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Global Warming Potential

Global Warming Potential (GWP)

Global Warming Potential is a measure of the adverse impact a green house gas might have upon the atmosphere. Green house gases such as carbon dioxide, nitrogen oxide, methane and hydrofluorocarbons are released into the atmosphere by human activities. The green house gases remain within the atmosphere for many years until natural depletion occurs. During this time green house gases absorb infrared radiation from the earth's surface at varying degrees, dependant on their particular molecular makeup, which contributes to global warming.

The Global Warming Potential (GWP) is a measure of the ability of a green house gas to absorb infrared radiation, compared to the ability of carbon dioxide, which has a GWP rating of 1. The GWP is calculated based the amount of infrared radiation absorbed by 1 kg of the green house gas within the atmosphere over a period of 100 years, relative to carbon dioxide. A green house gas with a high GWP indicates that it absorbs large amounts of infrared radiation and will contribute more to global warming. Environmental Profiles for building materials and components measure GWP in the equivalent reference unit of kgCO2, which is recorded under the Climate Change assessment category of each profile.

Table of Example GWP Ratings

Global warming potential ratings table

Source: Code for Sustainable Homes: setting the standard for sustainability in new homes. (February 2008).

Construction materials such as insulation products and foamed plastics are produced by industrial processes that release green house gases into the atmosphere. To highlight the amount of green house gases released, the impact on the environment and to global warming, manufacturers may give their products a GWP rating.

In order to comply with the Code for Sustainable Homes (CSH), materials used within the construction of the below key areas must have a GWP rating of less than or equal to 5 (GWP5):

  • Roofs (including loft access)
  • Walls (internal and external, including lintels and acoustic insulation)
  • Floors (including ground and upper)
  • Hot water cylinder, pipe insulation and other thermal stores
  • Cold storage tanks (if installed)
  • External doors