Houston Urban Heat Island Effect
Like other cities, Houston's urbanized areas are hotter than surrounding rural areas by 6 to 8 degrees F – a phenomenon called the urban heat island effect. These higher temperatures contribute to air pollution, higher energy costs, and other detriments to the city’s quality of life. Roads, buildings, and other hard surfaces absorb and retain heat, leading to surface temperatures 50 to 70 degrees F hotter. The removal of trees as the region develops also removes the cooling effects that vegetation provides. Hard surfaces and vegetation loss also contribute to flooding and water quality deterioration.
Cool Houston! is a program designed to reduce urban temperatures through use of cool technologies - reflective and green roofing, paving with light colored or porous materials, and a greatly expanded forest canopy.
| Cool Houston! Plan |
 The Cool Houston! Plan ( 2.17 MB) provides guidance on what we can do to reduce heat island effects on the Houston region.If you would like to receive a copy of the Cool Houston! Plan, please send an email with your mailing address to: coolhouston@harc.edu. |
Recent News
- Cool Paving at Rice University (
) - Rooftops to Rivers: Green Strategies for Controlling Stormwater and Combined Sewer Overflows ( 3.03 MB)
Green infrastructure is a cost effective was of reducing stormwater and reducing heat island effects. This new report illustrates the various applications (such as porous paving and greenroofs) along with nine case study cities. - Houston Heat Island Research: Research studies have measured the extent of Houston's heat island and also demonstrated improved heat island modeling
- State Implementation Plan (SIP) finding
The Texas Commission on Environmental Quality stated in its 2006 SIP for reducing ozone levels in Houston that "modeling is not capable of determining the effects of urban heat island measures, like tree planting, in the (Houston-Galveston-Brazoria) area using the most currently available data." Further detail on this finding is contained in Chapter 4 of the Proposed Eight-hour Ozone SIP Revision for the Houston-Galveston-Brazoria Area ( 99 KB), pages 4-8 and 4-9, published December 31, 2006. - Including Trees in State Air Quality Plans: Davey Resources Group has completed a thoughtful review of the requirements of including trees in State Implementation Plans (SIP).
- Urban Heat Island Effects - Atlanta Story: As cities across the country increase the amount of paved surfaces, this also increases their core temperatures. Listen using Real Audio (4:00 minutes long)
- Health and the Urban Heat Island Effect: Urban health is affected by higher temperatures and ozone formation linked to urban heat island effects. Listen using Real Audio (3:49 minutes long)
- Scientific journal article focuses on Houston's heat island
- Texas passes legislation in support of urban heat island actions
Cool Roofs
Flat, dark-colored roofs like those on many retail centers, apartments, warehouses and offices can exceed 160 degrees F in the summer – enough to affect the temperature of whole neighborhoods. Greater use of more reflective roofing with high albedo (a measure of the reflectivity of solar radiation) helps cool urban air temperatures. Greater use of green or garden roofs also reduces urban temperatures and helps reduce runoff that contributes to flooding. Cool Houston! proposes the widespread use of reflective roofing on all low-slope roofs. The Cool Houston! Plan provides information on these technologies, their benefits, and what we need to do to have more cool roofs.
Links to information on cool roof products:
Links to information on cool roof products:
Cool Paving
A dark surface on parking lots can reach 160 degrees F or hotter. Parked cars on hot pavement emit gasoline fumes contributing to air pollution. Rainfall on this surface is heated before it flows into waterways, where it harms temperature-sensitive species and introduces heated pollutants. Light-colored pavements offer a cooler alternative, reducing surface heat and lowering the temperature of storm water runoff. Porous paving offers a good solution for low traffic areas such as parking lots and light duty roads, cooling the city and reducing urban runoff. The Cool Houston! Plan provides information on paving technologies and a course of action on encouraging their use.
Trees and Vegetation
From 1972 to 1999, the Houston region lost about 400 square miles of tree canopy, or 25 acres per day, causing Houston's urban heat islands to grow larger and hotter. Trees remove pollutants from the air. They cool air temperature through shading and a process called evapotranspiration. Current tree shade provides Houston area residents with $26 million in annual energy savings, at the same time increasing property values and the quality of life in the region. Trees slow storm water movement, lower total runoff volume, reduce flooding, and control erosion. The Cool Houston! Plan provides a new look at the role of trees in the Houston region and how we can greatly expand the benefits of our tree population.
Links to information on trees & vegetation:
Links to information on trees & vegetation:
- Houston's Regional Forest - released Oct. 24, 2005 on the functions, structure and values of the region's forest lands
- Carbon Sequestration/Forestation Workshop - held Nov. 3, 2005 in cooperation with the Greater Houston Partnership
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