Green Homes

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Building My Net Zero Energy Home: The Back Story

6/5/2012 2:09:00 PM

Tags: Super Green Net Zero Energy Home, net zero energy, green homes, efficiency, passive solar, net zero, green building, Dan Chiras

In January 2011, my home in east-central Missouri burned to the ground. The fire was caused by mice that had chewed the wires in the floor. The wires generated sparks that started the house on fire. 

House 

This tragedy afforded me an opportunity to rebuild the house. After I was over the shock, it didn’t take long for me to realize that I was going to build a net zero energy solar home. It would be as green as green could be.  

A net zero energy home, for those not familiar with the term, is a superefficient home equipped with enough renewable energy generating capacity to meet its needs and offset any fossil fuel like natural gas burned to power the home. So, bottom line, the house will produce as much – very likely more -- energy than it consumes each year.   

I hired my friend and colleague architect James Plagmann with whom I have worked on numerous solar homes. James is no ordinary architect, he’s a sustainable architect with a deep understanding of what it takes to design and build a green, passive solar, and super-efficient home.  

Although he’d never designed a net zero energy home, I knew it wouldn’t take him long to figure out what we needed to do. I teach course on the subject at The Evergreen Institute and have been working on this idea since the early 1990s.  This project is my third attempt to achieve net zero energy.  

The first foray into net zero was my off-grid passive solar home in Evergreen, Colorado. I started building that home in September 1995 and finished up in May of 1996.   

This home was earth sheltered and so well insulated sheltered that it required very little outside energy. I selected the most energy-efficient lights and appliances I could find, so my electrical demands were met entirely by a tiny 1.1 kW solar electric system.   

Because the house was passively heated and cooled, there were no boiler pumps or furnace fans to move heat about. That also contributed to its extremely low electrical demand.  

We also collected rain water from the roof, and stored it in a 5,000 cistern alongside the house, so there was no need generate electricity to pump water up from a deep well. 

I never achieved net zero energy on that house, because of design problems I ended up having to burn a cord of fire wood each year to provide backup heat. A cord of pine contains about 17 million BTUs of heat. Because a kilowatt-hour of electricity contains 3,413 BTUs, I’d have to generate another 4,578 kWh to offset the wood consumption. My little 1.1-kW PV array only produced about 1288 kWh and that was used to power the house during the year.   

My second attempt at net zero was my educational center and home in Missouri, which I started working on in 2009. The first step on our road to net zero energy was a complete energy retrofit of our 2,400-square foot classroom building and my residence. I then started installing renewable energy capacity – solar and wind systems – to provide electricity.  

In 2009, I installed a 4-kW PV array that generates about 6,000 kWh per year.  

In 2010, I installed a 2.5 kW Skystream wind turbine on a 126-foot tower.  It generates about 3,000 kWh per year.  We quickly discovered that the PV array and wind turbine produced a lot more electricity than was required to power the home and the lower level of the classroom building, which was supplied by a circuit from the house. So we not only achieved net zero energy, we were net positive. 

Later that year I also installed a 2-kW PV array, a grid-tied system with battery backup to power the upper level of the building in which my office, bathrooms, dining area, and classroom are located. That year, I also installed two solar thermal systems – one on the house and the other on the classroom – to provide hot water for both buildings. 

In 2012, I added another PV system, a 1.5-kW array to provide additional power to the classroom building.  

By now, my six renewable energy systems were producing way more electricity than the facility required. The entire facility was become net positive. Each year, we produce a generous surplus of electricity. That will end soon as Linda moves her business, Evergreen Candleworks, which manufactures soy candles and soy-based lotions and moisturizing bars, into the lower level of the classroom building. 

To achieve net zero in the Evergreen Institute, I employed efficiency measures but added a lot of renewable energy capacity at the facility. That’s a common approach when trying to achieve net zero energy with existing buildings. You’ll see numerous articles in Solar Today and other magazines that feature people who have taken this approach. They’ll replace energy-inefficient appliances and electronics with much more thrifty models; seal up their building, making them more airtight; add insulation to slash demand, and then install a solar hot water system and a large, 10-kW PV array to achieve net zero energy. 

In the new house building that James and I will be blogging about over the next five or six months, I am taking the most efficient and desirable approach – I’m implementing radical energy efficiency measures coupled with modest capacity.  

Since we already have a PV and wind system, we will tap into them systems to provide electricity. They collectively produce about 9,000 kWh per year. That should provide considerably more electricity than we need to power this super energy-efficient, passive solar, net zero energy home.   

I will also install a solar hot water system on the house to replace the one lost in the fire. It will lower our overall energy demand as well and will help further reduce our carbon footprint. 

In the next blog, we’ll start describing some of our earliest decisions on the path to net zero and some of the design considerations. Until then, be sure to turn the lights out when not in use…


Contributing editor Dan Chiras is a renewable energy and green homes expert who has spent a lifetime learning life’s lessons, which he shares in his popular blog, Dan Chiras on Loving Life. He’s the founder and director of The Evergreen Institute and president of Sustainable Systems Design. Contact him by visiting his website or finding him on .



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Post a comment below.

 

RANDY JONES
7/20/2012 2:54:09 PM
Thanks for the article you gave me so many great choices in building my more efficient block home.GOD bless

Heather Hinckley
6/8/2012 6:23:39 PM
I was wondering what the cost was of those various arrays, etc that you had installed. Did you get federal and state tax deductions for the cost plus installation? Thanks for your article!

Lucy Mullis
6/7/2012 4:35:16 PM
Dan, The update for your new Net-Zero home is quite interesting. I am looking forward to your future updates as to what strategies and why you are using them as your building construction progresses for you Net-Zero home. Thanks.







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