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Passive Solar Design & Daylighting
Buildings designed for passive solar and daylighting incorporate design features such as large south-facing windows and building materials that absorb and slowly release the sun's heat. No mechanical means are employed in passive solar heating. Incorporating passive solar designs can reduce heating bills as much as 50 percent. Passive solar designs can also include natural ventilation for cooling.

Proper building orientation, with the longest walls running from east to west, allows solar heat to enter the home in winter, while allowing in as little sun as possible during summer. Shading and overhangs also reduce excessive summer heat, while still permitting winter sun. In passive solar designs, the optimal window-to-wall area ratio is 25-35 percent.

Daylighting uses natural sunlight to light a building's interior. In addition to south-facing windows and skylights, clerestory windows–a row of windows near the peak of the roof–can let light into north-facing rooms and upper levels. An open floor plan allows the light to spread throughout the building. Daylighting in businesses and commercial buildings can result in substantial savings on electric bills, provides a higher quality of light, and improves productivity and health. Daylighting in schools has been shown to improve student grades and attendance.

For more information, visit EREN's Passive Solar Heating, Cooling and Daylighting

Building Envelope
The building envelope includes everything that separates the interior of a building from the outdoor environment, including the windows, walls, foundation, basement slab, ceiling, roof, and insulation. The building envelope remains one of the easiest and most important ways to improve the energy efficiency of a building.

For more information, visit EREN's Building Envelope page

High Performance Glazing
Windows are rated on its U-value (which indicates how well the window insulates), shading coefficient (how well the window keeps out solar heat gain), and visible transmittance (which indicates how well light passes through the window). High-tech efficient options include windows with gas-fill between the window panes and low-emissivity (low-e) coatings.

For more information, visit EREN's Building Envelope page

Photovoltaics
Photovoltaics (PV) offer a way to convert the sun's radiation into electricity that can be used in a house. PV can either be used in a stand-alone system (in combination with a battery bank and/or backup generator) or in a grid-tied system (connected to the utility grid).

For more information, visit EREN's Photovoltaics page

Solar Hot Water
Solar hot water heaters use the sun to heat either water or a heat-transfer fluid in collectors. There are passive systems, which rely on natural convection and gravity to circulate the fluid, and active systems, which use pumps and other mechanical equipment. Sometimes the plumbing from a solar heater connects to a house's existing water heater, which stays inactive as long as the water coming in is hot or hotter than the temperature setting on the indoor water heater. When it falls below this temperature, the home's water heater can kick in to make up the difference. High-temperature solar water heaters can provide energy-efficient hot water and hot water heat for large commercial and industrial facilities.

For more information, visit EREN's Solar Water Heating page

Natural Ventilation
Natural ventilation utilizes stack effect and wind pressures to supply outdoor air to building interiors for ventilation and/or space cooling purposes. The aim is to have an airtight building envelope while controlling outdoor air supply to provide the required ventilation. Features of naturally ventilated buildings include operable windows, exhaust vents located high in the building with intakes located low in the building, and open building plans to facilitate air movement.

For more information, visit Advanced Building's Natural Ventilation page

Mechanical HVAC Equipment
HVAC stands for heating, ventilation, and air-conditioning. HVAC equipment has energy-efficiency ratings that list how many Btu per hour are removed for each watt of power it draws. The higher the efficiency rating the more energy is saved. These ratings are posted on an Energy Guide Label, which must be conspicuously attached to all new equipment.

Building Materials
Materials that are considered "green" contain some of the following criteria: recycled content, recyclable, sustainably harvested, low embodied energy, environmentally friendly manufacturing process, non-toxic, low VOC (volatile organic chemicals), and made in the USA.  Minimizing construction waste is also an important factor to consider in the green building process.