Getting to Zero
This post first appeared at SCOCO.org.
It’s easy to be confused by the acronyms. Here is a partial list.
Zero Energy Homes (ZEH). These homes produce at least as much energy from renewable sources as the other (PG&E supplied) power used to operate the house over a year. These homes are sometimes called Net Zero Energy Homes.
Near Zero Energy Homes (NZEH) For a home that uses more energy over a year than it produces. These homes are called “Pretty Darn Efficient Homes (PDEH).” Often the only thing keeping a house from Net Zero Energy are the occupants and their energy use choices. For example, some super tight insulated homes with PV on the roof are occupied by people who will not cook with anything but natural gas. It can be difficult to offset the gas energy use with renewable sources.
Zero Energy Ready Homes (ZERH). The Department of Energy has a program to help builders build Zero Energy Ready Homes. These homes are made from scratch with all the infrastructure to add renewable energy, such as electric car charging devices, integrating renewable energy with grid-supplied power, and the framework needed to install PV on the roof. These homes are air-sealed, with high insulation levels and controlled heat recovery ventilation that brings in the fresh air and exhausts the stale air without too much energy loss. Another benefit of a Zero Energy Ready Home is that the HVAC equipment, including the duct system, will be sized correctly so that homeowners are comfortable but use the minimum energy for heating and cooling.
All these homes have the essentials: heat recovery ventilation systems, high levels of insulation, and air sealing. Add energy storage and renewable energy, a right-sized heat pump to warm and cool your homes, and you are there. This is true of new and existing homes. Though building the most efficient homes from scratch is more accessible, with all the proper energy efficiency and comfort systems, most of us live in homes built in the 1970s, 80s, and older. Builders can create a new home that is ready for the future. A retrofit generally aims to make a home more energy efficient, comfortable, and healthy. But a retrofit can reach near zero or even net-zero energy homes. It just takes a lot of work and expense.
The acronyms represent the home building and retrofit community's capacity to achieve higher energy efficiency, comfort, and indoor air quality. Most of us can follow this pathway for near-zero energy retrofits. Make a home healthy and efficient to operate, and add as much solar or wind to meet as much of your energy load as possible.
In California, we are halfway there. The law in California says that new homes must have solar power. The law also says we will reach 50% renewable energy by 2030. To get closer to zero with a retrofit, The Bay Area Regional Energy Network, BayREN, is there to help local governments, individual homeowners, multifamily building owners and operators, and small to medium-sized businesses. You can find the most qualified contractor for your retrofit project and get all the rebates and tax breaks. You’ll learn how a high-performance house works by going through the process.
Join the Cleaner Contra Costa Challenge and take concrete measures that are tangible but manageable ways to whittle down your energy use and get closer to zero. You can also choose measures that save water and include clean transportation options.
The next step in the race to zero-energy homes may be the addition of electric cars that are charged by the sun but can also serve as battery backups. Combining the energy use of several houses and creating zero-energy neighborhoods is possible. Zero-energy diets are not out of the question…
Sam Rashkin, an expert in zero energy who worked for many years with the Department of Energy, works with builders nationwide through his “Future of Housing Program.”
Many builders in our area are making zero, near zero, and zero energy-ready homes. A local group, One Sky Homes, won a DOE Housing Innovation award in 2014 for its zero-energy home projects. Here’s a link to a list of builders and designers who build in the Bay Area to the highest standards.