FAQ
Q1. What are the benefits of a green roof?
Q2. How do I start to plan for a green roof?
Q3. What are sedum plants?
Q4. Do sedum plants die off in the winter?
Q5. Will other plant species encroach on the sedum blanket?
Q6. Is irrigation needed?
Q7. Will plant roots damage my waterproofing?
Q8. Will my roof be able to take the extra weight?
Q9. Is my existing flat roof suitable?
Q10. What is the minimum and maximum slope suitable?
Q11. What maintenance is required?
Q12. What does a green roof cost?
Q13. Will my roof last longer with a green roof?
Q14. Will a green roof improve the thermal efficiency of my roof?
Q15. Is a green roof fire safe?
Q16. What is Xero Flor’s Warranty?
Q17. What are the FLL Guidelines?
A1. What are the benefits of a green roof?
- Conserves energy by moderating temperature on roof and surrounding areas
- Reduces storm runoff volume flow rate and peak
- Reduces the Urban Heat Island Effect
- Restores the ecological and aesthetic value of urban open space
- Provides Biodiversity habitat
- Protects conventional roofing systems, typically doubling the service life of the underlying waterproofing membrane
- Helps achieve LEED certification
A2. How do I start to plan for a green roof?
Learn your loading weight:
It is fundamental that the saturated weight of a desired green roof system is made available to a structural engineer to assist in the correct design of the supporting deck.
Check roofing:
We suggest the roofing should be certified and confirmed ‘leak free” by a leak detection specialist prior to the installation of a any green roof system.
Choose an experienced green roof supplier with a proven system using superior components. Protect your investment and go with a green roof supplier with a proven track record. The right selection of plants need to be chosen for the location in question. Other requirements are: nutrients, a balance between moisture and drainage, and aeration to the root systems. Components include: plants, growing medium, water retention fleece, drainage layers and a root barrier, etc.
Choose a landscape that best suits your building and development needs among the various types: Intensive, Semi-Intensive or Extensive.
Installation:
Trained and approved contractors should install green roof systems because the methods and practices are different to the installation of landscaping over natural ground. Xero Flor’s pre-cultivated system can be installed by roofing contractors.
Maintenance:
Every green roof system requires some form of maintenance for a period of time following the initial installation. Extensive systems are low maintenance while Intensive systems require more.
A3. What are sedum plants?
Sedums are plants known as succulents, also known as 'Stonecrops' - drought resistant plants commonly found growing within the cracks of rocks or along roadside verges. They are ideal for extensive green roofs as they need very little maintenance or water and survive well in harsh environments.
A4. Do sedum plants die off in the winter?
Extensive roof finishes consisting of predominantly sedum plants do not die off as such. They regress (shrink back) during winter and can turn a dark red color. This is a natural phenomenon and very much of the nature of this plant species to prepare it for the coming cold weather. In fact, it is an important process of the species to make it hardy and resistant The plant quickly returns to a predominately 'green' state in spring, with the differing species flowering from May through to the end of August.
A5. Will other plant species encroach on the sedum blanket?
Being grown in only 20mm of free-draining mineral substrate as opposed to soil, the blanket offers insufficient moisture to sustain most other plant species other than the existing sedum species, which thrive in this environment.
The Xero Flor XF301 vegetation blankets require thorough watering after installation. Subsequent watering is then largely dependent upon the time of year. It is advisable to water for the first few weeks during very warm weather conditions to allow the plants to acclimatize to their new location and recover from the shock of being transplanted from the growing field. The roots of the plants are already established into the integral moisture retention blanket, so after this initial period the plants should only require occasional watering during lengthy drought periods.
A7. Will plant roots damage my waterproofing?
The roots on sedum plants will not penetrate the waterproofing, but it is normal practice to incorporate a root-inhibiting plastic layer beneath the blankets as a precaution against stray wind borne seeds (e.g. sycamore) that may try to temporarily establish as saplings within the substrate when conditions allow. These can be removed as part of a schedule of routine maintenance in the unlikely event that any should find their way onto the roof.
A8. Will my roof be able to take the extra weight?
Xero Flor® sedum blankets offer the lightest roof greening option. Weighing as little as 37kg/m² or 7.47 lbs/ft sq (saturated weight) they can be safely used on most flat roof decks designed to take a bituminous or single ply waterproofing. If there is doubt as to the suitability of the existing deck structure to take the loading, as structural engineer should be consulted.
A9. Is my existing flat roof suitable?
Most traditional flat roofs with a minimum fall of 1:60 or above with Bituminous, EPDM, TPO, asphalt or Single ply waterproofing are suitable, so long as the supporting deck can carry the additional weight. Adequate drainage is important and access to carry out routine maintenance safely.
A10. What is the minimum and maximum slope suitable?
Xero Flor® XF301 can be used on slopes between 1°- 30°.
A11. What maintenance is required?
Green roofs require weeding, fertilizing, cleaning around the drains, removing debris and leaves, initial irrigation and in some cases on-going irrigation.
A12. What does a green roof cost?
While pricing varies on the system you wish to install, on the extensive systems start from $12 per square foot, installed, and includes one year of maintenance.
A13. Will my roof last longer with a green roof?
Xero Flor® vegetation blankets protect the waterproofing from ultra-violet radiation and thermal shock. These are the two main elements that age and eventually cause the waterproofing to fail. It is generally accepted that installing a green roof will double the estimated life expectancy of a newly installed waterproofing system.
A14. Will a green roof improve the thermal efficiency of my roof?
The green roof will offer positive thermal benefits in the respect of controlling the temperature variations on the roof surface and underlying structure. In particular, they help to keep the building cool during hot weather.
A15. Is a green roof fire safe?
Xero Flor’s specially engineered growing medium and specifically chosen vegetation and plants conform to the German FLL standards and therefore do not pose a fire risk. It is essential to have the right plants and soil to avoid fires.
A16. What is Xero Flor’s Warranty?
Xero Flor’s warranty on accessories is 5 years. Vegetation warranty is 1-2 years.
A17. What are the FLL Guidelines?
Xero Flor® is a member of the German FLL Roof-Greening Working Group. The German FLL provides a guide for the planning execution and upkeep of green roof sites.
