Secrets behind the walls of 3 high performance green homes
The NeoTerra Home
It's easy being green; after all, there are many ways to design and build a high performance green home.
Here's a look behind the building science of three high performance homes built with different techniques and technologies, but with similar goals in mind to reduce energy and water use, live sustainably and have a comfortable, durable home.
Some were built to meet green building certifications such as LEED, Passive House, or Energy Star. Others were built to those standards but the owners chose not to seek actual certification.
Frame construction with batts & spray foam
The owners of the NeoTerra (New Earth) house studied building programs such as Passive House and built their home with many of those techniques but opted not to pursue certification.
The home, situated at about 2,800 feet above sea level on a Georgia hillside, takes full advantage of its setting to incorporate passive solar design.
The lower levels of the home were constructed with precast pre-insulated concrete walls fabricated by Superior Walls.
The upper levels were built with 2x6 frame construction using a flash-batt system that mixes spray foam insulation and batt insulation. The sprayfoam filled the stud bays to a depth of 2 inches and the rest was filled with fiberglass batts or blown-in insulation.
|The NeoTerra home uses Andersen Windows and a concrete slab for its solar passive heating design. Photos courtesy of NeoTerra.|
To take advantage of the south-facing windows, the home uses a suspended concrete slab, 2.5 inches thick on a steel joist system. The owner embedded 25 sensors into the slab to track temperature performance through the seasons.The owner considered using the structural insulated panels, but had trouble finding a local contractor experienced with that construction style. The placement on the steep hillside also contributed to a higher degree of difficulty.
The owner also received a waiver to use high solar gain windows from Andersen that were not normally allowed under local codes. But the goal was to allow solar heat through the windows to heat the slab floor for passive solar heating. The large windows also offer spectacular views of the Georgia countryside. The Andersen 100 series windows were an economical choice for a home with a lot of window area.
The roof and some of the exterior use ribbed galvalume metal siding manufacturing in the state, and the exterior also features Nichiha fiber cement siding made in Georgia.
The owner said the home delivered a 3 air changes per hour in a blower door test. Current state building codes require a 7 ACH, but in 2017 that will drop to 3, so the home already meets the next level of code requirement.
"There will be substantial energy savings but it's also a much more comfortable house," the owner said.
Award-winning ICF home
A coastal colonial-style home built with insulated concrete forms achieved a HERS Rating of 27 and met all the requirements of the Department of Energy Zero Energy Ready Home certification program and ENERGY STAR Certified Homes Version 3.0.
|The Shore Road Project|
The 4,100-square-foot Shore Road Project in Greenwich, Connecticut was designed by Crozier Gedney Architects. Lois Arena of Steven Winter Associates was the project energy consultant and the builders were Murphy Brothers Contracting.
Also the home meets the indoor air quality specifications of the U.S. Environmental Protection Agency’s Indoor AirPlus and the water-saving requirements of EPA’s WaterSense program. It also meets the insulation requirements of the 2012 International Energy Conservation Code (IECC), which is a DOE program requirement.
It more than meets the program’s Renewable Energy Ready Checklists by having a 4.5-kW Dow Powerhouse Solar Shingle photovoltaic (PV) system already integrated into the roof.
The home also includes the following green features:
- FoxBlocks full insulated concrete form (ICF) exterior wall construction
- Closed-cell spray foam insulation in attic & rafters
- Bryant dual fuel heat pump & ERV system
- Dow Powerhouse Solar roof shingles: 4.5 kW PV system incorporated into the roof system.
- Energy-efficient Marvin & Andersen windows and doors
- Hardi-plank clapboard siding & Versatex trim
- Water-saving plumbing fixtures and Energy Star appliances
- Navien tankless on-demand hot water system w/ Enovative wireless hot water recirculating system
- LED & CFL lighting (50/50 split). All ceiling fans are Energy Star rated
- Reclaimed 100-year-old wormy chestnut used for the Kitchen island counter and Office desk top; the Den sliding door, fabricated from a hundred year old oak, toppled by Hurricane Sandy.
- Recycled blue jean insulation used in the interior walls and floors for sound attenuation.
- Low or No VOC paints were used throughout the home
Factory built walls and spray foam
The Proud Green Home of St. Louis utilized panelized wall construction and spray foam insulation as part of the building science behind the high performance home.
The home used factory-built trusses and wall panels, with Huber Zip System sheathing attached on the walls that sped up construction and greatly reduced on-site waste during framing. The only waste was roof sheathing, and because the sheathing was made with non-toxic epoxy, scraps were collected on site and were later ground into landscaping mulch.
The exterior and interior walls were factory-built by Mattingly Lumber and Millwork in Madison, Illinois, along with the roof trusses, and delivered to the job site.
|The Proud Green Home of St. Louis|
With panelized or factory built wall construction, a building professional can save time and money, as well as job site waste, and deliver a home that will perform better.
The builder, Hibbs Homes, chose the 7/16-inch ZIP System roof and wall sheathing from Huber Engineered Woods, and used advanced framing techniques as well. Together these building systems offer a more durable, efficient building envelope than traditional framing and sheathing techniques.
The home’s ZIP System created a thermal envelope comprised of continuous, insulated panels sized from architect Curtiss Byrne’s plans. The panels were manufactured off-site from engineered, oriented strand board layered with a highly efficient insulating foam in the center.
These continuous panels reduce the amount of seams in the thermal envelope to create a better barrier against air and moisture exchange. The ZIP System also meets the requirements for several green building codes, including the NGBS ICC-700 standards used to verify the home.
The panels to frame the home were shipped to the site and fastened to the frame of the home by our subcontractors. The panels were then taped together using a specially constructed, permanent adhering tape to further reduce thermal bridging.
The builders also used Optimal Value Engineering or advanced framing techniques to optimize the home’s energy efficiency and reduce waste and lumber costs.
With advanced framing techniques unnecessary framing redundancies are eliminated without compromising the structural and architectural integrity of the home while still surpassing building codes, more room is available for insulation. The design used raised heel, or energy, trusses in the home’s construction. Energy trusses are oversized and increase the height on exterior walls, allowing more room for insulation on the outside edge of the home.
The combination of advanced framing, ZIP system and spray foam insulation were carefully planned to work together to reduce thermal exchange and increase the home’s energy efficient performance.
The spray foam insulation from Dow Building Solutions was applied on site to the stud bays as well as the rim joist of the full basement under the home.
- Factory-built wall systems with sheathing and trusses.
- Raised heel energy trusses for better attic insulation
- Advanced framing intersection of interior wall and exterior wall.
- Advanced framing insulated headers, use 2 ½ inch rigid foam insulation on either side of header framing, with 2, 2x6 top plates.
- Advanced 2x6 frame on 24-inch on center with three stud corners
- Continuous air barrier from foundation to roof
- Rim joist caulked or gasketed to still plate.
- Subfloor, bottom plate, drywall, caulked glued or gasketed to next piece.
- Electrical boxes caulked, glued or gasketed at wire penetrations and holes.
- Ceiling drywall taped to wall drywall.
- Drywall as continuous air barrier in ceiling.
- Attic R-38 blown-in insulation.
- R-19 batt in walls or closed cell spray foam.
- Passive radon vent
- Insulated R-10 foundation slab
- Insulated R-13 basement walls
- Windows: Marvin Integrity, Low-E glass, Argon filled U factor .29
- Therma Tru insulated doors
- Roof: Durable standing seam metal
- Exterior: Stone veneer, brick & fiber cement siding
- Geothermal heating and cooling
- Ductwork in conditioned space and sealed with mastic
- WaterSense compliant fixtures
Read more about green home construction techniques.
Topics: Building Green, Certification / LEED, Energy Audits, Energy Recovery & Heat Recovery, Energy Star, Exteriors, Foundations, Home Design & Plans, Insulated Concrete Forms - ICF, Interior Design, Lumber and Structured Panels, Maintenance & Repair, Proud Green Home of St. Louis, Roofing, Siding, Thermal Envelope