House on a Knoll
Excerpt of text from the “Energy Smart Homes” edition of Fine Home Building
In 2008, when my business partner Alan and I decided to form a design/build firm, we agreed to build to the highest standard of sustainability and to do it cost-effectively. With all of our projects we hoped to achieve an inherent synergy between design for human comfort, building in response to the site, and achieving long-term sustainability. We quickly agreed that the Passive House Standard, which was just being introduced into the US, would be the most extreme and clear measure of our success. To demonstrate that we had the ability to reach the standard we built our first prototype, the 1500 sq.ft. house we called the GO Home. To reach the passive house standard in Maine’s cold climate, we reinvented the way we collaboratively design and build homes. The GO Home was completed in 2009 and was Passive House certified, LEED Platinum, and the USGBC residential project of the year.
Since the building of the GO Home we’ve built several other high performance projects based on our refined design and building approach. This particular home, tucked away on the outskirts of Bath, Maine is one of them. This home is based on one of our pre-designed plan packages that delivers—depending upon the site— a house that meets Passive House standards, that’s comfortable and attractive and that is a modest cost to build—roughly $160 per sq.ft. This is how we achieve such a grand result on such a low budget.
Make It Compact
Wendy and her husband Bill came to us because they were interested in building the smallest and most sustainable home they could for their retirement. Of the plans we offer, they chose to work with our 1000 sq.ft plan. The 1000 sq.ft plan is compact, with one bedroom, 2 bathrooms an open kitchen, dining and living room as well as a small study.
We were excited by the idea of working with their desire to live in a small, highly efficient home, but we wanted to ensure that the home looked inviting and that the interior spaces functioned well and were comfortable to live in.
The shape of the house was influenced by our desire to create a simple, but well-proportioned home. The main living space is placed beneath the main, peaked portion of the home, with the supporting functions contained beneath a shed roof that wraps the side and back of the main component. The entry porch is recessed into the shed on the south façade, and the screen porch is carved into the shed in the north east corner.
To create interior spaces that have a small foot print but feel generous, we designed an open floor plan for the kitchen, living and dining areas. These spaces also provide direct access to the bedrooms and bathrooms in order avoid hallways and redundant circulation. We also increased the height of the ceiling in the main space, as well as the size of the windows. The result is an interior that feels open with a strong exterior connection.
Adapt It to Its Site
Wendy and Bill’s site was challenging and in many ways tempered the performance potential of the home. The site is surrounded by beautiful mature hardwood trees, which made it difficult to get all the passive solar gain required to meet the Passive House standard. We all agreed that preserving the trees was more important than meeting the standard, given that the house would still perform exceptionally well with regard to energy use.
The building site also sits on a narrow ridge running north to south. The house plan was developed with the intention of having its longest axis running east to west, so that the living room wall full of windows faced south toward the sun. On this narrow site, however, the longest axis of the home runs north to south and the window-filled living room wall faces east. While the siting of the home doesn’t provide ideal access to the sun, it does provide terrific views of the protected forest and land behind the home. We didn’t totally give up on passive solar gain, though. We modified the plan and placed three massive tilt-turn windows on the south-facing gable end of the home. The windows provide abundant daylight in the kitchen, dining and living area and provide much needed solar gain during the heating season. The windows also are a play on scale and have a profound impact on how the home looks upon approach.
Build It Well
Our version of high-performance cost-effective construction relies on a super-insulated slab on grade, hybrid SIP walls, a truss roof, triple glazed German windows and ventilation with heat recovery.
We build atop a slab, and not a full height basement for several reasons. Most importantly, a slab on grade foundation is the most cost-effective way of providing high levels of insulation and thermal mass on the interior. To ensure that the energy from passive solar gain is modulated and stored, and does not result in overheating, it is critical to have a large thermal mass area exposed to the solar gains. In many cases a slab on grade requires little excavation work and can accommodate challenging site conditions such as ledge, as was the case in this house.
Our wall section is made up of a 2×4 load bearing stud wall insulated with blown in dense pack cellulose with 8-in. thick EPS SIPs wrapping the exterior. The R-value of this assembly is about R-50, with almost no thermal bridging. Additionally, this wall is easy air seal properly. This approach also enables all of the mechanical, electrical and plumbing systems to be run through the 2×4 wall conventionally, as opposed to creating chases in the SIPs. Finally, the SIP panels are factory cut so there is less site waste and reduced labor for installation.
We typically like to use some sort of truss for our roof construction. The benefit of the raised-heal truss is that they are a very cost-effective structural system and are easy to install. We blow 24-in of cellulose onto our attic floors. In addition to the insulation, we install a layer of ZIP sheathing on the underside of the trusses and tape the seams. This layer provides an air barrier above the condition living space below. We also find that the air barrier is effective in controlling moisture transfer through the roof assembly, but we install eave and gable end vents anyway to reduce the potential of condensation on the underside of the roof deck.
The beauty of this type of design and construction is that if the building shell is built well and oriented correctly then the house needs very little space heating or cooling to be comfortable year round. The super insulation, combined with the thermal mass maintain constant temperatures around 70 degrees. As a result the main mechanical system for the house is not the heating system, but the ventilation system, which ensures tempered fresh air throughout the house. The heating system for this house is a little bit of electric resistance baseboard, which keeps the house at 70 degrees for about $200/ year. Because there will be little or no air leaking into the building, a ventilation system is required to ensure indoor air quality and to control moisture levels inside the building. The secondary benefit of the tight building shell is the that the ability to continually flush the building with fresh air thought the ventilation system is improved because there are no leak to disrupt or short circuit the designed air flows. When planning a ventilation system we supply fresh air, tempered with an HRV, into the bedrooms and living spaces, and exhaust from where moisture and smells are created most—in the bathrooms and kitchen.
Don’t Sacrifice Aesthetics
Even when working within the constraints of a tight budget, we still acknowledge the value of creating inviting and attractive spaces. When funds are limited we focus the available resources on materials that are durable and that will age gracefully over time. In particular, we allocate larger portions of the budget to finishes and materials that will endure the most use, such as flooring, countertops and bathroom fixtures and materials. Accommodating wear and tear and moisture successfully means that over time, the surfaces within the home develop a desirable patina, and add character to the space instead of detract from it.
In this home, we worked closely with the clients to develop the material pallet for the home. The intent was to keep the interior clean and simple to maintain focus on the surrounding landscape, but to also introduce a few beautiful, natural accents like the white oak floor and kitchen cabinetry and the soapstone countertops. The bathrooms are modestly adorned with simple white wainscot, pedestal sinks and floor tiles to evoke a traditional cottage style reminiscent of many of the small dwellings that dot the Maine coast.
That idea is reflected on the exterior as well. We selected natural cedar shakes for the walls that will weather to a silver grey and denote coastal living. Instead of asphalt shingles, we installed an anodized standing seam metal roof that is both durable and long lasting. To conserve money we opted not to install any elaborate trim details on the exterior of the home. However, we did flare a wall section on the front of the home to create an eave above the large windows. The detail protects the windows from rain, but also adds character to the front façade and suggests the high level of craftsmanship put into this home. Less expensive exterior finishes could have been selected, but this is not a cheap home. It’s an inexpensive home, designed to be attractive and uncomplicated to build. Complemented by extraordinary energy performance, this house is simply sustainable.