What are the benefits of green roofs?
Can people walk on the green roof?
What maintenance is required?
What will my green roof look like throughout the year, especially winter?
Which native varieties are appropriate?
Can a green roof be installed on a sloped roof?
Can a retrofit support a green roof?
Do I need to consult a Structural Engineer?
How is my roofing warranty affected if a green roof is installed?
How does a green roof affect the lifespan of a roof?
Can green roofs be a fire hazard.
Do green roofs cause leaks?
Will plant roots grow into the original roof?
Can a green roof be installed with solar panels?
Does wind pose risk to the green roof?
How does the thin layered XF301 pre-vegetated mat system meet the Toronto Green Roof Construction Standard and Municipal Code 492?
How does the green roof comply with plant selection and coverage requirements by certain municipalities, such as Toronto’s Municipal Code 492?
How do I get approval of my green roof application in Toronto and other municipalities?
How do I get wind uplift approval required in some municipalities?
*More questions, or need details, please contact us.
What is the difference between an Extensive green roof and an Intensive green roof?
Extensive roofs have less growing medium and have a limited plant palette. They can be very lightweight, require less maintenance and are more economical.
Intensive roofs have deeper engineered growing medium and support a wider variety of plants, shrubs and trees. They are heavier, require more maintenance, and are costlier.
What are the benefits of green roofs?
Stormwater Management
Engineered pre-vegetated systems can absorb as much as 80 percent of stormwater runoff that affects quality of local water resources which supply drinking water and serve as fish and wildlife habitat – saving substantially on underground stormwater storage. See municipal case study.
Energy Consumption
A green roof’s thermal resistance means savings from reduced energy for cooling.
Urban Heat Island Effect
Evapotranspiration helps cool the air and reduces the urban heat island effect. Widespread greening of urban rooftops would reduce local ambient temperature from 0.5 to 2 degrees Celsius.
Air Quality and Emissions
Plants improve air quality and help reduce levels of CO2 and other toxins. More Info.
Biodiversity and aesthetics
Creation of more natural green spaces is not only therapeutic and pleasing, these green roofs offer an urban habitat for birds, butterflies and pollinating insects.
Food Production & Education
Opportunities for urban agriculture and education are numerous. See here.
Increases Life Expectancy of Roofing Membrane
There are decades-old vegetated roofs that have never been replaced. Michigan State University took a 10 year sampling of the waterproofing components under Xeroflor’s XF301 on the Ford roof and found virtually no age related deterioration or damage underneath the green roof. Green roofs have been known to double or triple the lifespan of the roof membrane as green roofs cover the waterproofing membrane, protecting it from UV rays and extreme daily temperature fluctuations. Less frequent re-roofing means less costs and less waste over time.
Can contribute to LEED points and the building’s prestige.
Suitable green roof installations can contribute up to four full credit points and 20 contributing points. See here.
Can people walk on the green roof?
For regular traffic and maintenance, pavers are required on green roofs as most plants could be crushed walked on – as they would be on ground level. Green roofs that are composed of our moss-sedum carpet can have occasional traffic every couple of weeks for maintenance purposes, but we recommend paver stones if more regular access is needed.
What maintenance is required?
All living roofs require some level of care and maintenance so that they don’t simply survive but thrive. Properly selected vegetation is vital to your green roofs success. Even with hardy, drought tolerant and native plants that tend to require less maintenance will need more care the first season to help them establish well on the rooftop. A watering spigot is recommended on all rooftops to help with the initial establishment period and any with any subsequent supplemental irrigation needed. It is recommended to all building owners to have a maintenance plan above and beyond the first year. On-going maintenance: Extensive green roofs require the least amount of maintenance yet still need weeding, occasional irrigation and debris removal as well as clearing drains. See the maintenance guideline for Extensive green roofs.
Intensive green roofs require regular maintenance – the amount depends on selected vegetation. Please contact us for a maintenance plan specific to your green roof.
What will my green roof look like throughout the year, especially winter?
This depends on the type of green roof installed. Green roofs are very dynamic and change dramatically throughout the seasons. Intensive green roofs take on a different life and feel as shrubbery and grasses change colour and are covered by snow in the winter. A moss-sedum extensive green roof carpet will be reddish in very early spring as it comes out of dormancy. In late Spring and Summer it will become a vibrant green and grow up to 6 inches and flower many colours. In Winter, it will go dormant once again becoming a gorgeous reddish-purple.
Which native varieties are appropriate?
Hardy, native plants appropriate for green roofs vary across Canada. Some suggestions for the Greater Toronto Area can be found here. Please contact us for your specific region.
Can a green roof be installed on a sloped roof?
Yes, up to a maximum of 20 degrees with proper mechanisms to prevent sliding or shearing. Please contact us for further details.
Can a retrofit support a green roof?
Yes, it may. A structural engineer needs to be consulted. Xeroflor’s patented sedum-moss green roofs are very lightweight (starting from 8 lbs per square foot saturated) and thrive on many retrofits around the world including Chicago’s O’Hare airport cargo facility.
Do I need to consult a Structural Engineer?
On retrofits, a structural engineer needs to be consulted to determine the structural capacity of the roof. With that information, a Xeroflor representative can advise you on the best system to suit your needs.
How is my roofing warranty affected if a green roof is installed?
Most roofing manufacturers will warranty their system if a green roof is installed above however it is always best to check with the manufacturer prior to installing a green roof. Call us to talk to discuss warranty.
How does a green roof affect the lifespan of a roof?
Greening a roof is expected to lengthen a roof’s lifespan by two or three times, according to Penn State University’s Green Roof Research Center.
Can green roofs be a fire hazard?
Yes, improper design and maintenance of a green roof can pose a fire risk.
ANSI (American National Standards Institute) has adopted VF-1 Fire Design Standard for Vegetative Roofs which addresses three fundamental green roof design considerations. These include:
1. Location of a rooftop, where the green roof abuts vertical surfaces.
2. Dividers in the green roof called “firebreaks” that are intended to limit the spread of fire from one section of the rooftop to another, and
3. The maintenance of green roof systems to minimize their flammability.
Design Standards & ANSI
Do green roofs cause leaks?
No, a green roof does not cause leaks. Poor installation or incorrect specification of the roofing materials might result in leaks.
Will plant roots grow into the original roof?
To prevent any damage caused to the roof by roots or rhyzomes always ensure that a ‘root-resistant’ element is present.
Can a green roof be installed with solar panels?
Yes. A green roof can boost solar panel efficiency. As the green roof lowers the ambient temperature on the rooftop on a hot day, it also keeps temperature of the solar photovoltaic panels down helping them do their job better.
Does wind pose risk to the green roof?
Yes, a green roof can be at risk of wind damage due to improper design and shoddy installation. Good design, proper installation and carefully chosen plants ensure that a green roof is able to withstand wind and other harsh conditions on rooftops. Furthermore, we have tested various systems to the CSA 123.24 Standard Test Method For Wind Resistance Of Modular Vegetated Roof Assembly.
Design Standards & ANSI
How does the thin layered XF301 pre-vegetated mat system meet the Toronto Green Roof Construction Standard and Municipal Code 492?
The XF301 pre-cultivated green roof systems will provide plant survivability comparable to that of an un-irrigated system with growing media at a minimum of 100mm, as required in the Toronto green roof declaration.
Rainwater capture and storage is a critical factor on plant survivability on un-irrigated green roof systems. The XF301 Sedum Standard pre-cultivated green roof system has a water retention capacity of 36 L/m2, which is in the same range as a typical system with 100 mm growing medium (30-40 L/m2). When un-irrigated, both systems capture and store similar amount of water for the plants to use and to tie the plants over to the next rainfall for survivability.
How does the green roof comply with plant selection and coverage requirements by certain municipalities, such as Toronto’s Municipal Code 492?
The XF301 system contains selected sedum species that are heat and drought tolerant with minimal water needs. The plants are pre-cultivated on our farms so they arrive on site mature and well-established and therefore can better withstand water stress compared to young seedlings. This further increases survivability on rooftops.
How do I get approval of my green roof application in Toronto and other municipalities?
The City of Toronto requires a permit application including a “Green Roof Declaration Form.” Xeroflor Canada provides a Survivability Report with details about the success of our local projects to assist with the permit process. Xeroflor will help clarify any questions pertaining to the form, or approval process, and help you obtain the necessary information.
How do I get wind uplift approval required in some municipalities?
We work with engineers who provide a stamped report describing how our green roof design addresses wind uplift pressures (including a description of how the pressures were determined).
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