Seven Secrets of Affordable Zero-Energy Buildings

This blog's title is also the title of a white paper I'm updating and also likely a future online webinar. Here's the short blog version to let you in on some of the secrets. Please use the comment section below if you have questions or comments or contact me directly. Your feedback will inform the longer versions. Feel free to share these secrets!

Designed by Griffy Creek Studio LLC, the new Von Fange home, in Bartholomew County, is producing more energy than it is using.

One: This is not rocket science. A zero-energy building produces as much or more energy on site than it uses in a year by turning sunlight into electricity with solar photovoltaic panels (PV). If your total kilowatt-hours produced equals or exceeds total kilowatt-hours consumed over 12 consecutive months, you have achieved this goal. Tapping free, unlimited solar radiation for all your electricity needs was indeed invented for NASA's space program, so it was rocket science, but we have come a long way since the 1960s. Computing power has increased exponentially while the price has fallen according to Moore's Law. Solar PV prices drop roughly 20% each time production doubles (Swanson's Law). My first energy-positive project was Chrisney Branch Library, built in 2009. Since that time, the cost of solar PV has dropped by 80% per kilowatt-hour. Chrisney Branch Library was built for less than the typical cost of a library branch, including the cost of its seven secrets. The technology was proven affordable then. It is 80% more affordable now. Today, you will find many states, regions, cities, and companies with goals to achieve zero energy buildings by 2030 or 2050. The secret is you could do it in 2009. It is easier now. Why wait? This is not rocket science.

Two: The building does not have to be exotic. Habitat for Humanity chapters around the country probably have more zero energy buildings than any contractor. They are leaders in the Department of Energy's Zero Energy Ready Homes program. Like many individuals and organizations, they have realized that investing in solar power is a better affordability strategy than being tied to endlessly rising electricity costs. I teach my architecture students how to design a building that utilizes natural energy flows to function comfortably with very little mechanical input. Passive design has been around for millennia. Shading, thermal mass, orientation and other basic concepts don't necessarily add complexity or cost. You don't have to build an airtight foam box to have a zero-energy building. Conventional stud framing with a few tricks works just fine. You don't even need to start with a new building. Existing buildings embody the energy that went into their construction and they can be retrofitted, even if they are historic buildings. Solar PV itself has no moving parts. You don't need to operate your PV system, just watch it spin the meter backwards when the sun shines.

Zero-energy-ready farmhouse renovation/addition. Standing-seam metal roofs reflect heat and they are great for clamp-on solar PV installation.

Three: Go all electric. This may seem counterintuitive, but it leads to simplicity and affordability in ways that may surprise you. Gas companies have done an excellent job of selling their product as the cheap alternative to electricity for decades. Forget your gas bill. Forget your gas furnace. Forget your gas water heater. Forget your gas range (this is where I lose some serious cooks - please keep reading). Forget all those pilot lights. Forget gas combustion in your living environment, and the combustion byproducts you inhale from them. The key piece of this preposterous secret is another space-age technology, the electric heat pump, which moves heat energy from one place to another instead of creating it from scratch. The surprising secret is that you can currently leverage federal tax and electric utility incentives to get a ground-source or geothermal heat pump for about the same price as an air-source heat pump, and there is no HVAC system I know of that compares to the efficiency and comfort of a variable-speed geothermal heat pump that allows you to tap into planet Earth to borrow heating and cooling energy. That technology also provides most of your hot water needs, which can be augmented with an electric heat pump water heater. As for your gourmet gas stove that you cannot live without, please, consider gourmet induction stoves that have better performance with much less risk. The federal tax credits for geothermal and solar PV are decreasing (for now), but they are still significant (26%). Part of the cost differential of geothermal over conventional air-source heat pumps is the cost of installing the ground loop, which can be a horizontal trench or a vertical bore hole. Trenches are cheaper, but bore holes can go just about anywhere. I have used both successfully, including one double well installation in a 5-foot-wide strip in a crowded alley. For my own home, an old farmhouse renovation, we installed a trench geothermal system that is 80% more efficient than a gas furnace. The federal tax rebate and utility rebate eliminated the cost differential between a conventional air-source heat pump and the ground-source heat pump. Make sure all your other appliances are Energy Star rated and that your lighting is LED. The lower your energy use, the less PV panels you have to buy to get to zero net energy. If you must keep your gas range, just know that you will still be paying the minimum monthly gas bill with all the associated health and safety risks. You may decide it isn't worth it, especially if you try induction cooking.

Electric induction ranges can be sexy, too!

Four: PV panels don't have to be located on your building. While mounting solar PV panels on the building may be the least expensive method, it may not be the best for your project. Chrisney Branch Library is nestled in the shade of century-old oak trees for free passive summer cooling. Its solar PV panels bask in the full blazing sunshine (in this case bi-facial panels also are the roof and they let dappled light through). The ground-mount in that case took the form of an outdoor "Learning Power Pavilion" that was adjacent to an elementary school outdoor learning lab. It may not make sense to cut down trees to mount solar panels on the roof if an existing building is shaded. On a commercial project, you may want to consider a parking lot canopy for solar mounting if your building is shaded. If you are designing a roof for solar mounting, standing seam metal roofs are great because you can easily attach solar without penetrating the roof system. Even if you aren't adding solar initially, it is a good idea to plan for it. Prices will continue to fall. Go ahead and put in the conduit and save room for components like inverters and battery back-up systems. If a new structure, design the roof for the small added dead load so you are ready to go when you spring for the PV system.

The Learning Power Pavilion at the Chrisney Branch of Lincoln Heritage Public Library

Five: Solar PV is an investment with immediate and long-term financial returns. Based on the skyrocketing demand for solar PV installation, this may no longer be a secret. What if you could harvest unlimited, free, clean fuel from the sun that you could use to power your home and fuel your electric vehicles? The cost of the fuel never goes up. The equipment to pull off that trick keeps getting cheaper. For many, the payback on the initial investment for the equipment is less than ten years. After that, you are literally enjoying free electricity from our nuclear reactor 93 million miles away for the remainder of the life of the equipment (usually warranted for 25 years). It is a safe investment with steady returns and it will insulate you from increasing electric costs. You might do better in the stock market or you might not. If you can build the cost of this into your initial project financing, the monthly savings will be immediate, as your utility savings will be more than your added monthly mortgage payment. When you get that electric vehicle, the investment case for your own power production gets more compelling with the avoided cost of gasoline.

Six: Model the building early in the design process. Architects today have a cornucopia of amazing software tools to analyze a building's energy performance before it is built. Unfortunately, many architects leave this to engineering consultants who may not model until later in design process, when changes are less effective and more expensive to make. These tools can be used to optimize the building as a system from the earliest stages of design, leading to the best performance at the lowest cost. Will those expensive windows allow you to downsize the heating and cooling equipment and pay for the windows? If you shaded the windows on the south, how might that impact the cooling load? If you turn the building 30 degrees does that add or subtract energy use? How much solar PV do you need to offset the building total energy use? Will they fit on the south slope of the roof? What is the best slope for the roof? How much will the solar PV system produce with those panels at that angle in that location? Model early and often. Optimize performance verses cost. Downsize systems with informed design. Save project money that can be applied to a solar PV purchase.

Seven: Act soon to leverage incentives. Because the cost of solar PV continues to drop, tax credits and other incentives are not as critical to making the case for zero-energy buildings as they used to be, but there are still some attractive incentives out there that are currently threatened with extinction. The federal tax credit is 26% this year, for solar PV and geothermal, but it will be reduced to 22% next year, on the road to disappearing in the future. Electric utilities generally offer $1500 for new geothermal systems. You can check https://www.dsireusa.org/ for your state incentives and visit your electric utility to find information about their rebates. Public utilities offer net metering, which means you get more money for excess power you sell back to the grid. In Indiana, those rates are also being cut back over time. If you are served by a rural electric cooperative, net metering is probably not an option and you will sell back excess power at the wholesale rate (this inspires many rural customers to consider battery backup). These incentives tend to come and go with changing political winds. Don't be surprised to see the 30% federal tax credit return. It is also increasingly possible that electric utilities may be paying a carbon fee in the future, since that legislation has bipartisan and corporate support. That will likely be an accelerator for solar PV and other forms of renewables. Stay tuned.

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