Swatch Profile Green Roof 2030 Palette Blog

Swatch Profile Green Roof 2030 Palette Blog

August 20, 2013

The 2030 Palette is an interactive web platform containing a set of principles and actions, called Swatches, for the planning and design of sustainable and resilient buildings and communities worldwide. Each Swatch contains a written recommendation and rule-of-thumb, images and graphics illustrating the physical application of the rule, as well as more detailed information for its successful implementation.

TU Delft Library / © Harry Cook

Due to its high solar exposure, the design of a roof is a critical thermal consideration in any energy efficient building. Incorporating vegetation on a roof deck can mitigate unwanted heat gain by the evaporation of water from plant leaves cooling the surrounding air and lowering soil surface temperature. These vegetated roofs can also reduce the urban heat island effect in an area, retain stormwater, and provide green space and park areas. Green Roofs. a key Swatch within the Site scale of the 2030 Palette, provides the guidelines for vegetated roof design.

Green Roof: Recommendation

Green roofs provide water retention, green space, and improved water and air quality while reducing energy consumption.

A Green Roof is a system of layers installed on top of a roof deck that mimic natural soil and support plants. The top layer, the vegetation, is planted in a growing medium that is carefully designed to provide the necessary nutrients for plant growth but is usually lighter than traditional soil. Below the growing medium is a filter layer that filters water and then a drainage layer collects and controls water run-off. The lowest layers include a protection fabric, a root barrier, a waterproof membrane, and insulation that all work together to protect the roof deck.

The depth, weight, and specifications of each layer depend on the type of Green Roof installed. While there are a myriad of different technologies and systems, Green Roofs largely fall into two categories: Extensive or Intensive .

Ellis Residence (Extensive) / © Art Grice

Extensive Green Roofs are shallow systems, 200 mm (8 in) or less, that support low maintenance plants such as succulents, herbs, small grasses, and perennials. Preferred species can usually survive in stressful environments with exposure to sun, moderate wind, and drought. Extensive Green Roofs are usually designed for performance goals such stormwater management and are not suitable for roof gardens. They can also be designed without permanent irrigation and are often more cost efficient than Intensive Green Roofs .

Swatch Profile Green Roof 2030 Palette Blog

EWHA Womans University (Intensive) / © André Morin / DPA / Adagp

Intensive Green Roofs are thicker systems with a deep growing medium that can support more intensive plant species such as grasses, shrubs, and even trees. They are most commonly used as roof gardens and can include walkways, lawn, plazas, playgrounds, or even ponds. Intensive Green Roofs are considerably heavier and costlier than Extensive Green Roofs and require high maintenance and permanent irrigation systems. There are also Semi-Intensive Green Roofs that fall in between of the Extensive vs. Intensive spectrum.

Green Roof: Rule-of-Thumb

  • Extensive: 60-200 mm thickness (2½-8 inches) – green protection layer for roofs with little load-bearing capacity. Shallow soil suitable for less demanding plants (low maintenance).
  • Semi-intensive: 120-250 mm (4½-10 inches) – green roof with deeper soils, planted with grasses and shrubs (higher maintenance).
  • Intensive: 150-1,000 mm (6-39 inches) – roof garden with permanent irrigation and deep soils, suitable for lawns, shrubs, and trees, walkways, and even playgrounds and pools (highest maintenance).

InterContinental Sanya Resort / © Patrick Bingham-Hall

To learn more about this strategy, browse images of exemplary applications, and find helpful design tools and resources, sign-up for the 2030 Palette at www.2030palette.org !

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