Extensive Green Roof R Value

The university of michigan performed a valuation study comparing a 2 000 square meter conventional roof and a green roof.

Extensive green roof r value.

In other words go above r 20 and make green roof decisions for other reasons than energy. For a conventional roof. Green roofs save energy compared to uninsulated roofs or poorly insulated roofs or even better black poorly insulated roofs. 8 to 20 per square foot.

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. They provide shade to the top of a building evapotranspiration. In general the average r value of soil is 0 25 per inch so for a 12 soil depth the r value of the soil would be r 3 excluding assumptions on soil wetness and evapotranspiration. The cooling effect of each green roof component was demonstrated.

Highlights green roofs u value was experimentally determined on a paslink test cell. Green roof with rock wool substrate provided the higher energy savings. The study looked at a range of benefits of green roofs including stormwater management improved health benefits. Once you have more than r 20 in a roof assembly that is you meet the code things pretty much don t matter.

Published literature showing extensive green roofs have r values between 1 8 and 4 8 while intensive green roofs have r values between 5 and 20. Trnsys software simulation was implemented to quantify the energy savings. 15 to 50 per square foot. Sailor et al jbp 2011.

The relation between u values and the substrate moisture was linear. Annual energy savings green roof soil depth 33 annual energy and energy cost savings per square meter of roof for green roofs on lodging l and office o buildings with three different soil depths 5 15 and 30 cm compared to a conventional roof. Green roofs reduce the temperature of the building and the surrounding air in multiple ways.