well through both outer space and our own atmosphere. These waves transfer heat by energizing the molecules of objects in their path. Radiant heat is what we feel when the sun shines on our skin, or when we stand near a fire or sit next to a warm radiator in our house. We ourselves also produce radiant heat, which others standing near us can feel.

Radiant heat is collected in our homes when the sun shines through our windows and transfers its energy to interior walls, floors, furniture, etc. This occurs regardless of outdoor temperature, and can be collected even in winter. (Of course, radiant heat can also be provided by a building’s heating system, via radiators.) Any radiant heat that has been captured and stored in a building during the day will then continue to warm the room at night, through re-radiation, unless it’s allowed to escape back outside toward cooler temperatures.

Radiant heat can be blocked with opaque barriers like walls, shutters, awnings, drapes and the dense foliage of plants. Even translucent window shades and a moderate amount of foliage can reduce the amount of radiant heat entering a building. Radiant heat can also warm the exterior of a building, and if the walls are uninsulated, this heat will be transferred to the interior by conduction.

Conduction is the transfer of heat through direct contact between a warm object and a cooler one. This is the heat that hurts our bare feet if we walk on hot pavement in the summer, or burns our hand if we accidentally touch a hot wood stove. Conduction also happens to our bodies if we take a cold shower: heat leaves our body very quickly, and we shiver in response (shivering, which generates heat, is how our body tries to protect us from too much heat loss). The rate of heat flow by conduction increases with greater differences in temperature between two objects.

Through conduction, the warmer side of a wall (outside in summer, inside in winter) will transfer its heat to the colder side of the wall, resulting in a net cooling of the warmer surface. This is the reason that exterior walls are insulated: to slow or prevent the movement of heat from one side to the other. Shading or sun-lighting the exterior of a building can affect conductive heat transfer by reducing or increasing the temperature difference between the two surfaces.

Convection is the transfer of heat due to the motion of fluid or air. Both water and air become less dense as they’re heated (i.e., their molecules become more dispersed), which causes them to rise. The same process also happens in reverse: water and air sink as they cool. In both cases, the movement generates a convection current, sometimes called a draft, or wind. These currents may also be created by putting pressure on the fluid or vapor, as with forced hot-air heating systems.

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Fig. 1.5: Both this window shade and the foliage of a nearby tree will block the transfer of radiant heat through the window glass. The tree will also help keep the house’s exterior walls cool.

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Fig. 1.6: When objects of two different temperatures come into contact, the warmer object loses heat to the cooler object, causing it to warm up. Given enough time, and no further addition of energy, both objects will eventually be the same temperature.

What Is Infrared Light?

Infrared waves are part of the electromagnetic spectrum, which is the range of all possible radiation frequencies. This spectrum extends from extreme long-wave radiation, such as radio waves, to extreme short-wave gamma radiation. It includes wavelengths that may be thousands of meters long and those that are smaller than an atom.

Infrared light lies in this spectrum between the waves of visible light and microwaves. Longer infrared wavelengths, called far infrared, are about the size of a pinhead. They are thermal, which means they produce heat. Shorter wavelengths, called near infrared are too small to see and not hot at all; they are the ones used in a TV remote control.

Convection currents are complex and hard to predict, but for our purposes, the basic concept is this: moving air carries heat away from its source, whether that source is a living body, a stove burner, a hot-air radiator or a whole toasty house. Our focus is on how to shape landscapes to make the most of convection, so summer breezes can help cool a house (and ourselves, inside), and chilly winds steal less heat from our homes. A more complete discussion of wind patterns relative to landscape design is presented on pages 16-19 and below.

Change of phase is a natural process in which energy is consumed or released. The following is an extreme simplification of a process that’s scientifically quite complex.

Water molecules exist naturally in three different forms — solid, liquid and vapor — that in science are called phases. They move back and forth between these phases depending on how much energy they contain. In their solid phase (ice), most of the molecules contain little energy and move around so little that they seem to be motionless. Water molecules in their liquid phase have a moderate amount of energy, with some of them moving slowly and others moving fast, but most of them somewhere in between, which keeps the water in its liquid form. In the vapor phase, water molecules move so fast that they escape the bonds of their liquid form and spread out into the surrounding air, creating humidity.

Heat is transferred anytime water changes phase. When substances move from a slower phase to a speedier one, energy is consumed. This happens both when liquid becomes vapor (evaporation) and when ice becomes liquid (melting). In the other direction, when liquid becomes solid or when gas becomes liquid, energy is released. The physics involved in these reactions is complex, and it’s all based on nature’s unceasing effort to create equilibrium.

Fig. 1.7: Convection currents, driven by the sun’s uneven heating of the earth’s surface, are the primary cause of large-scale weather patterns. They also explain the flow of cool and warm air inside a building.

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For our purposes, however, the relevant principle is this: evaporation consumes energy.