Green Roof Details, Design, Architecture, Structure, Examples
Green roof details include the parts of a green roof, such as waterproof, root, drainage and filter membranes. Green roof design refers to the relative configuration of layers or components of a green roof. Green roof architecture is the sum total of design dimensions, components, and compatibility of a green roof.
This article discusses green roof details, design and architecture, as outlined below;
-Parts of a Green Roof (as an aspect of Green Roof Details)
Green Roof Details
Green roof details refer to the parts of a green roof and their specifications.
This said, it is important to note that the details (parts, specifications) of any green roof are dependent on the type of green roof involved, and the additional modifications (if any) that have been made.
Below is a brief discussion of green roof details, in terms of parts and specifications of green roofs;
-Parts of a Green Roof (as an aspect of Green Roof Details)
Parts of a green roof are; water proofing membrane, root membrane or barrier, drainage layer, water retention layer, filter layer, and vegetation layer [1].
The water proofing membrane of a green roof is a synthetic polymer layer that is usually of significant mechanical resilience, as well as resistant to biodegradation and root penetration.
Arguably the best membrane for waterproofing in green roofs is Polyvinyl Chloride (PVC), as it meets all basic criteria for optimal performance, and is also less expensive and mire accessible than most alternatives.
Green roof water proofing membranes help in water conservation and stormwater management, alongside other components like vegetative and water retention layer.
Root membrane or root barrier is usually located above the water proofing membrane, and plays the role of protecting the membrane and overall building, from damage by plant roots.
Alternatively, it can be said that the root barrier membrane separates the water proofing membrane from the rest of the green roof assembly. Its role is very important to this effect, since it is necessary to delineate the plant segment of the green roof from other segments.
Like the water proofing layer, the root membrane is usually made from mechanically resilient polymer materials.
Drainage layer or element works along with the filter and water retention layer for both water conservation and building protection.
The drainage layer is usually lightweight, and made from recycled polymer and/or granular aggregate materials.
Water retention layer is used mostly with extensive green roofs, and its primary function is to retain water from precipitation events, to be used by plants on the green roof for their growth.
Attributes of this component include high porosity, anchorage, insulation and moisture retention capacities.
The use of water retention layer is often optional, and most necessary when plants with extensive root systems and/or significant water demand are present. Water that is retained can serve as a supplement for irrigation water that is used to support plant growth on green roofs.
While the thickness may vary widely, a range of 0.5 to 1.0 inch is not uncommon for green roof water-retention component.
Filter layer (also called ‘separation layer’) in a green roof overlies the drainage layer/membrane, and is used to prevent particles of the plant-growth medium, like soil, from entering into and clogging the drainage membrane [2].
It is usually made from synthetic fiber, and is designed to permit water flow through without silt passage.
Vegetation layer, comprised of substrate and plants; is arguably one of the most important and elaborate parts of a green roof [3].
Based on vegetation (among other factors), green roofs are classified and distinguished into intensive, semi-intensive and extensive types.
In addition to its significant aesthetic role, the vegetative layer optimizes the green roof’s function for carbon sequestration, climate change mitigation, and air quality optimization.
Choices of plant species that are grown on green roofs, are usually made on the basis of compatibility considerations with regards to the architecture of the building and its geographic circumstances.
Among the applicable options are; sedum, small shrubs, grasses, and moss.
Green Roof Design
Green roof design is mainly the choice and relative positions of various layers within a given green roof assembly.
The difference between one green roof design and another is therefore based on the presence or absence of various layer components.
Aside the layers themselves, choices of materials and plants in a green roof also define its design.
It must be noted that while they are closely related, green roof design differs from green roof architecture, which is more concerned with geometry and areal dimensions.
Green Roof Design Guidelines
Green roof design guidelines are simply the things to consider when designing a green roof. They are also important for the installation of these roofs, and include the following;
1). Layout of the roof should be extensive for large surface-area buildings, and modular for extremely large, or small, surface areas.
2). Water retention layer may be used in regions with relatively minimal rainfall levels
3). Material choices should be made with consideration of physicochemical conditions
4). Intensive roof design is only recommendable for roofs with significant exposure and where sufficient maintenance is available
5). Net weight of the green roof assembly must be minimized as much as possible, by adjusting choice of materials and components
6). Where needed, additional structural support should be provided
7). Choice of vegetation must be made to limit air pollution and urban heat island risk
Green Roof Architecture
Green roof architecture is a sum total of the details, design and specific dimensions of a green roof.
The most important, defining attribute of green roof architecture is the dimension of components.
These dimensions are decided based on decisions made during the preliminary assessment of building requirements, as well as the details and design of the roof.
When developing the architectural outlay of any given green roof, the two main objectives are compatibility and sustainability.
This means that the green roof architecture must be developed according to a structural model that is fully compatible with the building itself, and must be able to ensure significant resilience and longevity.
Aesthetics is a rather secondary aspect of green roof architecture, although it is also important. The aesthetic symmetry and intricacy of a green roof comes only after its compatibility and sustainability objectives have been met.
Aesthetic factors, like geometry, are also directly dependent on these criteria.
Green Roof Structure
Green roof structure is a term that is used to describe the complexity, resilience and components of a green roof.
It may be used in place of green roof design or architecture, in some contexts.
Examples of Green Roofs
Examples of green roofs are found in;
1). The ACROS Fukuoka Prefectural International Hall of Japan
2). National Park De Biesbosch, the Netherlands
3). City Hall, Chicago
4). Vancouver Convention Centre, Vancouver, BC
5). The Nanyang Technological University, Singapore
6). Moesgaard Museum, Højbjerg, Denmark
Conclusion
Green roof details include the components that make up a green roof.
Parts of a green roof are;
1. Water proofing membrane
2. Root membrane
3. Drainage layer
4. Water retention layer
5. Filter layer
6. Vegetation layer
Green roof design is the arrangement of components relative to each other.
Green roof architecture comprises of the details, design and dimensions of a green roof, and aims to achieve compatibility, sustainability, and aesthetic symmetry.
References
1). Cascone, S. (2019). “Green Roof Design: State of the Art on Technology and Materials.” Sustainability 11(11). Available at: https://doi.org/10.3390/su11113020. (Accessed 23 December 2022).
2). Seferyan, L. A.; Chubarov, V. E.; Chubarova, K. (2021). “Modern architectural – planning, organizational, technological, constructive solutions at green roofing.” IOP Conference Series Materials Science and Engineering 1083(1):012049. Available at: https://doi.org/10.1088/1757-899X/1083/1/012049. (Accessed 23 December 2022).
3). Young, T.; Cameron, D. D.; Sorrill, J.; Edwards; T.; Phoenix, G. K. (2014). “Importance of different components of green roof substrate on plant growth and physiological performance.” Urban Forestry & Urban Greening 13(3). Available at: https://doi.org/10.1016/j.ufug.2014.04.007. (Accessed 23 December 2022).
