Although the two technologies are not really competitive they are rarely seen as compatible. Nevertheless we often get involved in solving issues where building design suddenly includes a green roof, although a rainwater harvesting system has already been planned or installed.

Research shows that run-off from green roofs is usually of a high quality. 

Green roofs are vegetated ground filters in which the loosened root area increases the breakdown and retention of pollutants. The run-off is generally fit for storage and usage.

Different build up of the green roof can have different impacts (see picture above).

The significant drawback is that the captured water is discoloured.

The other drawback using green roofs with rainwater harvesting systems is that roof run-off is significantly reduced.

If you are planning a green roof and want to capture the optimum amount of water it would be wise to consider the various merits of the different systems and the use of greywater re-cycling as well.

Greywater recycling adds additional dimensions to all the opportunities

Greywater recycling has taken off recently and is becoming very popular with major developments particularly in the South and London region of the UK.