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  • Denise Garcia

Post #10: Blowing Past Code

Updated: Aug 31, 2019

The following blog will chronicle the construction of a new Zero Energy Ready Home

designed by Domain Design Architects and located on San Juan Island, Washington. Denise Garcia and her husband, Eric Schmidt, who together have degrees in architecture, landscape architecture and city planning, have been passionate about environmentally responsible design since their student days at MIT. Their new ZERH home is the culmination of over 30 years each of professional experience. We hope this blog will inspire others to consider building a Zero Energy Ready Home.


A small doe walks just under our house on the far side of Fish Creek, visible in the middle of the photo.

San Juan Island, August 30, 2019

Cape Drive Zero Energy Ready Home

Blog entry #10: Blowing Past Code!

It's been 11 days since the last blog post and work has accelerated on the house. The solar panels are installed on the roof and now tied to the electrical grid. In the San Juan Islands, that grid is owned by OPALCO (Orcas Power and Light Cooperative). Excess electricity generated by our solar array will be fed directly into the power grid. In return, we'll receive credits which can be used toward our electric bill. In the summer months we'll be producing more electricity than we use and in the winter months, less than we use. Our electrical credits from OPALCO will ensure that we stay "Net Zero" throughout the year. In addition, we'll receive a federal tax credit of 30% for the cost of the array (including installation). Washington state will eliminate sales tax on panels made in the state. Our Silfab 370 -watt photovoltaic panels are made in Bellingham, WA.

In the garage, our new solar panel inverter sits next to our 200-amp load center. A solar inverter or PV (photovoltaic) inverter, converts the variable direct current (DC) output of a photovoltaic solar panel into a utility frequency alternating current (AC) that can be fed into a commercial electrical grid.



With the completion of the solar array, we got down to the business of making sure our house meets the air-sealing requirements of Net Zero certification by performing the first of two blower door tests. On a beautiful sunny day, our energy consultant, Elizabeth Coe, arrived to perform the test. Elizabeth has been advising us throughout the process of building our home, from preliminary design to now. Her work has been critically important to the realization of our Net Zero energy goal.

For weeks, the crew has been air sealing every penetration in the building envelope, from tiny nail holes to vent terminations. Here, Elizabeth and Dave (our site superintendent) tape up the threshold and hardware openings in the Dining Room patio door in preparation for the blower door test.

The door between the Garage and Mud Room served as the portal for the blower door test. Here, Elizabeth has set up her fan, pressure gauge and laptop as she begins the test.

A blower door test measures the air-tightness of a house by putting its interior volume under negative pressure, then measuring the rate at which outside air infiltrates into the interior. This measurement is called "air changes per hour" or ACH. The lower an ACH score, the better. The 2015 International Residential Code requires all new houses to achieve an ACH of 5.0. New homes going for Energy Star certification must achieve a rating of 3.0 or less. New Net Zero homes typically achieve an ACH rating of 2.0 to 0.6. Our score: 0.97, blowing past both the 2015 IRC and Energy Star and putting us well below the mid-range for Net Zero. With the sealing of 2 small areas found during the test, we'll do even better at our final blower door test. Looking forward to that!

With the blower door test behind us, the insulation subcontractor started his work. Here, loose fiberglass insulation, called BIBs, are blown in to the stud cavities in the kitchen. BIBs deliver a higher R-value per inch compared to fiberglass batts, as the material fills the cavity completely, leaving no gaps or air pockets. All of the exterior walls will be insulated with BIBs, giving us an R-23 cavity. Added to the 8.6 R-value of the exterior rock wool insulation, we achieve an overall wall R-value rating of 31.6, blowing past the code-required value of 21.0.

Before the BIBs were installed, metal knife plate brackets were fastened to kitchen studs in preparation for the floating shelves that will be located there.

In the Living Room, wall cavities have been filled with insulation, as well as the roof/ceiling. Our house is now extremely quiet, as the insulation adds a sound barrier as well as a thermal one.

The acoustical properties of fiberglass insulation are important where private spaces such as bedrooms and bathrooms abut more public spaces. Here, sound insulation has been added between the Dining area and both the Master Bedroom (left) and the Powder Room (right).

On the exterior of the house, the crew has begun to install rock wool insulation boards over the Zip Wall sheathing. This 2" layer of thermal, fireproof material will act as a permeable layer over the entire house, keeping it warm in the winter and cool in the summer. 1x4 wood slats are installed over the rock wool, creating a 3/4" rain screen cavity behind the siding. The cavity allows any moisture that gets behind the siding to drain down and exit via a continuous vent at the bottom of the wall. This will greatly increase the lifespan of the siding and prevent the kind of rot problems and siding failures that can sometimes be seen in typical homes.

Rain screen straps are attached through the rock wool to the wall studs with long screws and will provide the blocking needed to attach our fiber-cement siding.

On the north side of the house, rock wool panels have been added around the windows in the Master Bedroom. Once the 1x4 rain screen straps are installed, the crew will begin to trim out the windows with tight-knot cedar casing.

As an exterior insulation material, rock wool is hard to beat. It's permeable, allowing moisture to drain through it, rather than pooling behind it. It provides a fireproof layer to homes that are in remote and/or rural locations where firefighting services may be more challenging. Finally, it's easy to work with. Here, a knife looking like ones used to cut bread, makes short work of trimming a panel..

Stacks of rock wool panels await installation on the west side of the house.

Rain screen installation has started on the east wall of the Living-Kitchen wing. Soon, the siding will be installed and the house will take on its final form.

Looking up from our dock, we can see the start of the deck framing at the Dining Room.

Cantilevered deck joists await the installation of deck boards. After much thought, we decided to use Garapa decking boards. While not as hard as Ipe, Garapa is quite durable, especially when compared to cedar. Like Ipe, it's a tropical hardwood that can be left to weather to a silvery gray (which we plan to do). Garapa is less expensive than Ipe. Best of all, it will be FSC-certified.

Viewed from the marina across from our lot, the house is continuing to take shape. With the addition of the fiber-cement siding which will be installed soon, the final form will begin to take shape.


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