The Building Environment, City-Wide Committee Urban Landscaping Group Recommendations

The City-Wide Committee for The Building Environment Urban Heat Island Reduction Group Recommendations

Houston, Texas August 2000 TABLE OF CONTENTS

Preamble and Background...... Pages 1- 3

Urban Heat Islands...... Pages 4-5 Annual High Temperature in Los Angeles by Year - Chart Sketch of an Urban Heat-Island Profile - Chart Meteorology and Air-Quality Simulations - Chart

Goal and Objectives...... Pages 5-12 Increased Vegetation Actions City of Houston Ordinances, Chapter 10 Building and Neighborhood Protection Chapter 26 Off Street Parking and Loading Chapter 28 Miscellaneous Offenses and Provisions Protection of Street Trees Chapter 33 Planting and Development-Tree and Shrub Ordinance Chapter 42 Subdivisions, Development and Platting Policies Enforcement Incentives Increased Surface Reflectivities Street, Road, and Parking Lot Surfaces Recommendation Building Roofs Recommendation THE BUILDING ENVIRONMENT, CITY-WIDE COMMITTEE HEAT ISLAND REDUCTION GROUP RECOMMENDATIONS

PREAMBLE

The formation of ozone is a complicated process that involves volatile organic compounds, nitrogen oxides, sunlight, and temperature. The average temperature in Houston has increased over the years as development has replaced open pasture and forested land with homes, shopping centers, and streets. This has led to the formation of an urban heat island in which the ambient temperature is several degrees higher than the surrounding area. The goal of this document is to recommend actions that the City of Houston can take to reduce this effect, which will result in lower ozone levels throughout the region.

Studies have shown that vegetation can have two positive influences on reducing ozone. First, ambient temperatures can be lowered by shade and evaporative cooling from trees, shrubs, and grass. This cooling of the urban heat island lowers ozone formation by directly reducing the amount of volatile organic compounds (“VOCs”) that evaporate and by lowering the chemical reaction rate that causes the formation of ozone. Another phenomenon is the actual absorption of ozone, nitrogen oxides (“NOX”), and particulate matter by trees and shrubs.

City policies and ordinances that encourage and mandate major increases in tree canopy are a cost effective and aesthetically pleasing method that can help the Greater Houston area clean the air. The Heat Island Reduction Committee hereby recommends a series of new policies and changes to several existing planning ordinances that relate to trees, shrubs, and other related plantings that will accomplish this objective.

BACKGROUND

The City of Houston formed the Clean Air Partnership with the Greater Houston Partnership, the Business Coalition for Clean Air, Harris County, the League of Women Voters, the Medical Community, the Houston-Galveston Area Council and local environmental leaders. Clean air is made the number one priority of the Clean Air Partnership and a commitment is made to meet the ozone standards and fine particulate standards. 17th April 2000

The City of Houston entered into a Memorandum of Agreement with the U.S. Environmental Protection Agency to explore the energy and air quality benefits of heat island reduction with the goal of achieving significant implementation of heat island reduction measures and quantifying projected ozone reductions such that they may be included in the State Implementation Plan (“SIP”). January 1999 The regional Air Quality Planning Committee of the Houston-Galveston Area Council with direct participation from the Pollution Control Division, Harris County, the Greater Houston Partnership, the Bureau of Air Policy, City of Houston, Air Quality Committee, League of Women Voters, City of Baytown and Galveston-Houston Association for Smog Prevention issued the Air Quality Reference Guide for the Houston-Galveston area in July of 1999. Page 26 of this guide concludes: While biogenic sources do emit VOCs into the atmosphere which may contribute to ozone formation, they also remove significant amounts of CO, SO2, NOX, O3 and PM from the air, and cool the air through shade and transpiration, thus reducing VOC emissions from other sources. There is some debate about the relative reactivity of biogenic emissions, that is, their tendency to form ozone. Further investigation is needed to adequately understand their role. Although biogenic VOC emissions are important in the modeling of ozone formation, reduction of such emissions is not considered to be practical or desirable. Biogenic sources generally emit negligible amounts of NOX. July 1999

The Houston Environmental Foresight Achieving Clean Air began reviewing air quality issues in 1998. In their recommended goals (draft 5/10/00) they include reducing the “urban heat island effect” by providing for “massive and permanent tree planting effort(s)” in the neighborhood of 10 million new trees, “half of them by 2007”. An additional specific goal is to “protect and increase urban vegetation, especially trees”. This is to be implemented by adopting stricter laws that eliminate damage and cutting of useful trees, and increasing the extent and amount of useful vegetation in the region through conservation, open space, and parks programs. May 2000

In conjunction with the Planning Department’s participation in the City’s Clean Air Task Force’s efforts to develop inputs to the SIP resulting in reduction in NOX emissions by 75%, the Planning Department requested citizen participation on the Building Environment City-Wide Committee. May 2000

The City-Wide Committee convened June 8, 2000, and formed three subcommittees, including the Urban Landscape/Environment Subcommittee, subsequently named the Urban Heat Island Reduction Group. The charter of this subcommittee is to produce suggestions to modify land use regulatory codes to mitigate heat island effects. June 2000

The committee has determined that landscape initiatives, including trees and planted permeable surfaces, have been proven to be an effective and economical means for reducing urban temperatures. In addition, trees have been demonstrated to be effective and efficient direct absorbers of ozone and airborne particulates. Moreover, these landscape initiatives have the potential of countering the severely negative national image of a Hot Houston with Bad Air and transforming the City’s image into Cool Green Houston with Clean Air.

Specifically, the U.S. Department of Forestry calculated in a study published in 1994, concerning “Air Pollution Removal by Chicago’s Urban Forest” that a single tree with a caliper of nine inches removes two pounds of sulfur dioxide, 1.1 pounds of ozone, 200 pounds of CO2 and two pounds each of particulates and nitrogen dioxide annually. It is well documented that urban temperatures exceed rural temperatures. Houston’s summer urban temperatures exceed the surrounding rural temperatures by approximately 8 degrees. Trees reduce urban temperatures through shade and transpiration. It is estimated that for each degree fahrenheit reduction in urban temperatures, peak load electricity demand decreases 1.5 – 2 %. Studies conducted in Los Angeles with the Urban Airshed Model showed that planting a moderate number of trees reduced the smog by 3%. These studies indicated the possibility of reducing ozone by 5 to 15 parts per billion for each one degree C drop in temperature.

It is generally acknowledged that trees emit VOCs; however, it is equally accepted that in the formation of ozone, NOX is the limiting reactant, and that the cooling and pollution absorbing effect of trees far exceeds any negative aspects.

Various cities have included intensive landscape efforts as either effective parts of the SIP submitted to reach compliance with EPA standards or part of overall regional efforts to clean the air. These landscape-based approaches have been received with enthusiasm by the EPA. These cities include Los Angeles, Atlanta, New York, Salt Lake City, Sacramento, and Chicago.

In their final 1999 Amendment to the 1997 Ozone SIP Revision for the South Coast Air Basin, Los Angeles included on page B-54 through B-60 control measures to encourage activities that would lower ambient temperatures. These activities include using lighter, more reflective surface materials, and increased tree planting. The recommendation concludes that street trees need to be planted in public as well as private places such as parking lots, plazas, street medians, sidewalks, residential yards, corporate lawns, parks and shopping plazas. Implementation of these measures could be based on local government ordinances, legislative strategies for incentives, public outreach, and emission credit mechanisms. We believe that the cost effectiveness and the political feasibility of such measures would be high.

On June 1, 2000, the EPA issued a “Stationary Source Voluntary Measures Draft Policy” which specifically recognized the planting of shade trees in conjunction with heat island programs as examples of stationary source voluntary measures. This policy recognizes that many designated non-attainment areas find it increasingly difficult to attain National Ambient Air Quality Standards, and that one way to find additional innovative emission reductions is through voluntary measures (such as tree planting) that are an alternative to the traditional command and control approaches.

URBAN HEAT ISLANDS

Over the past decades as cities have grown, temperatures have increased in metropolitan areas as open, vegetated space has been replaced by houses, buildings, roads, and parking lots. This urban heat island phenomenon was recognized by researchers in the 1960s, and is dramatically shown by the increases of the annual high temperature in Los Angeles as the city was transformed from an urban agricultural city in the 1930s to the industrialized area today.

Annual High Temperature in Los Angeles by Year

In urban heat islands, the temperatures towards the center of a city are up to 8F higher than the ambient temperatures in the surrounding countryside.

In addition to the primary effect of requiring more energy for air conditioning, researchers have linked the rise in temperature caused by the urban heat island to increases in ozone pollution. For every degree Fahrenheit rise in temperature, the incidence of smog increases by 3 percent. A study conducted by the Heat Island Group at the Lawrence Berkeley National Laboratory for the City of Los Angeles showed that ambient temperatures could be lowered in areas by 9F by increasing the surface albedo or reflectivity. These lowered temperatures would result in lowering the concentration of ozone as much as 40 parts per billion. The U.S. EPA has awarded a grant to this group to study the urban heat island effect in Houston and its impact on the level of ozone. This study should be completed later in the Fall of 2000.

GOAL AND OBJECTIVES

The goal of the City of Houston’s Urban Heat Island Reduction Group is to help the Houston/Galveston area reach attainment of the ozone air quality standard through reducing the urban heat island effect in Houston. This will be primarily accomplished by increasing the overall albedo of the city. By increasing the area’s overall albedo, energy in the form of sunlight is reflected back into outer space rather than being absorbed by surfaces such as roofs, roads, and parking lots where they, in turn, heat the ambient air and raise its temperature. The two principle methods for accomplishing this are:

 Increased vegetation  Increased surface reflectivities

INCREASED VEGETATION

Increased vegetation cools the environment by increasing reflectivity and evaporation of moisture from the leaves of trees, shrubs, and even grass. Another phenomenon associated with vegetation is called dry deposition of ozone, which directly absorbs ozone from the air. The Heat Island Reduction Group recognizes the importance of increasing the vegetation in the Houston/Galveston area, and a major part of the group’s effort has been focused on strengthening the City of Houston’s ordinances that deal with vegetation.

Based on the above conclusions, the committee believes the city should adopt a suite of objectives aimed at achieving a significant increase in trees and green permeable surfaces. The subcommittee developed four primary objectives:

1. The protection of existing trees and other landscape plantings;

2. An increase in the number of trees and other landscape plantings and area of groundcover surface on city rights-of-way, parks, and administrative and maintenance facilities, on residential and commercial property, and in County and State controlled land, especially where such planting would replace paving and/or shade existing roofs;

3. A conversion from dark to light and heat-reflective surfaces on roofs; and

4. The encouragement of other area municipalities, counties, school districts, and agencies to adopt programs that increase the number of trees and other landscape plantings and areas of ground cover.

ACTIONS

In order to accomplish these objectives, the subcommittee recommends a series of action steps. Many of these action steps deal with modifications to the existing City regulatory framework. Houston is extremely fortunate to have in place a regulatory framework which addresses tree preservation, and public and private landscape requirements. This framework, which is constructed as various elements of five ordinances, can provide the vehicle for significantly increasing Houston’s tree canopy cover. The relevant ordinances are:

Chapters: 10 Building and Neighborhood Protection 26 Off Street Parking and Loading 28 Miscellaneous Offenses and Provisions-Protection of Street Trees 33 Planting and Development-Trees, Shrubs, and Screening Fences (“Tree and Shrub Ordinance”) 42 Subdivisions, Developments and Platting

The following are recommendations to accomplish our objectives. Many of these action steps deal with modifications to existing city regulatory codes. The recommendations are grouped into the relevant ordinances along with some policy and enforcement issues.

Chapter 33 Planting and Development-Tree and Shrub Ordinance

 Increase the density of trees by establishing specific tree spacing standards.  Specify required tree canopy percentage cover at initial planting with a stated goal of coverage after subsequent five and ten year intervals.  Require applicants for any permit that affects the site (vs. structure) to include the location, caliper size and canopy area of all existing trees in any right-of-way adjacent to the property for which a building permit is sought.  Require permit applicants to include the location, caliper size and canopy area of all existing trees greater than 4 inches in caliper on any lot, property, or tract for which a building permit (other than for interior construction) is sought.  Modify this ordinance such that residential properties are included as a category that requires mandatory planting of trees.  Remove the buyout option and future credit provisions in those cases where a cash contribution may substitute entirely for tree planting.  Revise and expand the list of acceptable and protected trees based on benefit in terms of shade, pollution absorption, and noise reduction.  Avoid “grandfathering” in existing parking lots and require the planting of trees and shrubs in and around existing parking lots, providing for a goal of mature tree canopy cover of 40% within the parking lot boundary.  Require the planting of street trees and esplanade trees on both sides of all streets and down the center of all esplanades in all newly permitted development locations.  Make compliance with this ordinance a requirement for obtaining all building permits. (This would apply to commercial renovation projects which do not change the “footprint” of the existing building, as well to other situations.)  Require that the design and implementation of a landscape plan that is required for a permit be certified by a licensed landscape architect as having complied with all applicable ordinances.  Require that a landscape plan which requests credit for tree preservation be prepared by a certified arborist or registered landscape architect and that the preservation techniques be certified as in compliance.  Encourage planting of trees at regular spacing throughout a parking lot and the preservation of existing groves of trees.

 Provide the reviewing city agencies more flexibility in determining compliance with related ordinances in order that compliance might be expedited and less onerous in its enforcement (refer to the City of Austin Forestry Department).  Rewrite the definition of green corridors, shortening the minimum distance required for establishment of a green corridor and requiring a smaller percentage of property owners’ agreement.  Make trees and shrubs a mandatory requirement of buffer zones.  Increase the amount of green space required in construction of apartment buildings and establish a minimum percentage of planted area per unit.

Chapter 42 Subdivisions, Development and Platting  Add “green” to the requirement for permeable space (permeable green space), increase the amount required, and expand it to include all new building sites.  Require living plant material in permeable green space.  Prohibit later conversion of permeable area to hard surface with compensation elsewhere on the same lot.

Chapter 28 Miscellaneous Offenses and Provisions Protection of Street Trees

 Expand City Forester’s authority and budget to best implement the provisions of the new ordinances and policies. Fund with fees on permit applications and fines including fines stemming from upgraded protection for street trees.

Chapter 10 Building and Neighborhood Protection

 Create “no mow” zones to reduce heat, reduce the need for mowers, and improve water quality. Encourage the use of naturalistic detention and retention ponds with minimal paved surfaces.

POLICIES  To the extent possible, provide for the planting of trees in existing esplanade spaces.  Require esplanades on new streets where the right-of-way allows (PW&E Design Manual).  Create landscaped esplanades on existing streets at four or more lanes (PW&E Design Manual).  Include planting street trees along the rights-of-way and esplanades in all contracts for paving, widening, etc., of new and existing streets.

 Require the placement of sidewalks to allow a tree planting strip between the curb and sidewalk; not adjacent to the curb (PW&E Design Manual – dictates sidewalk locations).  Expand reporting of violations to other departments, including PWS and Solid Waste.  Enlist broad-based support of citizens, city employees, etc., with a “we’re all in this fight together” attack.  Enlist television and press coverage for violators as well as outstanding compliance.  Establish and support an “Orchids and Onions” program to publicly reward the “good guys” and publicize non-compliant projects and developers (refer to San Diego and Denver for successful programs).  Expand the required amount of apartment green space.  Educate all city departments and their staff regarding current efforts to reduce the heat island effect and request suggestions on how they might contribute.  Coordinate the Heat Island Reduction efforts with the established Cool Green Project.  Give “deputy status” to certain existing nonprofit organizations to assist with the enforcement and/or monitoring of planting and other related ordinances.  Require Metro to integrate tree planting with all improvements  Increase the amount of bicycle trails in the city and county, including the flood control zones, and include shade tree planting with the initial construction.  Remove or relax exceptions to current platting procedures that inhibit tree planting.  Significantly increase the support and staff for the City Forester and facilitate communication between the Forester, Parks Department, and Planning Department.  Transfer the responsibility of reviewing initial and ongoing compliance with the existing Tree and Shrub Ordinance (Article V, Chapter 33) from the Planning Department and Parks Department to the City Forester.  Develop and furnish upon request, a list of licensed Landscape Architects and Certified Arborists to developers who inquire about landscape ordinances.  Provide incentives to property owners to plant trees in existing parking lots at a maximum spacing with approved arboricultural practices.  Remove disincentives to planting trees in new parking lots by including planted islands in the parking space count as spaces.  Identify, fund, and document the performance of a pilot project in the city in which an existing parking lot is planted with trees, such as the Astrodome.

 Encourage adjacent property owners to share parking spaces with flexible use arrangements, and allow such arrangements as credit toward meeting existing minimum parking spaces.  Modify the existing Tree and Shrub Ordinance (Article V, Chapter 33) to expand the definition of Green Corridors so that residential areas are eligible.  Direct all appropriate city departments to coordinate with utility companies who offer underground installation and accelerate existing programs to place lines underground.  Provide incentives for property owners to preserve trees in their property, exclusive of the building setback.  Relax restrictions on planting in street esplanades so that trees can be planted closer to the ends of medians and to each other without arbitrary spacing requirements.  Develop and disseminate a public awareness program for property owners, developers, contractors, and designers on the value of planting more trees.  Encourage the replacement of unnecessary paving with groundcover or planting beds for trees in existing development.  Require the replacement of diseased, dying, and dead street trees with viable specimens of approved species within five years, with incentives for early compliance.  Require that plans submitted for review for compliance with existing tree and open space ordinances be prepared and stamped by a licensed Landscape Architect or signed by a Certified Arborist.  Establish a procedure for ensuring that protected trees in sites to be developed are located and adequately preserved before the plat is submitted to the city.  Direct all city departments to ensure that the development of city-owned property will comply with tree ordinances.  Adopt strict policies which require the City of Houston to adhere to its own tree ordinances, and provide punitive clauses for non-compliance.  Investigate federal and state funding sources for use in implementation and enforcement of tree ordinances, including those relating to air quality, water quality, and economic development.  Require replacement of dead trees in the right-of-way regardless of date of planting.  Encourage the construction of reflective roof surfaces (white) in new construction.  Encourage the retrofitting of existing dark roofs to reflective roof surfaces.  Mandate soil structures conducive to tree growth and that minimize root induced damage to sidewalks and streets in all street and sidewalk paving and repair projects.

 Encourage the shading of existing and new parking lots with structural shading devices, such as canopies, and give partial credit against shade trees for parking lots with permanent shade structures (refer to Conoco complex on North Dairy Ashford Road).

ENFORCEMENT

 Adopt stringent policy requiring city’s strict adherence to tree ordinances, and punish violators with specific disciplinary action.  Enforce maintenance. Require the replacement of dead trees that were required for compliance with an ordinance. INCENTIVES

 Streamline city permit approval process. Expedite with special privileges if landscape benefits are realized or proposed.

 Establish programs such as Cool Houston Awards (refer to Orchids and Onions). Top Shade Producer Top Ozone Absorber Best Sun-to-Shade Parking Lot Best Effort at Tree Preservation

INCREASED SURFACE REFLECTIVITIES

Also important for reducing the heat island effect are programs to increase the area’s albedo by using more reflective materials for paving and roofs. Studies show that for both of these, light colored materials reflect significantly more solar heat, thereby lowering the surfaces temperature, which in turn, lowers the ambient air temperature.

STREET, ROAD, AND PARKING LOT SURFACES

Two methods can be used to increase the albedo of pavement: using cement or using a light chip seal on the top of asphalt. A chip seal is a thin layer of asphalt covered with light colored aggregate that makes up the top surface. While the albedo of weathered asphalt averages 0.12, the albedo of a chip seal and cement pavements is in the range of 0.25.

Most streets in Houston and Harris County are cement which has a naturally higher albedo. However, many times cement surfaces are overlaid with an asphalt wear coat for repair purposes. Also, most parking lots are constructed of asphalt.

A collateral benefit of using a chip seal to increase the albedo of asphalt and lower its surface temperature is reduced deterioration. The cooler surface temperature increases the strength of the asphalt resulting in longer lasting streets, roads, and parking lots.

RECOMMENDATION: Require developers, shopping centers, etc., to use either cement or place a light colored aggregate chip seal on top of asphalt paving. Also, the City of Houston should adopt a policy to require a light colored aggregate chip seal on roads it builds or resurfaces with asphalt.

BUILDING ROOFS

Reflective materials can be incorporated into roofs to increase their albedo. Light colored roofs will reflect much more of the sunlight than dark colored roofs resulting in lower roof temperatures that will reduce heating the air above the roof. Below is a graph of roof temperature as a function of albedo that shows how much cooler a roof becomes as lighter colored materials are used.

Roof Temperature Rise Versus Roof Albedo

A problem in the Houston area is that the climate promotes dark stains from water and mildew. Attempts in the past to prevent this have had only marginal success; however, it is anticipated that newer materials will be better at preventing the darkening of roofing materials.

The primary collateral benefit of roofs with higher reflectivity is reduced air conditioning cost. The energy also saved will result in lower NOX emissions from power generating sources. Also, as with roads, cooler roofs will last longer.

There are many roofing materials currently commercially available that have increased albedo. These include asphalt shingles, coatings, membranes, metal, and tile roofs.

RECOMMENDATION: Modify the building code to require roofing material with a high albedo to be used. This would apply to all buildings including houses. Existing commercial buildings would be required to be reroofed or have a top coat added by April 1, 2005. Existing houses would be required to use high albedo roofing materials when they have new roofs installed.