Bob Ward Companies of Edgewood, Maryland worked with the NAHB Research Center to build one of the first ultra energy-efficient production homes in the Mid-Atlantic region. Although the home does not boast 100 percent net-zero annual energy consumption, it is a significant step beyond the builder’s current ENERGY STAR® qualified home designs. It is also the first time Bob Ward Companies included renewable energy systems in a home. Combining state-of-the-art energy-efficiency features with solar thermal and photovoltaic technologies, the home is expected to perform about 50 percent better than a standard code-compliant home of similar size.
From foundation to framing to mechanical systems, the team identified a package of cost effective energy upgrades that could be incorporated into the home. Because all of Bob Ward Companies' homes are already built to the ENERGY STAR® level, the company and its trade contractors are already familiar with many high performance measures. For instance, their ENERGY STAR rater, Energy Services Group, also performs careful air sealing details on every home; their HVAC contractor, N.M. Phillips, sizes heating and cooling systems carefully using the ACCA manuals and installs high efficiency equipment. This ultra-efficient home was really a step to achieve the next level of energy efficiency rather than an entirely new goal.
The energy-conscious components included:
Advanced Framing Techniques: Optimum Value Engineering (OVE)
Efficient framing reduces unnecessary lumber, and increases thermal performance of walls. Turned stud corners, cantilevered roof trusses, header hangers, and ladder-blocking at interior-exterior wall intersections all contribute to an overall efficient framing design.
Details about Advanced Framing are available in the PATH Technology Inventory, including manufacturers and general CAD details. The Advanced Framing Techniques TechSpec provides a comprehensive overview of this technology.
Cross-linked Polyethylene (PEX) Plumbing
Pex piping was installed using a central plumbing manifold system, which reduces wait time for hot and cold water, and energy loss, since less hot water is left in pipes.
Details about Cross-Linked Polyethylene (PEX) Piping are available in the PATH Technology Inventory, including manufacturers and many resources. The Home Run Plumbing Systems TechSpec provides a comprehensive overview of this technology.
High Performance Glass and Glazing
Low-e windows with a U-value of about 0.33 were installed instead of traditional-glazed windows– an approximate 35% improvement over standard double-pane glazing.
Details about High Performance Glazing are available in the PATH Technology Inventory, including manufacturers.
HVAC Equipment and Duct Installation within Conditioned Spaces
All duct work was installed in conditioned spaces within the home, tightly sealed with foil tape. Transfer grills ensured an adequate return air pathway.
Details about HVAC Equipment and Duct Installation within Conditioned Space are available in the PATH Technology Inventory. The Whole-House Ventilation Systems TechSpec provides a great overview of this practice.
Insulation Alternatives: Blown or Foamed Through a Membrane
To improve air tightness and ensure complete cavity fill, a netting was applied to wall studs, and fiberglass insulation was blown in.
Details about Insulation Alternatives: Blown or Foamed Through a Membrane are available in the PATH Technology Inventory. The Insulation Alternatives TechSpec provides a great overview of this practice.
Photovoltaic Systems
An array of photovoltaic panels and two solar thermal panels were placed on the roof. The photovoltaic system generates electricity that can either be used in the home directly or fed back to the utility during times when excess power is produced.
Details about Photovoltaic Systems are available in the PATH Technology Inventory, including manufacturers.
Precast Concrete Foundation and Wall Panels
The home used a Superior Walls™ precast concrete foundation with an R-12.5 insulating value plus additional R-13 cavity insulation was installed when the basement was finished.
Details about Precast Concrete Foundation and Wall Panels are available in the PATH Technology Inventory, including manufacturers. The Precast Concrete Panels TechSpec provides a great overview of this technology.
Solar Water Heating and Tankless Water Heater
A solar water heating system is used in tandem with a tankless water heater to supply all domestic hot water. In a region like the Mid-Atlantic, the solar water pre-heating is estimated to reduce energy purchased from the utility for water heating by at least 50 percent. The tankless water heater eliminates standby losses of a tank storage heater, resulting in a 10-20 percent reduction in energy use for water heating.
Details about Solar Water Heaters and Tankless Water Heaters are available in the PATH Technology Inventory.
Whole-House Ventilation System
To provide exhaust from the kitchen and bathrooms, and to assure a consistent air exchange and introduction of outside air, a programmable whole-house ventilation system was installed.
Details about Whole House Ventilation Systems are available in the PATH Technology Inventory, including manufacturers. The Whole-House Ventilation Systems TechSpec provides a great overview of this technology.
Additional Energy Consumption Reduction Measures
The primary goal in this home is the overall energy consumption of the home as a whole. Other technologies included:
- ENERGY STAR® appliances
- An extensive air sealing package to minimize air infiltration
- Continuous rigid insulation on the exterior walls adding an additional R-6.5 outside the wall framing
- 14 inches (approximately R-49) of loose-fill fiberglass insulation in the attic
- Energy-efficient lighting package to include fluorescent fixtures, compact fluorescent bulbs, and motion sensors on exterior lighting