Sustainable Building Principles
Green building begins with responsible site selection and design. By taking site characteristics into consideration early on in the design process, one can develop a plan that incorporates such elements as capturing and storing rain water, improving solar gain for energy efficiency and daylighting and utilizing existing vegetation for summertime shading.
Passive solar orientation: The building should be designed to maximize the east-west dimension and faced south within 15 degrees east or west to optimize solar gain in the winter. Designing your house with sufficient window area to the south can save up to 40% of the energy consumption of the same building turned 90 degrees. North-facing walls have few or no windows, and small east-west windows facilitate ventilation. Orient roofs to accept photo-voltaic panels and solar water heaters. Location: Reduce transportation energy use (i.e., reduced commute time) by siting the building within proximity of and convenient to the population who will use it. Build on land that is in the worst condition, not the best, thereby preserving the most ecologically valuable land in its natural state.
Earth Sheltering: The practice of building into a hillside or a berm to compensate for temperature extremes, protect the building from inclement weather, and take advantage of the vast thermal mass of the ground, which remains at a constant temperature at a certain depth below grade. Shading: Provide shading where appropriate with overhangs/portales and vegetation.
|Example of a home sited with windows to the south for passive solar gain.|
Passive Solar Heating: Design strategies, such as direct gain, sunspaces, or trombe walls which may utilize windows, insulation, and mass, create an energy-efficient system without the need for heating from mechanical equipment.
Cooling: Space cooling represents 10% of annual energy use in residential buildings. Controlling solar heat gain in the summer is critical to reducing the need for cooling. Methods for cooling load avoidance include: passive solar design and orientation that minimizes solar gain in summer as the sun is higher in the sky; careful selection of window glazing; vegetation for shading; reflective roofs; green roofs; portales and overhangs.
Photo-voltaic Panels: Devices that convert sunlight directly into electricity. PV’s generate power without noise, pollution, or fuel consumption, and are useful where utility power is not available, reliable, or convenient.
Solar Hot Water Heaters: These devices collect the sun’s energy to heat water for indoor use for showers, dishwashing and laundry.
Trombe Wall: This passive solar heating strategy consists of a thermal storage wall directly behind vertical glazing. During the day, the wall heats up and releases its heat to the space behind the wall. Insulation: Use of insulation can minimize the effect of outside environmental conditions on the indoor environment and keep thermal energy inside the building. Insulation performance is measured by its “R-value” or resistance to heat flow.
Retrofitting: A building’s biggest energy use is typically associated with its construction, and retrofitting saves energy by avoiding energy expenditure in demolition or construction, while at the same time preserving cultural heritage.
Radiant Heat Flooring: This approach takes advantage of lower water temperatures by maintaining a constant building temperature. The floor becomes a large thermal mass or thermal storage system.
Daylighting: Lighting uses between 20-25% of electricity in the U.S. In most of these buildings, 50% of this energy is wasted because of inefficient fixtures or equipment, poor maintenance, or inappropriate use. Daylighting is the optimal use of natural light, and can save 40-60% of home energy costs.
|Daylighting||Installation of geothermal heat flooring. Photo: Marilyn Gendron||Solar oven|
Water Efficiency Methods
Use of gray water: Gray water is defined as untreated household wastewater that has not come in contact with toilet waste. Gray water includes wastewater from bathtubs, showers, wash basins, clothes washing machines and laundry tubs. It does not include wastewater from kitchen sinks or dishwashers or laundry water from the washing of material soiled with human waste, such as diapers. New Mexico state law now allows private residential gray water use for household gardening, composting or landscape irrigation.
Rainwater Catchment Systems: Capturing rainwater for irrigation or drinking water can reduce the use of treated drinking water. Building roof and gutters are used to collect the rainwater and direct it to cisterns for storage. The use of terracing in landscaping also captures and stores rainwater for use by vegetation.
Native Landscape: Landscape that is adapted to thrive in the local environment, where it needs no supplemental irrigation or fertilizer, is ecologically diverse enough to resist pests, and provides free storm water management.
|Rainwater catchement barrel (Regalos de la Tierra Raincatchement Systems). Photo: Lisa Jimenez|
US buildings are responsible for 40% of all material flows and produce 15-40% of the waste in landfills. At least 50% of this “waste” could be reused or recycled. The average American spends 90% of his or her time indoors. With this in mind, it makes sense to build with natural, nontoxic materials.
Green Building Materials are those that are healthy for the indoor and outdoor environments, help minimize building energy use, have low-embodied energy (avoid products that result from energy-intensive manufacturing processes), are durable, reusable, nontoxic, recyclable, and/or biodegradable, and are locally obtained. Some examples of green construction materials include:
Adobe: An earthen, sun-cured brick that is labor-intensive but considered a low-embodied energy material. Adobe uses less than 16% the production energy of concrete block. Adobe lacks the insulating properties of straw, but provides a large thermal heat sink that absorbs heat during the day and releases it during the night, thereby moderating the building’s internal temperature. The same is true for puddled adobe and rammed earth. Puddled adobe is a mud mixture formed and layered by hand rather than pre-made into bricks, while rammed earth forms mud into thick, durable, monolithic walls through tamping down of earth into molds. Cob is earth and straw molded by hand into sculptural walls that work well in hot, dry climates along the same principle as adobe. Cob construction in other climates may require supplemental insulation.
Straw bale construction utilizes this waste product from the farming industry. Straw is a low-embodied-energy material that provides good insulation and fire resistance. Papercrete is made from shredded paper and cement and formed into blocks and laid like adobe brick.
|Adobe, cob materials||Reuse of wine cork for wall||Strawbale truth window|
Homeowners in this exhibit have created a variety of spaces that aid in heating, are protected from the elements, provide privacy and a more natural environment in which to live and work.
Sunspaces: Sunspaces are areas of the building, such as a greenhouse, that store lots of energy when the sun is available and give off that radiant heat to the rest of the building when and where it is needed.
Courtyards: Courtyards can be used to create an outdoor space that is protected from high winds, provides warmth in the winter and cool shade in the summer, as well as privacy.
Outhouses/composting toilets: Composting toilets eliminate the need to use water to dispose of sewage.
|Inner courtyard with adobe wall buit by Adobe Techniques|
Facts and terms from: Green Building: Project Planning & Cost Estimating, RS Means, 2002.
Photos by Marya Gendron, except where noted.