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What is a green roof?
Green roofs are vegetated rooftops, or roofs covered with living plants. Like any planted area, living roofs experience periods of growth, flowering, and dormancy, and so they are sometimes referred to as living roofs.
Why install a green roof?
Green roofs offer an enormous range of benefits. The most commonly cited are: stormwater mitigation, reduction of the Urban Heat Island Effect, thermal efficiency and energy conservation, noise reduction, aesthetics, improved air quality, and increased biodiversity.
What is the difference between extensive and intensive green roofs?
An extensive green roof uses a thin (8cm to 20cm) layer of substrate to create a carpet of plants, often sedums and grasses. Extensive green roofs often occur on structures that cannot support more than just shallow substrates, and so these roofs are only minimally accessible to people.
An intensive green roof can support much greater depths of substrate, and therefore much larger plants. Depending on the building's structural capacity, an intensive green roof can support features that might be found in ground-level gardens, like trees and stone garden planters. These areas tend to be designed for public use.
If the plants are suitable for the roofscape, why is at least one year of maintenance recommended?
Whether at grade or on the roof, most plants show better long-term performance if they've had the benefit of proper establishment. Installing some method of emergency irrigation (for periods of extreme drought) is a wise investment. This can simplify maintenance, and help the plants acclimate to the individual site. One or two visits to the roof per year for weeding and/or evaluation of plant survival is vital not only to ensure that the roof is functioning as it should, but also to keep weed pressure down and allow the plants to establish properly.
How do green roofs fit into LEED certification?
The Leadership in Energy and Environmental Design (LEED) Green Building Rating SystemTM is an internationally accepted benchmark for the design, construction, and operation of high performance green buildings. Green roofs can contribute as many as 15 points towards a building's LEED rating.
How do I install a green roof?
If you choose to install a green roof on your own be sure to do your homework first, and definitely consult with the experts. Since it's still a new concept in the Pacific Northwest, we have much to learn. Plus, successful installations will help secure positive perceptions of rooftop greening. Various companies install green roofs, from landscapers to roofers, and the specialized green roof components are necessary to ensure proper drainage, loading, etc. Here are some recommended links:
Soprema - Membranes and associated structures
RoofScapes -Membranes and drain mats
Stream Organics - Suppliers of specialized soil
Flynn Canada - Complete installation of commercial green roofs
Paradise Cityscapes - Installation of private green roofs
BCIT Centre for the Advancement of Green Roof Technology - Hub for green roof infrastructure network in GVRD, and engaged in ongoing research, education and demonstration.
What about plants for a green roof?
NATS Nursery has been an expert in Pacific Northwest Native plants for over 19 years. Visit the CATALOGUE to learn about the plants we have available for your green roof and living wall projects. Please note: there are many other species that may be suitable for your roof or wall, depending on its individual ecology. Also note: it is important that you discuss these projects with us as soon as possible to ensure the correct lead-in time so that you are able to get the unique species you may want.
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