Enough sunlight falls on the Earth's surface each minute to meet world energy demands for an entire year. The sun is a fusion reactor delivering 1.52 x 1018 kWh/year to earth. All of mankind's energy needs total less than 0.1% of this amount. The United States receives more energy in the form of sunlight in less than 40 minutes than from all the fossil fuels we burn every year? Source: Solar Energy Research and Education Foundation

The average American family spends over $1,500 per year on utility bills. This expense can be reduced by 10% to as much as 90% percent depending on how  aggressive you want to be about getting more efficient. Figures for businesses are much harder to quantify due to varying sizes and types.

Heating and cooling your home uses more energy and drains more energy dollars than any other system in your home. Typically, 44% of your utility bill goes for heating and cooling. What's more, heating and cooling systems together in the United States emit over a half billion tons of carbon dioxide into the atmosphere each year, adding to global warming & other health issues. They also generate about 24% of the nation's sulfur dioxide and 12% of the nitrogen oxides.

Using the sun to heat your home through passive solar design can be environmentally friendly and cost effective. In many cases, you can cut your heating costs by more than 50% compared to the cost of heating the same house that does not include passive solar design.

Solar Orientation
Simple, but confusing? Latitude 50.00° North. The sun really only rises exactly in the east and sets exactly in the west on two days of the year - the first day of spring and the first day of fall. The sun rises in a direction north of east and sets in a direction north of west during the spring and summer months (northerly latitudes). The sun rises in a direction south of east and sets in a direction south of west during the fall and winter months (northerly latitudes). The sun reaches its peak (zenith) at a point due south of the observer (northerly latitudes). The time this occurs is defined as solar noon. The sun's zenith is closer to the horizon during fall and winter months, and is higher in the sky during spring and summer months. The sun rises earlier and sets later during the spring and summer months, with the opposite being true during the fall & winter months.

Most energy-sensitive architects and builders understand that a south facing orientation tends to increase solar heat during winter months. However, it can also produce extreme heat on the west facing sides of the structure in the summer, thus negating any overall benefit. In fact, sometimes there's an overall decline in efficiency. As the illustration below shows you, in the winter months the sun arcs much lower in the sky and the path is much shorter than in the summer. A building project should be evaluated for orientation, but don't automatically assume that facing true south is the best. It can be, but only when other features are incorporated. Your building can be angled as much as 15° east or west of true south and still be energy efficient. The southern orientation of the building could vary by up to 30° from true south without significantly harming its heating season performance, but because such a large variance could seriously reduce cooling performance, it is recommended that the orientation should not vary by more than 15° either to the east or west of true south.
 

Eave Projection: The eaves or soffit width can make a big difference. By using the proper projection off the main structure for your particular location, your building can be mostly in the shade by 10:30AM in the summer, keeping it cooler, and be kept out of the shade during winter months, which keeps it warmer. Proper eave projections can also enable you to use more glass surfaces since they'll permit winter solar heat, but also shade the same windows in the summer.
 
 
 

For example, in June - July when the summer sun is moving from about 65 to 75 degrees overhead between 10:30AM & noon, a south facing building with only a 36" eave or soffit on the south side will be virtually in the shade on the south side, will have little or no east side solar heat (deflection is also occurring), and of course will not have any solar heat on the west or north. With a more typical 12" to 16" soffit, the south side is absorbing a lot of heat, thus increasing cooling costs. Conversely, in December - January the winter sun arcs at about 22-25 degrees in the sky, and the solar heat can help warm the south exterior and pass through the windows to warm the interior.Graphic courtesy of North Carolina Solar Center.

Landscape Features: Trees can be very helpful or very restrictive in passive solar designs depending on how close they are to the structure and what type of tree it is. Evergreen trees should ideally be kept on the west, north and northeast if they are close to the building. Deciduous trees which lose their leaves in the fall are usually best on the south side, but if you will be using rooftop solar photovoltaics you wouldn't want them too close or too high. For passive solar energy, during the summer they can provide additional shading, and after losing their leaves in the fall they will permit winter sun to warm the building. Taking full advantage of trees and shrubs can provide shading, wind break and other benefits.

Window Glass: Energy efficient window glass can really help to keep summer heat from penetrating your windows, especially on the west side, but also allow winter solar heat to keep your structure warmer - without ruining your furnishings. Besides normal consideration of double or triple pane for heat & cooling losses, depending on window size and compass orientation, we recommend using inexpensive transparent, Low-E coatings (Low Emissivity) applied by the window manufacturer when ordering your windows.

Particularly on west facing windows, the Low-E coating dramatically reduces the amount of solar heat passing through to your interior in the summer. When it's combined with sealed gases like Argon in double or triple pane, Low E coatings can either keep heat in or out, and reduce ultraviolet ray penetration by up to 84%. What Low-E does (see graphic): 1. The Low-E allows most natural light to enter freely, but absorbs a significant portion of short-wave heat energy. 2. In the summer, long-wave heat energy is reflected back outside, lowering cooling cost. 3. In winter, internal long-wave heat energy is reflected back inside, lowering heating cost.

Unlike other insulating features of the home, the efficiency of windows is typically expressed in terms of an U-value. U-value measures the conductivity of the window (this is the inverse of R-value.) Therefore, the lower the U-value the better.

Using a lot of glass material may be aesthetically desirable, but balance should be maintained. Plain glass has a very high U value. Even high performance double and triple pane windows will still cause relevant losses, so this is a factor to consider. Too much glass on a particular side of a building can be very costly in lost energy efficiency. The idea should be to use enough glass material to keep the structure light and reasonably bright, but to understand that for every square foot of glass there is some relevant loss of heating & cooling efficiency. Windows on the north side should be few in number and small in size, to reduce heat loss from this exposure. The eave or soffit projections can be sized to enable the use of more glass, more efficiently.

Wind Barriers: The proper use of "wrap" or a wind barrier prior to final siding will help restrict unwanted air flow in the wall and ceiling cavities, but unless it's installed properly, it's a waste of money. Tyvek is a brand name familiar in most parts of the country. We often see this material applied using only a staple gun. This method is a big waste of your money. This material can be very helpful, but all edge seams, cut ends and window/door openings must be sealed properly - not just stapled.

Absorption Materials: The use of stone, brick or tile in the interior can absorb winter solar heat during the day through window openings, and then slowly release it throughout the evening. Decorative water columns are also used. However, unless it is also kept shaded in summer months, it's effect is negated or worse. There are many interior features which can be utilized to store heat during the day in the winter to reduce overall heating costs. The same holds true for keeping cooling costs down, but it makes little sense to gain in one respect and then lose it in another. Solar angles throughout the year, window sizes, eave projections and total mass of the absorption material are all considerations.

Insulation & Caulking: Proper insulation and caulking during construction is obviously very important. One of the most important factors is to be certain the insulation is properly sized, but equally important is that it be installed correctly. We often see buildings with the correct thickness of material, but the installation is inferior. Many construction companies use low-cost labor to install the insulation, and the building owner ends up paying for it, over and over again in higher heating/cooling costs.

The required thickness of wall and ceiling insulation varies from area to area, but as a general rule, using fiberglass as a basis; 6" in the walls and 12" in the ceiling is the minimum. This generally means the outside frame walls will be made using a nominal 6" thick dimension. However, unless other construction practices are kept to the highest standards, the insulation properties are seriously diminished. Proper installation of insulation materials is critical.

For even a small home we'll usually recommend $300 in caulking alone, but in the coldest periods you can walk around in your bare feet without drafts. This isn't a reflection of using caulking to make-up for lousy carpentry. The intent is to compliment good carpentry. It's a matter of properly sealing joints and other areas so air penetration into your interior from the sill areas, corners, etc. is minimized. Those that say you shouldn't make a building too tight usually do not understand how to build a truly energy efficient home. It is true you can make a building too tight, but through the proper use and installation of certain construction products, your energy efficiency can be increased dramatically.

Fresh air exchange is important in any residential or commercial building. However, compared to typical construction which usually results in a fresh air exchange ratio of about 8 to 1 or even 10 to 1, a really energy efficient building will have about a 2.5 - 3 to 1 exchange ratio. A building should also have sufficient exhausting in kitchens, baths, etc. This is important to keep the air quality fresh and healthy. In contrast, a 10 to 1 ratio means you're literally just blowing in the wind - wasting all kinds of heat and cooling. A home does have to breathe, but there's a difference between enabling a home to breathe and inefficient construction which causes undesirable air flow.

Gas vs. Electric: It's more efficient to "heat" with gas than electricity. Electricity does well on inductive loads like motors and such, but resistive loads (heat elements) are better heated with natural or propane gas. You're far better to use gas for central heating, hot water, your kitchen range/oven and even your clothes dryer. Maytag, for example makes an excellent gas clothes dryer in case you weren't aware you could even buy one. Most newer modern gas appliances are now 99+% emissions efficient, also making them desirable over electrical units which require more energy derived from fossil fuels.

Note: In a forced air heating system, extreme care should be taken to insure all ducts are thoroughly sealed at joints and well insulated to insure maximum efficiency.

High Efficiency Appliances: High efficiency refrigerators, water heaters, furnaces, air conditioners, etc. are available. Efficient appliances save resources and money, reduce environmental impacts, and keep your home cooler in the summer by eliminating the heat wasted by inefficient appliances. They do cost more up front, and sometimes the pay back for the extra cost takes 5, 7 or 10 years depending on the appliance and the amount of use. However, if you can afford the extra up-front cost, and you intend to own the structure a long time, they are definitely worth it. They are especially helpful and recommended if you produce your own electricity (being off the grid) with alternative energy.

Geothermal Energy: Using relatively stable underground temperatures to assist heating in the winter and cooling a structure in the summer is very viable. A year-round average underground temperature of say, 50-55 deg. is sufficient to pre-warm fluid systems when outside temperatures may be hovering below freezing. The colder the outside air the more viable these systems are - if sized accordingly. Conversely, that same average underground temperature can cool fluids and be used to provide "air conditioning".

The geothermal system uses the earth as a heat/cooling source and "sink". The heat is exchanged with the earth via a system of buried plastic pipes called the ground heat exchanger. In the winter, the fluid within the pipes extracts heat from the earth, carries it through the system and into the building. In the summer, the system reverses itself. Heat is pulled from the building, carried through the system and deposited in the cool earth. In addition waste heat from the system can be used to provide domestic hot water at no cost in the summer and at a substantial savings in the winter. The graphic image illustrates a "closed loop" system.

Caution is advised to used established industry methods and equipment for geothermal energy. Attempts at "home built" versions may not function efficiently - although this is not to say you can't build your own system. One key point to remember is that "air" is a poor conductor by itself. Air space is an insulator because air does not conduct well. So just forcing a whole lot of air through an underground trench loop isn't effective. Plus air can absorb unhealthy Radon gases, etc. If air is used (not recommended), there must be an "exchanger" of some type for the circulated air to pass through, much like the heat exchanger in a forced hot air heating system or the exchanger in an air conditioning system. It's better to use a fluid to absorb ground temperature. If sized & built properly, a geothermal system can be extremely energy efficient.

Compact Fluorescent Lighting: A regular light bulb produces about 5-7 times more heat energy than it does light. That's why they're very hot when you touch them. A compact fluorescent bulb is just the opposite, producing 5 times more light than heat. They're barely warm to the touch. In addition, while most regular bulbs have an average life of about 800 - 1000 hours of use, a C.F. may have a life of 8-10,000 hours, or ten times as long. Also, it takes a lot less electrical energy to produce the same light output.

C.F.'s cost more, about 8-10 times as much as a regular bulb of equal light output, but over the life of the bulb they save enough electrical energy to pay for themselves. Here's an example. A regular 100w bulb costs about $1.50 and lasts 1000 hours. It will consume about $8 in electricity at $.08/kWh. So that's a total of $9.50 per 1000 hours. Now multiply this by 10, or $95. An equivalent 100w C.F. lasting 10,000 hours costs about $16 and will use only 27 watts to produce 100w of light. The C.F. will consume about $22 at $.08/kWh. The total for the C.F. is $38.

The difference is about $57 per bulb over a period of 10,000 hours of use. If you have say, 30 light bulbs in your building, then the potential savings is $1,710. If you figure this over a ten year period you will save about $171 per year by using C.F.'s for 30 light bulbs.

C.F.'s make sense, however some lighting fixtures will not accommodate the larger bulb size since C.F.'s are a little bigger in size. Also, some fixtures are intended to be flood or spot lights, and C.F.'s aren't as good for this purpose. We usually recommend them for any fixture they'll fit into nicely, unless the fixture is intended for occasional decorator purposes as a flood lamp.

Color & Materials: Exposed surfaces affected by summer/winter solar heat is a factor. The total surface areas and their color or material should be considered. Darker colors absorb more heat in the winter, but also in the summer. The top four absorbing colors are black, red, brown & navy blue. Balance of the type of materials and color can make a difference in overall efficiency, although with the proper insulation & other design features there's plenty of room for decorative colors.

These are just some of the considerations which should go into the design of a truly energy efficient building. The more the better. You don't have to dig a hole in the side of a south facing hill to achieve high efficiency. You also don't have to ruin a beautiful architectural concept just to make it efficient. But a little compromising on some key issues may make all the difference in the world. However, never compromise on the quality of workmanship going into your project.