The structural insulated wall panel systems (SIPs) have many advantages when creating a well-insulated and air-sealed building shell that is cost effective to produce. The panels we chose to use on the prototype are 6-inch thick urethane panels, that are 4 feet wide by 24 feet long, factory manufactured and pre-cut by Winterpanel in Vermont. The most significant advantage of the SIPs is that they provide an uninterrupted thermal barrier for the shell that is also a durable and easily sealed air barrier.

The Passive House requirements for a building’s shell are very specific. To qualify for Passive House Certification, a building should not have any thermal bridges in the foundation or building shell, and the building, when complete, must meet strict air sealing requirements verified by a blower door test. The SIPs system has allowed the prototype’s construction to conform to these Passive House requirements, while still allowing for simple and cost effective construction.

The second advantage of the SIPs system has to do with the size of the panels and the ability to have them factory pre-cut to fit each building design. These benefits are maximized by utilizing our computer designs in the actual production of the construction components. By utilizing advanced three-dimensional computer models, we are able to coordinate all the expensive building shell components (including windows, SIPs and structural frame), and then incorporate the computer’s accuracy in the actual construction process. By putting emphasis on planning and leveraging that in the construction, we can improve the speed, accuracy, and quality of the site work.

One frequently asked question regarding SIPs panels is the environmental impact of the foam insulation used in the panels. The three standard foam types used in SIPs panels are urethane foam, and Expanded Poly Styrene (EPS). We choose to use urethane foam for the prototype’s panels because it has a higher R-value per inch, resulting in a thinner panel and a higher total R-value per unit cost. The criticism of this foam type is that the R-value decreases over time. The total aged R-value of the urethane, however, is still higher than the comparable EPS R-value per unit cost. While both foam options are considered green products according to the USGBC, it has been suggested that the EPS production is more environmentally friendly of the two foams. G•O Logic has used both foam types and considers their application on a case-by-case basis.

With the grade beam footings complete, the next step in the construction process is the erection of the hybrid timber frame.

The concept behind the structural timber frame system was to create a structural system that is simple, quick to install, and easy to replicate. The structural concept also required a separation of the load bearing structural system from the thermal shell of the building, which enables greater flexibility in configuring the facades as well as reducing the potential for thermal bridges in the shell.

The thermal envelope of the building is created using SIPs (structural insulated panels) that are as large as 24 feet long by 4 feet wide and factory cut to fit the structural frame and façade. The benefit of the size of these structural panels is that they only need to be attached to the structural frame at the floors and roof, resulting in a reduced quantity of framing materials and fasteners. The use of SIPs in conjunction with the hybrid timber frame also results in a building shell that is easy to air seal and has virtually no thermal bridges.

The timbers that we choose for the structural frame at the exposed locations are locally harvested white pine, with some standard dimensional framing where the structure is not exposed. To reduce the cost of the frame, we worked closely with our structural engineer Albert Putnam to simplify the basic design and the structural connections. The details for the frame connections have been reduced to the most basic form, including butt joints, hidden metal straps, and hidden lag screws at the connections. We reduced the number of framing members to save costs, incorporating the minimum members to create a stable structure. The timber frame also relies on the SIPs panels for its lateral resistance, thereby avoiding expensive let-in bracing in the actual timber frame.

The roof structure of the building was created with a scissor truss spanning the north to south walls. The scissor truss was chosen because it is cost effective to build and install. The scissor truss also allows for the easy installation of a thick layer of blown-in insulation in the web area of the truss, easily accommodating an average of 24 inches of cellulose. The scissor truss also allows for spatial flexibility on the 2nd floor with the opportunity to create an insulated attic area, loft space of vaulted ceiling.

Air and water vapor can enter a home by diffusing through building materials or by infiltration or air leaks. In many ways a house, due to wind pressures, act like the cabin of an airplane that experiences large pressure differences inside and outside the cabin. In the case of an airplane, a poorly sealed cabin would result in a very uncomfortable and cold ride for the passengers (not to mention there would be too little air to breath). And while a house does not deal with the effects of the upper atmosphere, it does experience pressure differences that draw air in and out of a building, similar to that of the pressure difference caused by the upper atmosphere on an airplane.

Most residential construction in the US does not utilize an air barrier under the foundation, and if an air barrier is installed, it is done in a piecemeal fashion. An air barrier below the foundation is necessary, as a surprising amount of air can be drawn into the building through the soils. This is a particular concern in Maine because of radon, a poisonous gas that can pollute the air infiltrating through the foundation.

When installing the air barrier under the foundation, it is important to remove any debris that might puncture the air barrier from below and then continue to protect the air barrier through the construction process (as it is made of plastic). There are other material options for air barriers, but plastic is moisture resistant, flexible and easy to install under the foundation. In addition, it is important to have a flexible material since the air barrier will be installed under the concrete slab, and then continue up the foundation and attach to the wall panels—unlike traditional construction that discontinues the air barrier under the foundation. We have also taken special care to ensure the continuity of the air barrier, including double caulk lines and tape at all joints.

Once the underslab insulation was installed we proceeded with installing the foundation formwork, another process that was rather simple and quick. For the foundation of the building we will be using a grade beam system, similar to a slab on grade.

To create the grade beam, we used prefabricated, insulated formwork called: insulated concrete forms (ICFs). While the system costs are comparable to an ordinary wood-framed formwork, the thermal performance is significantly greater.

ICFs are made of clipped together insulated panels, in which the concrete is poured. The plastic clip system that holds the panels together also supports the rebar, holding it securely in place during installation.

The benefits of the prefabricated, clip together sections are the reduced cost and improvement of energy efficiency with fast installation.

The flowable fill discussed previously has created a quick, even pad on which a layer of high-density expanded polystyrene insulation is installed. The insulation sheets come in large sizes – 4’ x 16’ x 6” thick – making them quick and easy to install. Our total installation time with only two people involved was about an hour.

Typically a building sits right on top of a concrete foundation, without any separation from the ground. Imagine standing outside with a heavy wool coat on and no shoes — your coat is trying to keep your body warm, but you are losing a lot of heat through your feet. When you put boots on, you are separating your feet from the ground and providing a better insulation. Adding a layer of insulation on top of the flowable fill creates a barrier between the foundation and the ground. This separation provides a complete thermal and moisture break between the earth and the building’s concrete foundation, just like boots prevent your feet from getting wet and cold. Supplying the building with a highly insulated foundation allows the house to retain more heat than in a conventional construction practice where there is no separation between the house and ground.

As with any building, creating a solid foundation is important as it provides the base for the rest of the structure. In order to improve the thermal performance of the building, as well as reduce construction costs, a slab on grade foundation was designed for the prototype. Typical residential foundations consist of concrete foundation walls that are installed below the frost line on undisturbed soil or compacted gravel. An alternative to excavating and installing foundation walls below the frost line is to install a layer of rigid insulation horizontally under the entire building. This layer of insulation thermally isolates the building from the ground, as well as maintains the earth’s geo thermal heat under the area of the building, and thereby prevents frost heaves at the building’s foundation during the winter months.

To ensure the thermal performance of the foundation, we installed 6” of rigid EPS insulation under the entire building. The potential liability of installing this thickness of rigid insulation, is that the structure of the insulation can bridge over voids in the compacted layer beneath the building during the foundation installation, but then settle with the weight of the completed construction. To ensure that the substrate is completely smooth and compacted, a layer of concrete and sand called “flowable fill” was installed. This layer of highly aerated concrete is very easy to install and manipulate to create a level and fully compacted substrate. The result of these construction layers and systems is an extremely well insulated and quickly installed foundation.

Flowable fill is a mixture of coarse sand and cement that is heavily aerated to make it – you guessed it – flowable! It came out of the truck like a frothy milk shake and was easily placed inside shallow forms. When the flowable fill cures it is crumbly and easily raked or dug up which allows for fine tuning and leveling of the pad.

A layer of high-density insulation will be placed on top of the flowable fill, providing a complete thermal and moisture break between the earth and the building’s concrete footing. The combination of the flowable fill and the high-density insulation are fundamental details that provide the prototype house with a highly insulated foundation at an affordable cost.

Despite this spring’s torrential rains, excavation for the utilities and the driveway proceeded rapidly. By restricting the footprint of the utility work and quickly replacing the topsoil in disturbed areas, we prevented the site from deteriorating into an unworkable mud pit.

It was decided early on in the project to have all the utilities enter the building from below grade. Although this not the least expensive option, it has distinct advantages. The first advantage is aesthetics as we can avoid telephone and power lines connecting to the building. The second is based on the Passive House recommendation of providing one single utility service enter into the building from below grade. Having one point of entry allows for better air sealing and reduced thermal bridges at the service entry locations.

The water line leading from the street to the house is buried at a depth of 5 feet in order to protect it from freezing in the winter. Included with the water trench, we installed a 100 foot long, ½ inch diameter tube with a closed water loop connected to a water to air heat exchanger that will act as a preheat for the incoming ventilation air. Strangely enough, we have also run an additional closed water loop in the septic tank to utilize bio thermal heat exiting the building. To verify the performance of these lines, we have installed heat probes with both loops. We will be posting the performance of the house on line when it is complete- be sure to check that out.

Orange area proposed house site

The building site for the prototype was chosen for its gently rolling topography, open space and proximity to Belfast’s downtown. The three acre lot was previously used as a hay field and woodlot, but in the recent years has only been maintained as a meadow. This gently sloping landscape allows for inexpensive, low-impact construction, while the open meadow allows for predictable solar gain.

Deciding the location of the house on site is a specific task, which will impact the site’s existing ecology and appearance, as well as the home’s future use, including creating solar access, public and private spaces. Careful planning must also be implemented before construction begins to manage the impact of the site disturbance. The GO Home’s location was chosen based on conserving as much of the trees and meadow as possible, while also creating sufficient privacy for the house from the road.

Most rural and suburban homes orient the primary façade, including the main entry and windows, towards the road. While we did orient the protorype’s front door to the road for clarity for arriving visitors, we then rotated the majority of the glazing towards the south for optimal solar gain and privacy. Articulating the difference between solar and social orientation in the siting of a house requires more consideration and critical thinking, but certainly is beneficial for both.

According to Ann Kearsley, Landscape Architect of Ann Kearsley Design, paying attention to the movement of the site (earth, water, air and sun) is key to limiting the disturbance of the landscape. Ann has been working collaboratively with G•O Logic to create a low impact construction site for the prototype house (see previous blog).

During the site planning and design process we took the following elements into consideration: water drainage, existing vegetation and sunlight. Planning for, and managing storm water runoff during and after construction is critical because the building will disturb the natural flow of water of an existing site. We tried to set the building elevation in the site to minimize excavation or filling. Because the site is sloped we needed to create a level area for the building and manage the resulting water runoff. To divert the run off away from the building we created vegetated bio swales that will become a distinct landscape element. Improper management of water drainage will result in soil erosion, which becomes a problem by creating unstable soil conditions for vegetation.

Top soil is also affected by site construction. Standard building practices, such as driving trucks all over the site and stockpiling topsoil in large piles, can destroy the top soil’s organic structure. Limiting the area of construction in the planning process on the site plan and during construction with fencing is important in order to minimize the overall impact on the landscape. The top soil excavated from the house site and driveway was stockpiled in shallow piles, mulched with hat and seeded to prevent erosion. Once construction around the house is complete, the stockpiled topsoil will be re-graded around the house to complete the landscape.

Pay attention. Start by noticing. Start with the land, with the field; start with that drift of milkweed, monarch magnet; with the flattened grass ovals of deer beds; start with the lupine near the ledge outcrop, protected from the bush hog blades by the jagged stone or maybe by the mower’s annual remembering, his choosing to turn wide around that small blue stand of Maine wildflower; start with those two sentinel apple trees, remnant of an orchard row, traces of other, earlier, hands on the land. Or start with the collapsing stonewalls bounding the field,
the ashes and maples and shadblow growing up through those tumbled lines, widening trunks dismantling over generations the carefully stacked harvest of winter frosts and spring plows. Evidence of habitation: who’s been here, who’s here now. Evidence of labor: landform expressing technology and intention and, when the work stops, wildlife’s swift re-occupation.

Move. Follow the paths that rainwater takes through the field towards the woods at the bottom of the slope. Feel the topography in your gait, long strides through tall grass on shallow slopes, small stumbles when knees soften in low spots, eddies of sedges marking depressions and swales where water is held longer, draining slowly into the soil. At the edge of the woods turn around, look back up the slope to where you started, eyes now level with the road, body a register of
distance and the change in elevation. Circle the field, inscribing a path, feeling for that restful place between edge and open where structure can engage transition.

We’re introducing a building into the continuum of occupation and life on the site and, in doing so, will redirect the course of habitation and the character of this place. Our choices about where to build and how to build will determine whether any of the present inhabitants continue to make this landscape their home and whether occasional visitors might be tempted to settle down. And, as every property is part of a much larger, regional ecological matrix, our actions will also precipitate changes in the surrounding area, the impact of our presence rippling out beyond the site boundary.

Our first engagement with the site’s ecology, that complex web of relationships among plants, animals, soil, sun and water, will cause disruption and dislocation. Construction takes up space, casting shadows, interrupting water flow, and obstructing movement. We plan the construction staging to reduce this disruption, limiting crews and equipment to a small area immediately around the structure. Topsoil is removed from the building site, stockpiled in low berms, overseeded with a cover crop and kept healthy until we can re-place it around the house next spring. The site drainage pattern is reconfigured so water moves around the building and is reconnected with the existing flow in undisturbed areas downslope. We work to anticipate the site’s response to disturbance, integrating new development with existing conditions and creating opportunities to enrich and expand the ecological health and function of this landscape.

Ann Kearsley RLA, MLAUD
www.annkearsley.com

By Matthew O’Malia
Special to Roll Call
June 22, 2009, 5:43 p.m.

Read the Article at the Roll Call

I am a small-business owner and partner in G•O Logic LLC of Belfast, Maine, a design and building company building the next generation of sustainable, energy-efficient homes. So I understand first-hand the importance of investing in clean energy and the importance of Congress strengthening the Clean Energy and Security Act. If we invest in a clean energy economy now, we’ll create millions of jobs and set our country on a track to compete in a 21st century economy. Not only will my small business and thousands of others like mine be able to expand, but all of the local businesses we rely on for manufacturing, shipping, storage and many other tasks will benefit as well.

Buildings consume 40 percent of the energy produced in the United States, more energy than all of the cars on the roads today. And while automobile fuel efficiency is seriously debated as a path to save energy and money, building energy performance has not received as much scrutiny, even though we have the tools and technology to create super-efficient buildings today. A strong renewable electricity standard will mean these tools get used and these jobs created to make our buildings more efficient and begin to build the foundation of an American new energy economy.

G•O Logic has developed home designs that reduce energy consumption by 90 percent for space heating and 80 percent overall. These houses look and feel like custom-designed, conventional homes and are built for average construction costs. The energy efficiency comes from cost-effective design improvements — thicker walls with a lot more insulation, better passive-solar utilization, and an air-tight envelope coupled with a heat-recovery ventilation system. In simple terms, a 90 percent more energy-efficient home saves an enormous amount of money and energy — around $90,000 in heating costs, 22,000 gallons of heating oil, and 285 tons of CO2 over the term of a 30-year mortgage.

A stronger renewable energy standard in the energy bill would provide small businesses, like mine, with an important opportunity to provide quality, energy-efficient housing that people can afford to build and heat and cool. And this opportunity would not just benefit small businesses. It would also create an entirely new market for green jobs that are good-paying, skilled and valuable to the economy. And these are jobs that can never be shipped overseas.

In fact, study after study has shown that investing in clean energy creates jobs, and at a far faster rate than investments in dirty energy sources like oil and coal.

Researchers at the University of Massachusetts found that investments in clean energy produce two to three times as many jobs as investments in dirty energy. The Department of Energy and the National Renewable Energy Laboratory have issued similar findings.

Why settle for half as many jobs when we could have double or even triple?

And don’t forget that creating more energy-efficient homes and businesses will jump-start the local economies in a multitude of ways. Once homes and businesses stop wasting energy, it means more money in people’s pockets. The Department of Energy’s home weatherization program cuts energy costs by an average of 30 percent per home. Those savings will spur consumer spending — helping to create even more jobs.

A strong American Clean Energy and Security Act can open new doors to future green jobs, a green economy and energy security. G•O Logic, among other innovative small businesses, is ready to help lead the way, with the skills and vision necessary to implement this ambitious plan. But we need the help of elected officials. I urge Congress to act now to create a stronger energy bill that will provide the support needed for a strong green economy and a brighter future.

Matthew O’Malia is principal of G•O Logic LLC, a design and building company in Belfast, Maine.