Two Important Net Zero Homes in Austin

The Cripes Round Rock, Texas Home

The Cripes worked with Solluna Builders to design and build their home. This company specializes in custom house design and has extensive experience with net-zero energy homes. The combination of a plentiful amount of sun in Central Texas, relatively mild winters, and the reduced size requirements for the homemade net-zero energy a guiding goal of the project.

While many homeowners who dream of building a sustainable home might be tempted to move into the countryside and away from the stricter regulatory powers of homeowners associations and local zoning laws, the Cripes home is an example of a sustainable, energy-efficient residential building project that is located in a conventional planned-unit development (PUD).

They did, however, face several regulatory challenges during the building process. Local lenders were not open to financing a non-traditional house, and the owners thus had to reduce their overall loan and pay for much of the construction in cash.

The utility company in the jurisdiction where the home was built did not have a net-energy rebate program. The homeowners, thus, lost out on a potential opportunity to accelerate the payback time on their solar PV system. However, the company did offer credit surplus amounts so that the Cripes could consider investing in an electric vehicle to utilize the excess energy produced from their rooftop solar panels.

A Blueprint for Achieving Net Zero Energy

As mentioned above, this building project's main goal was to produce a surplus of energy through a residential solar PV system and an energy-efficient building design. After the first year of occupation, the Cripes were able to achieve net-zero status.

Their home included a geothermal HVAC system and an efficient heat pump for additional heating and cooling. In addition, a rainwater harvesting system reduced their monthly water bills by $70 for an average annual savings of $840.

Other features incorporated into the home that helped maximize energy efficiency included bio-based spray foam insulation, high-quality thermal windows, and a 5kW grid-tied solar electric system. An online monitoring system for their solar panel system allows them to make periodic adjustments to maximize the amount of energy produced. The Carrier Puron Geothermal heat pump offers 722 square feet of living space per ton of cooling and provides free hot water as a byproduct. The home is furnished with the latest energy-efficient appliances, including a magnetic induction cooktop. 

Water Savings in the Heat of Central Texas

The average high temperature in Austin, Texas, during August, is a sweltering 97 degrees. For homeowners trying to maintain a green lawn during the long summer months, an enormous amount of water would be needed.

However, the Cripes home maintains a thriving, beautiful lawn landscape even during a horrific drought that saw 100 days with temperatures routinely triple digits. The Cripes home landscape contains no turf grass, which needs excessive water to thrive in hot climates. Instead, the home utilizes an ecological xeriscaping technique that focuses on native plants that radically reduce the watering need. A 500-gallon rainwater collection system is connected to hose bibs that irrigate the garden and lawn.

This landscape design allows the yard to thrive with nothing more than a careful allocation of the limited summer rainfall. Inside the home, dual flush toilets, a high-efficiency clothes washer, and low-flow showerheads even further reduce the home's water usage. While their neighbors either settle for dead, brown grass or run up their water bill with excessive lawn irrigation during the summer, the Cripes maintain a beautiful yard with a monthly water bill that is usually under $20.

The Cripes home offers a healthy home interior as low and no-VOC paints, varnishes, and finishes were used throughout the home. Their customized cabinetry was all made from formaldehyde-free plywood. Exhaust fans and a high-efficiency fresh air intake that works with the heating and cooling system protect the home's indoor air quality. A ZipSystem exterior wall sheathing has a moisture barrier that protects from any mold or mildew growth, while the polished concrete floors are a simple, beautiful, and VOC-free addition to the home.

The Red Sky Project

A couple of miles away from the Cripes home, The Red Sky Project is another fantastic example of a sustainable, net-zero energy home that thrives in the harsh climate of central Texas. The Red Sky Project is a massive renovation of a 150-year-old barn into a high-performance, net-zero energy home. This old barn's renovation included several upgrades, including a 4.5 kW solar system, a spray foam envelope geothermal heating and cooling, and large overhangs as part of a larger passive solar design.

This project included resilient concrete and bamboo flooring inside and locally-harvested stone for a beautiful exterior cladding with a minimum embodied energy rating. Geothermal heating and cooling and an energy recovery ventilator (ERV) maximize this home's energy efficiency.