Topic 6
Creating a green roof has great potential to beautify buildings and make a unique architectural statement, but it is also good for the environment. By getting to know the plant species that are adapted to the unusual growing conditions of a rooftop, everyone can plan its own living roof project and help to make the world a greener place.
However, there are many challenges that might be faced when installing green roofs.
Challenges associated with installing green roofs on new or existing buildings, if not properly reviewed or addressed, can increase costs and deter owners from installing such roofs. Potential challenges can include structural considerations, issues associated with installing a green roof on a historic building, knowledge of applicable codes, and issues associated with roof construction and maintenance. Green roofs occasionally fail to perform at the level for which they were designed. Potential failures include leaks, plant loss, inadequate drainage, soil erosion and slope instability.
The key challenges of installing green roof include:
- Siting and design
- Maintenance and operation.
Another important thing to consider is a selection of contractor. Inexperienced green roofing contractors can cause budget overruns and improperly installed green roofs and chronic performance problems.
SITING AND DESIGN
- Variations from a roof’s design weight can result in structural failure,
- The dead load of a green roof assembly should be determined on a project-specific basis;
- Engineers should assess the likelihood that a green roof will have a material impact on other load areas, including seismic loads, snow drifts, and intentional rainwater retention,
- Designers should review architectural plans to determine design load capacities, or back calculate them from an assessment of the existing structure,
- Supplemental reinforcement measures may be taken to allow a building to support a green roof, but these can be cost prohibitive.
MAINTENANCE AND OPERATION
- Wholesale roof failure is the inability of a green roof to perform at the level for which it was designed,
- Wholesale failures include leaks, plant loss, inadequate drainage, soil erosion, and slope instability.
While green roofs are definitely low maintenance, they aren’t no-maintenance. There are a few things that has to be done at least a few times per season to keep the green roof growing its best:
Watering
Watering will be necessary for the first season when plants are getting established, and during any extended periods of drought.
Weeding
Passing birds will deposit weed seeds onto the roof, and the wind will blow additional weed seeds onto it as well. To keep the weeds from taking over the rest of the green roof, the roof has to be weeded at least a time or two during the growing season.
Pruning
Pruning will only be necessary if the plants that are growing taller, or if overall look of the roof garden is starting to get a bit shaggy. At most, this would only have to be done once during the growing season.
