Bob Ward Companies is helping to zero in on Zero Energy homes.
The M.E.G. concept was developed to complement and extend existing ENERGY STAR principles and to incorporate a whole-house systems approach to achieve superior energy efficiency and exceptional performance. The two primary features of M.E.G. are:
- Significantly reduced building loads through constructing an efficient shell and using high efficiency equipment and lighting, and
- Integrated renewable energy systems such as solar thermal and solar electric systems to produce energy right at the home.
The M.E.G. home design takes the first steps toward the next level of energy efficiency, moving beyond ENERGY STAR performance and closer to achieving net zero-energy use.
*Superior Wall Foundation R-12.5 System1
The pre-fabricated foundation system offers the advantages of structural integrity, good thermal performance, and moisture/water protection as well as quick installation. The system can also be installed during cold winter months when temperatures often prevent poured concrete systems. The system is available in either an R-5 or R-12.5 wall. Insulation can be increased by placing additional fiberglass or cellulose between the steel-reinforced concrete studs. The studs are predrilled for wiring and plumbing and are faced with galvanized steel for wallboard attachment. The Dow Styrofoam has been tested under UBC-23 and UL-1715 and does not require a thermal barrier over the foam plastic.
Band Joists – Air Sealing
It is important to air seal as well as insulate the band joist areas. Here the band joists were sprayed with a 1”-2” layer of foam and then netted and blown with the BIB system as you will see upstairs. Penetrations to the outside such as electric entrance cable, water, and sewer lines should also be sealed. On upper floors, also note that all plumbing and electric penetrations to the lower level and attic are sealed.
High Efficiency Heating and Cooling Equipment. Carefully Fabricated and Sealed Ductwork
ACCA Manuals J, D, and S are used to properly size system and select equipment. High efficiency cooling units such as the ultra high efficiency unit from Trane, has enhanced dehumidification in cooling mode and a variable speed motor to adjust the unit output to better match cooling loads. These high efficiency units, many of which have multi-speed compressors, can be sized closely to the peak load without loss of performance or comfort while minimizing energy use. Rated efficiencies as high as SEER 19 for an air-air system are possible with commercialized technology.
Ductwork joints are tight and sealed with foil tape – UL 181. Mastic can also be used to seal ducts. All ducts are located within conditioned space as you will see as you walk through upstairs.
Manifold Plumbing System and PEX Piping
- Parallel-piping system can conserve water because wait times for hot water at distant fixtures are reduced
- Easy to isolate individual runs
- Parallel piping systems (as with all plumbing systems) should be designed to limit the distance from the manifold to the outlets.
- Flexible PEX piping can speed installation time and reduce labor costs
- As seen upstairs, there are no intermediate fittings that pose greater risk of leaks
Tankless Water Heater
Demand water heaters, especially when combined with a parallel piping system, are more energy efficient than a conventional tank heater and standard tree plumbing system because they eliminate standby losses and reduce piping losses. The demand heaters can also be installed in more locations due to flexible venting and size characteristics. The estimated costs are about 2 to 3 times that of a tank heater.
Mechanical Ventilation System
Duct from the back wall of the sunroom to the return trunk in the lower level brings in outside air whenever the air handler operates. The outside air mixes with return air from the house, is conditioned by the central heating/cooling equipment, and delivered to the living space. A damper is installed in the duct to prevent continuous air flow from outdoors. The exhaust side of the mechanical ventilation system is coupled with the bath exhaust and can be seen from the second floor.
Blown Fiberglass Insulation
Blown insulation, whether fiberglass or cellulose, offers more consistent air sealing properties than batt insulation. Blown insulation fills around obstructions like electrical boxes and plumbing piping. However, careful air sealing details as specified below can achieve a tight building envelope with either material. R-values in the house:
Walls – 2” x 4” – R-15
2” x 6” – R-23
Attic – R-38+
Sunroom Ceiling and Garage Ceiling will be batted – R-38
Use Optimum Value Engineering (OVE) framing details to reduce thermal bridging and increase overall R-value of entire wall
OVE measures include:
- 3-stud corners
- Ladder nailers where interior partitions intersect exterior walls
- Non-load bearing headers on non-load bearing walls
- Insulated headers on load-bearing walls, e.g., additional rigid insulation to the interior of header assembly (rather than OSB filler)
Cost savings can be achieved here by eliminating unnecessary framing members and reducing construction waste.
High Performance Windows
- Low-e argon-filled windows
- U-value = 0.36 (U-value is overall insulating value for the whole window including frame.)
- Solar Heat Gain Coefficient = 0.30 Only 30% of the light striking the window is transmitted as heat
Ducts within Conditioned Space and All Joints Taped
Note double wall between kitchen and garage to provide adequate room for insulation. Supply ducts in garage ceiling to master bedroom will be insulated. Ductwork and plenums are carefully fabricated and all seams taped.
Flexible PEX piping eliminates most concealed connections and reduces potential for leaks. Sweeps rather than 90o elbows reduce flow restriction. The PEX piping is usually quicker to install than copper or rigid plastic pipe.
Install whole-house mechanical ventilation
High efficiency and quiet bath fan(s) with automatic controls can provide a reliable and simple solution for mechanical ventilation. When included with a manual override option, the normally low exhaust flow rate may be boosted to a higher level for point source exhaust in areas of high humidity (bathrooms and kitchens). Since the units will be set to operate on a periodic basis, the fans should not only be efficient but also have a low-zone rating.
The Fantech multi-port exhaust fan that is located in the attic will provide both bath exhaust to remove moisture and low-level whole house ventilation. A Tamarack Technology Airetrak control will operate the fan intermittently at low speed and then the push-button control allows the fan to be boosted to high speed for about 20 minutes. A twist timer will be installed in the hall bath and interfaced with Airetrak via a relay located in the attic. A duct also exhausts from the kitchen to facilitate distribution throughout the house. When coupled with the outdoor air intake in the lower level, a semi-balanced system is achieved, which means that the house will not be excessively pressurized or de-pressurized.
Note that the plumbing and electrical penetrations to the attic are sealed. Penetrations between floors are also sealed to provide additional assurance that there will be no leakage through the floor joist space.
Note crimp connections between the PEX and copper stub-outs. The manufacturer provides a special tool for making these connections. Conventional shutoffs can also be located at each fixture.
1″ insulating sheathing board with sealed and taped joints to the exterior of the framing.
This enhancement eliminates “thermal shorts” through framing members, moves the dew point surface to outside the framing member (reducing moisture problems within the wall cavity), and reduces the negative effect of header and multiple framing members at openings. When a low perm rating insulation such as extruded polystyrene is used and the seams are taped, an additional air barrier or housewrap is not required. In addition, an internal vapor barrier is not recommended.
Install a solar preheat system with 80 gallon storage tank.
- Two solar hot water panels installed on the south-facing hip roof
- Original gable roof was redesigned to provide this south-facing roof area
- The solar acts as a pre-heat system boosting cold water temperature by as much as 80 degrees. The backup demand heater will operate only as needed. A glycol anti-freeze solution will be circulated through the collectors and then through the storage tank located in the basement. When hot water is called for, it will run through the tankless heater activating the electric element – if required.
Install a photovoltaic (PV) solar electric system on rear roof.
- 3kW system estimated to produce about 2500 kWh per year
- System faces east/southeast
- DC electricity produced converted to AC by two inverters in basement
- Net-metering – Electricity not used in the house is sent back to the utility and customer is credited at the same rate as purchased utility energy.
1 * Manufacturer and/or Trade Contractor probably on site.