Noise and sound Insulation

The combination of soil, plants and trapped layers of air within green roof systems can act as a sound insulation barrier. Sound waves are absorbed, reflected or deflected. The growing medium tends to block lower sound frequencies whilst the plants block higher frequencies.The amount of sound insulation is dependent on the system used and the substrate depth. A green roof with a 12 cm substrate layer can reduce sound by 40dB and one of 20 cm by 46-50dB. A study by Kalzip [www.kalzip.co.uk] compared sound insulation of their standard unvegetated roof system with that of the Kalzip vegetated ‘NatureRoof’:

Standard Unvegetated 33dB

Vegetated [dry] 41dB

Vegetated [wet] 51dB

100mm Concrete Wall 43dB

Even limited coverage can help with sound insulation

This suggests that a green roof can reduce sound by 8dB compared with a conventional roof system. This could be particularly important in areas of high noise pollution such in the approaches to airports, as these levels are sufficient to provide noise insulation to buildings under aircraft flight paths.