Green Roof R Value

Green roofs can have lower energy cost than conventional roofs and sometimes compete well against white roofing effects are more pronounced for lodging buildings.

Green roof r value.

1982 wong et al. Skylights and roof hatches are another component of roof thermal performance. They provide shade to the top of a building evapotranspiration. 2003 evapotranspiration schmidt 2003 berghage et al.

Once you have more than r 20 in a roof assembly that is you meet the code things pretty much don t matter. You should of course see the manufacturer provided technical data sheet for the r value of specific products. For a very good introductory overview article on r value see r values over at the website of. For example a code may require that skylights have only an r 5.

Let s imagine a roof that should have an r 30 value. Plants need water to grow so the green roof is designed to retain some degree of moisture. Increased r value a measure of the resistance of a material to heat flow of the roofing system along with reduced temperatures on the roof lessen hvac loads resulting in energy cost savings. The plants in a green roof absorb water through their roots and then use surrounding heat from the air to evaporate the water while some roofs can reach temperatures of up to 90 f in the summertime these two features can allow.

A green roof may improve property values and marketability especially in urban areas with little green space. Neglected thermal storage moisture dependent performance and. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. R value of about 2 5 ft f btu.

For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3. In other words go above r 20 and make green roof decisions for other reasons than energy. Green roofs save energy compared to uninsulated roofs or poorly insulated roofs or even better black poorly insulated roofs. Every construction design architect engineer a e knows a material s r value is an important factor when specifying insulation products with many regulations requiring minimum values for wall ceiling and roof assemblies.

Codes may specify a smaller r value for these components compared to the rest of the roof. Determining insulation r value accuracy. R value of various materials. R value minke et al.

Traditional roof green roof n sensible et r q q q substrate 0 where r n net radiation q sensible sensible heat flux due to convection q et. Green roofs reduce the temperature of the building and the surrounding air in multiple ways.