How I Developed My Passive Solar Home
In September 2010, my wife and I bought 80 undeveloped acres in Otter Creek, Wisconsin. Our goal was to retire to this place someday, and to build a comfortable home that demonstrates the best design principles for saving energy.
We spent the next several months crafting a design and finding the right location for a passive solar home. We engaged an architect experienced with passive solar design, Kevin Flynn of Eco Deep, and included Craig Tarr of Energy Concepts in our early discussions. Craig designed our active systems for collecting hot water on our roof and converting sunlight to electricity with our photovoltaic array.
Craig insisted we use an elaborate energy model to compare various options before making decisions about:
- whether to use wall panels manufactured in advance,
- how thick the wall and roof insulation should be,
- which windows would yield the best performance, and related details.
What resulted is a home that is super sealed, super insulated and costs very little energy to keep comfortable. I write this during a major cold snap — outside it is 20 degrees below zero. We have not added any heat since we arrived three days ago. With direct sun warming the rooms it is more than 60 degrees inside at noon.
A couple of key building components include the following.
- Walls 12” thick with two sets of 2×4” studs. That cavity is filled with expanded foam in the outside 3” and the remainder is blown cellulose insulation yielding an R value of 55.
- The ceiling has 24” of blown insulation in the attic, yielding an R value of 80.
- Overhang on south windows is calculated to keep summer sun out while allowing maximum winter solar gain.
- There are some windows with Green Awnings to allow vines to grow up to provide both summer shade and evaporative cooling.
- The walkout basement has many windows on the south side to help collect winter sun.
- Some interior walls are 6” concrete blocks filled with sand to absorb the sun’s energy on winter days and release it back into those rooms into the evening.
- We also have two root cellars for storing garden produce.
- They are tucked into the NW corner of basement and are cooled by allowing colder outside air to drop into the room as warmer air is pushed out using ducts without fans.
Other important outdoor structural elements:
- The landscaping surrounding our home includes windbreaks of evergreens on the NW side to block both winter winds and setting summer sun.
- We have a cistern that can collect up to 1,000 gallons of roof runoff that can be accessed from gravity fee pipe, as well as a series of raingardens that capture surface runoff and allow it to soak into the ground instead of quickly running down slope to our intermittent stream.
- An important feature of our home has been our unheated porch on the west side. We find that with its simple window and screen system we are able to be comfortable inside that space with the sun warming us and protected from the wind, when it is still too cool to be eating outside. The east side has a large patio for entertaining on more mild evenings.
- The garage is detached and unheated, except for the wood shop at the far east end. It has a wood stove and passive solar windows.
- Between the garage and home is a deck so that there are no steps between driveway and our first floor. The east side of the deck is a U-shaped structure that supports a roof over the deck, holds several utility panels, blocks winter winds and provides firewood storage for a full winter.
One of our regrets was that I was not able to be present every day during construction to work more closely with our builder. He did a fantastic job of finding local skilled labor to accomplish the wide variety of specialty tasks, yet would have benefitted from more input from me to speed construction. From breaking ground to move-in required eight months. That could have been reduced with more direct supervision.
A detail in the root cellars had to be adjusted after our second spring, when the sand floor became too wet from water seeping through the inadequate waterproof membrane. A new layer of cement has been added, so we expect that to allow us to decide how much moisture to add to the sand to control humidity to store some fruits.
But our regrets are few and joys have far exceeded the minor hassles and delays related to construction confusion. We continue to enjoy our time there with friends and family who have been able to come visit and relax. It is an extremely quiet place and has little light pollution, so star gazing is spectacular. We are blessed with a variety of birds, lightning bugs, tree frogs, damselflies, and many butterfly species.