Sustainable Design Group • 301.428.1040 • 22923 Wildcat Road, Gaithersburg, Maryland 20882

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Technical Approach

We approach every project with sustainable design and construction objectives. Our technology solutions are married with our monitoring control system, to give your house the ability to monitor energy and efficiency in real time so you can manage your energy consumption.

Healthy Indoor Environment
  • Material selections as free as possible of toxic materials such as Volatile Organic Compounds (VOC). Materials of concern are paints and adhesives, cabinetry, carpet, and padding.

  • Well vented combustion systems to avoid combustion by-products entering the indoor air space. Combustion systems should have sealed combustion or a dedicated outside air source for combustion air. Systems of concern include water heater, furnace, fireplace, and cooking systems.

  • Whole house ventilation that provides a dedicated fresh air source for the home.The system is an Energy Recovery Ventilation system (ERV). The ERV exhausts stale air from inside and delivers fresh air to the entire house. The air exchange is done through a heat exchanger that transfers the heat or cooling from the outgoing air to the incoming air to temper it close to the indoor air temperature.

  • Maintain relative humidity levels to minimize the growth of mold and mildew and to maintain comfort. This is controlled with the ERV and waterproofing systems that eliminate the risk of water leakage in the foundation or from the roof.

  • Air filtration to minimize the dust and particulates in the air with a HEPA filter system. UV light system can be used to minimize airborne bacteria.

  • Water filtration to remove unwanted bacteria, chemicals, and particulates from the drinking water system. A two-filter system consists of a particulate filter followed by a carbon filter. A UV light system can be used to minimize bacteria in the water.

  • Zoned heating and cooling system for good comfort control.

  • Air-tight building envelope to minimize drafts and infiltration of outside air pollutants.

  • Windows and skylights are designed to provide ample sunlight to the majority of the home. In the winter, it will be direct sun and in the summer, it will be indirect sunlight from a shaded source.

Energy Efficient Building Envelope
  • Wall, roof, and floor insulation levels that minimize the energy load of the building in the most cost effective manner. Typical levels are R-25 for walls and floors and R-50 for the roof. Higher levels can be used if they are determined cost effective in context of the whole house energy design.

  • Windows are selected based on their insulating value (U Value) and their solar heat gain coefficient (SHGC). Windows facing south have a high SHGC and a low U value.The south windows maximize the solar heat gain in the winter to heat the building during a sunny day. A shading device is needed to shade the south windows in the summer to prevent overheating. Windows on the north, east, and West have low SHGC and low U value. The low SHGC prevents solar heating in the summer. Windows are also selected for their air tightness and durability. No vinyl windows are used.

  • The envelope is air-tight to prevent uncontrolled air infiltration.

Energy Efficient Appliances
  • Lighting will be LED selected to provide the required light levels, color rendition index (CRI), and color temperature for the application.

  • Appliances will all be the most efficient within the EPA Energy Star rating.

  • Heating and cooling system will be selected based on the most efficient and cost effective for the loads of the home. Systems typically include 95% efficient gas furnace and water heater, geothermal heat pump, air source heat pump, and high efficiency ductless heat pump.

Sustainable Energy System
  • Resilience.  The home will be able to function with or without the grid connection. All critical functions of the building will be able to continue in case of a grid power failure.

  • Solar power system. The solar power system will be sized to provide 100% of the home's annual electricity needs. The home is connected to the grid and the solar system is interactive with the grid. If the solar energy system generates more electricity than the house can use, excess solar energy is sold back to the utility company. Only if the house needs more energy than the solar system can provide does the home draw from the grid.

  • Battery system. At a minimum, the home will have a battery system that will have the capacity to power the critical loads in the home for 3 days. Larger battery capacity can be used as needed. The batteries are charged by the grid when it is available and by the solar system. A separate critical loads panel will be powered by the solar energy system. The critical loads typically include refrigerator, freezer, well pump, igniters on the gas appliances, basic lighting, and basic communications systems. Heating, water heating, and cooking may be considered a critical load if gas is not available.

  • Backup heating, hot water, and cooking. Heating, hot water, and cooking can be powered by electricity or gas. An all-electric home will require a very large solar system and batteries sized to meet the desired backup level. If natural gas or propane gas is available, backup heating, hot water, and cooking can be provided by gas. Wood can also be considered for backup heating. Gas and wood as a backup system significantly reduces the solar energy system and battery size.

  • Electric car charging system. This allows the solar system to charge up to two electric vehicles.

Rain Water Management
  • Storm water will remain on the site. Gutters and downspouts on the house will drain to dry wells and rain gardens to allow the rainwater to drain into the aquifer on site and minimize runoff.

  • Porous surfaces will be used for driveways and patios.

  • Rain water may be collected for household use and irrigation. Local regulations will determine allowable uses for rain water.