Green Roof Enhances a Community Centre
March 4, 2009 Leave a comment
by JB Larano
(This paper was written by the author in 2008 which was submitted to BCIT Center for the Advancement of Green Roof Technology as part of the requirement towards the completion of the course Green Roof Technology-Details, Installation and Maintenance)
Introduction
The City of Richmond has an ambitious vision- to be the most appealing, livable and well managed community in Canada. The city’s infrastructure has seen parallel growth with the development of the downtown area, the current construction of the Canada Line rapid transit system and the Richmond Oval in time for the 2010 Olympic and the Paralympics Games.
In its response to sustainability and environmental issues, the city is taking active steps to incorporate sustainability measures in all of the city’s current and future infrastructure projects.
The purpose of this project is to demonstrate the viability and the benefits that green roof installations would bring to the city population and to the environment. Another purpose is to highlight the application of Green Roof technology in this building which includes details, installation and maintenance and life cycle cost analysis (LCCA). The project is an extensive type of green roof on new community center to be built for the city on a prime lot close to the city center
The incorporation of green roofs in one of the city‘s infrastructure building projects will not only promote the city’s acceptance of this technology but will also bring several benefits to the city and well-being of its residents. Foremost of these benefits are:
- Air Quality Improvement
Gaseous pollutants are absorbed through photosynthesis and airborne particulate matter is trapped in the leaves.
Gas exchange by the plants helps to add oxygen to the air therefore helping to reduce smog.
Rooftop microclimate is much cooler due to transpiration of the plants. This reduces the cost of the cooling the building as the air conditioners draw cooler air. This equals less electricity spent cooling the air which means less power generation from nuclear and fossil fuel burning plants which improves air quality further
Green roofs cool the ambient air temperature (reduce the Urban Heat Island Effect) in cities which means less smog days
- Temperature Regulation
- Urban heat island effect can be as much as 9 degree Centigrade according to NASA.
Green roofs help address the Urban Heat Island Effect which is the phenomenon of thermal gradient differences between developed and undeveloped areas. Most of the sun’s energy is re-radiated as heat from the sun rays bouncing off of surfaces. Planted areas only reflect 20% of the sun’s energy. Green roofs insulate buildings by external shading of the roof. They cool industrial buildings and create microclimates, which can alter the climate of a city as a whole.
- Reduction of storm water run off
Perhaps one of the most important benefits of a green roof is the ability for the roof to aid in Storm water retention, by slowing the flow off the roof during a storm event. It also serves as moderation for water temperatures and acts as natural water filters.
- Improvement of building performance
German studies show that plant material growing on a roof can help a building retain up to 50% of the heat typically lost to convection.
Waterproofing layer is protected from UV therefore extending life expectancy of membrane.
Green roofs have the capacity to provide sound insulation, additional thermal insulation.
and increased life expectancy of roof.
- Habitat and Ecological benefits
Possibilities for habitat preservation and protection of flora and fauna.
Replaces land taken by buildings and thereby contributes to preserving biological diversity.
Beautifies otherwise barren eyesores of our cityscape and provide unique opportunities for design and creativity.
Increased urban habitat for song birds and butterflies.
Health and horticultural therapy applications.
Movement, color, sound and texture of plants add to the overall health and well being of citizens
Design Intent
As mentioned previously, it was the city’s intent to showcase the Green Roof technology in this new building, hence a green roof design that combine extensive and intensive type is envisioned for the installation.
Richmond City Hall building-a fine example of sustainability.
The project site is located in the prime land close to the city hall. The site is bounded on the north by Granville Street, on the east by an existing baseball field which faces No. 3 Road, on the west by an existing Multi cultural center building and on the south by residential area. The building which is facing two major roads has to radiate an interesting architectural character in addition to the green roof that will greatly add visual interest to motorists who are driving along the streets. The general design and layout of the planting is on free form and non orthogonal lines to symbolize river and mountains for which Richmond has closely associated. The city, being located on the between the arms of Fraser river and the clear view of the North shore mountains lend an appropriate parallelism to the layout design intent. The green roof is accessible to the general public during week days, 4 times a day on groups and on a guide through city Green roof coordinator. The roof area is accessed by two exit staircases. The roof area allotted for green roof installation is 7100 sq.ft. for which 5,164 sq.ft is for extensive green roof while 1,936 sq.ft is for intensive green roofing. The number of people who can access the roof area is limited to the maximum number of occupancy allowed as per building code. The roof area as it is a part of new construction can support green roof installation loading plus extras on live load such as people visiting the site.
The stakeholders
The stakeholders or policy makers for the adoption, installation and operation/maintenance of this green roof are the Richmond residents, city councils and the general public who will be using the Community center. As stakeholders, the city residents and the center users need a green roof for this building that will provide visual and educational opportunities to learn the technology and benefits of green roof. The city council acts as the lead contact in making major decisions and formulating guidelines on the use, maintenance and operation of the green roof area.
Vibrant and healthy community
Based from the above parameters, building/site condition and analysis, it is believed that the green roof design as envisaged in this report will meet the needs of the stakeholders. The purpose and expectation will be met and the expenses for the installation and maintenance will be acceptable and within the generally approved city budget appropriation.
Green Roof system selection
Considering every aspects of the design intention, site and building condition/analysis, a combination of extensive and intensive type of green roofing system is to be used in the installation.
Sopranature” proprietary system by Soprema is to be used throughout the installation. “Soprema” has a track record of solid experience in the advancement of green roof technology through better research and manufacturing of various green roof components.
As such, it was decided to use various product lines under the “Sopranature”® system” which offers unique and innovative systems that combine waterproofing and plants on one roof. For the extensive green roof area, in terms of loading, the Soprema Garden Roof system is only 145 kg/m2 (30 psf). A simple hoisting machine or a retractable, accordion type lifting machine can easily transport the roofing green roof materials from ground to roof level. Likewise, for the intensive green roof portion, the weight of the Soprema Garden Roof system is only 490 kg/m2 (100 psf).
Plant selection
The plants were selected based on various selection criteria such as site analysis, design intent, plant characteristics and aesthetic values.
Drought resistant plant species.
As the project calls for the installations of both extensive and intensive green roof systems, the plants are appropriately and carefully selected on the basis of the above-mentioned criteria. Other selection criteria include the plant’s provenance, hardiness, height and spread and growth rate. Further, the following green roof plant criteria were considered to highlight the advantages and beneficial aspects of using such plant species:
- Thrives in extreme conditions without irrigation
- Tolerates direct sun, extreme temperatures, wind and emissions
- Competes for limited root space and moisture
- Quick cover, rapid rooting/ anchoring
- Forms a self repairing carpet
| PLANT SCHEDULE | |||||
| Plant Name | Qty. | Nursery size and installation | Foliage | Flower Color | Time of Bloom |
| A1- Festuca Rubra | seeding | Green carpet | n/a | Ever green | |
| A2- Erophyllum Lanatum | Pot and seeding | green | yellow | Spring through mid summer | |
| A3- Sedum Divergens | Pot and seeding | green | yellow | Spring through late summer | |
| A4- Aster Subspicatum | Pot and seeding | green | White | Early spring through summer | |
| B1- Sedum kamtschaticum | Cutting and seeding | Dark greenish,
purple |
Yellow | Late May | |
| B2- Hylotelepium | Spring and fall cutting | 1.5’-2’-0” succulent perenial | Starlike pink, white or red flowers | Summer and fall | |
Installation Method:
The installation method to be adopted based on vegetation establishment is combination of seeding and pot grown or plugs. The project is a large scale installation so it is imperative that cost and quality of planting is at premium. Here are the criteria why the following plant establishment methods were selected:
- Seed: The total area of vegetation is square meter. It is cost effective. Seed is less expensive. Can be hydro seeded.
- Pot grown or plugs: Also low in cost. Quality of installation is higher in early years. Well developed roots and canopy. Buy at wholesale prices. Can increase numbers for rapid density.
| Short Term ( 2 Year Establishment Period) |
| 1. Irrigation in dry period |
| 2. Light application of slow release organic fertilizer |
| 3. applications of complete fertilizer every 45-60 days in growing season |
| 4. weekly inspections and weeding |
| 5. achieve 95% coverage first year |
| Long Term Maintenance | |||||
| Inspection Items | Maintenance Check list | Spring and Fall | Summer | Winter | |
| Plants | Cutting,
Replacement /Addition
|
Yes | |||
| Soil media | Replenish
Addition Organic Fertilizer |
Yes
Yes As needed |
|||
| Filter layer | Yes | ||||
| Drainage Layer | inspection | Yes | |||
| Various proprietory components | Root barrier, drainage mat | Yes | |||
| Waterproofing membrane | Leak inspection | ||||
| Emitter | |||||
| Pressure | |||||
| Moisture Level | |||||
| Inpection chamber | Check cover and any damage | Yes | Yes | ||
| Wood curbs | Check and replace rotten curbs | Yes
As needed |
Yes | ||
| Gravel mulch | Cleaning, removing plant dry leaves and debris | Yes | Yes | ||
| Roof parapet | Check for plants ceeping to parapet, check for flashing and membrane | Yes | Yes | ||
Irrigation is necessary in dry period during summer days
Occasional application of organic light fertilizer as needed.
Weeding, once every two months.
Replenishment or addition of growing media.
Cutting and trimming quarterly.
Replace dying and damaged vegetation.
Inspect roof drains every week and clean inspection chamber for every dried leaves and sand that could clog the drain.
Inspect pavers and gravels in the non-vegetation zone and replace or repair wood curb that are rotten or badly warped.
Project Cost Estimate:
|
Total vegetation area = 7,100 sq.ft.
|
|||
| Component | Unit Cost | Total Cost | Remarks |
| Design and Specifications | 5% of roofing cost | $10,827 | |
| Project Admin & Site Review | 2.5% of roofing cost | $5,414 | Can be on hourly basis as required |
| Waterproofing membrane | $12.00/sq.ft. | $85,200 | Can be part of the building contract |
| Green Roof system:(curbing, drainage layer, filter cloth and growing medium | $7.00/sq.ft. | $49,700 | |
| Plants | $2.00/sq.ft | $14,200 | |
| Maintenance | $1.50/sq.ft. | $10,650 | 1st 2 years only |
| Irrigation system | $3.00/sq.ft. | $21,300 | |
| Installation/ Labor | $5.00/sq.ft. | $35,500 | |
| Roofing Project Cost | $216,550 | ||
| Total Project Cost | $449,341 | ||
THE COMMUNITY CENTER
BUILDING ELEVATIONS:
Roof deck with with dedicated patio/trellis for viewing.
DESIGN DETAILS
