The GO Home
LEED Platinum certification; 1st Passive House–certified home in Maine, 12th certified in U.S.; USGBC Residential Project of the Year Award 2011; EcoHome Magazine Design Merit Award, 2011; TreeHugger, Best Passive House of the Year Award 2012
The goal of the project was to demonstrate a development model for a near-zero-energy building built at costs comparable to standard residential construction. The design approach was to create a super-insulated building shell that makes use of passive solar gain to lower space heating demands, allowing the cost and complexity of the mechanical systems to be minimized. The metric used to determine the target level of energy performance for the building was the German Passive House standard, which represents an 86% improvement on the home’s space heating loads from code-compliant construction. The aspiration to create a sustainable, replicable, and affordable prototype home led to innovations in the building and landscape design and their construction, enabling The GO Home and its future iterations to save valuable natural and financial resources.
A building’s size and form directly impact its energy performance, use of materials, and disruption of the site. In order to optimize The GO Home’s performance and long-term sustainability, a simple, compact building form was developed, reducing the exterior surface area and resulting heat loss. This form also echoes the regional vernacular of the Northeast, where spare, peaked roofed structures were built for the very same reasons centuries ago, and continue to be used today. The GO Home comfortably accommodates the evolving needs of a contemporary family of five, with a plan optimized for maximum flexibility in a compact space. In the public areas, a generous open plan with large windows allows a variety of concurrent uses. Upstairs, the timber-frame structure allows the non-load-bearing partitions to be reconfigured as future use patterns dictate. On the site, the building’s compact footprint and location maximize solar gain while minimizing disruption to the existing site’s ecology. In addition, habitat resources are preserved and enhanced using topography developed for storm water management to create micro-environments that support a greater variety of native plantings.
The GO Home is a 1,500 square-foot, single-family residence built in a rural state with a low population density and cold climate. The goal of the project was to demonstrate a development model based on a near-zero-energy building built at costs comparable to standard residential construction, with minimal disturbance to the healthy ecosystem of the existing site. The design approach was to create a super-insulated building shell that makes use of passive solar gain to lower space-heating demands, allowing the cost and complexity of the mechanical systems to be minimized. The metric used to determine the target level of energy performance for the building was the German Passive House standard, which represents a 86% improvement on the home’s space-heating loads from code compliant construction. The GO Home was certified as the 12th Passive House in the United States in July 2010 and is on track to receive a LEED Platinum rating from the U.S. Green Building Council. The aspiration to create a sustainable, replicable, and affordable prototype home led to innovations in the building and landscape design and their construction, enabling The GO Home and its future iterations to save valuable natural and financial resources.
A building’s size and form directly impacts its energy performance, use of materials, and disruption of the site. In order to optimize The GO Home’s energy performance and long-term sustainability, a simple, compact building form was created, reducing the exterior surface area and resulting heat loss. This form also echoes the regional vernacular of the Northeast, where spare, peaked roofed structures were built for the very same reasons centuries ago, and continue to be used today. The GO Home comfortably accommodates the evolving needs of a contemporary family of five, with a plan that has been optimized for maximum flexibility in a compact space. In the public spaces, a generous open plan with large windows allows a variety of concurrent uses. Upstairs, the timber-frame structure allows the non-load-bearing partitions to be reconfigured as future sleeping and working use patterns dictate. Onsite, the building’s compact footprint and location maximize the solar gain while minimize disruption to the existing site’s ecology. In addition, habitat resources are preserved and enhanced using the topography developed for storm water management to create new micro-environments that support a greater variety of native plantings.
The GO Home’s compact form and construction have been created as a response to the climate and micro-climate in which it is built. The local climate has a bone-chilling 7,400 heating degree days, qualifying it as a “cold” climate. Given the relatively clear skies during the winter months however, it is an excellent candidate for passive solar gain to compensate for the cold outdoor temperatures. In response to these conditions, The GO Home’s building form is compact and exceptionally well-insulated, with large triple-glazed windows oriented toward to the south. The building was located on the site to ensure the passive solar gain would not be interrupted while making use of a forested edge at the property’s northern boundary to block the prevailing winter winds. The public spaces have been configured facing south with an open plan so that the passive solar gain can be utilized through out the house. In addition, The GO Home is built to the Passive House standard, which requires that the building shell reduce the space-heating load by 86% from code-compliant construction. This improvement on energy performance allows the home’s remaining heat load to be cost-effectively accommodated by a small solar-electric system mounted on the roof of the building, resulting in a near-zero-energy building on an annual basis.
Energy Flows and Energy Future
Reducing the space-heating demand of new construction in such a cold climate has a significant environmental benefit, and if properly designed, a critical first-cost and life-cycle cost savings as well. Because The GO Home’s energy demand for space heating has been reduced by 86%, the resulting heat required to keep the building at 70 degrees is very low (2000Kwh peak demand), which allows The GO Home’s traditional heating system to be drastically simplified by a small amount of electric baseboard controlled by a thermostat in each room. The significant financial savings resulting from minimizing the heating systems is reinvested in the building-shell improvements, including walls at R49, foundation at R70, roof at R80, and triple-glazed R5 windows and doors. The combination of these improvements, in conjunction with heat recovery ventilation, results in a home with energy costs for space heating at less than $300 per year, with energy costs savings over 30 years of $170,000 (including inflation), which is nearly equal to the original cost of construction. Furthermore, on account of the minimized heat load, a 2.8 KW solar electric system and a separate evacuated-tube solar thermal system mounted on the roof will cover the building’s space heating and hot water needs, resulting in a grid-tied near-zero-energy building on an annual basis.
Light and Air
Given the targeted budget and affordability goals for The GO Home, the focus of the well-insulated building shell has been to establish basic interior comfort for temperature, light, and air through simple or passive means, thereby reducing the need for extensive, complex, and costly mechanical systems. The super-insulated building maintains constant indoor temperatures, and is exceptionally well air-sealed (registering .5 ACH with a blower door test). A heat recovery ventilation system rated at 95% efficiency provides fresh air in the bedrooms and living rooms, constantly flushing them with filtered and tempered outdoor air, while exhaust air is drawn from the bathrooms and kitchen, where moisture and odors are created. During the summer months, passive cooling is provided by cross ventilation from operable windows on the east and west elevations of the building. Besides the natural light that enters the building from the windows on the first and second floors, the bedroom doors have translucent glass panels allowing natural daylight to penetrate into the upstairs corridor, reducing the need for supplemental lighting. The large, south-facing windows are equipped with translucent roll-down shades to provide interior light control, comfort, and privacy.
Materials and Construction
The optimization of materials used during the construction process is environmentally beneficial as well as cost-effective. The design and construction of The GO Home was done as an integrated design-build process, with the benefit of computer modeling being used directly in the construction process. Specifically, the building shell is constructed using structurally insulated panels that were patterned and optimized on the computer, making the most efficient use of the materials. The computer file was then exported to the fabricator who cut the panels with CNC technology. All waste materials were fully recycled in the factory. The GO Home’s building shell is also constructed to be durable, using high-quality interior and exterior materials. Moisture-control measures include a sealed warm-side air barrier on the interior and vented cladding materials on the exterior to ensure the building shell’s longevity.
Land Use and Site Ecology
A primary goal of the site development was to minimize soil disturbance, which disturbs the existing ecosystem and results in the release of CO2 from organic matter in the soil. On the site, the house was located along the property boundary and close to the public road. The intent was to consciously restrict the construction area to a small portion of the property, minimizing both disturbance and the hydrological impact of the development. A slab-on-grade foundation system was chosen to reduce the amount of excavated soils. The loam from the building and staging areas were removed and stockpiled on site and sown with a cover crop to prevent erosion and desiccation, as well as to protect the viability of important micro-organisms in the soil. The construction staging was pre-planned to avoid unnecessary soil compaction and vegetation removal as well. The disturbed areas were restored with native grasses, trees, and shrubs, all providing new layers of habitat resources for the existing ecological community, and re-establishing a web of connections to the carefully preserved pre-construction landscape. The runoff resulting from the impervious surfaces of the house and driveway were seen as an opportunity to create new micro-environments that enhance habitat resources by supporting a greater variety of native plantings.
Storm water falling on the site is managed on the site. Rainwater landing on the limited areas of impermeable surfaces, which include the roof and driveway, is directed via the re-graded topography to a gently sloping vegetated swale where native tall grasses and wildflowers reduce the rate of flow, facilitating groundwater recharge. This native plant meadow, which contains species that can withstand a wide range of soil saturation from drought to inundation, is located directly outside the large, south-facing living room windows. This meadow is intentionally located in the foreground of the view out to the existing field, providing an immediate, intimate experience of the vital and complex life unfolding in the landscape adjacent to the house. The design and thoughtful construction phasing, as well as the use of native, non-invasive species well-adapted to this climate, meant that no permanent irrigation was required or installed on this project. All plumbing fixtures in the house are specified and installed as low flow, conserving both water and the energy required to heat the lower volumes.
Collective Wisdom and Feedback Loops
The GO Home is a prototype demonstrating that near-zero-energy homes are possible for the mainstream housing market at costs comparable to standard construction. To achieve this goal, innovation in the design, detailing, and construction processes are necessary. As an architectural design/build firm, our development process for these prototype homes has been modeled after the integrated design-to-production process of manufacturing industries. In this model, an in-house, iterative development process from concept to manufacturing ensures continuous feedback loops, quality control, and continuity of concept during all the stages of the process. Each design is based on the lessons learned from previous iterations, improving on the accumulated successful designs and technologies. Each new design is cost- and energy-modeled to ensure its performance and cost-effectiveness. All through this process, including construction and commissioning, feedback is collected and integrated into subsequent design iterations. The result of the design/build project delivery structure is improved efficiency in the design and construction, improved performance, and lowered design and construction costs. These improved efficiencies are the critical elements required to bring super-energy-efficiency in building to the mainstream housing market.