Key to Sustainable Home Design
When considering a major addition or building a new green home, the process of planning, design, and construction should take into account the following key points:
• Scale of Home. What is your vision and how big or small you need to be to have a sustainable home? Scale requires thinking for the future, considering the change and accounting for expansion or modifications. Big is not better but the “Shoebox” footprint may not be for everyone. We encourage serious considerations about the size and scale of your home so that you can foresee and adapt to some of the necessary changes that the future holds.
• Location. The home location shall be also carefully considered as it can be a key to the carbon footprint each of us produces or reduces from our daily routines of commuting to work. Location can make the home sustainable potentially in that the commercial services, suppliers, food stores, and restaurants are located within walking distance of your home. This obviously could save time and can reduce the dependency on automobile transportation.
• Siting / House orientation. When considering a major addition or remodel of your home, consider good practices of passive design and solar orientation. The orientation is important to situate your home to take advantage of the sun, views, heat exposure, and daylighting. For example, morning light can be delicate in space and is desired for breakfast areas while it can be annoying if shining into a bedroom. Meanwhile, the western exposure will flood the room with golden overtones, orange, and reds and for some geographic locations, it will feel on fire. This could present opportunities for amazing sunset views as well as heat gains that may affect the comfort of the home. Designers generally agree on the southern exposure orientation and the bolder more uniform lights that this exposure offers. Northern light is also more uniformed, softer and diffused that often is seen as consistent calming lighting, never too harsh or too dull. Orientation and design features such as good windows, and building overhangs make the house orientation an important design parameter.
• Building Envelope. When detailing the building envelope, we have to consider the thickness of the wall, the insulation value, and type that fits in this wall thickness, the vapor barrier, air infiltration, thermal bridging, flashing, protection from water penetration and the finished skin of the building. The detailing should be considered as a whole, as an integrated system. The higher insulation values and the type of insulation can create a more comfortable home and the energy that is spent to heat or cool will be retained by the building envelope and this will reduce the cycles of heating or cooling. A good example of the cycles of heating and cooling is the Thermos vs the Coffee Maker. While the thermos preserves the liquid in the hot or cold temperature the coffee makes will produce the hot coffee and after a while, the pot will get cold and the hot plate will try to heat and reheat the coffee if the pot until the machine setting finally turns off. This is similar to the tank-style water heaters vs tank-less water heaters. Tank-less water heaters are energy efficient and they will heat the water on demand.
The most important of all building envelope component is the roof. An R-49 or higher roof insulation is recommended for our climate zone 4. The color of the roofing system also affects the roof’s ability to absorb the sun’s energy. The higher the reflective index or the lighter the roof color, the cooler the roof would be. The solar reflectance index is a measure of the constructed surface's ability to reflect solar heat, as shown by a small temperature rise. At the same time, the ventilation of attic space by low (eave) and high (ridge) vents is important as it allows the heat to escape and it extends the life of the roof. These building envelope components affect the home’s energy efficiency and comfort.
• Ventilation. Ventilation of the home is important for health and air quality. This consists of natural and mechanical ventilation designs. The natural cross ventilation can efficiently remove the stale air by opening doors and windows to allow the outdoor fresh air to fill the house. Mechanical ventilation can provide a uniformly distributed air and temperature that speaks comfort and directly affects energy consumption and efficiency. Mechanical ventilation can also regulate the humidity by removing the air moisture during summer or by adding moisture to the dry air for comfort during winter.
• Passive House features. These include solar, wind, geothermal energy, thermal mass, shading, daylighting, and window design. Some of these passive house features were listed or explained above such as solar orientation, envelope insulation, and ventilation. The thermal mass, for example, is effective in improving the building comfort and it is ideally placed within the building situated centrally to receive the low angle sun energy during the winter but not hit directly by the sun’s high angle during the summer. When used well and combined with passive solar design, thermal mass can play an important role in major reductions in energy use in active heating and cooling systems.
• Material Selection. All the appliances, equipment, lighting shall be selected with the energy efficiency in mind. High-efficiency HVAC, low flow water conservation plumbing fixtures, Energy-Star appliances, and LED lighting will translate into energy savings and utility cost reductions. The finishes such as paints, flooring, cabinetry, and countertops. shall be carefully selected to provide not just a visual appeal but a structurally sound use, ease of maintenance, and no VOC. These recourses should be renewable, selected locally, and should have a recyclable content, such as quartz, metal, plastic, and paper that are reused and recycled into innovative building materials.
Following is our newest completed residential new construction home in Fairfax County, Virginia. The scope included reuse of existing footers to minimize the land disturbance area, thicker exterior wall construction with upgraded wall and roof insulation. Energy star roofing, 97 % high-efficiency HVAC systems. Energy-efficient windows and doors, tankless water heaters, LED lighting, and other design and site-specific sustainable features.