The Coldwell Banker Real Estate Smart Home Marketplace Survey, released last winter, found that nearly half of consumers say smart home technology is important for their current home or their next home purchase. Noted Lindsey Turrentine, editor-in-chief of CNET.com, which is partnering with Coldwell Banker on a smart home test in Kentucky: “This market will continue to develop as the technology becomes even more mainstream.”

The smart home test in Kentucky is just one example of how the Coldwell Banker® brand continues observe the way the “connected home” is transforming the way we live. In the Bay Area — the tech capital of the world, Coldwell Banker Residential Brokerage in Northern California recognized an opportunity to contribute to a local smart home experiment of sorts through the “Tiny House in My Backyard” (THIMBY).

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The project, which we covered last month in Part 1 of our series, revolves around building an affordable, 100% solar-powered tiny house on the site of the Berkeley Global Campus in Richmond, which will be part of Sacramento Municipal Utility District’s “The Tiny House Competition – Build Small and Win Big” on October 15, 2016 at Cosumnes River College. This Friday, September 30, you can see the tiny house for yourself at UC Berkeley’s Kroeber Plaza from 9 a.m. to noon.

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So just how is this interdisciplinary team of about 25 UC Berkeley graduate and undergraduate students going to achieve the ambitious goal of being off-grid, waste-recycling and 100% solar-powered through smart home technology? We turned to Ian Bolliger, project manager, to get some more insight into the most cutting edge smart home technologies they are using for their tiny house.

Can you tell us about specific smart home technologies that are used in THIMBY to control, automate, and/or optimize functions?

The main technology in THIMBY that qualifies as a “smart home” technology is an experimental home energy management system (HEMS) that controls the heat pump, radiant floor system, and energy recovery ventilator (ERV). It uses temperature measurements, data about homeowner behavior, and local weather data and forecasts to optimize the thermal comfort of the home while meeting constraints on solar generation, battery size, and air quality. However, this will not be implemented by the SMUD competition. It’s a very large-scale project, and will likely be implemented within one year.

What technology will be available for the competition?

The SolarEdge StorEdge inverter is one of the “smartest” inverters on the market. Like most inverters, it uses maximum power point tracking (MPPT) to maximize the output from the solar array at any given level of solar insolation. It can operate both on- and off-grid, which is ideal for THIMBY because the house as a whole is intended to have the same functionality. It also charges the battery in a “smart” way, inverting energy from the solar panels to go directly to loads when there is sufficient supply, and passing DC current directly to the batteries when there is excess. In other words, it doesn’t pass electrons through the battery or convert to AC and back to DC when not necessary.

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How essential is smart home technology in making tiny homes function in general, and specifically with THIMBY?

This is definitely a bigger question. I think smart home technology is typically most useful for larger homes and/or commercial/industrial buildings. THIMBY is close to a 100% passive house, meaning that heating and cooling needs are quite minimal. Heating and cooling (and lighting) represent the lion’s share of somewhat flexible and controllable electrical loads, which is where “smart” technologies have the biggest potential for cost savings and CO2 emissions reduction. With our tiny home, the smart home technology is particularly crucial for off-grid functionality. Because we don’t have the grid as an essentially infinite power source, we have no options if we run our battery down. Thus, we have to leave some margin for error when using electricity, and it’s the reduction of this margin of error through modeling that makes our smart home technology so valuable. Essentially, smart home technology allows off-grid residences to downsize their power generation and storage capacity, saving money and reducing the embodied energy and embodied emissions of the house.

On the flipside, I do think it is easy to follow the hype of smart home technology without putting it in context. With THIMBY, our goal was to reduce electrical demand as much as possible through a tight building envelope and through high-efficiency appliances and lighting. That, along with the THIMBY’s small size, provides the main energy efficiency of our house, greatly reducing the demand relative to a typical house today. It’s only after those gains are realized that smart controls come in to reduce the remainder of our electrical demand. So I would emphasize that “smart construction and design” was our number 1 priority, and “smart home technology” provided an extra boost in efficiency after that.

Have you chosen products (Warmboard Inc.’s radiant heating, cork insulation) that aid in creating a foundation for smart home technology? Have there been any unique challenges posed by the project when it comes to integrating smart home tech?

Again, our main focus was to create a foundation for an energy-efficient house, for which smart home technology was one piece in the puzzle. Also, when I say energy-efficient I mean not only the energy consumed as the house is operational, but also the embodied energy that was needed to produce the materials and equipment that comprise the house.

The cork insulation was chosen for its high insulation performance, natural waterproof characteristics, and, most importantly, its negative carbon footprint. Because cork comes from regenerating bark every 3-4 years, its use actually represents carbon sequestration. It was the only high-performance option we found that was both affordable and sustainable and met the design criteria for our particular use case.

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Using an ultra-efficient air-to-water heat pump with a hydronic (as opposed to resistive) radiant heating system allows us to use our hot water tank as thermal energy storage. The ability to pump extra heat into the tank at times when our battery is full and solar panels are generating excess energy allows us to capture more of the available solar energy without having to add more battery storage capacity. Controlling this flow of energy requires the smart energy management system. In other words, combining this HEMS with the Warmboard and Sanden CO2 heat pump allows us to obtain the functionality of adding a 2nd Powerwall along with that of space and water heating at a fraction of the cost of using separate equipment to meet each of these needs individually.

What you are doing is big and bold on a number of levels (tiny home size notwithstanding). Has there ever been a time when you considered backing off the goal of being 100 percent solar powered?

This was one of the goals that the team settled on very early on, and we have not strayed from that objective. Again, eliminating fossil fuels, especially for heating and for cooking in an off-grid setting, is quite difficult, but THIMBY is an experiment in how cost effectively you can eliminate the emissions associated with residential life. The design of the house has certainly evolved throughout the planning, and even the construction, phases. But our overall objective has remained constant: Make the most affordable house possible given a commitment to 100% renewable energy generation, to minimizing the embodied energy and carbon footprints of our home, and to creating a house that homeowners would be excited and eager to live in.

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