LEED Overview: A Net Positive Home

LEED Overview: A Net Positive Home

This LEED Platinum pending home is the product of successful collaboration of owner, architect, builder, and subcontractors, all of whom worked to ensure that the owners’ functional, design, budgetary, and sustainability goals were achieved. The home is “net positive,” meaning that it produces more energy than it consumes -- 48% more on an annual basis, to be exact! – and remarkably efficient, all without comprising on functionality, comfort, and design.

Below is a summary of the home’s attributes described within the framework of the LEED rating system.

Innovation & Design Process

Integrated Project Delivery: From concept to completion, the owner, architect, and builder collaborated closely to ensure that the sustainability goals of the project were kept at the forefront of conversation and in the decision making process. LEED calls this team-based approach Integrated Project Delivery (IPD), as contrasted with a more typical linear build process where an owner provides input to an architect who creates a design for a builder who gives build instructions to subcontractors. A clear advantage of IPD is that all of these voices are heard throughout all phases of the design/build process, including conceptual design, LEED planning, energy and envelope design, and construction.

Sustainable Sites

Landscaping: Conventional turf was completely avoided to reduce needs for mowing, watering, and fertilization.  A rainwater catchment system was included in the design for future installation in order to allow the collection of water runoff from the roof for use on the gardens.

Drought-Tolerant Plants: 45% of installed plantings are drought tolerant, further reducing landscaping water use, and allowing the owners to skip installation of any kind of irrigation system altogether.

Surface Water Management: careful planning and intentional design minimized impermeable surfaces. Only 8% of the lot consists of impermeable surfaces, with 92% preserved for vegetative landscaping, reducing problems associated with water runoff as well as the heat island effect.

Water Efficiency

Indoor Water Use: high efficiency plumbing fixtures were selected throughout the house in order to reduce water consumption from normal occupant use. In concert with LEED guidelines, fixtures with low average flow rates were prioritized -- faucets less than 1.50 gpm (gallons per minute), shower fixtures than 1.75 gpm, and toilets less than 1.10 gpf (gallons per flush).

Energy & Atmosphere

Optimize Energy Performance: among the more remarkable aspects of this home is its exceptional efficiency. The HERS Index (Home Energy Rating System) was created to measure structures’ total energy efficiency, much like fuel efficiency of automobiles is quantified in miles per gallon. A HERS Index score reflects a home’s overall energy performance and is calculated with variables representing attributes of exterior walls, ceilings and roofs, attics and foundations, windows and doors, vents and ductwork, and HVAC and water heating systems. The lower the HERS Index score, the more efficient the home. For example, a home with a HERS Index score of 150 is 50% less efficient than a standard new home, a home with a HERS Index score of 100 is equal to the efficiency of a standard new home, and a home with a score of 50 is 50% more efficient than a standard home.

This home achieved a remarkable HERS Index score of -9, meaning that it is a whopping 109% percent more efficient than a standard home. It produces more energy through renewable resources than it consumes (i.e. Net Positive), with a forty high-efficiency solar panel panels, a 13.8 kWdc system, installed on the roof.

Materials & Resources

Environmentally Preferable Products: LEED places an emphasis on building components that “minimize material consumption through recycled and recyclable content, reclamation, or overall reduced life-cycle impacts.” Among the attributes of this home consistent with these objectives are:

  • Locally sourced framing lumber
  • Locally sources wood flooring
  • Water-based floor finish
  • Low VOC, water-based interior paints
  • Recycled cellulose insulation

Waste Management: in order to reduce the quantity of debris and waste sent to landfills, the construction team made an effort throughout the construction process to reuse or recycle as much as possible. These efforts clearly paid off, with an estimated 92% of construction materials removed from the site diverted from landfills.