The International Green Construction Code (IGCC) is a model code for cities seeking to promote sustainable building practices through their building codes. The IGCC promotes transition from the current voluntary green construction certifications, like USGBC’s LEED, to mandatory green construction codes. As the most recent revisions of the IGCC are currently under review, Green Building Law Update hopes to promote awareness by examining some of the code sections.
404.1 The heat island effect of building and building site development shall be mitigated in accordance with Sections 404.2 and 404.3.
404.2.3 Where shading is provided by trees, such trees shall be selected and placed in accordance with all of the following:
1. Trees selected shall be those that are native to, or non-invasive and adaptive to, the region and climate zone in which the project site is located. Plantings shall be selected and sited to produce a hardy and drought resistant vegetated area;
2. Construction documents shall be submitted that show the planting location and anticipated ten year canopy growth of all trees and that show the contributions of existing tree canopies; and;
3. Shading calculations shall be shown on the construction documents demonstrating compliance with this section and shall include only those hardscape areas directly beneath the trees based on a ten year growth canopy. Duplicate shading credit shall not be granted for those areas where multiple trees shade the same hardscape.
How do trees decrease the urban heat island effects and increase building energy efficiency?
Buildings should not be the only element of our urban cores that are going green. Many U.S. cities are looking to reject their concrete jungle moniker by greening community spaces including public streets. Increased use of tree plantings in streetscaping has gained favor in cities including Houston and Nashville. Houston alone planted over 40,000 trees this past year. These urban planting projects may seem merely cosmetic to the average citizen. But, in fact, vegetation reduces the urban heat island effect.
The urban heat island effect is the variance of an urban core temperature from its surrounding areas. The increased temperature can vary from an additional 2-5ºF during the day and up to 22ºF at night. The heat island effect is caused in part by the high concentration of heat absorbing hardscape materials (concrete, bricks, etc.) in urban areas. As hardscape materials are shaded, divert heat, and reflect sunlight the heat island effect can be reduced.
The IGCC seeks to mitigate the heat island effect by requiring at least 50% of hardscape materials to meet reflective, permeability, or shading standards. Section 404.2.3 allows shade from the tree canopies to factor into a building’s heat island mitigation.
These IGCC codes will reward existing streetscape vegetation programs and may encourage increased tree planting efforts. Construction costs may be lowered since trees can serve as both landscaping and shade.
Unlike the other IGCC options for hardscape shading, trees also divert storm water runoff, naturally reduce air pollution, and actively cool the air around them.
Overall, the shade and cooling provided by trees allow buildings to reduce their energy consumption. One of the most effective ways to green our buildings may be to look at the amount of green (or lack thereof) surrounding them.
Photo Credit: torontocitylife