Project Files: Episode 60 —The Geo Home
Tesla solar roof, heat pumps make for net-positive energy home in Houston
Sustainability means many things to many people. For Austin, Texas-based GIGA Construction, the key driver of sustainability is energy independence. The company builds homes with integrated solar roofs with battery backup. One of those is Geo house, a net-positive energy home built for health, safety, and a sustainable, nature-inspired living experience. Designed by GIGA Construction, Geo house is the first project in the Houston 610 loop to pair a Tesla solar roof with battery backup for complete electrical grid independence.
GIGA Construction puts a lot of focus on building a healthy home, something Garrett Stepanovich, company president, said that based on current construction standards, isn’t done enough. The solar-powered Geo house, completed in late 2021, is 3,530 square feet, single-story, with 5 bedrooms and 3½ baths. It’s designed to keep energy requirements low with an airtight envelope, insulation, and as many Energy Star appliances as possible. All the lights are LED, and building components such as cabinets are sustainable sourced using recycled content.
Finally, for external building enclosure, GIGA Construction used Huber Woods engineered wood sheathing, which allows the seams to be taped or sealed, either with a physical tape or a liquid flash. Combined with airside testing such as the blower door test, the final result is the home is essentially built like a giant Yeti cooler.
The Geo home is run fully off a 15 kW, south-facing Tesla glass solar panel roof, allowing it to operate completely off the grid — including the HVAC system, which in most residential homes is the No. 1 user of power.
With the solar roof, a standard unitary system — which has a hard start — would have pulled far too much electricity. To account for this, the project’s HVAC consultant, New Balance A/C, and distributor Johnson Supply recommended the Mitsubishi M- and P-Series single-zone mini-split systems: 3 SUZ outdoor units, 2 SVZ multi-position air handlers, and 1 PEAD horizontal-ducted indoor unit.
The Geo house HVAC system has 3 individually controlled comfort zones and continuous fan movement for steady indoor temperatures. Powered by the sun, the Mitsubishi Electric system uses heat drawn from the outdoor air to keep Geo warm during the winter without burning fossil fuels. As a matter of fact, there are no gas lines within the building envelope.
Stepanovich acknowledged there’s a stigma about solar that it won’t produce enough energy for the home at certain times. Sure, it doesn’t operate as efficiently when it’s cloudy, he said. But, he continued, “If you pair solar with battery backup, your home will remain off the grid. It's all about mirroring smart solutions together and being seamless with the design.”
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He said that with an HVAC system that’s a low drawer of power, it’s “actually pretty simple” to pair that system up with a solar array that's average size.
The Mitsubishi variable-capacity heat pumps fit the bill. Thanks in large part to their inverter-driven compressors, they use minimal electricity, generated by the home’s photovoltaic array, and the home can operate off-grid using the power of its two 13.5 kWh backup batteries for approximately four days. This gives Geo sustainable heating and air conditioning even during the night and on cloudy days.
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