Image Credit: All photos: Eric Whetzel Anthony from Rethink runs conduit through the air barrier at the attic floor level. The conduit starts at the electrical panel in the basement and ultimately ends at the panels on the roof. Two Roflex gaskets — one on top, another on the bottom — protect the integrity of the air barrier where a 3/4-inch electrical conduit must pass through. The disconnect box on the right is too close to the house to allow installation of insulation, furring, and siding. It didn't take long to correct the problem by adding an extension and moving the box out a few inches..
Editor’s note: This post is one of a series by Eric Whetzel about the design and construction of his house in Palatine, Illinois, a suburb of Chicago. The first blog in his series was called An Introduction to a New Passive House Project; a list of Eric’s previous posts appears below. For more details, see Eric’s blog, Kimchi & Kraut.
After deciding to pursue a combination of Passive House and The Pretty Good House concepts, which entail careful planning and attention to air-sealing along with a significant amount of insulation, we knew we could have a shot at net-zero or zero net energy (ZNE) — meaning we could potentially produce as much energy as we use with photovoltaic (PV) panels installed on the roof.
To find an installer in our area, we used the website Energy Sage. In addition to publishing useful articles and information about solar, they also work with installers who can provide consumers with competitive bids. It didn’t happen overnight, but in about a week or two, we got three or four bids and ultimately decided to go with Rethink Electric in Geneva, Illinois.
Based on the suggestions from Energy Sage and Rethink, we ended up with the following system:
Also included was web-based monitoring of the system’s production.
In theory, this system could produce more energy than we use (it’s just my wife, my daughter, and I who will be living in the house). But there a few caveats: we need to stick to all-LED lighting, use Energy-Star-rated appliances, hope the heat-pump water heater works as advertised, and be careful not to use electricity when it’s unnecessary. That means making sure we turn off the lights as we’re leaving a room, and limiting phantom electrical loads.
Installing the system
Based on other projects I’ve read about, even homes initially built to the ZNE standard sometimes fail, in terms of overall performance, because of occupant behavior. Only time will tell what impact our solar array will have on our utility bills. It looks like the worst-case scenario would be needing to add four to six more panels to get to ZNE or even carbon positive.
Installation by Rethink went really well, and they were happy to work with me on properly air sealing the conduit that runs from the basement at the main panel up into the attic. The conduit eventually terminates on the roof, where it is connected to the panels. (See Images #2 and #3 below.)
It was only after the installation that I realized an important detail had gone all wrong (see Image #4 below). It was my screw-up. I was so worried about getting the air sealing details right on the interior, from the main floor to the attic, that I completely forgot to let Anthony know about extending his disconnect box 6 inches, to what will be our finished surface (once two layers of Roxul and two layers of 1×4 furring strips, along with cedar siding, are installed).
The day after the box went in, I came walking around the corner of the house, saw this, and literally slapped my forehead (while spitting out a few choice expletives), as I realized my screw-up. Thankfully, Anthony was able to come back out and make the necessary adjustment (see Image #5).
Here’s the cost breakdown on our system (if trends continue, a similar system should be less expensive in the future):
Initial investment: $12,519.50
Federal investment tax credit: $(3,755.85)
Net cost in the first year: $8,763.65
Solar renewable energy credits: $(3,816.00)
Net cost after all rebates: $4,947.65
It will be interesting to follow the performance of the solar panels over the course of a calendar year or two, just to find out exactly how well they perform. I’ll come back here and post information on our monthly utility statements, noting output of the panels and our use, to give people a better sense of actual performance. Hopefully this will help others in the planning stages of their own projects to decide if solar (and how much of it) is right for them.