An American Passive Home: Page 4 of 4

Intermediate

Inside this Article

Pura Vida demonstration home.
Pura Vida, a common saying in Costa Rica meaning ”pure life,” is the name of this demonstration home built by the author and his wife in Oregon, Illinois, in 2007.
Pura Vida interior.
A timber-frame structure, Pura Vida demonstrates an efficient home that looks and feels conventional.
Insulated concrete forms.
Insulated concrete forms include the support that keeps the forms from being pushed apart during the concrete pour.
Large south-facing windows.
Large south-facing windows, specified for their high solar heat gain coefficient, admit ample sunlight to warm the house on sunny winter days.
The “earth room” under construction.
The “earth room” under construction. Once complete, this space will provide a source of free heating and cooling.
Enerboss
A 4.5 kW Marathon water heater provides hot water to the heat-exchanger coils within this all-in-one Enerboss, a heating, filtration, and heat-recovery ventilation system.
A 4.5 kW Marathon water heater
This 4.5 kW Marathon water heater provides hot water to the heat-exchanger coils within the all-in-one Enerboss, a heating, filtration, and heat-recovery ventilation system.
An air-to-water heat pump.
An air-to-water heat pump provides domestic hot water.
Wind-electric generator.
A small wind-electric generator offsets a small portion of the home’s electricity use. It would produce much more on a tower tall enough to clear all obstructions in the area.
Two pole-mounted PV arrays.
Two pole-mounted PV arrays offset about 27% of the home’s electricity use.
Battery bank.
A battery bank provides backup power in the event of a utility outage.
OutBack MATE3
An OutBack MATE3 keeps tabs on the RE system.
OutBack Radian series inverter.
This OutBack Radian series inverter and load center also serves as an AC and DC enclosure. The system’s charge controller sits to the right.
Wood floors and exposed posts and beams.
Wood floors and exposed posts and beams lend warmth and beauty to this efficient home.
Pura Vida demonstration home.
Pura Vida interior.
Insulated concrete forms.
Large south-facing windows.
The “earth room” under construction.
Enerboss
A 4.5 kW Marathon water heater
An air-to-water heat pump.
Wind-electric generator.
Two pole-mounted PV arrays.
Battery bank.
OutBack MATE3
OutBack Radian series inverter.
Wood floors and exposed posts and beams.

We believed we had a wind resource that was sufficient to justify a wind-electric system. Our chosen turbine, the Skystream, is predicted to produce about 2,600 kWh per year given an 11 mph resource, and about 900 kWh per year in 8 mph winds. After several years of operation, the system has produced roughly 500 kWh per year, or the equivalent of $50 of energy, which is expensive electricity when you consider the $21,000 installation cost. 

It is clear now that the information we started with was not sufficient to justify using wind energy at our site. Factors contributing to our turbine’s lower-than-anticipated production include a tree line that sits about 800 feet to the west, resulting in turbulent wind from the prevailing wind direction. A taller tower would undoubtedly help with this problem, because the farther you get away from the earth and its obstructions, the more wind there is. As a well-known small-wind expert has said, we unknowingly chose expensive energy over an expensive tower.

Over the past several years, the cost of photovoltaic systems has come down dramatically. During that time, we collected information on the energy demand for Pura Vida. We found that during the fall and spring, when there was no energy use for heating or cooling, the average demand was between 600 and 700 kWh per month.

In 2011, we installed a 4.3 kW grid-tied PV system that should average about 400 kWh per month. Twenty-four batteries provide backup for power outages and provide enough energy to live without the grid periodically—assuming that the backup heating would be provided by the wood heater instead of electricity. Performance data is being collected by the OutBack MATE3 energy monitor and we should have an accurate performance picture by the end of 2012.

Future of APH

We believe that building super-energy-efficient homes will have a significant impact on U.S. energy use. If the building cost of an APH is within 15% of a conventional building method, a conservative energy cost savings estimate is more than $1,000 each year per home.

One outcome of the recent economic downturn has been that the American consciousness has been awakened to the importance of common-sense solutions to important challenges. For families paying to heat and cool their homes—and as a nation that needs to use less fossil fuel—emphasizing energy efficiency in homebuilding is a simple yet promising way to address these challenges.

Access

Victor Zaderej has been passionate about energy use in homes, businesses, and transportation for 30 years. He holds two engineering degrees from MIT, and an MBA. Through his company, Solar Homes, he helps design energy-efficient buildings. He is currently the manager of Advanced Solid State Lighting at Molex.

Solar Homes • solarhomesus.com • Green building design

McCanse Builders • mccansebuilders.com • Builder

Pura Vida Systems:

EnerSys • enersys.com • Batteries

Nu-Air Ventilation • nu-airventilation.com • Heating, cooling & heat recovery system

Nyle Systems • nyle.com • DHW heat pump

OutBack Power • outbackpower.com • Inverter & charge controller system

Southwest Windpower • windenergy.com • Wind generator

Suntech • am.suntech-power.com • PV modules

WaterFilm Energy • gfxtechnology.com • Wastewater heat recovery

Water Heater Innovations • marathonheaters.com • Hot water storage

Comments (1)

zap101's picture

Yours is a fine home. Sharing the bad and the good outcomes is useful. The break out of costs of the insulation is helpful adding a cost per sqft/ payback might show the bang for your buck sort of speak. For example the under slab insulation cost per sqft/ pay back # of years in energy saving verses non insulated slab.

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