Subtropical climate vegetated roof
A subtropical climate vegetated roof (SCV roof) is a type of
Green roofs are used for various reasons including:
Although similar characteristics and principles exist, there are several differences between the two types of environmentally sound roofing systems. These differences are comparable to the differences found between regions of the United States in conventional landscaping and gardening or the variations found in forms of landscaping. Plant species and landscaping methods utilized in northern parts of the United States are not suitable for humid, subtropical regions of United States due to the extreme temperatures and rain events that occur. This accounts for the most significant difference between a green roof in northern United States and a subtropical climate vegetated roof (SCV roof).
A subtropical climate vegetated roof that is well designed according to the specific geographic locations climate can lower roof surface temperatures by as much 38° and depending on the amount of the event retain up to 88% of rainfall.
Technology and terminology
Compared with other parts of the United States, the number of vegetated roofs currently in the Southeast is significantly less. Vegetated roofs in humid subtropical regions rely on the same core green roof terminologies that are used throughout the world and other parts of the United States. Extensive, intensive, soil media, ballast, filter fabric, drainage layer, waterproof membrane are some of the core green roof component terms associated with SCV roofs.[3]
Regional terms, plant palettes, and technologies are forming to adapt to recent innovations and increased popularity of green roofs in the humid, subtropical regions of the United States. All forms of green roofs have the potential to retain
Recent advancements in soil engineering and plastic technologies allow vegetated roofs the ability to adapt to different locations within the humid, subtropical region of the United States. Soil media
As defined by green roof industry standards, extensive green roofs have a soil media of less than 6 inches in depth and intensive green roofs have a soil media of more than 6 inches in depth.[5] Most SCV roofs that are greater than 6 inches in depth are expensive and found on residential high rise structures, often containing pools and other amenities.
An SCV roofs requires a unique soil media mixture to adapt to the harsh
There are three basic SCV and green roof systems available in today's market: built-up, modular, and mat. These systems vary from manufacture to manufacture and are composed of different materials such as: foam, high density plastic, and fabrics. Many of the systems have geographic limitations and do not perform well in humid, subtropical regions based upon the intent of the system and the materials being used.
Built-up
Multi-layered systems containing the following functional layers: root barrier, protection layer, drainage layer, filter layer, growing medium and plant level.[6]
Modular systems
Self-contained units, typically square in shape, that require only the soil medium and vegetative layer for a functioning green roof. These systems are easy to install and remove. Some modular systems are pre-grown at nurseries to client specifications, forming an instant vegetative layer.[6]
Mat systems
Singled-layered systems of this type are drained by a multi-layer fabric mat called a “drainage mat” that combines soil separation, drainage, and protection functions. Current research suggests that the depth of the soil media, material, and number of layers affect the success rate of an individual green or SCV roof.[6]
Suitable plant pallets
A suitable plant species for SCV roofs consist of the following features: drought tolerant, minimal root structure, minimal height, ability to form a vegetative mat, non-rangy, heat tolerant,
-dependent plants are not suitable for SCV roofs and should be avoided and can lead to expensive failures.Some of the most successful SCV roof plant species are in the families
Green roofs in the northern continental United States rely on
Example SCV roof plant palette
Common name | Scientific name | Cultivar | Family | Recommended size | Spacing | Growth habit |
---|---|---|---|---|---|---|
Sedum | Sedum rupestre |
'Lemon Coral' | Crassulaceae | 4" | 18" | Spreading groundcover |
Ice Plant | Delosperma cooperi | n/a | Aizoaceae | 4" | 24" | Spreading groundcover |
Dianthus | Dianthus gratianopolitanus | 'Firewitch' | Caryophyllaceae | 1 gallon | 18" | Clumping Groundcover |
Bugleweed | Ajuga reptans | 'ChocolateChip' | Laminaceae | 1 gallon | 18" | Spreading Groundcover |
Moss Verbena | Verbena tenuisecta |
n/a | Verbenaceae | 4" | 24" | Spreading groundcover |
Challenges
SCV roofs confront a magnitude of challenges due to the adverse weather conditions of the Southeastern United States. High humidity levels, excessive rain amounts, prolonged heat, mold, mildew, insects, disease, weeds, soil borne disease, maintenance concerns, and sloped roofs are the major challenges faced in designing a SCV roof. High humidity levels, excessive rain amounts, prolonged heat lead to decreased plant health on CAM plants that are standard in green roof design. The decreased plant health causes diseases, insects, root rot, and plant fatality.
Soil-borne diseases occur more frequently due to warm, rainy, humid environment rhythm of the humid, subtropical region.[9] SCV roof plants are researched and tested at several different universities throughout the southeast to avoid system failure and economic loses. Mold and mildew can form on areas of the roof and building when proper ventilation is not taken into consideration and are also repercussions of high humidity levels and prolonged heat.
One of the greatest challenges to SCV roofs can be
Sloped roofs that are prevalent in the southeastern United States also pose a significant challenge for SCV roofs. Soil media erosion and poor plant establishment are the most common problems and can occur on any angle of sloped roof if not designed properly. Erosion blankets and green roof soil media stabilization products are used to mitigate the effects of sloped roofs. Flat roofs and low sloped roofs are conventional roof slopes by the building industry in the southeastern United States and allow for successful implementation of SCV roofs.
Standard roof slopes
Flat roofs – 1% to 2% slope
Low slope-3:12 to 5:12
Medium Slope-6:12 to 9:12
High Slope-10:12 to 12:12
- Subtropical regions in the US where SCV roofs could apply
Here are some of the states where humid subtropical climates can be found:
- Eastern half of Texas
- Louisiana
- Arkansas
- Alabama
- Mississippi
- North Carolina
- South Carolina
- Tennessee
- Georgia
- Kentucky
- most of Florida
- Virginia
- southern West Virginia
The climate in many of these states can vary and be extreme.
Benefits (Performance ratings)
- Reduces stormwater volume (50%–85%)[5]
- Improves stormwater quality through load reduction[5]
- Saves water by rainwater harvesting[5]
- Reduces heat island effect[5]
- Lowers surface temperatures by 40–50 degrees Fahrenheit[5]
- Energy savings can reach 15%–30%[5]
- Reduces noise for building occupants[12]
- Increases the life of the roof and reduces roof maintenance[5]
- Contributes to invertebrates[12]
- Filters air pollutant particles[12]
- Increased storm event safety
- Neighborhood diversity
- Aesthetic value
- Reduces need for ditches
Costs
Initially, vegetated roofs can have a high short-term capital but the long-term energy and maintenance savings outweigh them. Even the U.S. Green Building Council and some new advances in green roofs suggest that green buildings don't necessarily have to cost more than a conventional one.
Successful examples
Project name: Shadow Wood Preserve Green Roof Demonstration
- Location: Ft. Myers, FL, USA
- Size: 2400 sq.ft.[5]
Project name: Charles R. Perry Construction Yard, University of Florida
- Location: Gainesville, FL, USA
- Size: 2600 sq.ft.[5]
Project name: Student Union Expansion at the University of Central Florida (UCF)
- Location: Orlando, FL, USA
- Size: 1600 sq ft[5]
References
- ^ "Public Benefits". 29 May 2020. Archived from the original on 8 June 2018. Retrieved 25 November 2010.
- ^ a b c d "Connecting From Off-Campus" (PDF). University of Florida Libraries. Retrieved 2014-10-18.[permanent dead link]
- ^ "Vegetation technology". 29 May 2020. Archived from the original on 11 October 2018. Retrieved 19 November 2010.
- ^ "Connecting From Off Campus - UF Libraries". emeraldinsight.com.lp.hscl.ufl.edu. Retrieved 2014-10-18.
- ^ a b c d e f g h i j k "Green Roofs/Eco-roofs" (PDF). University of Florida. 22 December 2008. Retrieved 2014-10-18.
- ^ a b c Vegetation technology
- ^ "CAM plant". 30 August 2020.
- ^ a b CAM plant
- ISBN 9780520014978.
- ^ "Green Roof Wind Uplift Challenges".
- ^ Green Roof Wind Uplift Challenges
- ^ a b c Public Benefits
External links
- "Connecting From Off-Campus" (PDF). University of Florida Libraries. Retrieved 2014-10-18.[permanent dead link]
- "Connecting From Off Campus - UF Libraries". emeraldinsight.com.lp.hscl.ufl.edu. Retrieved 2014-10-18.
- "Green Roof Plants • Information on Green Roofs • IGRA". igra-world.com. Archived from the original on 2018-10-11. Retrieved 2014-10-18.
- "Public Benefits • Information on Green Roofs • IGRA". igra-world.com. Archived from the original on 2018-06-08. Retrieved 2014-10-18.
- "CAM plant - definition from Biology-Online.org". biology-online.org. Retrieved 2014-10-18.
- https://books.google.com.lp.hscl.ufl.edu/books?hl=en&lr=&id=KNktsuZMtboC&oi=fnd&pg=PA125&dq=soil+diseases+humid+subtropical+regions&ots=RVN_l-UXUA&sig=MUA4wZo4IVPddW6FS8KcNbyqwUA#v=onepage&q=warm%2C%20rainy&f=false
- "Green Roofs/Eco-roofs" (PDF). University of Florida. 22 December 2008. Retrieved 2014-10-18.
- "Green roofs swing temperatures in urban jungles - USATODAY.com". usatoday.com. Retrieved 2014-10-18.
- http://www.epa.gov/region08/greenroof/pdf/green%20roof.pdf
- "Reach Information Portal". Archived from the original on 2011-07-15. Retrieved 2014-10-18.
- "Green Roofs - Systems with Drainage Mats". conservationtechnology.com. Retrieved 2014-10-18.