What is Urban Heat Island Effect (UHI)?

The UHI occurs when urban or developed land is hotter than surrounding rural and undeveloped land. Sunlight energy is absorbed by rooftops, pavements, structures, and other surfaces and then converted and released as heat energy into the air. Since the spacing of man-made structures is much more dense in urban areas, more heat is released causing the outside temperature in a city to be sometimes 6-8 degrees (F) hotter than rural areas.

Invisible Structures' Product Line can help mitigate the effects of Urban Heat Island (UHI).
Cool pavements, more trees, green roofs, and unique development options make ISI's product line a perfect choice to help fight UHI in you site plans. Grasspave2 and Gravelpave2 address many components of Urban Heat Island mitigation including: thermal conductivity, heat storage capacity, density, albedo (see chart to right), and emissivity. Grasspave2 has the added component of "air-conditioning effect."

Grass urban heat island mitigation

"Thermography and visible light photographs show gravel and grass surfaces can be cooler than dense paved surfaces" – images reprinted with permission from The National Center of Excellence on SMART Innovations for Urban Climate and Energy (www.asuSMART.org), Arizona State University.

Gravel heat island mitigation

Gravel surfaces can substantially cool down faster at night time than adjacent dense pavements as seen through this thermographic image. – images reprinted with permission from The National Center of Excellence on SMART Innovations for Urban Climate and Energy (www.asuSMART.org), Arizona State University.
 

Grasspave2 and Gravelpave2 best porous paver for urban heat island mitigation

This chart compares the temperatures below vehicles on different Permeable Paver Types. Only Grasspave2 and Gravelpave2 measured below the ambient outside temperature - They are the "Best in Class." Click to view larger graph. Test was conducted by Sasaki Design Firm.

Product

Albedo Number**

New Asphalt
.04
Aged Asphalt
.12
Grasspave2*
.40
Draincore2*
(Green Roof)
.40
Slopetame2*
.40
Gravelpave2
(Light Aggregate)
.16
Grass has an effective albedo of 0.4, including a reflectance of 0.25 + 0.15 "effective reflectance" to account for evapotranspiration of well-watered grass. **Larger is better

 

 
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