#Efficient and durable coastal home blends site-sensitive design, traditional materials, and high-tech systems
Located in Cannon Beach, on the Oregon coast, this home has breathtaking views and is also conveniently located within a short walk of the town center and the beach. The home’s owners have a strong commitment to environmental sustainability, and they were actively involved in the design and building process. From the outset, they asked their architect, Nathan Good, to design “a small home that is healthy to live in, using materials and systems with a dramatically reduced impact on the environment.”
The house has a modest footprint, and its interior spaces are efficiently designed for multiple uses; a window seat also serves as a twin-size guest bed, and the study doubles as a guest bedroom. The L-shaped home is also carefully designed to wrap around a majestic, 200-year-old Sitka spruce that shelters the site.
Disaster-resistant, bioclimatic design
Building in such an exposed, hilly location means that the home could have a potentially big impact on the site, and vice versa. In this cool, damp climate, a long-lasting home requires extremely durable materials and carefully thought-out building assemblies. Gale-force winter winds and dense local forests make fires another big risk. In fact, a previous home on this site, as well as the owners’ prior home in another part in Cannon Beach, had both burned down in a fire.
A detailed site assessment, including sun-path diagrams and a microclimate study, enabled a comprehensive design approach. The team tucked the home into a south-facing hillside and positioned it for ideal passive warming and good daylighting. The passive solar design, good insulation, and high-thermal-mass materials keep the home comfortable even during extended power outages. A Rumford-style wood-burning fireplace supplies back-up heating, if needed.
The home’s vegetated upper roof reduces the burden on the municipal stormwater system by absorbing rainwater and reducing runoff. It is also fire resistant, helps insulate the home, and has a life span of at least 50 years. Although it had a higher initial cost compared to some more traditional types of roofs, its durability should pay off over the life of the home. People seem to think it looks better, too. Nathan Good reports, “The roof has become a delight for the owners and neighbors and those who walk through the neighborhood.”
With a well-rounded list of durable materials, the home should stand the test of time and require little maintenance. Some are natural, local, traditional materials, like cedar and stone. Others are more modern. Curved steel beams make up part of the home’s structure, and the home was one of the first in the Pacific Northwest to use Durisol insulated concrete forms (ICFs). These composite ICFs are made of recycled wood chips and cement with mineral rockwool insulating cores. Aside from being resistant to rot, termites, and fire, they add thermal mass, have an above-ground R-value of 25 and are rated for Zone 4 seismic performance.
Comprehensive energy strategies
Extensive research and modeling in the design phase put the home’s projected energy use at 58% less than what is required by Oregon Energy Code. Daylighting studies and DOE-2 energy modeling were crucial in creating the most efficient thermal envelope and fine-tuning the mechanical systems and passive solar design.
The home’s primary energy source is the 5.9-kW photovoltaic (PV) array on the roof. A combination of solar-thermal collector tubes and a ground-source heat-pump system heats both the living space and domestic hot water. Excess summertime thermal energy is stored in the bedrock beneath the house for later extraction by the heat pump. A “short basement” — a conditioned, unvented crawl space that contains the heating ducts and adds to the home’s thermal mass — also helps minimize temperature swings.
The home’s innovative energy system was also originally equipped with multizone energy recovery ventilators (ERVs), which warm incoming fresh air with heat from outgoing stale air; these were subsequently replaced with a single air handler.
High-tech monitoring and evaluation
Engineers on the project and staff at the Oregon Department of Energy (ODOE) led an extensive commissioning process of the home’s systems. More than 60 sensors installed in the house allow the ODOE and Oregon Institute of Technology (OIT) to track the house’s energy usage remotely, providing valuable data for this and future projects. Early identification of design and installation glitches allowed them to quickly correct problems, including excessive noise from the heating and ventilation systems. One of the most significant discoveries resulting from the measurement and verification was that the heat pump performed at about half the manufacturer’s stated level. When representatives from the heat-pump manufacturer were presented with monitoring data, they agreed to replace the 1.5-ton heat pump with a more energy-efficient 2-ton unit.
The team originally set an ambitious goal of getting the home energy use as close as possible to net-zero (generating as much energy as it consumes annually), a challenging if not impossible goal for such a cloudy locale. Energy consultant Charlie Stephens estimates that the home is currently generating about 56% of its energy use through its on-site solar PV system. The systems are still being fine-tuned to get closer to the net-zero goal.
The keys to this project’s successes were its integrated design process and its post-occupancy evaluations and corrections. In order to familiarize all team members with the goals of the project and the use of new and unfamiliar equipment and systems, the team had many meetings before and during design and construction. The team included the architect, owners, interior designer, landscape architect, energy consultant, and contractor. They conducted five half-day eco-charrettes (brainstorming sessions on ideas for efficient use of energy and resources in a new building), which also included various content experts and neighbors.
“Involving the contractor early in the design process was paramount,” Nathan Good notes. “His contribution to conducting abbreviated life-cycle cost assessments was critical to the selection of building systems and materials.” Nathan stresses that the support and involvement of the local building official was also critical to the success of the project: “Pre-design meetings with the building official paved the way for a number of local pioneering features, including the vegetative roof, the ICFs, the ERV system, and the unvented and moderately conditioned ‘short basement.’”
Simple is often best
Charlie Stephens says that one of the main lessons learned from this project is, “Complexity breeds problems.” For example, “monitoring initially allowed us to spot a number of system problems, [but] a residential project doesn’t enjoy the continued technical support that a commercial building project does, so problems go undiagnosed, and the control functions ultimately failed to provide a reliable system for the owners.” The team ended up largely separating the monitoring and control functions to improve reliability and reduce overall energy consumption.
The air-handling side of the HVAC system has also been dramatically simplified. Charlie says, “While one can indeed use a properly controllable ERV or HRV as an air handler, there are drawbacks. They impose a heating load due to efficiency well under 100% whenever they’re running as a space-heating air handler, and three of them use a lot more power than a single, larger one would. There were no larger ones with the necessary control features at the time, but a single, variable-speed air handler with an interlocked or built-in HRV would do the job better.” The owners have in fact had a new, simpler air handler installed to replace the ERVs.
Charlie says that more fully packaged heat pump—based systems (mostly air-to-water) are now available in Europe and should soon be adapted for the U.S. market. “Building net-zero-energy homes will be a lot easier when we have more packaged systems to use,” Charlie says, “but, as always, attention to the shell first!”
Energy equipment decisions can be tricky
Another lesson, Charlie notes, was “the solar-thermal system isn’t contributing much when you really need it: during the winter, when there’s hardly any sun on the Oregon coast,” so it’s not particularly cost-effective in this case. He reports that the roof PV system has operated well overall, though its output might be slightly compromised by salt spray from the ocean air.
After a year of collecting data, the design team was unsatisfied with the performance of the geothermal heat pump. Components were replaced based on their findings, but the system still doesn’t appear to work as efficiently as anticipated.
The home continues to be monitored and evaluated as part of the owners’ quest to get as near as possible to achieving a net-zero-energy home. It's clear that the location makes this a challenging goal, but each adjustment they make brings them a little bit closer.
General Specs and Team
|Location:||Cannon Beach, OR|
Completed: March 2005
Builder: Rich Elstrom, Elstrom Construction, Gearhart, OR
Architect: Nathan Good, AIA, Nathan Good Architect, Salem, OR
Interior designer: Georgia Erdenberger, IIDA, , Portland, OR
Landscape architect: George Erdenberger, Portland, OR
Associate architect: Leonard Lodder, Studio 3 Architecture
Mechanical engineer: Gene Johnson, SOLARC Architecture and Engineering
Energy consultant: Charlie Stephens, Adjuvant Consulting
Monitoring consultant: Bob Rogers, Oregon Institute of Technology
Solar energy consultant: Doug Boleyn, Cascade Solar Consulting
Foundation: semi-conditioned shortened concrete-slab basement; composite ICFs (R-21, Durisol)
Walls: composite ICFs (R-25 above grade; R-21 below, Durisol); timber framing at exposed framed openings
Roof: 2x14, 16 in. o.c.; between curving steel beams, two 1/2-in. layers of CDX plywood; triple-layer roof membrane; drainage mat; 4-in lightweight soil; 3-in. closed-cell spray foam insulation under roof deck; remaining roof cavity filled with formaldehyde-free fiberglass (R-58)
Windows: double-pane, low-E2, argon-filled wood frame(U-factor = <0.32; SHGC = 0.41)
- Multizone energy-recovery ventilation (ERV) system with in-line hydronic coils for supply air heating (subsequently replaced with a single air handler)
- Passive solar heating; majority of interior receives functional daylighting; clerestory windows and light shelves used
- Thermal mass moderates heating and cooling
- Operable windows provide cooling and ventilation throughout
- Roof overhangs for strategic shading
- High-performance building envelope
- Building automation control system
Heating/cooling: Hydronic forced-air heat (evacuated-tube solar thermal collectors, two 120-gallon water storage tanks with 4500-W electric heat element, GSHP, ERV; no cooling system needed
HERS score: 94 (old scoring method)
Blower door test: 0.23 air changes per hour at 50 Pascals
Duct-blaster test: 80 cft. per minute at 25 Pascals
Annual energy use: 13.3MMBtu
Note: This estimate has not been revised since the new air handler was installed, so the actual energy usage could now be less.
- On-demand circulator for instant hot water
- Low-flow toilets and plumbing fixtures
- Efficient, dual-drawer dishwasher
- Native plants used in landscaping; no irrigation system required
- Small bioswale to filter stormwater
Indoor Air Quality
- Window and interior layout facilitates natural ventilation
- Multizone ERV system
- Interior materials are zero-VOC and urea-formaldehyde-free
- Rumford fireplace with glass doors and outside air source
- Vapor-permeable exterior walls with external rainscreen
Green Materials and Resource Efficiency
- Pervious paving
- Living (vegetated) roof
- FSC-certified wood used throughout, including ICFs, framing, siding, exterior trim, and cabinetry
- ICFs made of cement and wood fibers, lined with mineral wool insulation
- Wind-fallen trees used for interior heavy-timber framing, flooring, and stairway
- Doors made from reclaimed sinker logs
- Windows made from sustainably harvested cedar
- Structural steel beams and rebar of 90-100% recycled content
- Foundation of 25% fly ash concrete; 35% fly ash concrete in ICFs
- Recycled-content (windshields) tiles and beach pebbles used as bathroom tiles; locally salvaged bathtub
- PVC-free materials (except for the underground electrical sleeves, electric wiring sleeves, and PVC in some appliances)
- 95% of construction waste was diverted from landfill; wood waste was ground for boiler fuel; plastering backer board scrap was ground up and used as a soil amendment
Alternate Energy Utilization
Photovoltaic: 5.9 kW STC DC grid-tied, roof-mounted system made up of 36 165-Watt modules and two 2,500 W inverters.
Cost: approx. $29,000 State of Oregon tax incentives provided 55% savings on the total cost of the system; combined with incentives from the Energy Trust of Oregon, the payback period for the system was reduced from 28 years to less than 10 years
Earth Advantage: platinum