Solar Decathlon Team Designs Net-Zero Energy Home for Baby Boomers
Tom Lombardo posted on September 24, 2017 |

The Solar Decathlon is a biennial home design competition that addresses ten facets of sustainability. Sponsored by the US Department of Energy, the Decathlon's goal is to encourage student teams to design net-zero energy homes that are efficient, sustainable, and affordable. Among the thirteen competing teams is Solar Decathlon first-timer House by Northwestern, a group of students from Northwestern University, just outside of Chicago, who is constructing a net-zero energy home that they've dubbed "Enable" - a blend of the words ENergized and adaptABLE. This one caught my interest because it's designed for "late middle-aged" empty-nesters nearing retirement, a demographic that I'm somewhat rapidly approaching. Let's take a look at some of Enable's features.

Image courtesy of House by Northwestern
Image courtesy of House by Northwestern

Net-Zero Energy

Enable is a two bedroom, two bath, ADA-complaint, net-zero energy home with nearly a thousand square feet of sustainable living space. Its power comes from a 6.5 kW grid-tied solar array featuring twenty-two Sunmodule 295-watt solar panels tilted at 24 degrees to maximize production in the summer. A 25 kWh AGM battery bank stores excess energy for use at night and during extended periods of overcast. (For a typical US home, that battery would provide about one day of autonomy. Enable, as an energy-efficient abode, could run for two or three days on battery power alone.) The photovoltaic array delivers enough wattage to power the house, charge the battery bank, and juice up an electric vehicle in the garage. Energy production, storage, distribution, and use are monitored and governed by a home energy management system.


The designers employed many facets of Building Information Modeling (BIM), including energy modeling to ensure a tight building envelope and photometric modeling to optimize the lighting. In addition to smart LED light fixtures and Energy Star appliances, Enable takes advantage of an air-source heat pump for all of its heating and cooling needs - even hot water. Like all highly efficient buildings, Enable is airtight, so a mechanical ventilation system (that's "architect-speak" for a fan) with a heat exchanger delivers fresh air with minimal loss of heating or cooling. Appropriately, a Nest thermostat gives the empty-nesters a friendly interface for monitoring and controlling the HVAC system.

Photometric Modeling Helped Design the Lighting System (Image courtesy of House by Northwestern)
Photometric Modeling Helped Design the Lighting System (Image courtesy of House by Northwestern)


Enable's living walls feature drywall that breaks down formaldehyde, as well as indoor foliage to naturally filter the air. Walls and windows are covered in PURETi, a substance that destroys volatile organic chemicals (VOCs) when exposed to light. A rain collection system provides water for houseplants, and WaterSense appliances allow the house to use 30% less water than a typical home. The countertops look like stone, but they're really made from recycled glass, which has a smaller carbon footprint.


3D modeling helped the team to design Enable's open floor plan, which maximizes natural convections for optimal passive ventilation and makes efficient use of interior space. Enable's "convertible room" can serve as an office, den, or extra bedroom. Its south-facing sunroom provides fresh air in the summer and passive heating in the winter.

Image courtesy of House by Northwestern
Image courtesy of House by Northwestern


In terms of age, family, and career status, I am approaching the target demographic for this house. I wish I could say the same about the price tag - $400k is a bit out of my range. But keep in mind that this is a concept house - a "one-off" design, as it were. As the materials and techniques become mainstream, I could see that price dropping by a factor of two before too long.

Here's House By Northwestern's promotional video:

Video courtesy of House by Northwestern


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