California is focused on reducing GHG sources and emissions from all of its industries to address climate change. Buildings are a major GHG contributor because of the energy they use to keep interiors at a comfortable temperature, the production and transportation energy embodied in their building materials, and the off-gassing of materials and building waste that are sent to the dump.  This section focuses on switching energy sources in buildings from “dirty” to “clean” supplies and on highlighting buildings that are constructed or retrofitted to use less energy.  Zero Energy or near-Zero Energy Buildings limit the amount of energy (and thus carbon) needed from the energy grid and from natural resources. Sustainable construction methods and on-site renewable energy can go a long way toward creating buildings that are truly energy efficient, if not self-sufficient.

California’s Long Term Energy Efficient Strategic Plan calls for all new residential construction to be zero net energy (ZNE) in 2020 and for all new commercial buildings to be ZNE by 2030.  San Mateo County currently has nine zero energy Buildings verified or close to being verified, according to the New Buildings Institute’s online database (as of 08/21/2020). To increase the number of San Mateo County’s ZNE buildings, new construction should look to passive or high-performance building techniques coupled with on-site renewable energy. Renewables for buildings consist of energy sourced from easily replenishable resources, such as sunlight, wind, rain and geothermal heat.

Zero Energy Buildings

Buildings that strive to be energy self-sufficient and produce all their own power on-site are known as Zero Energy Buildings. In contrast to Zero Carbon Buildings (which are primarily concerned with emissions from operational energy use or embodied carbon in building materials), Zero Energy Buildings operate using only on-site renewable energy sources. Projects that receive this certification must go through a year-long process to show actual rather than modeled performance and must operate as claimed to harness energy from the sun, wind or earth. The New Buildings Institute has a comprehensive state-by-state listing of Zero Energy Buildings.

Energy-Efficient Building Construction

According to the U.S. Environmental Protection Agency (EPA), energy-efficient buildings, commonly known as  “green buildings,” go beyond the traditional architectural practice of creating structures concerned with form, function, durability and comfort. They add components that are environmentally responsible and energy/water/material resource efficient throughout a building’s life cycle. Also known as sustainable or high-performance buildings, these buildings incorporate climate-specific systems. In their simplest and earliest form, buildings that respond to the natural climate are referred to as vernacular architecture. Although all vernacular buildings vary from region to region, they all take their cues from the local climate and respond to it with often ingenious biomimetic solutions to heat, cool or insulate the structure.

Biomimetic architecture is a more contemporary take on the same idea that looks to nature for its solutions. It is part of a larger movement known as biomimicry, which is the examination of nature, its models, systems, and processes for the purpose of gaining inspiration in order to solve human-made problems.

Passive solar design is one of the best known energy-efficient building systems from the 1970s, using Trombe walls for thermal mass, south-facing living spaces and shading of window glazing.

Another low-tech but nonetheless very energy-efficient technique is using vegetation to shade a building’s south- or west-facing facades. Studies have shown that deciduous trees can lower the temperature of building surfaces by 20 to 45 degrees Fahrenheit, thus drastically lessening the cooling demand from air-conditioning (AC) units. This effect is significant since AC accounts for 10% of all global electricity consumption today.[1] The heat island effect of parking lots is well documented, and the benefit of using vegetation to cool the urban environment has been widely proven as well. [2]

One of the best methods to get energy efficient is to create a tight building envelope and use high-performance windows. A high-performance construction version of this idea is called Passive House design, which allows the interior to maintain a stable temperature without having to resort to heating or cooling. A residential example, Project Green Home in Palo Alto combines Passive House design with Zero Energy certification.

Program Certification Matrix: from fewest (left) to most (right) energy-efficiency features.

Credit: International Living Future Institute

Renewable Energy Sources

In contrast to passive solar design, which takes advantage of the natural energy from the sun directly, active solar design captures the sun’s energy and stores it for later use through mechanical or electrical means. Active solar design refers to photovoltaics (solar panels or PVs) and/or thermal hot water (storing the sun’s energy in water). The current 2019 California Building code requires all new three-story-or-less residential construction to be powered by solar arrays, covering roughly 60% of the home’s predicted energy use. According to Google’s Project Sunroof, approximately 91% of all buildings in San Mateo County are solar viable.

Wind energy is another renewable option. Research on buildings using a Built-Environment Wind Turbine (BEWT) reveals a commercial minefield of failed businesses and results. According to Paul Gipe, author of Wind Energy for the Rest of Us, [3] installation of BEWTs can involve a lot of greenwashing, since  many of the turbines don’t work as advertised or are located in such a way that they don’t generate the desired energy. Wind is attractive, though, because it could help to smooth out the “duck curve” (energy spike seen between 4 and 9 p.m.) by providing energy not tied to solar panels’ diurnal swings. California’s current capacity for energy generated by wind turbines is 5.9 megawatts (MW), with a potential for 303 MW, according to’s Wind Exchange. also produces the Small Wind Guidebook, which indicates that wind turbines work on sites that are larger than one acre, have been approved by local zoning and have reliable wind resources. Campus sites within San Mateo County such as institutional, recreational and commercial sites that clock wind at 6.5 meters a second at 80 meters high could benefit from this renewable energy source. Also, using a wind turbine certified by the Small Wind Certification Council is recommended.

An example of a residential project using both wind and solar in San Francisco’s Mission District can be found here. An example of a BEWT that didn’t work is the San Francisco Public Utility building. It featured a façade of wind turbines that were integrated into the design of the building but, disappointingly, broke down after one year.

Solar and wind offer intermittent renewable energy, while geothermal energy remains available when the sun sets or the wind dies down.  Geothermal energy is on the rise for large-scale plants and Power Purchase Agreements (PPAs) with local Community Choice Energy (CCE) programs such as Peninsula Clean Energy (PCE) in San Mateo County. Geothermal energy uses pipes drilled down into the earth to capture the earth’s natural heat and generate electricity. A study done in 2013 for the San Mateo County Jail compared a traditional central utility plant (CUP) with a geothermal utility plant. The report found that while the yearly operation savings were better for geothermal energy, the installation costs were much higher, possibly due to siting considerations, and overall the payback was too delayed, resulting in the geothermal option being abandoned. [4] Improving insulation in a home may also be more cost effective than installing a geothermal system. Installation of a geothermal system needs to be considered on a case-by-case basis and is heavily based upon individual circumstances like siting.

Building Codes, Enforcement and Reach Codes

California’s Building Standards Code, consisting of 12 individual codes, is collectively known as Title 24 and includes some of the nation’s strictest energy-efficiency and general requirements for new or retrofitted construction involving both residential and nonresidential buildings. All parts of Title 24 are enforced by local building officials and are intended to promote safety and build energy efficiency in new and existing buildings. The California Energy Code (Part 6 of Title 24) sets the energy baseline or “standard” beyond which local governments may adopt reach codes to push energy efficiency further. The California Green Building Code, or “CALGreen” (Part 11 of Title 24), sets a baseline of mandatory measures for energy efficient and sustainable project practices, with more aggressive voluntary tiers that local jurisdictions can choose to adopt.  Both Part 6 and Part 11 contain specific requirements for resource conservation, and both parts address energy and resource efficiency as means to curb climate change. The state updates Title 24 every three years. The latest update was done in 2019.

The California Energy Commission has ambitious goals for Zero Energy Building codes that include adopting zero energy for the residential and commercial sectors in 2020 and 2030, respectively. Local cities have also been pushing for even stronger and faster implementation of energy efficiency through additional code requirements generally known as “reach codes.”

Currently only four entities in San Mateo County promote the installation of  energy-efficient photovoltaics in their reach codes. Menlo Park, for example, has established reach codes that require new nonresidential buildings and high-rise residential buildings to include on-site solar panels.  Advocacy groups such as the Campaign for Fossil Free Buildings and Citizens’ Climate Lobby are asking city councils to adopt reach codes that hasten the achievement of carbon emission reduction goals by requiring all new buildings to be powered by all-electric energy sources.

There are two different ways to implement reach codes:

  1. Whole Building or performance-based reach codes (also known as Brisbane’s approach), under which minimum performance requirements are set for new construction projects, but individual measures and feature selection are left to the owner/designer/builder
  2. Prescriptive-based reach codes, which require demonstrating compliance with minimum acceptable safety and performance standards

The City of Brisbane has implemented a building efficiency program designed to address energy and water use in buildings over 10,000 square feet. This program requires building owners to use the Energy Star Portfolio Manager tool to “benchmark” their energy and water consumption on a yearly basis. The goal of the program is to track improvements in efficiency over time, work with building owners to increase efficiency and reduce overall energy demand, thus saving resources and money.

As cities ask their residents to take steps to improve energy efficiency, the cities themselves often follow suit. Palo Alto has installed solar panels on five city-owned sites, including the Baylands Interpretive Center and the Municipal Services Center. These buildings serve to reduce the city’s overall energy use and, because of their high visibility, encourage residents to take action as well.

 2019 Half Moon Bay Library  Noll + Tam Architects           LEED Platinum/ Net Zero Energy

2012 Sacred Heart Schools Stevens Library      WRNS Architects    LEED Platinum/ Zero Energy

Features: LEED Platinum. Designed to meet the Living Building Challenge Petals of Energy, Water, Habitat and Materials

Energy Efficiency in New Buildings

Energy-efficient construction is a component of the green building ordinance, which can also include requirements for water efficiency, green materials and waste reduction. Ensuring new buildings are operating with “clean” energy and are energy resilient requires using on-site renewables or being part of a microgrid that shares the burden of energy generation over several sites or an entire community. Microgrids are a good option for larger educational or corporate campuses.

The Clean Coalition has thought a great deal about how to improve energy efficiency in commercial and nonresidential installations using approaches such as feed-in tariffs, community microgrids and Advanced Energy Communities (see Richmond, Calif. here). Often many strategies are required to work in concert in order to meet a building’s energy demand. Significant energy reductions can be achieved through wall, ceiling and foundation insulation and by following “Passive House” or similar designs. New buildings are often able to achieve Zero Energy certification if their envelopes are designed to limit energy demand as much as possible.

A residential example of a Zero Energy construction is Zero House, built by the Endeavour Centre with Ryerson University. It is a single home but the design is suitable to be built as part of a multi-unit complex too. The Zero House design meets all of the following goals: Zero Energy, Zero Carbon, Zero Toxins and Zero Construction Waste. It also captures greenhouse gases by using plant-based building materials to sequester carbon in the frame, insulation and finishes of the house, thus making the building itself a carbon sink.

Energy Retrofits in Existing Buildings

The number of homes powered solely by electricity grew steadily from 2009 to 2015. More than 13,000 homes in San Mateo County are now powered by rooftop solar panels and send energy back to the grid, generating a rebate from PG&E if they are net positive (i.e., make more energy than they use over the course of a full year).  Adding solar panels to residential buildings to make them more energy efficient has become commonplace, but it is often more economical to make other energy-efficient switches first. Ways to improve energy efficiency in either residential or commercial buildings include updating or retrofitting a building’s envelope (by using higher insulation values in the roof, walls and floors); increasing the efficiency of existing heating, air-conditioning and hot water equipment; and upgrading the building’s lighting (improving daylighting, lighting controls and LEDs).

The Rocky Mountain Institute has reported that in some instances, retrofits can also save money if they replace both gas and air-conditioning equipment. A report by Energy and Environmental Economics, Inc. (E3) looked closely at the implications of going all-electric in both new and existing residential homes in six climate zones in California and found the same result.[5] The E3 report posits that for electrification retrofits to succeed at scale, three things need to occur: contractors must understand best practices, international markets must be looked to for a wider range of high-efficiency electric technologies, and “retrofit ready” heat pump water heaters and heating, ventilation and air conditioning  (HVAC) systems must be developed for more consumer choice at lower cost.

Existing tenants or renters that cannot switch out the heating and cooling equipment in their buildings can still improve their GHG emissions by sourcing “clean” energy from the grid through a Community Choice Aggregation (CCA) energy supplier such as  PCE in San Mateo County. This grid-provided “clean” energy helps to lessen an existing building’s operational GHG emissions. An option for buildings outside of CCA areas is to use  Renewable Energy Credits, which are similar to offsetting an airplane flight by contributing to a GHG-emission-lessening project.

San Mateo County Energy Watch offers programs to support homeowners in retrofitting their homes with more efficient appliances. A toolkit provides an easy way to evaluate and improve a home’s efficiency. Significant rebates and financing are available, and there are programs geared especially toward low-income residents. By assisting residents who want to make their homes more efficient, these programs work to reduce emissions throughout the county. Another option homeowners might consider to reduce their energy use and help boost resale value is BayREN’s Green Labeling and Home Energy Score.

Homeowners who are considering going all-electric can check out local rebates for solar panels, energy-efficient electric equipment and free Induction Cooktop Loaner programs.  Homeowners looking to dive into installing their own solar PV system should check out the Solar Living Institute, home to the Solar Living Center in Hopland, Calif. A possible alternative to purchasing solar batteries could be using an EV vehicle as a battery backup during power outages with a switch box offered by many vendors. Check out some of the informational guides here for helpful examples of heating, water and home appliances that will work in an all-electric building. Contractors can earn rebates on heat pump water heater installations and receive training from BayREN.

Energy Equity

Extreme heat events in San Mateo County are trending upward, a development that is particularly stressful for vulnerable and low-income populations. According to a recent report on energy equity, the energy sector impacts disadvantaged populations in four areas: energy access, energy affordability, environmental hazards and employment. [6]

Emergency room visits due to heat, both sexes, all ages, all races/ethnicities, age-adjusted rate per 100,00, 2016. Credit:

The disturbing trend in extreme heat events points to the need for education, financial incentives and rebates (similar to the California Solar Initiative and California Proposition 39), and innovation.  According to the Building Decarbonization Coalition’s recent study, a grant-only approach to enable low- and moderate-income (LMI) and renter households, who together represent more than 40 percent of California’s population, to participate in building energy efficiency or renewable programs would dwarf any public expenditure in this area that the state has made to date.  The study’s findings suggest that a tariffed on-bill program based on the PAYS (pay as you save) system implemented by eight states over the last 18 years might be more effective.  Essentially, the program would allow utility companies to pay for cost-effective energy improvements (such as solar panels) and then recover their costs over time from LMI or renter households through a dedicated charge on the utility bill that is less than the estimated savings from the improvements. [7]

Green Certification and Rating Systems

Cities and municipalities often permit new and retrofit work using different types of energy rating systems and certifications. Many cities have been employing the LEED system, which has been in practice since 1998. However, the New Buildings Institute published a report in 2008 revealing that many LEED buildings were in fact performing worse than anticipated (modeled) and some were even performing below the standards set in the EPA’s Energy Star program. Thus, using performance-based certification rather than a prescriptive approach will ensure that energy goals are met. There are many other rating systems available, such as the  performance-based rating system Living Building Challenge (which focuses on self-sustaining buildings), WELL (which focuses on healthy buildings) and PHIUS+ (a certification system by the Passive House Institute that promotes highly insulated, energy-efficient buildings). The ultimate energy goal is Net Positive Energy, in which buildings generate more power over the course of the year than needed and thus are considered restorative to the environment.

The Living Building Challenge is a philosophy, certification, and advocacy tool for projects to move beyond merely being less bad and to become truly regenerative.

Credit: International Living Future Institute

If cities and municipalities decide to use a rating system, they should carefully consider what they wish to achieve and use the rating system in conjunction with California’s CALGreen code. The cost to certify projects is usually passed on to the developer or owner, which can prove to be prohibitive for some projects.  Policy makers should consider how the rating system will be met by the public and whether it will be seen as a hurdle, a barrier or an incentive. The use of a rating system does allow, however, for a third-party check in the context of new commercial, institutional and public projects.



[2] McPherson, E.G., J. R. Simpson, P. J. Peper, S. E. Maco and Q. Xiao. 2005. Municipal forest benefits and costs in five US cities (PDF) (6 pp, 267K). Journal of Forestry 103(8):411-416

[3] Gipe, P. (2018). Wind Energy for the Rest of Us: A Comprehensive Guide to Wind Power and How to Use It. Wind-works.Org

[4] Nelson, Ryan, and Dave Troup. PG&E 2013 ET12PGE1501. San Mateo Jail Geothermal Feasibility

[5] Energy and Environmental Economics, Inc.  April 2019.  Residential Building Electrification in California – Consumer economics, greenhouse gases and grid impacts.

[6] Seidman, Nancy, Alice Napoleon and Kathryn Maddux.  Synapse Energy Economics, Community Action Partnership and Regulatory Assistance Project. April 2020.  Energy Infrastructure – Sources of Inequities and Policy Solutions for Improving Community Health and Wellbeing

[7] Mast, Bruce,  Holmes Hummel and Jeanne Clinton.  Building Decarbonization Coalition. July 2020. Towards an Accessible Financing Solution – A policy roadmap with program implementation considerations for tariffed on-bill programs in California