What Makes a Home "Green"?

Multi-year drought, distressed forests and intense wildfires bring awareness of the local impacts of climate change. Efforts to address climate change have long focused on cutting greenhouse gas (GHG) emissions and more recently on sequestering carbon. But because the impacts of climate change are now upon us, we need to add to our efforts resilience planning. What is the focus of these efforts related to our buildings?

In reviewing many “green building” programs, the most common characteristics are: energy efficiency, water conservation and selecting materials that are sustainable and used in a resource-efficient way.

Because energy use is strongly linked to GHG emissions, reducing energy consumption in homes tends to decrease damage caused by burning fossil fuels. There are many ways to reduce energy use in homes: install more efficient appliances, select higher performance windows, or add thicker insulation.

Water conservation makes sense in most regions of the country, excluding only those where fresh water is abundant. In California, water is directly linked to energy, for close to 20 percent of our energy use statewide is consumed in transporting and treating water. Residential water conservation emphasizes careful selection of plumbing fixtures and appliances but also promotes rainwater collection.

Choosing materials for a green home involves selecting materials that are naturally renewable (for example, wood from sustainably harvested forests), have recycled content, or are harvested/manufactured regionally. These materials also need to be incorporated in structures as efficiently as possible.

Other green building criteria worth considering are:

·         Designing and building homes that last longer. Although rarely thought about, designing to make future changes easier helps save materials. Selecting materials that require less cleaning and less maintenance are also aspects of durability.

·         A green home is small. Scaling down is unpopular with Americans, but greatly reduces impact.

·         A green home provides superior indoor air quality and promotes human health. Avoiding materials and furnishings that involve toxins and outgassing is key. Good natural and mechanical ventilating is also important.

·         Because transportation involves our biggest consumption of fossil fuel, selecting a location that is close to work, shopping, schools and public transportation could be the most impactful of all criteria, but is rarely addressed.

Resilience focuses on livable conditions in buildings after a disaster; on backup power; and on access to potable water. These strategies are being woven into “green building” programs but expanded to community scale. Photovoltaics with on-site storage can provide basic services and information during power outages. We know how to build tight buildings out of non-combustible materials to resist wildfires. Mechanical ventilation with HEPA (high efficiency particulate air) filters can handle smoke and ash from wildfires. Rainwater collection, composting toilets and recycled water are other resilient strategies.

Retrofitting Homes to Become All-Electric

Weaning homes off natural gas and other fossil fuels would significantly reduce carbon emissions. Scientists report that fossil fuels consumed in our buildings across the globe account for 28 percent of climate change, while natural gas leaks upstream from our appliances account for another 25 percent of global climate change. Fuel burning appliances are entrenched in our homes, making the shift to electric appliances a challenge, even to homeowners so inclined.

The City of Santa Barbara is finalizing an all-electric code for new construction, joining more than 40 other cities and counties in California. Most likely, Santa Barbara and Ventura counties will consider similar code changes soon, but what can be done about existing structures, nearly all of which are not all-electric?

Redwood Energy, a California energy consulting firm, has published, within the last few weeks, a peer-reviewed report laying out detailed information on how the conversion of an existing home can be simple, relatively inexpensive and without building modification, not even upgrading the electrical service. This report, A Pocket Guide to All-Electric Retrofits of Single-Family Homes, lays out two paths toward electrification.

One path is an appliance-by-appliance conversion. This incremental approach, where an electric equivalent model replaces a gas-burning appliance may have no cost difference, especially if the old appliance needs replacing anyway. If a new 240-volt circuit is needed, there would be an added cost of between $85 and $600.

The second path is where all appliances are replaced at one time. This can cost between $3000 and $20,000 or more, depending on whether building upgrades are included like adding insulation or new high-performance windows.

Most existing homes have a 100-amp service panel; a few older ones may have only a 60-amp panel. The report lays out how a 3000 square foot home can be completely electrified without upgrading a 100-amp service. Choosing efficient appliances such as heat-pumps that are three to five times more efficient makes this possible. Switching to water heating or space heating/cooling heat-pumps usually means running new 240-volt lines but appearing on the market for the first time this past year are 120-volt models than can plug into any wall outlet.

Another strategy is using circuit-sharing plugs where one 240-volt outlet can handle, for example, an electric dryer and a heat-pump water heater, or a magnetic induction stove and an electric vehicle charger. These circuit-sharing plugs range between $200-$500 but save money by requiring fewer new circuits and often no panel upgrade.

Redwood Energy’s report is full of useful information on design, assessing existing electric panels, rebates and tax credits, plus utility and community choice energy incentives (coming to Santa Barbara this October). It contains an extensive catalog of devices that covers everything from heating and cooling to cooking, water heating, whole-house ventilation, countertop ovens, kitchen hoods, power-sharing plugs, and even slow cookers.

Gas Versus Magnetic Induction Cooking

To meet its goal of 100 percent renewable electric power by 2030, the City of Santa Barbara is crafting an all-electric reach code together with a ban on natural gas hookups in new construction. In these deliberations, the appliance that has become the focus of controversy is the magnetic induction cooker. Because it directly heats a pan using electricmagnetic fields, an induction unit can provide great power, instant adjustability, excellent thermal efficiency, and precise control. The energy efficiency of induction coils is more than double that of gas burners--80-90 percent goes to the cooking of food compared to 38 percent for gas units.

Since an induction cooktop, commonly a glass ceramic sheet, does not get hot except directly under the pot and even then, only moderately hot, it is safer than a gas range and much easier to clean. The lack of a hot surface means no hard-to-clean baked-on spills.

The Southern California Gas Co. (SCG) and its front group, Californians for Balanced Energy Solutions (CBES), funded from rate payers’ monies (illegally?), promote kitchens with gas appliances. They claim Californians want to cook with natural gas. Magnetic-induction cooking, widespread in Europe and Asia, is still a relatively new technology in the US. However, according to the National Kitchen and Bath Association, induction cooking, accounted for 15 percent of stove sales last year. It is even becoming the preferred choice for many top chefs.

What SCG and CBES do not reveal to the public are the health issues linked to gas ranges. Physicians for Social Responsibility and 3 other national research groups reviewed two decades of peer-reviewed studies on indoor air quality linked to gas appliances. Their findings show that gas stoves are exposing tens of millions of people to levels of air pollution in their homes that would be illegal outdoors under national air quality standards.

This explains why gas companies have fought so hard, so long, to fend off regulation of gas stoves, while claiming natural gas to be a clean fuel. Children risk respiratory issues and reduced brain performance when exposed to gas combustion residues, especially when combustion is incomplete. The EPA reports that children are 42 percent more likely to have asthma challenges when living in a home with a gas cooker.

There is the question about electromagnetic radiation exposure from induction cookers. Studies in Europe and the US, including one from the World Health Organization, show no health risk, even for pregnant women and young children. As close as one centimeter (approximately 3/8”) from a magnetic coil reveals no measurable effects on health.

Another consideration is the roughly 25 percent cost premium for induction ranges over gas ones, but this differential is decreasing as induction stoves gain market share. Perhaps the most important consideration is that natural gas has no role in a clean energy future, nor as a part of solving climate change.

What to Know About Home Battery Storage

The Santa Barbara County Office of Emergency Services advises being prepared for 5-7 days of power outage. Because of ever more frequent and intense natural disasters, people are wanting backup for blackouts.

Home Battery Storage

Battery storage is the perfect partner for solar electrical generation. It keeps power flowing to the home during outages--the main reason people want batteries—as well as by helping save on utility bills (for solar systems that provide less than 100 percent of electricity). California has time-of-use billing, where customers pay more for electricity during high demand times (evenings and summer afternoons). With a solar + battery system, software automatically switches to stored energy during high demand/high-rate periods and draws from the grid during low demand times, thereby reducing utility bills.

Understand that a grid-linked solar array provides no power during a blackout. A photovoltaic (PV) system is required to shut down automatically during an outage to ensure that it does not “backfeed” the grid and risk injuring workers repairing lines.

California and its public utilities appreciate home batteries, for when aggregated, they flatten out demand curves. This means fewer power plants just for peak periods, ones that are expensive for limited use and pollute more than non-intermittent power plants.

Battery Options and Hardware

The most common situation is an existing or planned PV array tied to the utility grid (called “net-metering”). For an existing solar array, the battery choice is usually an alternating current coupled system. The panels produce direct current electricity which is converted via an inverter to AC that can be used in the home or fed back to the grid. When a battery is added (most typically a lithium-ion battery), it also needs an inverter to convert the DC stored power into AC. Some batteries such as Tesla Powerwall 2.0 incorporate this second inverter into the battery.

The second grid-tied option—a DC coupled system—is chosen when the battery and solar array are installed together (both use DC). Cost is reduced somewhat by needing only 1 inverter. Sonnen and Enphase batteries, other popular options, offer one or both coupling choices. Both have numerous sizing possibilities by being able to create battery banks.

Sizing and Cost

The average US home uses about 30 kilowatt-hours (kWh) per day. The Tesla Powerwall 2.0 provides 13.5 kWh of storage and, together with supporting hardware and installation, costs around $11,000. When fully charged, this would provide 45 percent of the average family’s usage.

Figuring out critical circuits, often called “survival circuits” is important to determine the minimum you want to power during an outage. Lights (especially LEDs), computers, radios/TVs, and refrigerators do not draw a lot of current. Electric cookers, whole house air conditioning systems and any appliance with resistive heating elements draw a lot of power. Motors and well pumps draw a big surge of power during startup, sometimes more than a battery can supply. More storage can be added, but because of expense, few people purchase the amount required to fully power their normal patterns. Enphase and Sonnen are more expensive per kwh of storage capacity than Powerwall but are longer lived.

Rebates and Tax Incentives

The federal tax credit for residential solar arrays, currently 22 percent, also covers home batteries. It terminates December 2022. California has enacted the Self-Generation Incentive Program (SGIP) to continue incentivizing home battery installations. The average cost covered is 25 percent but can go a lot higher in high fire areas. California’s mandate to achieve a clean energy grid by 2045 will have to rely heavily on solar generated electricity and battery storage. Home systems will need to be a big component.