Posts by Vicente

Passive Solar Design

Beyond Sun Tempering

Thermal mass materials have the ability to conduct and store energy, both heat and cold, and to release that energy back into the living space when it’s needed.

Heat always moves to colder surfaces.In the solar home, the free solar energy first heats up the air. Since the mass floors and walls are cooler, the heat is absorbed and conducted into these materials. Later, when the sun has set and the room air temperature falls, it will reach a point where the mass materials are warmer than the room air temperature.Since heat seeks out cold, the stored energy will now return to the room. The more mass in the home, the more energy that can be stored.

The amount of south facing glass to be installed is related to the amount of thermal mass in the home, and the reverse is also true. In the sun tempered design, the home does not have the mass needed to absorb the amount of solar energy delivered when glass amounts exceed 7%. With slab construction, the mass is built in, but when carpeted, it can’t work for you. When you tile your slab, you have added thermal mass and you can increase the amount of south glass accordingly.

The Direct Gain System: Glass and Mass

The direct gain system is the easiest and most cost effective way to use solar energy. The structure itself is the solar system. The south windows are the collectors. The walls and floor are the storage. (mass). Orientate the structure and windows as close to true south as possible.

  • The ideal thickness for mass materials is 4 to 5 inches.
  • Use mass materials in the construction, for floors and walls. (adobe, concrete, brick, rock)
  • Water is the best mass, storing far more energy than other materials, BUT it’s not structural.
  • A masonry fireplace adds thermal mass but should be located on an interior wall.
  • An interior mass wall performs better than an exterior wall.

Insulate the exterior of your walls, keeping the masonry inside, protected from outside temperature extremes.
Provide for night time insulation on large glass areas. ( insulating curtains, moveable insulation, shutters. )
Provide adequate overhangs on the south side to prevent direct gain during the cooling season.
Use light colors on low mass construction. (ceilings, and partition walls)

Glass to Mass Ratios

Each design starts with 7% south glazing. (net) To increase beyond 7% we must also add thermal mass, usually starting with floor mass and then walls.

An additional 1 sq. ft. of south glass may be added for every:

5.5 sq. ft. of sunlit thermal mass floor *
40 sq. ft. of floor not in direct sunshine
8.3 sq. ft. of thermal mass wall

* The maximum amount of sunlit floor is 1.5 times the south window area
The recommended maximum amount of south glass for direct gain is 12-15%



The most ancient structures of the Southwest region of the United States still standing are represented in buildings made from adobe used in homes and Southwest missions. The early settlers of the region constructed homes of adobe because the materials were plentiful and at hand. Due to the lack of wood or masonry material, adobe was the choice of early shelters. Today, we have discovered that this material is not only abundant but also adaptable to changing climate and temperatures.

With the advance of the railroad, other materials used in the East made their way to the Southwest region and changed the face of local architecture. Most of the homes at the time were constructed of adobe due mainly to its high availability and low cost. It became more associated with the lower class which family members participated in the manufacturing of bricks using their feet and wooden molds. They relied entirely on the earth to provide the materials and not on any external shipments. Modern times have shown a trend towards adobe construction not only on aesthetics but also on practicality.

There are those who consider adobe the material of the poor, but now the thinking by the rich has renewed interest in this ancient building process. In some places, such as Santa Fe, New Mexico, these homes may cost beginning at $100,000. Certainly adobe homes can be constructed much cheaper. The manufacturing of adobe brick has become an industrial process. The camp of owners falls into two categories, those who hire contractors and those who do their own construction.

What are the characteristics of Adobe?

Traditionally, adobe brick measures 10x14x4 inches. Ideally, the mixture contains 20% clay and 80% sand. These materials are mixed with water and acquire a more fluid state that allows it to be poured into wooden forms with the above dimensions. When the water evaporates, the brick becomes hard, and it is then removed from the form. It is stacked one upon the other like fallen dominoes. About 30 days later, the bricks become as strong as cement.

The use of straw is commonly considered an essential part of the adobe brick, however, contemporary bricks of adobe do not contain it. The use of straw is thought to impart rigidity to the brick and prevent it from cracking during the curing process. If, however, the proper proportion of sand to clay is used this should not occur.

“High Technology” Abode

The basic mixture of clay and sand in adobe has been altered using emulsified asphalt. This is the component used in road construction. This imparts to the adode a waterproof quality. This incorporation is not fully accepted since the outer wall will be covered by stucco (plaster). If the wall is an inner patio or garden then its use is justified. “Purists” are not accepting to this idea and prefer the natural quality of adobe brick. Using asphalt will release gases that may prove harmful to man or the environment but no long-term studies of its effect have been done.

Why use Adobe?

There are advantages and disadvantages associated with its use. From the homebuilder, the easy of use makes the material attractive. In its mud form, it is easy to cut and shape. Taking from the childhood experience, using mud seems to make for a pleasant experience.

Although it is fairly simple to construct ones own material, the cost remains at $2000 to $3000 for a modest structure. The difference is the cost of transportation of the material and or the cost using traditional or high tech brick.

The amount of required energy and associated pollutants of the manufacturing process relies mainly on the type of material. By comparison, adobe may require 2000 BTUs compared to traditional Eastern brick requiring 30,000 BTUs.

Because there are minimal transportation costs of material, this is ideally suited for the environmentalist. As for the Solar Enthusiast, this is the simplest way to create a thermal mass. To combine these two concepts it has become known as Solaradobe.

English version of “Building with Adobe” coming soon!



Robert Foster
Southwest Technology Development Institute
New Mexico State University

Solar energy is the energy force that sustains life on the earth for all plants, animals, and people. The earth receives this radiant energy from the sun in the form of electromagnetic waves, which the sun continually emits into space. The earth is essentially a huge solar energy collector receiving large quantities of this energy which manifests itself in various forms, such as direct sunlight used through photosynthesis by plants, heated air masses causing wind, and evaporation of the oceans resulting as rain which can form rivers. This solar energy can be tapped directly as solar energy (thermal and photovoltaics), and indirectly as wind, biomass, and hydroelectric energy.

Solar energy is a renewable resource that is inexhaustible and is locally available. It is a clean energy source that allows for local energy independence. The sun’s power flow reaching the earth is typically about 1,000 Watts per square meter (W/m2), although availability varies with location and time of year. Capturing solar energy typically requires equipment with a relatively high initial capital cost. However, over the lifetime of the solar equipment, these systems can prove to be cost-competitive, as compared to conventional energy technologies. The key to successful solar energy installation is to use quality components that have long lifetimes and require minimal maintenance.


Electricity can be produced from sunlight through direct heating of fluids to generate steam for large scale centralized electrical generation (solar thermal electrical generation). Electricity can alternatively be produced from sunlight through a process called photovoltaics (PV), which can be applied, in either a centralized or decentralized fashion.
“Photo” refers to light and “voltaic” to voltage. The term describes a solid-state electronic cell that produces direct current electrical energy from the radiant energy of the sun, as represented in Figure 1. Solar cells are made of semi-conducting material, most commonly silicon, coated with special additives. When light strikes the cell, electrons are knocked loose from the silicon atoms and flow in a built-in circuit, producing electricity.

PV Terminology
Solar Cell: The PV cell is the component responsible for converting light to electricity. Some materials (e.g., silicon is the most common) produce a photovoltaic effect, where sunlight frees electrons striking the silicon material. The freed electrons cannot return to the positively charged sites (“holes”) without flowing through an external circuit, thus generating current. Solar cells are designed to absorb as much light as possible and are interconnected in series and parallel electrical connections to produce desired voltages and currents.

PV Module: A PV module is composed of interconnected solar cells that are encapsulated between a glass cover and weatherproof backing. The modules are typically framed in aluminum frames suitable for mounting.

PV Array: PV modules are connected in series and parallel to form an array of modules, thus increasing total available power output to the needed voltage and current for a particular application.

Peak Watt (Wp): PV modules are rated by their total power output, or peak Watts. A peak Watt is the amount of power output a PV module produces at Standard Test Conditions (STC) of a module operating temperature of 25°C in full noontime sunshine (irradiance) of 1,000 Watts per square meter. Keep in mind that modules often operate much hotter than 25°C in all but cold climates, reducing operating voltage and power by about 0.5% for every 1°C hotter, thus a 100W module operating at 45°C (20° hotter than STC yielding a 10% power drop) would actually produce about 90 Watts.

A thin silicon cell, four inches across, can produce more than one watt of direct current (DC) electrical power in full sun. Individual solar cells can be connected in series and parallel to obtain desired voltages and currents. These groups of cells are packaged into standard modules that protect the cells from the environment while providing useful voltages and currents. PV modules are extremely reliable since they are solid state and there are no moving parts. Silicon PV cells manufactured today can provide over thirty years of useful service life. Some manufacturers provide warranties of up to 25 years on their PV product (at 80 percent of original power rating). A 50 Wp PV module in direct sunlight operating at 25°C will generate 50 Watts per hour (referred to as a Watt-hour­[Wh]). This same module will produce less power at higher temperatures; at 55°C this same module can only produce about 42.5 W. Modules can be connected together in series and/or parallel in an array to provide required voltages and currents for a particular application.

PV systems are made up of a variety of components, which aside from the modules, may include conductors, fuses, disconnects, controls, batteries, trackers, and inverters. Components will vary somewhat depending on the application. PV systems are modular by nature, thus systems can be readily expanded and components easily repaired or replaced if needed. PV systems are cost effective for many remote power applications, as well as for small stand-alone power applications in proximity to the existing electric grid.

PV is a relatively new and unknown technology, which offers a new vision for consumers and business as to how power can be provided. PV technology is already proving to be a force for social change in rural areas in less developed countries. The unique aspect of PV is that it is a “radical” or “disruptive” type of technology as compared to conventional power generation technologies. PV is a technology that does not build from the old technology base, but rather replaces that base from the bottom up. PV allows people the opportunity to ignore traditional electrical power supply structures and meet their own power needs locally. In rural regions of the world today, where there are no power companies offering electricity, PV is often the technology of choice.

The best performing renewable energy electrification systems are those that meet the expectations of the users. It is important to satisfy the basic needs of the user in order to ensure acceptance of renewable energy systems. Ownership and subsequent accountability is the key to system sustainability for PV.

One 50 Wp PV module is enough to power four or five small fluorescent bulbs, a radio, and a 15-inch black-and-white television set for up to 5 hours a day. Obviously this is only a modest amount of energy, however this represents an important quality of life improvement for many rural people without electricity. A small PV solar home system can cost as little as $550 to 650. This represents a significant monetary investment for a rural campesino in Mexico and several months’ worth of income. The need for financing and innovative financing instruments that can assist rural people to obtain better services through the private marketplace is obvious.


The fast growing world market for PV greatly reflects the growing rural electrification demand of less developed countries around the world. The global PV market has grown at an average rate of 16 percent per year over the decade with village power driving demand. Table 2 shows the total worldwide PV production in 1980 was only 6.5 megawatts (MW) and by 1997 this had increased to 126.7 MW.

Table 2. Worldwide PV production
1980    1986    1989    1991    1993      1996     1997

TOTAL (MW) 6.5          26.0         40.2       55.4        60.1          88.6        126.7
Source: O’Meara, 1998.

U.S. module production is leading world growth as well. In 1993 the U.S. produced 21 MW of PV, of which 14.8 MW was exported. By 1997, global demand led to a record breaking PV production year with a 42 percent leap in worldwide production. The U.S. produced 46.4 MW with $175 million in sales and exported 33.8 MW (73 percent of production) overseas (EIA, 1998).

There are over 500,000 homes using PV today in villages around the world for electricity (Flavin and O’Meara, 1998b). In Kenya, more rural households receive electricity from PV than from the conventional power grid (Kozloff and Shobowale, 1994). The single largest market sector for PV is village power at about 45 percent of worldwide sales. This is mostly comprised of small home lighting systems and water pumping. Remote industrial applications such as communications are the second largest market segment.


For many applications, especially remote site and small power applications, PV power is the most cost-effective option available, not to mention its environmental benefits. New PV modules generally retail for about $5 per peak watt, depending on quantities purchased. Batteries, inverters, and other balance of system components can raise the overall price of a PV system to over $10 – $15 per installed Watt. PV modules on the market today are guaranteed by manufacturer’s from 10 to 20 years, while many of these should provide over 30 years of useful life. It is important when designing PV systems to be realistic and flexible, and not to overdesign the system or overestimate energy requirements (e.g., overestimating water-pumping requirements) so as not to have to spend more money than needed. PV conversion efficiencies and manufacturing processes will continue to improve, causing prices to gradually decrease.

PV conversion efficiencies have increased with commercially available modules that are from 12 to 17 percent efficient, and research laboratory cells demonstrate efficiencies above 34 percent. A well-designed PV system will operate unattended and requires minimum periodic maintenance, which can result in significant labor savings. PV modules on the market today are guaranteed by the manufacturer from 10 to 25 years and should last well over 30 years. PV conversion efficiencies and manufacturing processes will continue to improve, causing prices to gradually decrease, however no dramatic overnight price breakthroughs are expected.


PV is best suited for remote site applications that have small to moderate power requirements, or small power consuming applications even where the grid is in existence. A few power companies are also promoting limited grid-connected PV systems, but the large market for this technology is for stand-alone (off grid) applications. Some common PV applications are as follows:

Water Pumping
Pumping water is one of the most competitive arenas for PV power since it is simple, reliable, and requires almost no maintenance. Agricultural watering needs are usually greatest during sunnier periods when more water can be pumped with a solar system. PV powered pumping systems are excellent for small to medium scale pumping needs (e.g., livestock tanks) and rarely exceed applications requiring more than a 2 hp motor. There are thousands of agricultural PV water pumping systems in the field today throughout Texas. PV pumping systems main advantages are that no fuel is required and little maintenance is needed.

PV powered water pumping system is similar to any other pumping system, only the power source is solar energy; PV pumping systems have, as a minimum, a PV array, a motor, and a pump. PV water pumping arrays are fixed mounted or sometimes placed on passive trackers (which use no motors) to increase pumping time and volume. AC and DC motors with centrifugal or displacement pumps are used with PV pumping systems. The most inexpensive PV pumpers cost less than $1,500, while the large systems can run over $20,000. Most PV water pumpers rarely exceed 2 horsepower in size. Well installed quality PV water pumping systems can provide over 20 years of reliable and continuous service.

The reason users like to use PV water pumping systems can be seen in example survey results obtained from Mexico for the SNL water pumping program (22 end-users surveyed) provided in Figure 7 (Foster, 1998). The increased leisure time, less site visits, and considerably less operation and maintenance.

Figure 7. Perceived end-user socio-economic benefits from photovoltaic water pumping systems use for ranchers.

Gate Openers
Commercially available PV powered electric gate openers use wireless remote controls that start a motorized actuator that releases a gate latch, opens the gate, and closes the gate behind the vehicle. Gates are designed to stop if resistance is met as a safety mechanism. Units are available that can be used on gates up to 16 feet wide and weighing up to 250 pounds. Batteries are charged by small PV modules of only a few watts. Digital keypads are available to allow access with an entry code for persons without a transmitter. Solar powered gate-opening assemblies with a PV module and transmitter sell for about $700.

Electric Fences
PV power can be used to electrify fences for livestock and animals. Commercially available packaged units have maintenance free 6 or 12 Volt sealed gel cell batteries (never need to add water) for day and night operation. These units deliver safe (non-burning) power spikes (shocks) typically in the 8,000 to 12,000 Volt range. Commercial units are UL rated and can effectively electrify about 25 to 30 miles of fencing. Commercially packaged units are available from about $150 to $300, depending on voltage and other features.

Water Tank De-Icers
For the north plains of Texas in the winter, PV power can be used to melt ice for livestock tanks, which frees a rancher from going out to the tank with an ax to break the surface ice so the cows can drink the water. The PV module provides power to a small compressor on the tank bottom that generates air bubbles underwater, which rise to the surface of the tank. This movement of the water with the air bubbles melts the tank’s surface ice. Commercially available units are recommended for tanks 10 feet in diameter or greater, and can also be used with ponds. Performance is best for tanks that are sheltered, bermed or insulated. Installation is not recommended for small, unsheltered tanks in extremely cold and windy sites. Approximate cost for a complete owner-installed system, including a PV module, compressor, and mounting pole is about $450 (Foster, 1994).

Commercial Lighting
PV powered lighting systems are reliable and a low cost alternative widely used throughout the United States. Security, billboard sign, area, and outdoor lighting are all viable applications for PV. It’s often cheaper to put in a PV lighting system as opposed to installing a grid lighting system that requires a new transformer, trenching across parking lots, etc. Most stand-alone PV lighting systems operate at 12 or 24 volts DC. Efficient fluorescent or sodium lamps are recommended for their high efficiency of lumens per watt. Batteries are required for PV lighting systems. Deep cycle batteries specifically designed for PV applications should be used for energy storage for lighting systems. Batteries should be located in protective enclosures, and manufacturer’s installation and maintenance instructions should be followed. Batteries should be regulated with a quality charge controller. Lighting system prices vary depending on the size; average systems cost from $600 to $1,500.

Residential Power
Over 500,000 homes worldwide use PV power as their only source of electricity. In Texas, a residence located more than a mile from the electric grid can install a PV system more inexpensively than extending the electric grid. A Texas residence opting to go solar requires about a 2 kW PV array to meet its energy needs, at a cost of about $15,000. The first rule with PV is always energy efficiency. A PV system can provide enough power for an energy efficient refrigerator, lights, television, stereo, and other common household appliances.

A great number of PV installations for homes have taken place in Mexico. The experience of PV electrification varies widely across Mexico and is demonstrative of the potential pitfalls of haphazard installations. Over 40,000 PV home lighting systems have been installed in Mexico, mostly through government programs (Foster, 1998). However, nearly half of these systems are not functioning today, mostly due to poor balance of systems hardware (i.e., the PV modules work fine), where improper batteries and poor quality charge controllers are used. It is important for any PV user to use quality equipment and install PV systems in accordance with local electric codes. This greatly reduces the potential for future problems.

Evaporative Cooling
PV powered packaged evaporative cooling units are commercially available and take advantage of the natural relation that when maximum cooling is required is when maximum solar energy is available. These units are most appropriate for comfort cooling in the dry climate of West Texas where performance is best. Direct evaporative coolers save 70% of the energy over refrigerated units. Battery storage is obviously required if cooler operation is desired at night. Array size would vary with the power requirements of the cooler motor. A linear current booster (LCB) is useful between the PV modules and the cooler’s DC motor if the cooler is coupled directly to the PV array. Packaged PV evaporative cooling systems for residences generally run from $500 to $1,500, depending on size.

This was one of the early important markets for PV technologies, and continues to be an important market. Isolated mountaintops and other rural areas are ideal for stand-alone PV systems where maintenance and power accessibility makes PV the ideal technology. These are often large systems, sometimes placed in hybrid applications with propane or other type of generators.

Consumer Electronics
Consumer electronics that have low power requirements are one of the most common uses for PV technologies today. Solar powered watches, calculators, and cameras are all everyday applications for PV technologies. Typically, these applications use amorphous PV technologies that work well even in artificial light environments such as offices and classrooms.

Electric Utility Applications
A potential future growth area for photovoltaics is the utility market, which currently amounts to less than 10% of U.S. PV installations. While PV today is not very competitive in grid-tied applications, a number of utilities across the U.S. are evaluating PV for off-grid and grid-tied applications. The White House and Department of Energy are promoting the “Million Solar Roofs Initiative,” whose goal is to put solar energy on these many roofs (both solar thermal and PV systems) by the year 2010. However, major power policy reforms and tax incentives are needed if this goal is going to be effectively realized.

Utilities have numerous uses for small power sources, often at remote sites that are difficult to power conventionally, such as lighting for transmission towers, water pumping, cathodic protection for structures, sectionalizing switches, monitoring systems and microwave communication links. While this utility market is not large these applications are cost-effective today.
The Photovoltaics for Utility Scale Applications (PVUSA) project initiated in 1986 is a joint effort between PG&E, DOE and other utilities across the country including the City of Austin Electric Utility. This project focuses on evaluation of PV within the U.S. utility sector. The City of Austin Electric Department is a PVUSA host site with an installed a 20kW experimental array in 1992. The City of Austin Electric Utility has also built a 300kW PV array by Decker Lake, as well as Several U.S. utilities are investigating using PV systems as a 2.7kW PV system located on a youth hostel in Austin to evaluate PV as a future demand-side management tool.

Another Texas utility, Central and Southwest Services, has also built a pioneering renewable energy demonstration park near Fort Davis. They have installed over 300 kW of different PV technologies connected to the electric grid. Both the Austin Utility and Central and Southwest are members of the Utility Photovoltaic Group (UPVG) which is comprised of numerous utilities and trade associations across the U.S.


The future is bright for continued PV technology dissemination in the Southwest U.S. and around the world. PV technology fills a significant need in supplying electricity, creating local jobs and promoting economic development in rural areas, while also having the positive benefits of avoiding the external environmental costs associated with traditional electrical generation technologies. People who choose to pursue a renewable and sustainable energy future now, are the ones showing the way for the future.


EIA, Energy Information Agency, “Solar Energy,”, U.S. Department of Energy, Washington, D.C., October, 1998.

Flavin, Christopher and Molly O’Meara, Karl Böer (editor), “Financing Solar Home Systems in Developing Countries: Examples of New Market Strategies,” Advances in Solar Energy, Volume 12, American Solar Energy Society, Boulder, Colorado, 1998a.

Flavin, Christopher and Molly O’Meara, “Solar Power Markets Boom,” World Watch, Vol. 11, No. 5, Washington, D. C., September/October, 1998b.

Foster, Robert, Photovoltaic Market Development and Barriers in Mexico, MBA Thesis, Graduate School of Business, New Mexico State University, Las Cruces, New Mexico, December, 1998, 206 pp.

Foster, R. E., “Photovoltaic Energy for Agriculture,” Energy Conservation and Management Division; Energy, Minerals and Natural Resources Department, Santa Fe, New Mexico, June, 1994, 6 pp.

Kozloff, Keith and Olatokumbo Shobowale, “Rethinking Development Assistance for Renewable Electricity,” World Resources Institute, Washington, D.C., November, 1994.

O’Meara, Molly, “Solar Cells Shipments Hit New High,” Vital Signs, 1998, WorldWatch Institute, Washington, D.C., 1998.


System Design – Installation and More Here!

What’s the correct angle for your PV modules? Here’s the answer!

Energía Solar – Indice

Adobe | Energiaelectrica | Piscina

El propósito de esta página es el de proveer información de caracter práctico sobre energía solar y el uso eficiente de la energía en general. Si Ud. está diseñando o construyendo una casa nueva, necesita información sobre cómo calentar el agua para su casa o su piscina de natación (alberca) usando la energía solar o necesita purificar el agua que va a beber, la información de esta página le será sumamente útil.

Esperamos que el material informativo de estas páginas le sea útil e interesante. Háganos llegar sus comentarios sobre cómo podríamos mejorar la presentación. En el futuro, trataremos de incorporar nuevo material, para así tentarlo a visitarnos nuevamente.

La Asociación de Energía Solar de El Paso (EPSEA) fué fundada en 1978 y es la única de su tipo que ha operado, sin interrupción alguna, por el mayor número de años, como una agrupación regional en los EEUU. EPSEA genera una publicación mensual (en inglés) sobre sus actividades y temas solares, la que es distribuída por correo a sus miembros.

Ademas de ofrecer presentaciones mensuales o seminarios públicos, EPSEA participa en algunos proyectos propios (destilador solar) o en eventos educativos. Sus miembros organizan o participan en seminarios sobre energías renovables, los que toman lugar en su área de influencia (zona sud-oeste de los EEUU y norte de México).

El objetivo de EPSEA es el impulsar el desarrollo y la aplicación de la energía solar, así como de otras tecnologías relacionadas a este tema, con énfasis en la ecología y los aspectos económicos y sociales de la región (oeste de Texas, sur de Nuevo México y norte de México).

EPSEA está afiliada a la Sociedad Solar del Estado de Texas y a la Asociación Solar de los EEUU.

EPSEA es una asociación de tipo no comercial (non-profit 501 (c) (3) bajo la ley de los EEUU).

Nota: Si vive al sur del Ecuador, reemplace la palabra sur por norte en todas las explicaciones o consejos. Numerosos detalles de construcción son peculiares de la técnica de construcción usada en los EEUU. Algunos conceptos son de caracter genérico y se aplican a cualquier material o tipo de construcción.


Passive Solar and Energy Efficient Home Design


It is a fact, that everything we build is solar. When we ignore solar energy during the design stages we end up with a building which may benefit from solar, though it is just as likely to be beat up by solar energy.  A passive solar design will not only lower your utility bills, it will be comfortable. Comfort is priceless.

The following guidelines are drawn from research and practical application, from successes and failures,  from the experience of our ancestors who lived in caves, and from recent computer generated studies.

Orientation: The longest wall of the home should face south. The winter sun rises South of East and sets South of West. Placing more glass on the South wall will ensure that your home receives free solar energy.

This same orientation helps to prevent the high summer sun from entering the home.

A compass will point to magnetic North/South, but a solar home or collector works best when it faces TRUE SOUTH.

In the El Paso area true south is 12 degrees East of magnetic South. This declination from magnetic south varies across the country depending on longitude.

Solar Access: Buildings or trees too close to your home could block the low winter sun.

Windows: The amount of glass on the South wall may equal 7% of the homes total square footage.
(Example: 2,000 Sq. Ft. = 140 Sq. Ft. of glass.)

To avoid overheating, this amount of glass should not be exceeded. The 7% applies to conventional home construction with standard floorm coverings such as carpet, vinyl tile, or wood. Increasing glass area above 7% will require additional thermal mass, i.e. concrete/tile floors, rock, brick, concrete or adobe walls.

The 7% amount is NET sq. ft. or the total window area less the trim etc.

Multiply the entire window by .8 to get the net glass area.

Example: A 3’0″X5’0″window is 15 sq. ft.
15 X .8 = 12 sq. ft. net

East and North glass should be limited to no more than 4% of total sq. ft. (Maximum)

West glass should not exceed 2% of total sq.ft.(MAXIMUM)

Landscaping: Plant deciduous or evergreen trees on the east, west and north sides of the home. Xeriscape! Avoid dark colors, inside and out.

Insulate exterior of slab/foundation with extruded polystyrene sheets. R-5 for moderate climates, R-10 for colder climates.

Sole Plate: Install sill sealer under the bottom plate of all exterior walls, on both the first and second floors.

Walls: In moderate climates use 2X4 frame walls with R-13 batts and R-4 rigid insulated sheathing boards (1″ expanded polystyrene). For Cold climates, use 2X6 frame walls with R-19 batts and the same R-4 sheathing.  Sprayed cellulose insulation should be considered because, though more expensive than batts, is more effective because it fills voids and reduces air leakage.”

Attic: Ceiling ­ Install R-30 insulation, blown in type is preferable, for moderate climates. Levels of R-38 to R-50 are recommended for colder climates

IMPORTANT: Prior to installing wall insulation, use cans of expanding foam insulation and/or caulk to seal all electrical and plumbing penetrations, around doors and windows.

Tape/seal all joints in ductwork.
Duct work should be installed in interior (heated) space so that heat or cold is not lost to unheated spaces (attic).
Furrdowns should be sheathed and sealed prior to installing duct.

Insulate walls surrounding furnace closets and seal return air plenum.

Doors: Install steel or fiberglass insulated exterior doors that have an insulation value of R-5.9 or greater. Lower R-value doors can be used in conjunction with a storm door.

Ventilation: Place and size windows to take advantage of natural ventilation and prevailing breezes.

Fans: The use of ceiling fans can drastically reduce the running time of air conditioners.

Contact your local county agent or state energy office for recommendations specific to your area.

Energy Efficiency Tips

It’s cheaper to save energy than to make energy.

No Cost and Low Cost Efficiency Tips

No Cost Tips

Turn water heater down to 120F (49C)
Clean refrigerator coils
Switch refrigerator to power miser setting
Set refrigerator temperature to 36-39F (2-3C)
Set freezer to 0-5 F (-18 to-15C)
Keep refrigerator/freezer full (water)
Turn off water while shaving and brushing teeth
Use cold water for wash and wash full loads
Collect rainwater
Use the right size pot/pan on the stove burner
Do not preheat your oven except for baking
Cover pots/pans when cooking
Drain some water from your water heater to remove sediment

Winter Tips

Turn thermostat down 10 degrees F (5.5C) at night
Turn thermostat down 10 degrees F (5.5C) when leaving for 4 hours or more
Keep curtains open on the south side of the house during the day
Keep curtains closed on north windows
Dress in layers of clothing

Summer Tips

Close curtains on the sunny sides of home
Turn off furnace pilot light
Open windows on the cool sides of home
Wear loose, light colored clothing
Use fans to circulate air in the home

Low Cost Tips

Install low flow shower heads and aerators on faucets
Insulate water heater
Insulate electrical outlets and switches
Caulk on the inside of doors and windows
Insulate/caulk all pipe penetrations in walls and ceiling
Install a bleed line on the evaporative cooler and run line to a tree
Replace furnace filter every month in winter
Replace light bulbs with compact fluorescent bulbs
Insulate the bottom and sides of waterbeds
Use a quilt or comforter on waterbeds
Purchase a water saving toilet or use toilet dams
Make a draft dodger for use on doors or windows

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