2012 Challenge Participant:
BPC Green Builders
Applicants: Mike Trolle - Builder, Rob and Linda Gould - Homeowner
Project Address: Norwalk, CT
Bdrms./Sq. Footage: 5 BD - 2,562 sq ft
Builder Website: www.bpcgreenbuilders.com
BPC Green Builders is managing the construction of this new contemporary style home, which is seeking certification from both the ENERGY STAR for New Homes program and the USGBC LEED for Homes green building program, with the goal of achieving the Platinum Level. The owners are committed to building a sustainable home that is energy efficient, water efficient, and resource efficient. These features include:
- The home is located on the water in Norwalk Harbor with views of tidal inlets as well as the Norwalk River. Working within the site's setback restrictions, the home was oriented with extensive roof overhangs to create passive winter solar gain and summer shading.
- The owners consciously chose to build a much smaller house (2,546 square feet of conditioned living space) than the local zoning regulations allowed for the site.
- Development of the relationship between the interior and exterior environment was a feature of the architectural design. The living space is enhanced by large glass windows and doors that open onto extended living space on a large outdoor patio. Roof overhang soffits continue into the house's ceilings to reinforce the interior-exterior continuity.
- The slope of the roof was designed to create a "waterfall" effect that can be viewed from the living room during stormy weather and directs rainwater back into the harbor.
- Rock gardens and native plants will be used on the property to reduce water consumption.
- The waterfront location dictated a slab-on-grade foundation to avoid possible basement flooding issues. The slab has been thermally isolated from the ground below with 6" of expanded polystyrene foam board (R-27) and from the frost walls with 3" of the same material (R-13.5).
- Advance framing technology was introduced to reduce water infiltration in driving coastal rain conditions by setting the wood sill below (and not on top of) the concrete slab.
- To reduce heat loss through the framing, the thickness of the walls was increased to enable a greater amount of insulation and to introduce a thermal break. Heat loss through the framing is known as thermal bridging, which is bad, and this strategy results in a thermal break, which is good! The exterior walls are being framed with 2x6's spaced at 19.2" OC using FSC certified sustainable lumber, with 2x2's nailed across the walls. This wall design creates 1-1/2" of space for insulation in front of the wall framing. The walls will be insulated with 7" of Agribalance 0.8lb spray foam (R-31.5)
- Heat loss in the corners was reduced by adding rigid foam board in lieu of the standard building practice of uninsulated wood posts.
- To reduce air infiltration, extensive layers of spray foam and sealant will be inter-layered between the wood framing and adjoining surfaces, such as the foundation, windows and exterior door frames. The wall sheathing will be constructed using a Zip-Wall system with taped joints to reduce air infiltration.
- Possible water infiltration in the walls was addressed with a rain drainage layer between the insulation and cedar siding.
- Windows and the sliding exterior doors will be fiberglass with exceptional thermal properties. The U-values will range from 0.17 to 0.20, which is the equivalent of R-5 to R-7. The windows greatly exceed the Energy Star standard of 0.30 (equivalent of an R-3.3). The fiberglass window frames will be very durable and low maintenance, which are important qualities in a coastal environment.
- The 2% slope EPDM roofs will be framed with engineered lumber, primarily I-joists, which do an excellent job of reducing thermal bridging. The roof joist cavities will be insulated with 12" of Agribalance 0.8lb spray foam (R-54)
- The home will be heated and cooled by a geothermal heat pump system. Careful attention will be given to fully air seal the ducts. The entire mechanical room and all ducts are located within the conditioned envelope. The homes design heating load is 23.5 MBH and its design cooling load is 21.4 MBH for the 2,546 square feet of conditioned space. Given the highly energy efficient design of the home, the load calculations have indicated that the system will operate on the first stage for the majority of the time, thereby reducing the amount of energy consumed.
- Gas and wood burning fireplaces are sealed units with Energy Star ratings. They were sized to avoid excessive overheating of this tightly sealed house. The wood burning fireplace has been designed to enable utilization of the heat generated.
- Ventilation is provided by an energy recovery ventilator (ERV) which draws exhaust air from the bathrooms (and ventilates them) while simultaneously providing fresh air to the entire house. The beauty of an ERV is that it transfers the majority of the heat and moisture from the exhaust air to the fresh air in the winter (and vice versa in the summer) which saves a considerable amount of energy.
- Natural cross ventilation of the home has been designed with the location of the glass windows and doors to take advantage of the east-west and north-south coastal breezes. Accumulating summer heat can be ventilated by opening easily accessible windows positioned at the top of the stairs.
Plumbing & Electrical
- Domestic hot water is produced by a high efficiency, condensing, tankless hot water heater. The unit is located on the second floor to minimize the linear footage of piping required and maximize the delivery of hot water to the bathrooms.
- The hot and cold water piping will be insulated with R-4 or higher.
- Low-flow faucets will be used throughout the home to conserve water.
- Dual flush toilets will be installed in the bathrooms for the same reason.
- The refrigerator, dishwasher, & clothes washer will all be Energy Star rated.
- The lighting will be a mixture of fluorescent and LED fixtures. Standard fixtures will have CFL bulbs.
- A 10kW solar photovoltaic system will be installed to support the home's electrical demand and will be grid tied to return electricity to the grid when more is produced than consumed in the home's operation. The low profile (less than one inch high), lightweight panels are designed for low-slope roofs and will not negatively affect the architectural silhouette of the home. The adhesive backed solar modules avoid penetration of the roof, typically associated with solar panels, which contributes to the air tightness of the house
Additional "Green" Features in the Home
- The home is designed to ENERGY STAR Version 3.0, even though not required.
- All the wood floors will be a FSC certified engineered floating floor.
- The bathrooms will have US Green Building Council approved ceramic tiles that contribute to LEED certification level.
- Bathroom vanities will be fabricated with FSC wood.
- The outdoor stone patio and rock gardens will be constructed using local materials, i.e. stone quarried within 500 miles of Norwalk, CT. The stones found on the property will be reused in the landscape design.