San Francisco Better Roofs Policy
Phase 1: Solar and Living Roof Requirement for New Construction
Overview
Roofs are an underutilized urban resource, a space that can supply energy, manage stormwater, support urban
agriculture, enhance biodiversity, and supply publicly accessible open space. A Better Roofs Policy for San Francisco
would develop roofs for public and private benefit.
San Francisco has the goals of a 100% greenhouse gas-free electric system by 2030 and reducing greenhouse gas
emissions to 80% below 1990 levels by 2050. The community has demonstrated a 23% reduction below 1990 levels in
2012, but substantial measures are necessary in order to meet the 2050 goal. Solar energy and living roofs are a key
opportunity to support these goals while improving quality of life, enhancing energy resilience, and reducing pollution:
 Solar energy: Solar is cost effective, generates predictable and reliable electricity with zero emissions or
pollution. The 2013 Title 24 Part 6 California Energy Standards require new construction to reserve 15% of roof
area as “Solar Ready”, i.e. unshaded and free of penetrations, to ensure that solar generation is not precluded
by the design of the building.
 Living roofs: Living roofs provide heat island mitigation and insulation, potentially contributing to renewable
energy goals while serving as a sink for greenhouse gases and particulates. Further, green roofs reduce
stormwater entering the sewer system, provide habitat, and can be designed to support urban agriculture. Solar
panels above living roofs operate more efficiently as a result of moderated roof temperatures.
 In a dense urban environment, some sites have less opportunity for solar energy generation due to shading by
existing or potential future structures. Living roofs tend to be less sensitive to shade; the palette of plants can be
adjusted to suit the location and yield significant energy and environmental benefits, as well as a valuable
amenity.
 Therefore, staff recommend San Francisco require installation of solar photovoltaic, solar water heating, and/or
living roofs in the Solar Ready zone on new residential, commercial, and municipal construction. Where living
roofs substitute for solar collectors, a project would be required to develop 4 square feet of living roof in lieu of
1 square foot of solar collector (4:1 ratio). For example, 400 ft2 of living roof interspersed with 150 ft2 of solar
collectors would be equivalent to 250 ft2 of solar panels.
Precedent
Solar
Two California cities require installation of solar: In March 2013, Lancaster became the first US city to require solar
installations on new residential construction. In May 2013, Sebastopol followed suit with a policy requiring solar on new
residential and commercial construction, as well as residential alterations. San Francisco’s dense, transit-rich urban
environment helps reduce pollution and greenhouse gas emissions from transportation, but presents the greatest
challenge in California for systematic incorporation of solar energy in new construction, but this challenge can be met.
Since 2010, the San Francisco Green Building Code has required new large commercial buildings to either generate 1% of
total energy needs with on site renewables or improve energy efficiency an additional 10% beyond all other applicable
requirements; however, the most common compliance strategy is purchase of renewable energy credits.
Living Roofs
Numerous US cities, including Chicago, Washington DC, and Portland OR require green roofs on certain commercial,
residential, and municipal buildings. In San Francisco, approximately one quarter of projects (approximately 50) have
incorporated green roofs as into their strategy for meeting the Stormwater Management Ordinance requirements.
Further, development of green roof is expected to reduce the amount of available non-potable water at a given site, and
to be an allowed use, so would aid in compliance with the 2015 Nonpotable Water Reuse Ordinance.
Page 1 of 2
Version: August 3, 2015
Solar + Living Roofs
Switzerland and London each require green roofs on new developments. London requires 10% of total energy use to be
generated on site with renewables, and Switzerland allows substitution of solar panels for green roof area. Similar
legislation is pending in the French legislature.
Better Roofs Policy Framework
Solar energy and living roofs in new construction are a big step. To systematically develop roofs as a resource, San
Francisco elected officials may pursue future policy development, such as:
 Energy storage
 Solar requirements for existing buildings, applicable at re-roof or major alterations
 Solar shading protection or insurance
Page 2 of 2
Version: August 3, 2015