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.
Green roof r value.
They provide shade to the top of a building evapotranspiration.
For example a code may require that skylights have only an r 5.
Here s a handy r value table that covers most types of roof coverings building insulation and a few other materials.
Once you have more than r 20 in a roof assembly that is you meet the code things pretty much don t matter.
Back in june 2012 i stated that green roofs should not be considered as dedicated insulation layers and thus should not be counted as part of a roof s total assembly r value.
R value minke et al.
For a very good introductory overview article on r value see r values over at the website of.
Green roofs can have lower energy cost than conventional roofs and sometimes compete well against white roofing effects are more pronounced for lodging buildings.
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 various materials.
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.
1982 wong et al.
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.
You should of course see the manufacturer provided technical data sheet for the r value of specific products.
Neglected thermal storage moisture dependent performance and.
Determining insulation r value accuracy.
A green roof may improve property values and marketability especially in urban areas with little green space.
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.
R value of about 2 5 ft f btu.
Plants need water to grow so the green roof is designed to retain some degree of moisture.
Let s imagine a roof that should have an r 30 value.
Green roofs save energy compared to uninsulated roofs or poorly insulated roofs or even better black poorly insulated roofs.
Codes may specify a smaller r value for these components compared to the rest of the roof.
2003 evapotranspiration schmidt 2003 berghage et al.
Green roofs reduce the temperature of the building and the surrounding air in multiple ways.
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.
