ENERGY

About The Petal

The intent of the Energy Petal is to create new sources of renewable energy that allow projects to operate year-round in a resilient, pollution-free manner. In addition, the Energy Petal prioritizes energy efficiency as a means to reduce wasteful spending, of energy, resources, and capital.

100% Electric

Currently, natural gas fuels our home's cooking stove and water heater. We will need to replace these two appliances with electric ones. The existing heating system is also gas-powered but was not in operable condition when we moved in. Instead of repairing it, we installed a highly efficient wood burning stove as a temporary heating solution to use during planning and renovation of the house. Even though combustion is not generally allowed in an LBC home, there is an exception for houses located in rural areas, acknowledging the fact that wood cut from the land could be burned. The LBC standard prohibits combustion as the home's primary heating source, so we are planning to put in a mini-split heat pump system.

Currently, we purchase electricity that is 100% renewable through Sonoma Clean Power's Evergreen Program.

20% Embodied Carbon Reduction

Before moving into our house in mid-2020, several pest control companies discovered evidence of wood boring beetles and termites and recommended fumigation to eliminate them. This treatment would entail covering our entire house with a plastic tent and pumping in 105 pounds of Vikane gas (99% Sulfuryl Fluoride), a greenhouse gas 4,800 times more potent than CO2. One treatment is equal to 225.6 tons of CO2, a carbon footprint equivalent to the construction of as many as 8 new houses the same size as ours. Put another way, you could drive 500,000 miles in your car before emitting a similar amount of CO2. We would have been very far from achieving a 20% Embodied Carbon reduction. We decided not to do the fumigation but work with replacing damaged wood and applying Boracare, a natural treatment during the renovation.

We decided to renovate an existing home instead of building a new one because renovation generally uses less carbon. Using a free software called Athena Impact Estimator (see wall assembly example) we were able to calculate the embodied carbon of the parts of the house that will remain after the renovation with 11 tons CO2-eq. The embodied carbon for the renovation will amount to 15 tons CO2-eq. This makes a total of 26 CO2-eq for building a house like ours new and results in a carbon saving of 43%, much more than we would have needed to achieve.

100% Embodied Carbon Offset

We will offset the embodied carbon of 15 tons CO2-eq by using carbon sequestering materials. Choosing to build with wood results in a carbon footprint because of manufacturing, transportation and construction. But at the same time wood sequesters 900 kg of CO2 per cubic meter. All wood materials that will be in our house after the renovation add up to 25 cubic meters of wood, therefore we sequester 22.5 tons CO2, even more than needed.

The additional embodied carbon that comes from more insulation is much lower than the carbon savings from less operational energy.

105% of Home Energy Needs must come from On-Site Renewable Energy Sources

We are planning to install solar photovoltaic panels on our south-facing roof, which will produce 105% of our home's energy needs. Even though the LBC does not require us to take the carbon footprint of solar photovoltaic panels into account, we decided to minimize its carbon footprint by using the smallest PV system possible. To do so, our home has to be extremely energy-efficient, and we will achieve this using the Passive House Standard. A Passive House minimizes the power needed to heat and cool, by building a very insulated and airtight envelope. We accomplish this by installing windows and doors with high insulation values, adding external insulation, designing our facade to maximize passive solar heat gain during winter days, and by using a heat recovery ventilation (HRV) system. A Passive House is also required to only use LED lighting and energy saving devices.

We estimate that a 8kW photovoltaic system will be sufficient to power our 2,300SF house and charge our electric car. We calculated that we would have needed a 18kW system following the current conventional building code instead of Passive House.

Household energy demands are highest in winter, and the energy derived from solar photovoltaic systems declines during the same period. Even a "net zero home" will draw two or three times the amount of energy from the grid than what it can generate during the coldest days. This makes it difficult for California utilities to meet consumer demand with 100% renewable energy sources. Minimizing heating loads during winter days plays a very critical role in enabling California to achieve 100% renewable energy year-round.