R-value (insulation) contain no trapped CFCs or HFCs (e.g., half-pound low density foams). On certain brands, twenty-year tests have shown no shrinkage or reduction in insulating value. This has led to controversy as how to rate the insulation of these products. Many manufacturers will rate the R-value at the time of manufacture; critics argue that a more fair assessment would be its settled value. The foam industry adopted the LTTR (Long-Term Thermal Resistance) method, which rates the R-value based on a 15-year weighted average. However, the LTTR effectively provides only an eight-year aged R-value, short in the scale of a building that
Sustainability in construction the carrying capacity of Earth . According to United Nations Environment Programme (UNEP), “"the increased construction activities and urbanization will increase waste which will eventually destroy natural resources and wild life habitats over 70% of land surface from now up to 2032." ” Moreover, construction uses around half of natural resources that humans consume. Production and transport of building materials consumes 25 - 50 percent of all energy used (depending on the country considered). Taking UK as a sample, the construction industry counts for 47% of CO2 emission, of which manufacturing of construction products and materials accounts for the largest