Have you heard about houses that don’t cost you anything for electricity and heat? Wouldn’t that be nice? Considering that home heating uses more energy and costs more money than any other system in our homes—about 29%—according to the Department of Energy, I’d say that sounds like a fabulous idea!
They’re called “net zero” homes or “net zero energy” homes, and you can have one, too. They don’t have to be funky-looking “pods” or domes or earth-sheltered, and the concept works with any architectural style in most neighborhoods. This one fits right into its neighborhood in El Dorado Hills, California. The concept also works for multifamily housing.
First off, how does a net zero home do this? By producing as much energy as it consumes for home heating and cooling and all electrical needs over a given time period. Several key features contribute to this net-zero energy balance.
A net zero energy home must have energy efficiency at its core. Reducing the overall energy demand also reduces the amount of energy that must be supplied later. A highly insulated and air-sealed building envelope is a must, as are high-performance windows and doors.
Net zero energy homes also require the most efficient appliances and mechanical systems, such as HVAC equipment. ENERGY STAR products are an easy choice to meet this need, as they are among the most efficient products available in their category and often have rebates available. Some, like heat pump water heaters, will also get you a 30% tax credit thanks to the Inflation Reduction Act.
Part of designing a net zero energy home is using sophisticated building energy modeling (BEM) using specific software tools like EnergyPlus. A tool like this can simulate the building in working order in the locale desired and calculate the heating, cooling, ventilation, lighting, and everyday-use electric needs, which they refer to as “plug and process loads.” It includes “Advanced fenestration models including controllable window blinds, electrochromic glazings, and layer-by-layer heat balances that calculate solar energy absorbed by window panes.” This is amazing! You could work with your designer and see exactly how moving windows around to expand or block views would affect the home’s energy efficiency.
Net zero energy homes can—but aren’t required to—incorporate passive design principles. These homes are not necessarily Passive Houses, but they may be. The Passive House approach is a separate certification, but there is a lot of overlap with Passive House design principles:
In some locales with favorable climate conditions, passive solar heating is an option, but net zero energy doesn’t depend on it.
With an energy-efficient design minimizing energy consumption, net zero homes will then need to balance the expected consumption with equal production. This could be on-site solar panels, community solar, or wind power. Thanks to the design with energy modeling, that figure is clear and not guesswork.
Some people take their home projects in steps as they can afford it. That could mean leaving out the renewable energy portion of the project at the start when first building the home. For them, the Department of Energy has a program called the Net Zero Energy Ready Home Program.
Why would anyone participate in this program? Its intent is to help homeowners end up with a home design that is capable of achieving net zero energy status in the future, along with meeting some other desirable characteristics like high indoor air quality. As the program states, “Ensuring that a building is highly energy efficient before adding renewable energy into the mix lowers the demands on the electrical grid (including peak demand) and paves the way for a smoother transition to all-electric (and all-renewable) energy.”
High-performance homes, whether net zero energy or not, are increasingly using energy monitoring and management systems. A smart thermostat is one example. Smart thermostats help you optimize your home’s heating and cooling for maximum efficiency by learning your family’s habits. If you like the house cold for sleeping, for example, you can program that and have your smart thermostat gradually bring the temperature up for the morning. Or if you leave the air conditioning set low when no one is at home, the smart thermostat can learn to adjust the setting to save you money.
A net zero energy home - in theory - can occasionally produce more electricity than it consumes, so why not send that power back to the grid and get paid the retail rate for it? That’s net metering. You may not get the same rate as you pay, as the utility operators have been pushing against the 1:1 model. They want to pay a wholesale price and charge retail. That’s called net billing. Each state handles this process in its own way, and you can find your state in the DSIRE database. As of mid-2023, just five states—Alabama, Idaho, South Dakota, Tennessee, and Texas—do not have state-mandated net metering. Idaho and Texas residents do, however, have programs available through their utility companies.
If you don’t send the power back to the grid, you can keep your home’s battery storage system topped up for times when the sun isn’t shining or the wind isn’t blowing. Battery storage is a sophisticated system that can provide a few hours to a few days of electricity, depending on the system you choose. You can also choose to send your battery power into the grid during hours of peak rates and earn some payback for your investment while your home is doing fine on your renewable energy!
The Inflation Reduction Act is the perfect storm for net zero energy homes. Many of the components needed for a net zero home are included and either qualify for a rebate or a 30% tax credit, including:
Finally, here’s a good resource for net zero energy homes. The case studies, in particular, show you real-world examples of success in building net zero energy homes and even remodeling homes to net zero or close to it.
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