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Terminology / Green Roof Definitions

Adaptation - In the context of climate change, an adjustment in natural or human systems in response to actual or expected climatic stimuli or their effect, whichmoderates harm or exploits beneficial oppurtunities.

Aggregate - Non-organic fragments that make up part of growing medium. (GRHC)

Allowances - An amount established in the contract documents for inclusion in the contract sum to cover the cost of prescribed items not specified in detail and providing for the variation between the predicted cost and the actual cost of construction. (GRHC)

Ballast - A material used to hold loose laid roofing materials in place. (GRHC)

Bidding - When a general call is issued to contractors to propose a competitive budget to complete a given project. (GRHC)

Bidding, Pre-qualified - When an owner issues an invitation to bid to a selection of qualified contractors. (GRHC)

Built-Up Systems - Green roof which is constructed / assembled directly at the final destination. The most efficient solution in regards of costs, environmental and general green roof benefits. “Monolithic systems are the Best Management Practice (BMP) in professional and modern green roof technology” (Breuning 1999).

Bid Securities - Insurance that provides the owner a mechanism for financial recovery should the low prime bidder default upon its bid, in the absence of a bona-fide and substantive error. (GRHC)

Bid Shopping - Given enough time the general contractor will immediately begin shopping the lowest bidder in order to procure a "final and best offer" from all bidders. To avoid this process, subcontractors withhold their bids to the general contractors until the last minute. (Bruce, 2005)

Biodiversity - The variableamong living organisms from all sources including, inter alia, terretial, marine and other aquatic ecosystems and the ecological complexes of which they are part this includes diversity within species, between species and of ecosystems.

Bonding of Subcontractors - Payment and performance bonds are written by a surety or and insurance company and insure faithful performance of the work contracted and pull payment to those companies that provide services or materials for the project. (ASPE 2003 : 30)

Cation exchange - The quantity of positive ions (cation) that can be absorbed by growing medium. (GRHC)

Carbon Footprint - Measures the total amount of greenhouse gases (GHG) caused by an activity or a person’s day-to-day life through the burning of fossil fuels for electricity,cooling, transportation etc., and is generally measured in units of tons (or kilograms) of carbon dioxide equivalent.

Climate change - Change of climate that is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable time periods.

Chain of Custody - A process involving the assignment of quality assurance responsibilities for the entire construction process. (GRHC)

Critical Path -A sequence of tasks that need to be carried out in order for a project to reach substantial acceptance and completion. (GRHC)

Commissioning -A process of achieving validating and documenting that the performance of the complete building and its systems meet the design needs and requirements of the owner. (Demkin 2001)

Compaction - Increase in growing medium density. (GRHC)

Counter-flashings -Metal sheeting placed at the base of a parapet wall to protect the membrane and base flashings. (GRHC)

Control joints - Joints which accommodate the movement in the surface component of the roof. (GRHC)

Dead Loads - All permanently placed materials on and below the roof (e ,g. green roof materials, green roof plants, ceiling fans). (GRHC)

Design Build -When a single firm is responsible for both the design and construction of a given project. (GRHC)

Direct Green Roof System - Is a system where the vegetation is not planted in containers or modules, but onto specially designed layers that are placed on top of the existing roof. Often called seamless system, wall-to-wall system or monolithic system. Direct green roof systems are the most efficient solution for greening roofs with the best protection for the roof.

Drainage Layer -System comprised of granular drainage material, drainage boards, drains, and/or pipes which remove enough water from the roof so as to not compromise the waterproofing system and building. Ideally this allows enough water to remain in the system to sustain plant life. (Breuning/ GRHC)

Ecosytem services The direct and indirect contributions of ecosystems to human well-being.

Erosion Blankets - Protective sheeting or woven fabric placed on top of growing medium to protect it from wind, water or mechanical erosion while plants are being established. (Breuning / GRHC)

Ethylene Propylene Diene Terpolymer (EPDM) -EPDM material is a thermosetting synthetic elastomeric membrane (RCI).

Evapotranspiration - The sum of water loss through evaporation and plant transpiration. (GRHC)

Expansion joints - Joints which are an extension of membrane flashings and permit the structure to expand and contract without breaking. (GRHC)

Extensive Green Roof -An extensive green roof system is typically one with a growing medium depth of 6" or less and no permanent irrigation system. (Breuning / GRHC)

Fertilization -The application of nutrients to plants. Can take to form of solids or liquids. (Breuning / GRHC)

Filter Cloth, Filter Fabric -A synthetic material laid over or included as a part of the drainage layer to prevent blockage of the drainage.

Food Security - Food security refers to the availability of basic foods and how accessible they are.

Friction coefficient -a scalar value which describes the ratio of the force of friction between two bodies and the force pressing them together. (GRHC)

Green Roof Assembly -An assembly consisting root barrier, drainage layer, filter cloth, growing medium, and plants installed on an impervious surface. (GRHC)

Green Infrastructure Green infrastructure refers to the array of products, technologies, and practices, such as green roof habitats, that use naturals systems to enhance overall environmental quality and provide ecosystem services, such as filtering air pollution, carbon sequestration, and stormwater attenuation.

Growing medium, Growing Media, Green Roof Soil - the particulate matter or substrate that anchors the plant roots to sustain plant growth. (Breuning / GRHC)

HVAC systems - Heating, ventilation and air-conditioning systems. (GRHC)

Hydrodynamic membrane -A membrane that relies on gravity to shed water. (GRHC)

Hydrostatic membrane -A membrane that is able to withstand pressure exerted by a fluid due to its weight. (GRHC)

Intensive Green Roof, Garden Roof, Roof Garden -An intensive green roof system is one with growing medium typically of a depth of 6" or more and permanent irrigation. (Breuning / GRHC)

Irrigation System (temporary or permanent) -Systems which deliver moisture to the growing medium making it available for plant use.

Life-Cycle Cost - The capital and operational cost of a construction item or system during the estimated useful life of a structure (e.g. building). (Breuning / GRHC)

Life Cycle Costing Analysis (LCC) - The capital and operational cost of a construction item or system during the estimated useful life of a structure (e.g. building). (Breuning / GRHC)

Live Load -All equipment and people on the roof. They are not permanent elements and cause the weight on the roof will fluctuate. (GRHC)

Loose Laid Green Roof System, Built-Up Systems, Monolithic Systems, Wall-To-Wall Green Roofs - Green roof which is constructed / assembled directly at the final destination. The most efficient solution in regards of costs, environmental and general green roof benefits. “Monolithic systems are the Best Management Practice (BMP) in professional and modern green roof technology” (Breuning 1999).

Membrane Protection Layer -A material used to protect the waterproofing membrane and/or an insulation layer against friction between roofing and green roof elements. (Breuning / GRHC)

Mitigation In the context of climate change, a human intervention to reduce the sources or enhance the sinks of greenhouse gases.

Modular Green Roof System, Tray System, Pre-vegetated Planters, Prefab Sectional System - A roof greening system which combines one or more layers in a pre-manufactured or pre-vegetated container (e.g. drainage, growing mediums, and plants). Pre-vegetated modular systems are a costly alternative for small projects and hobby gardeners. (Breuning)

Monolithic System - Green roof which is constructed / assembled directly at the final destination. The most efficient solution in regards of costs, environmental and general green roof benefits. “Monolithic systems are the Best Management Practice (BMP) in professional and modern green roof technology” (Breuning 1999).

Moisture Retention Layer - Layer installed below the drainage layer which stores water for plants' use after a rain event, or to spread moisture more evenly over a large area. Moisture retention fabrics are installed below the drainage and often have an additional function as membrane protection layer. (Breuning)

Negotiation - When an owner decides to hire a contractor as a sole-source provider based on previous experience or reputation.

Overburden -A term used primarily by roofing professionals to refer to the entire green roof system above the waterproofing. (Breuning)

Packaging Process -Process involving the establishment of a hierarchy of responsibility between the trades. (GRHC)

Plenum -The space that is used for air circulation in heating and air conditioning systems, typically between the structural ceiling and the suspended ceiling or under a raised floor. The plenum is typically used to house the communication cables for the buildings computer and telephone network(s). (GRHC)

Pre-bid conferences -Conferences held in order for the owner and design team to clearly communicate information, be it technical or procedural, to bidding contractors. (GRHC)

Pre-Design -The period of time before the design period begins where the scope of work is relined . (GRHC)

Punch List - A list of items of work to be completed or corrected by the contractor after substantial acceptance. (GRHC)

Polyvinyl Chloride (PVC) - A synthetic thermoplastic polymer prepared from vinyl chloride often compounded into flexible and rigid forms through the use of plasticizers, stabilizers, fillers, and other modifiers; rigid forms are used in pipes, flexible forms are used in the manufacturing of sheeting a roof membrane materials (RCI).

Schedule of Values - A statement furnished by the contractor to the architect reflecting the portions of the contract sum allocated to the various portions of the work and used as the basis for reviewing the contractor's application for payment. (AIA 2001)

Staging - A specified area used to store materials during construction. (GRHC)

Supersaturating – Can be a wanted or unwanted worst-case scenario in which the roof is flooded to a certain depth, caused primarily by reduced run-off into roof drains. (Breuning/GRHC)

Quality Assurance - Actions taken to ensure that standards and procedures for the implementation of a system or product are adhered to, such that they meet technical requirements. (GRHC)

Retrofit - When a green roof is built on to an existing roof. (GRHC)

Roof Assembly - A roof assembly is the interaction of all roofing components, including the roof deck, membranes, insulation, covering, etc, for weather proofing and thermal insulation. (GRHC)

Root Repellent Layer -A physical barrier which prevents roots from affecting the waterproofing system. (GRHC)

R-value -The measure of thermal resistance. R = K·m²/W (GRHC)

Semi-Intensive Green Roof -A semi-intensive green roof system is one with a growing medium depth of around 6" that is occasionally irrigated. (Breuning /GRHC)

Shop Drawings -Depict the conditions of installation throughout the construction process, including a profile schematic, details, information, and accurate dimensions and configurations. (GRHC)

Submittals -Product data, supplier's technical literature, MSDS, a statement by the supplier that the product is suited to, and approved, for the proposed use, samples, soil samples and test reports, cost estimate, and shop drawings. (Breuning / GRHC)

Urban Heat Island Effect -This is a phenomenon whereby urban areas experience higher temperatures than the surrounding countryside. This is caused primarily by the change in land cover from green open spaces to buildings, roads and other infrastructure which absorb solar radiation during the day and releases it as latent heat during the night.

Value Engineering -A meeting of minds between owners, designers, and contractors to reduce the costs of a project by substituting materials or construction methods with "approved" alternative products or methods that will provide acceptable results of equal or better quality. (Breuning / GRHC)

Vitrify -To make a surface non-porous. (GRHC)

Water Holding Capacity -The maximum volume of water that a medium can tolerate before super-saturation. (Breuning/GRHC)

Water capture -The quantity of water that is retained in any layer of a green roof system after new water additions have ceased and that cannot escape the roof except through evaporation or plant transpiration. (Breuning / ASTM e2397 -05: 3.2.1)


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