Environmental Engineering Reference
In-Depth Information
Maintenance of Vegetated Roofs
1. During the plant establishment period (approximately 2 years), periodic
irrigation will be required. After establishment, irrigation may be needed during
dry periods.
2. During the plant establishment period, visits every 3 to 4 months are rec-
ommended to conduct basic weeding, fertilization (if needed), and infill planting.
Thereafter, only two visits per year for inspection and light weeding should be
required (irrigated assemblies will require more intensive maintenance).
3. Drainage outlets should be inspected periodically to ensure that they drain
freely and are not clogged with debris.
4. The roofing membrane should be inspected periodically for drainage or
leaks. Leaks may be pinpointed using electric field vector mapping, provided
that the vegetated roof assembly and roof deck material are amenable to this
technique.
Cost of Vegetated Roofs
The construction cost of vegetated roof covers can vary greatly, depending on
factors such as:
• Height of the building
• Accessibility to the structure by large equipment such as cranes and trailers
• Depth and complexity of the assembly
• Remoteness of the project from sources of material supply
• Size of the project
However, under present market conditions (2011), extensive vegetated roofs
will typically range between $13 and $18 per square foot, including design,
installation, and warranty service (not including waterproofing, which can poten-
tially double the cost). Basic maintenance for extensive vegetated covers typically
requires about 3 person-hours per 1,000 ft 2 , annually.
8.3 CAPTURE-REUSE SYSTEMS
Construction
1. Calculate the annual yield from the proposed rooftop area, assuming 95%
capture efficiency. Then estimate building demand on both an annual and a
seasonal basis, including external use for irrigation. If demand exceeds potential
supply, the system must be coupled with the public supply system. If potential
roof yield is sufficient for irrigation needs, the capture system can be independent
but the storage capacity must equal the demand storage. In southern California,
the end of the rainy season and the beginning of the irrigation season is about
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