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reARCH Case Studies
Eco-Home at Hawk Ridge
General Information
Project Name:
Eco-Home at Hawk Ridge
Location:
Duluth, MN
Websites:
www.ecohomeduluth.com,
www.womenworking.org,
www.wagnerzaun.com,
www.conservtech.com
Architect:
Wagner Zaun
Architecture
Builder:
Women in Construction
Company
Building Size:
2,040 sq. ft.
Building Use:
Single-family home (currently unoccupied), open as a demonstration
project until spring 2008
Date of Completion:
May 2007
Ratings and Awards:
| • |
Energy Star Rating |
| • |
Duluth/Minnesota Power Triple E New Construction
program |
| • |
Home Energy Rating System (HERS) index rating
34 |
Overview
Eco-Home at Hawk Ridge is a solar model home
demonstrating energy efficiency, renewable energy, and green building.
This project has been a joint effort between Wagner Zaun Architecture,
Women in Construction Company, and Conservation Technologies, with
support from several other local agencies and consultants. The home
will initially be used for demonstration and educational purposes,
and the design and construction methods will serve as an example
of how to build Low-Energy, high-performance homes with attention
to conservation and health of people and the environment. The overall
concept features site-sensitive passive solar design with a high-performance
thermal envelope, a grid-tied solar PV array, a solar domestic hot
water system, and a solar hybrid heating design.
(Source: www.ecohomeduluth.com)
During the time of this project being open
as a demonstration home, the market viability of showing the home
has landed Women in Construction five jobs with similar aspects
after the first month on the market. Three more house sales followed
during the summer, and two during the fall. Not all of these projects
have requested to go as far, but the influence on the market and
the future of the work done by Women in Construction indicates that
the market is transforming. This model home demonstrates that not
only can a solar-integrated building (as Michael LeBeau of Conservation
Technologies suggests this approach should be called) be developed,
but that interest from the market is ready for affordable solutions.
This project also represents a demonstration
of successful integrated design and building relationships among
the partners to achieve the agreed-upon project goals. The decisions
for building shape and envelope dynamics required multiple models
developed with software. The initial strategy used integration of
design approaches to shrink the loads. This was done by evolving
the concept of the building through heat-loss modeling based on
Low-Energy-use targets. The dialogue between the architects at Wagner
Zaun and the building analysts at Conservation Technologies provides
a useful example of how teamwork and trust are crucial in developing
solutions through integrated design. The process of having multiple
contributing partners means that consensus and communication of
ideas, knowledge, and information are developed over time. Members
of the different professions each come with different perspectives
with the intention of meeting the end goal. This project embodies
this process of integrating design, building science, and renewable
energy being implemented through true collaboration.
Building Performance
Effective Energy
Use Solutions:
| • |
Smaller footprint/square footage
to reduce heating/cooling loads |
| • |
Drop energy loads with design choices, then
meet energy needs with solar technologies |
| • |
Super insulation |
| • |
Attention to building details for tightness |
| • |
Energy Star appliances and lighting |
Orientation:
| • |
Along true north-south for
solar gain |
Daylighting Strategies:
| • |
Large south side windows provide
daylighting into the main living spaces. |
| • |
Daylight in all habitable spaces enters
the building from at least two sides, some with three sides
except baths (main floor bath from one side). |
| • |
Open space planning allows living areas
to receive more daylight throughout the day. |
Passive Heating and
Cooling Strategies:
| • |
Minimized windows on the north
side, with fewer on east and west; west side of building was
pushed towards trees to increase window shading |
| • |
Proper overhangs and fewer windows on the
east and west sides reduce heat gain. |
| • |
Used a combination of modeling programs
to incorporate shading/overhangs and impacts on glazing types,
which gives some information on solar heat gain. |
| • |
Building roof and overhang design on the
south side were based on summer and winter sun angles, to
allow maximum winter sun to penetrate the building and to
block unwanted summer sun. |
| • |
Passive solar design:
| - |
Living spaces open to
the south; mechanicals, baths, bedrooms to the north |
| - |
Solar gain into two-thirds of house |
| - |
Large south side windows (58% of total
glazing for house) for solar gain at 16–18% of
the floor area |
| - |
Thermal mass in the radiant floor |
| - |
12% ratio of southern windows to floor
area, balanced to prevent overheating the building |
| - |
Tight, super-insulated structure prevents
energy loss |
| - |
Material selection: Dark grey
tiles over the slab |
|
| • |
Natural cooling:
| - |
House is designed to
maintain comfortable, natural cooling without air conditioning. |
| - |
Cross-ventilation through window placement |
| - |
Stack effect with lower operable windows
on main floor to bring in cooler air that is pulled
up the central stairway by warm air exhausted out of
upper-storey windows. |
|
Shading of Structure:
| • |
Two-foot overhangs |
| • |
Lower portion of the building on south and
west sides shaded by a few trees |
Envelope:
| • |
Assemblies, Components,
and Insulation R-values:
| - |
Walls: R-36
| · |
Double 2"
x 4" stud walls |
| · |
Wall thickness: 9.5" |
| · |
Dense pack cellulose insulation |
| · |
Double wall forms a thermal
break between the studs where 2.5" of cellulose
fills the space rather than wood |
| · |
Structural fiberboard sheathing:
R-1.2 |
| · |
Insulated rim board with
additional two-part urethane foam: R-31 total |
| · |
Cement board lapse siding |
|
| - |
Roof: R-60
| · |
Cellulose attic
insulation |
| · |
16" energy heel roof trusses |
| · |
Standing-seam metal roof |
| · |
Continuous soffit and ridge
vents |
|
| - |
Slab foundation:
R-20
| · |
Frost protected |
| · |
4" XPS foam insulation
under slab |
|
|
| • |
Building Tightness:
| - |
Blower door test results:
0.09 cfm/sf @ 50 Pa |
| - |
While addressing comfort, the design
considerations included special attention to thermal
bridging, tightness, and moisture control |
| - |
The following details were specified
to drive the construction process to control losses:
| · |
6 mm poly-sealed
Polyethylene vapor retarder on the warm side of
the wall system |
| · |
Attention was detailed as to
how the building is sealed, with care of how the
installation was handled |
| · |
Flashing and sealing to reduce
heat loss and risk of exterior water intrusion |
|
| - |
Inspections to ensure tightness were
conducted throughout the following construction process:
| · |
Plan review to
catch trouble spots involved in the design during
framing to keep the insulation process easy |
| · |
Low-pressure blower door tests
were performed before drywall was applied |
| · |
After the building was sealed
up but before the drywall was applied |
| · |
After initial sealing, corrections
were made for areas identified for tightening
and drywall was applied, further building diagnostics
were performed with another blower door test,
infrared camera scans for sealing potential leakage
points |
|
| - |
Common leakage points of concern include:
| · |
Seams in polyethylene,
connections of multiple materials, crowded spaces |
| · |
Missed insulation on plumbing
where a tub or shower covers the walls without
first being covered by rigid insulation |
| · |
Windows, doors, electrical penetrations
within walls |
| · |
Behind breaker boxes where insulating
is not properly detailed to make sure the penetrations
for the larger wires are sealed before mounting
the panel box |
| · |
Breaker boxes surface mounted
becomes a design issue as it involves plywood
with a finished wall behind |
|
|
| • |
Windows:
| - |
Triple pane, double argon,
Low-E coatings, with warm edge spacers |
| - |
South side: 5' x 6' lower level,
5' x 4' upper level |
| - |
U-value average of 0.20, R-5
| · |
0.19 U-value for
north, east, west windows |
| · |
0.21 U-value for south windows |
|
| - |
Solar Heat Gain Coefficient average
of 0.45
| · |
0.41 SHGC for north,
east, west windows |
| · |
0.63 SHGC for south windows |
|
| - |
Insulated fiberglass window frames |
| - |
Solar gain, one Low-E coating on south
windows, two coatings on rest of windows |
| - |
o Casement, picture, and awning windows |
|
Climate Control Systems:
| • |
Warmed ventilation air delivery
on second floor
| - |
Venmar HE – 1.3
AVS |
| - |
90% efficiency in heat recovery ventilation
system |
| - |
Fully ducted, balance ventilation
system with exhaust from kitchen and baths and fresh
air into living spaces and bedrooms |
| - |
Heating ventilation air that goes
upstairs has an exchanger with a duct coil pump controlled
by the thermostat for upstairs. |
| - |
Innovation: Liquid coil under
the slab that exchanges the heat in the house for preheating
ventilation air |
| - |
Tempering of incoming ventilation
air filtered before it meets the duct coil |
|
| • |
Radiant Heating and Domestic Hot Water
| - |
The heating plant uses
modulating equipment that also assists production of
domestic hot water. The on-demand water heater was chosen
to provide for multiple showers simultaneously. A separate
loop from the on-demand water heater provides the radiant
heat distribution.
| · |
Equipment: Takagi
T.K. Junior modulating on-demand natural gas fired
water heater. Output: 9,000–140,000 Btus
maximum |
| · |
Hydronic radiant heat distribution
in first floor slab, and second story bathroom
floor |
| · |
Outside combustion air is used
to avoid impacting inside air pressures. |
| · |
The heater has an electronic
igniter and is power vented with a pressure switch
to identify positive air flow in the correct direction. |
| · |
Integrated with solar domestic
hot water system |
|
|
Backup Heating/Power:
| • |
Scan high-efficiency EPA certified
wood stove; stove alone could heat the house with two cords
of wood during winter. |
| • |
Natural-gas-fired modulating instantaneous
water heater provides backup heat for the solar domestic hot
water system. |
Total Building Energy
Use:
| • |
The house is 65% more efficient
than 2004 International Residential Code |
| • |
Design of the house allows it to use 2/3
less energy than conventional construction |
| • |
$330/year at $1.30/Therm |
| • |
Design space heating load of less than 18,000
Btu per hour |
| • |
Space heating load of 10 Btu/sq. ft. of
living space |
Renewable Energy System Information
Solar System Description
and Size:
| • |
The solar system includes both heat and
power, generating 30,000 Btu/day from evacuated tubes to meet
the domestic water needs and 2 kW of photovoltaic panels to
power the home. |
| • |
Solar systems are flush-mounted
on the 10/12 pitch roof |
| • |
Solar thermal system:
| - |
16 Sunda Seido S-16 evacuated tubes
collectors |
| - |
80 gallon Amtrol Boilermate double-walled
heat exchanger |
| - |
Resol pump controller |
| - |
PAW – insulated pump station
integrated with:
| · |
Flow valves |
| · |
Check valves |
| · |
Temperature gauges |
| · |
Pressure gauges |
| · |
Pressure relief valve |
|
| - |
3 expansion tanks: one each for the
solar loop, ground loop, and storage tank |
| - |
Insulated water lines |
| - |
Sized for 2–3 people |
| - |
Output temperature range: 130°F–150°F |
| - |
Domestic hot water storage tank connected
to the on-demand water heater
| · |
The on-demand water heater
provides a 40–60°F temperature rise
and identifies preheated water and shuts off and
modulates, regulating to only heat to the required
Btu set-point |
| · |
Heat exchanger
pumps from the tankless on-demand water heater
and cycles away from the storage tank |
|
|
| • |
Solar electric system:
| - |
2kW system |
| - |
16 Kiosara 130-watt photovoltaic modules |
| - |
Sunny Boy SMA 2500 U
with Maximum Power Point Tracking – Grid synchronized
inverter |
| - |
Utility grid inter-tied for net-metering |
|
Solar System Cost:
| • |
Solar electric: $18,850
before rebates, $10,650 after rebates |
| • |
Solar domestic hot water: $6,500 (no rebates
offered) |
Financial Incentives/Donations:
| • |
Rebates from MN Dept. of
Commerce: $4,000 |
| • |
Rebates from local utility (Minnesota
Power): $4,200 |
Overall Costs:
Upfront costs were about 15–20% higher than a conventional
house to include energy-effective design and renewable resources
for heat and power.
Date of Installation
Completion: May 2007
System Designer:
Conservation
Technologies
System Engineer:
Krech Ojard
& Associates
System Installer:
Conservation
Technologies
Estimated Amount
of Energy Delivered by System:
| • |
Solar thermal domestic hot
water system: 30,000 Btu/day |
| • |
Solar electric system: 250 kWh/month,
3,000+ kWh/year |
Percent of Building's
Total Energy Use Provided by Solar:
| • |
75–80% of domestic hot
water needs |
| • |
75% of electricity needs |
Tools Utilized
The design team used a range of software tools
to develop a tight envelope and reduce the heating and cooling loads.
By working together to integrate effective strategies, the modeling
software helped the team reach the target loads for the Eco-Home.
Design Tools:
Sketchup was initially used by Wagner Zaun as a visual tool to for
looking at shading of the structure and sizing overhangs for passive
solar heating and daylighting
Modeling Software:
Conservation Technologies used the following modeling software to
optimize the envelope:
| • |
REM Design was used for energy
modeling, which allows the user to change out elements like
windows and insulation for impacts on heating energy. The
comprehensive program requires input about the climate, building
size, orientation, size and location of windows, thermal properties
of building components and assemblies, air tightness, ventilation
equipment, heating and cooling equipment, domestic hot water
equipment, and fuel sources. |
Motivation for Installation
| • |
To design a house that people
could relate to that matched the designs in a neighborhood,
but also included high levels of energy efficiency, passive
solar, renewable energy, and sustainable design practices
to effectively use resources while still meeting human health
and comfort needs |
| • |
Set a measurable, Low-Energy performance
target: A house that uses less than half the energy of
a conventional house |
| • |
Influence the market: On a budget
with relatively conventional practices and materials, develop
a project at market price to meet consumer interest with current
knowledge on building science, sustainability, and renewable
energy. |
Lessons Learned
During the design phase the process taken
to achieve a low energy house is as follows:
| • |
Create a set of performance
goals and targets that help define the passive solar strategies,
overall building form and size, and the desired relative amount
of energy usage or savings. |
| • |
Model a series of reports, including the
components, for determining the annual heating load and peak
heating load; these reports identify the leaks in walls, floor,
and roof, which are the low-hanging fruit to pick off with
proper sealing techniques, or by interchanging different envelope
systems or elements to increase the performance levels. |
| • |
Then do comparative analysis of the building's
performance against benchmarks of other similar sized buildings
to show how much CO2 equivalent emissions are offset
along with low energy performance levels and renewable energy
systems. |
| • |
Passive solar in northern cold climates:
| - |
Low-e standard double-pane windows
lose more at night after cloudy days than you will gain. |
| - |
Radiant floor slabs used as thermal
mass have a long time lag, and need larger temperature
swings to release heat at night and gain heat during
the day in a balanced way that also does not overheat
the house during prolonged sunny periods when the floor
does not release all of its heat. |
| - |
Balancing the passive
solar design with sizing a wood stove as backup heat
meant looking at the peak heating load, which was 20,000
Btu, and the smallest stoves available were encouraged
for the project. |
|
| • |
To include solar technologies, the first
step is to build a better building from the onset of design,
creating an envelope to control the loads.
| - |
For Building Integrated Photovoltaics
(BIPV) a 12" x 12" roof pitch is needed to
remove snow in northern climates. |
| - |
In order to avoid catching snow on
the solar panels throughout the winter season when the
roof pitch is closer to 20 degrees (3/12 or 4/12 pitch),
racks on the roof need to be mounted to lift up panels
and help shed snow load. |
| - |
Michael LeBeau of Conservation Technologies
suggested that we should be considering solar integrated
buildings, not building integrated solar. |
| - |
Pay attention to making a high-performance
envelope to make the building heat/cool at affordable
levels, which then allows the matching up with solar
electric/thermal heating to meet demand loads. |
| - |
This means determining
heating loads first by modeling the envelope, then picking
a target to meet demand with backup systems and supplement
with solar technologies. |
|
| • |
The other aspect of high-performance envelopes
is to eliminate condensing surfaces of thermal bridges by
putting a space between walls or using foam sheathing; air
sealing is the key for keeping moisture out of the structure,
along with high-performance windows. |
| • |
Impacts on design when selecting electric
appliances, etc., depend in the end on the habits of clients;
being safe sometimes means opting for the largest volume of
energy to meet unknown future client needs. |
| • |
According to Michael LeBeau, when addressing
electric loads it is important to never choose to heat a house
with electricity — regardless of how it is generated
— because other systems are much more efficient for
heat delivery. |
| • |
Michelle LeBeau of Women in Construction
stated that future projects will incorporate the following:
| - |
Passive solar |
| - |
Solar domestic hot water |
| - |
2x6 walls with 1" foam/dense
pack cellulose |
| - |
Double-pane windows |
| - |
Energy modeling by Conservation Technologies |
| - |
Continued work with local partners |
|
Other Sustainable Features
| • |
15,000+ pounds of CO2
equivalent emissions avoided yearly by integrated design construction
and renewable energy systems |
| • |
5,600 pounds of CO2 equivalent
emissions from the nearby coal plant will be offset by the
solar electric system |
| • |
Reduced square footage to minimize materials
use |
| • |
Stacked bathrooms to minimize plumbing runs
for efficiency purposes |
| • |
Environmentally preferred finishes and materials |
| • |
Regionally produced items were used to minimize
transportation-related fuel consumption and emissions |
| • |
Sub-slab radon mitigation system |
|
