Green roofs

Glossary of Terms

ACID: With a pH value less than 7
ALKALI: With a pH value over 7
APPROVED DOCUMENT B: Amendments to Building Safety Regulations 2010 in 2019 and 2020 (Volumes 1 & 2)
BALLAST: Material used to hold loose laid roofing materials in place
BIODIVERSE: A roof designed to create a desired habitat
BLUE ROOF: green roof system with additional water collection and retention capacity
BROWN ROOF: Using locally won soils and substrates and specifically used to encourage local wildlife
BIODIVERSITY: Variation of life forms that are able to co-habit sustainably
BIODIVERSITY ACTION PLAN: A plan formulated to protect and encourage a range of species at a local/regional/national/global level
BREEAM: Building Research Establishment Environmental Assessment Method
CAM: (Crassulacean Acidic Metabolism) plants that deal with drought conditions by closing their stomata during the day
CLIMAX VEGETATION: The total mature development of a plant or community of plants
COMPACTION: increase in growing medium density
CURTAIN WALL: A non-structural outer wall, often of glass or steel
DEAD LOAD: Combined weight of all permanently placed materials the roof
DESCRIPTIVE SPECIFICATIONS: Require specific products and methods of installation, compared to performance specifications
DIURNAL: Happening during the day or daily
DRAIN ACCESS CHAMBER: Rremovable cover installed around roof drains to protect the drains from clogging while allowing for easy access to the drains
DRAINAGE LAYER: For example Protecto-drain
ECO HOMES: As for BREEAM but specifically aimed at domestic property
EROSION PROTECTION LAYER: erosion control blanket or netting to protect green roof from wind and water erosion
EVAPOTRANSPIRATION: water conveyed to the atmosphere through evaporation and plant transpiration
EXTENSIVE GREEN ROOF: an extensive green roof has growing medium less than 150mm deep
FILTER FABRIC: a lightweight, rot-proof loose laid fabric, for example Re-cycled polyester geotextile 300gsm GE-PE-PECT-0300-Z
FLASHING: the weatherproof material installed between roof sheathing (or wall sheathing) and the finish materials to help keep moisture away from the sheathing
GREY WATER: Water collected [from a roof] and used for non potable applications such as toilet flushing, irrigation
GROWING MEDIUM: aggregate based substrate used for plant growth in green roofs
GRO: Green Roof Organisation
HYDRO SEEDING: Method of applying seed by mixing with water and gel and mechanically spraying onto the substrate
HYMENOPTERA: Bees, hoverflies, wasps etc
FIELD CAPACITY: Weight associated with maximum amount of water absorbed by green roof substrate before water starts to drain out, also called Saturated Weight
FLL: Forschungsgesellschaft Landschaftsentwicklung Landschaftbau
INTENSIVE: Substrates more than 150mm deep with a large range of plant types
IRRIGATION SYSTEM: Systems to deliver moisture to the growing medium and vegetation
LEAK DETECTION SYSTEM: Systems allow for detecting and pinpointing the exact location of leaks in the waterproof membrane
LIFECYCLE COST: The capital and operational cost of a building through its estimated useful life
LIVE LOAD: All non-permanent equipment and people on the roof.
MAXIMUM MEDIA DENSITY: Density of the substrate determined after compaction and hydration
MAXIMUM MEDIA WATER RETENTION (MMWR): terminology used by FLL, quantity of water held in a media at the maximum media density – see Field Capacity
MODULAR GREEN ROOF: Pre-grown, self-contained green roof system with all required elements combined, for example M-Tray®
NEUTRAL: With a pH value around 7
R FACTOR: The measure of thermal resistance. R = K·m²/
RHIZOMES: Underground stems that bud to produce new shoots and plants
ROOT BARRIER: Green roof component to prevent plant roots damaging the waterproofing membrane
SEDUM: A succulent plant ideal for extensive green roofs
SEQUESTRATION: To remove or separate
SUB-SOIL: Any soil from below the top soil horizon, generally with no or low organic content
SUBSTRATE: An engineered soil designed to provide a balance of nutrient and water retention
SUCCULENT: Plant that can exist in dry arid conditions by using water stored in its leaves
SUDS: Sustainable Urban Drainage Systems
SUSTAINABILITY: Capacity to maintain an ecological state indefinitely
TOPSOIL: Soil containing a high content of organic matter able to sustain vegetation
WATER PERMEABILITY: the coefficient, which when multiplied by the hydraulic gradient will yield the apparent velocity with which water, at 20°C will move through the substrate and drainage layers
WIND UPLIFT: Net upward force that occurs when the pressure below a roof is greater than above