DEFINITION
Blue refers to water, and it essentially means that water is being placed (or held) on the roof on purpose to store water (typically rainfall) for reuse such as irrigation or cooling water makeup, or recreational opportunities.

AKA
Roof pond, Roof Spray

PERFORMANCE CRITERIA
The reason's for creating a blue roof vary. In some climates this is a water detention strategy, in others it is a means of keeping water perched above the building for cooling reasons. Still other authors point to water (plus some aggregate) as a way of "seeding" a poor man's green roof. Over time, vegetation will settle upon the roof, take root and provide all of the benefits of a green roof.


ILLUSTRATION




Images courtesy Urban Omnibus


CASE STUDIES
links to separate pages documenting specific places or projects where this element is on display

ADDITIONAL RESOURCES
Landscape + Urbanism provides a breakdown of the various eco-roof typologies here.
Another good breakdown is at Urban Omnibus.
An blueroof project: The "Urbeach" urban rooftop renewable energy from beachlike space.
PlaNYC Stormwater Plan talks about Blue Roofs as LID here
Some more general info here