The basics of a zero net energy home is that
its produced energy is equal to or greater than it consumes.
The ability of the house to be zero-energy is primarily
dependent on three elements:
- Advanced shell design
- Super high efficiency heating system
- Photovoltaic power generation
The three elements work in unison and are
required to create as much energy as is consumed in a viable
economic package. The design team was committed to using
easily replicable construction techniques that could be
accomplished for not more than 115% of conventional
construction cost. A key element of uniqueness to the Rose
house is that in addition to demonstrating technical
innovation, it is all about affordable and appealing design
that is accessible to the general population.
The advanced shell design serves to minimize the heating and
cooling requirements of the home. A Structurally Insulated
Panel System (SIPS) is used for the roof. A Staggered Stud
System is used at the walls with recycled blown cellulose
insulation (R-25) allowing continuous insulation around the
studs and providing a breathable vapor barrier. Special
foundation insulation details minimize temperature changes.
The Super High Efficiency space conditioning system uses
less than half the energy of a conventional system while
providing fresh air and eliminating the need for a furnace
in favor of a solar heat pump. The heat pump gathers energy
from the back of the PV collectors and generates energy as
hot water. A 120 gallon thermal storage tank A clearstory
bank of windows provides generous day-lighting and natural
stack effect ventilation instead of air conditioning.
The 3.3KW Photovoltaic Array of Sharp solar PV panels is a
grid tied system that provides more energy than required at
times and less than required in others. The grid acts as a
big electrical storage bank that is required to make the
house function properly. During start-up of motors and
electrical equipment much more than 3.3 KW is required and
the grid provides that extra capacity.
As seen by the following diagram, overall during the year,
the house will supply more energy to the grid than it has
consumed. Since all appliances and the heating systems work
on electrical energy the house is a Zero-Net Energy house.
Solar PV power is the blue contribution below the line and
the various household loads are above the line.
The diagram is a computer model of this house. The WEB site
will show a daily and accumulated graph of. The actual
energy delivered by the photovoltaic grid and the household
energy loads.
THE COST OF A ZERO-NET
ENERGY HOME
The first cost of a "zero" net energy home can be reduced to
near that of a typical house. Some of the component cost
savings were possible because of new energy recovery
technologies, and low-cost, yet sophisticated programmable
controls. The majority of the cost savings however, came
from a design that gets multiple benefits from each feature.
These design elements and their relative cost savings will
be presented.
Envelope design with highly insulated staggered stud wall
system allows loads to be met with airflow rates provided by
the fresh-air ventilation system.
Use of a heat pump for domestic hot water heating, space
heating and space cooling.
Use of an energy recovery ventilator to provide
humidity-optimized fresh air and serve as a primary driver
for the heating coil, energy recovery and economizer
function.
Use of concrete slab construction to serve as thermal
storage both passively (direct gain) and actively (heat
pump).
Use of PV array to provide a source of waste heat, reduce
cooling loads and improve roof life, in addition to
providing all of the annual energy requirements for the
house.
Final costs for all system components will be presented and
compared to current conventional residential construction.
Preliminary results indicate that the additional costs of
the house from these features will be less than 15% -
including the net cost of the PV system after incentives and
tax credits.
Oregon Zero Energy
Home Base House
The following is a description of the "Base House" which is
used to for evaluation purposes the solar heat pump system
in Oregon. The design allows for good solar access both on
the roof and as a passive solar design. Maximum roof area
for solar measures 36 feet wide by 12 feet tall for (431
ft2).
ZEH Base House Design
- Heated Floor Area 1900 ft2
- Total Glazing Area 394 ft2
- Passive Solar Glazing Area 225 ft2
- Potential Solar Roof Area 500 ft2
- Total Solar Resource Fraction 100 %
- Water Heating .93 EF electric
- Space Heating Heat Pump SEER 13
- Heat Recovery Water 60% GFX
- Air 80% ERV
- Appliances Energy Star Clothes Washer
- Energy Star Dishwasher
- Energy Star Refrigerator
- Lighting Fluorescent (90%)
- Other Plug Loads 1000 kwh/yr
- Phantom loads 200 kwh/yr
Construction Details
These are just base starting point assumptions.
ZEH design Code design
- Walls U-0.045 various U-0.060 2x6
stud w/R21
- Roof U-0.027 conditioned attic
U-0.027 attic w/R30
- Floor U-0.025 micro-basement U-0.032
ventilated crawlspace w/R25
- Windows U-0.330 vinyl low-e, argon
U-0.400 vinyl low-e
- Solar Windows U-0.300 SHGC > 0.60,
w/NI none
- Doors U-0.200 U-0.500
- Infiltration 2.0 ACH50 7.0 ACH50
- UA overall 270 Btuh/F 360 Btuh/F
- oads and Consumption
- Portland Medford Redmond
- Design Temp (F)
- Design Load (Btu/hr)
- Heating (kWh/yr)
- Cooling (kWh/yr)
- DHW (kWh/yr)
- Appliances (kWh/yr)
- Lighting (kWh/yr)
- Other Plug (kWh/yr)
- These Values are +/- 20%
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