Blue roof

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A blue roof is a roof of a building that is designed explicitly to provide initial temporary water storage and then gradual release of stored water, typically rainfall. Blue roofs are constructed on flat or low sloped roofs in urban communities where flooding is a risk due to a lack of permeable surfaces for water to infiltrate, or seep back into the ground.

Contents

Water is stored in blue roof systems until it either evaporates or is released downstream after the storm event has passed. [1] Blue roofs that are used for temporary rooftop storage can be classified as "active" or "passive" depending on the types of control devices used to regulate drainage of water from the roof. [2] Blue roofs can provide a number of benefits depending on design. These benefits include temporary storage of rainfall to mitigate runoff impacts, storage for reuse such as irrigation or cooling water makeup, or recreational opportunities.

Stormwater management and other benefits

Flood mitigation

Due to the density of urban development, there is a general lack of permeable surfaces in cities. This lack of area for stormwater to infiltrate back into the ground leaves cities vulnerable to flooding.

A number of blue roof pilot projects have been implemented around the United States, the results from which highlight their efficacy in reducing stormwater runoff during and after severe weather events. [3] [4]

Pollution reduction

Pollution caused by combined sewer system overflows. Water urban cycel.jpg
Pollution caused by combined sewer system overflows.

While blue roofs do not remove pollutants from water by temporarily detaining it, they do reduce the load severe rain events place on storm sewers which stops emergency overflow from combined sewer systems from discharging untreated wastewater into rivers, streams, and coastal waters.

A significant blue roof pilot project intended to evaluate the potential of the systems for mitigating combined sewer overflow impacts was conducted between 2010 and 2012 by the New York City Department of Environmental Protection. The NYCDEP blue-roof projects are the first to utilize a novel passive blue roof tray design which relies on the lateral transitivity of non-woven filter fabric for drawdown control in a full scale pilot. Monitoring of these systems has demonstrated their performance as an effective means for mitigation of peak flows and alteration of timing in combined sewer systems. [5]

Water scarcity

On the opposite side of the spectrum, cities with limited rainfall are vulnerable to drought and extended periods of restricted water usage. [6] In drier climates, blue roofs act as a water conservation tool harvesting the water that falls on a roof's surface and collecting it at a controlled rate.

Design compatibility

Another major benefit of blue roofs are their ability to work alongside other rooftop systems such as solar panels (both solar thermal and pv), and HVAC mechanical equipment.

Some recreational blue roofs integrate rooftop waterplay areas that can also be used to irrigate a green roof, or to cool the roof of a building on hot days, in order to eliminate or at least reduce the HVAC load placed on mechanical refrigeration equipment.

Some blue roofs utilize stored water for beneficial on-site purposes cooling of solar panels and irrigation of a green roof. One example of a blue roof that provide ancillary services was the winning entry (First Place, 10,000 Euro prize) in the 2004 Coram Sustainable Design Award, by Steve Mann. [7]

Types

Active blue roof

Active blue roof systems control the rate at which water drains from a rooftop through mechanical means. Sometimes referred to as automated roof runoff management systems, active blue roofs use valve configurations and controls to monitor and regulate the discharge of stormwater runoff from roofs. Water ponded on the roof can be released in several ways, including via a pneumatically or hydraulically actuated pinch valve, [2] an electronically controlled valve connected to a timer, or manually opening the valve. Active blue roofs for stormwater detention using forecast integration were first proposed in 2008. [8]

Passive blue roof

Passive blue roof systems control the rate at which water drains from a rooftop through non-mechanical means. Unlike active systems which inhibit water flow through drainage pipes, passive systems temporarily detain water on the surface of the roof by lengthening the path the water must take in order to reach outlet drains. Blue roofs can include open water surfaces, storage within or beneath a porous media or modular surface, or below a raised decking surface or cover. [9]

Blue colored roof

A different type of "blue roof" has been proposed by researchers at the Lawrence Berkeley National Laboratory, who researched a pigment used by the ancient Egyptians known as "Egyptian blue." [10] [11] This color, derived from calcium copper silicate, absorbs visible light, and emits light in the near-infrared range, helping keep roofs and walls cool. [11] [12]

See also

Related Research Articles

<span class="mw-page-title-main">Stormwater</span> Water that originates during precipitation events and snow/ice melt

Stormwater, also written storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil (infiltrate) and become groundwater, be stored on depressed land surface in ponds and puddles, evaporate back into the atmosphere, or contribute to surface runoff. Most runoff is conveyed directly as surface water to nearby streams, rivers or other large water bodies without treatment.

<span class="mw-page-title-main">Green roof</span> Roof that is covered with vegetation and a growing substrate

A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. Container gardens on roofs, where plants are maintained in pots, are not generally considered to be true green roofs, although this is debated. Rooftop ponds are another form of green roofs which are used to treat greywater. Vegetation, soil, drainage layer, roof barrier and irrigation system constitute the green roof.

<span class="mw-page-title-main">Storm drain</span> Infrastructure for draining excess rain and ground water from impervious surfaces

A storm drain, storm sewer, surface water drain/sewer, or stormwater drain is infrastructure designed to drain excess rain and ground water from impervious surfaces such as paved streets, car parks, parking lots, footpaths, sidewalks, and roofs. Storm drains vary in design from small residential dry wells to large municipal systems.

<span class="mw-page-title-main">Permeable paving</span> Roads built with water-pervious materials

Permeable paving surfaces are made of either a porous material that enables stormwater to flow through it or nonporous blocks spaced so that water can flow between the gaps. Permeable paving can also include a variety of surfacing techniques for roads, parking lots, and pedestrian walkways. Permeable pavement surfaces may be composed of; pervious concrete, porous asphalt, paving stones, or interlocking pavers. Unlike traditional impervious paving materials such as concrete and asphalt, permeable paving systems allow stormwater to percolate and infiltrate through the pavement and into the aggregate layers and/or soil below. In addition to reducing surface runoff, permeable paving systems can trap suspended solids, thereby filtering pollutants from stormwater.

<span class="mw-page-title-main">Rainwater harvesting</span> Accumulation of rainwater for reuse

Rainwater harvesting (RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit, aquifer, or a reservoir with percolation, so that it seeps down and restores the ground water. Rainwater harvesting differs from stormwater harvesting as the runoff is typically collected from roofs and other area surfaces for storage and subsequent reuse. Its uses include watering gardens, livestock, irrigation, domestic use with proper treatment, and domestic heating. The harvested water can also be committed to longer-term storage or groundwater recharge.

<span class="mw-page-title-main">Balancing lake</span> Element of flood management system

A balancing lake is a term used in the U.K. describing a retention basin used to control flooding by temporarily storing flood waters. The term balancing pond is also used, though typically for smaller storage facilities for streams and brooks.

<span class="mw-page-title-main">Detention basin</span> Flood control measure

A detention basin or retarding basin is an excavated area installed on, or adjacent to, tributaries of rivers, streams, lakes or bays to protect against flooding and, in some cases, downstream erosion by storing water for a limited period of time. These basins are also called dry ponds, holding ponds or dry detention basins if no permanent pool of water exists.

<span class="mw-page-title-main">Retention basin</span> Artificial pond for stormwater runoff

A retention basin, sometimes called a retention pond,wet detention basin, or storm water management pond (SWMP), is an artificial pond with vegetation around the perimeter and a permanent pool of water in its design. It is used to manage stormwater runoff, for protection against flooding, for erosion control, and to serve as an artificial wetland and improve the water quality in adjacent bodies of water.

<span class="mw-page-title-main">Combined sewer</span> Sewage collection system of pipes and tunnels designed to also collect surface runoff

A combined sewer is a type of gravity sewer with a system of pipes, tunnels, pump stations etc. to transport sewage and urban runoff together to a sewage treatment plant or disposal site. This means that during rain events, the sewage gets diluted, resulting in higher flowrates at the treatment site. Uncontaminated stormwater simply dilutes sewage, but runoff may dissolve or suspend virtually anything it contacts on roofs, streets, and storage yards. As rainfall travels over roofs and the ground, it may pick up various contaminants including soil particles and other sediment, heavy metals, organic compounds, animal waste, and oil and grease. Combined sewers may also receive dry weather drainage from landscape irrigation, construction dewatering, and washing buildings and sidewalks.

The United States Environmental Protection Agency (EPA) Storm Water Management Model (SWMM) is a dynamic rainfall–runoff–subsurface runoff simulation model used for single-event to long-term (continuous) simulation of the surface/subsurface hydrology quantity and quality from primarily urban/suburban areas.

<span class="mw-page-title-main">Rain garden</span> Runoff reducing landscaping method

Rain gardens, also called bioretention facilities, are one of a variety of practices designed to increase rain runoff reabsorption by the soil. They can also be used to treat polluted stormwater runoff. Rain gardens are designed landscape sites that reduce the flow rate, total quantity, and pollutant load of runoff from impervious urban areas like roofs, driveways, walkways, parking lots, and compacted lawn areas. Rain gardens rely on plants and natural or engineered soil medium to retain stormwater and increase the lag time of infiltration, while remediating and filtering pollutants carried by urban runoff. Rain gardens provide a method to reuse and optimize any rain that falls, reducing or avoiding the need for additional irrigation. A benefit of planting rain gardens is the consequential decrease in ambient air and water temperature, a mitigation that is especially effective in urban areas containing an abundance of impervious surfaces that absorb heat in a phenomenon known as the heat-island effect.

<span class="mw-page-title-main">Surface runoff</span> Flow of excess rainwater not infiltrating in the ground over its surface

Surface runoff is the unconfined flow of water over the ground surface, in contrast to channel runoff. It occurs when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the soil is saturated by water to its full capacity, and the rain arrives more quickly than the soil can absorb it. Surface runoff often occurs because impervious areas do not allow water to soak into the ground. Furthermore, runoff can occur either through natural or human-made processes.

<span class="mw-page-title-main">Sustainable drainage system</span> Designed to reduce the potential impact of development

Sustainable drainage systems are a collection of water management practices that aim to align modern drainage systems with natural water processes and are part of a larger green infrastructure strategy. SuDS efforts make urban drainage systems more compatible with components of the natural water cycle such as storm surge overflows, soil percolation, and bio-filtration. These efforts hope to mitigate the effect human development has had or may have on the natural water cycle, particularly surface runoff and water pollution trends.

<span class="mw-page-title-main">Green infrastructure</span> Sustainable and resilient infrastructure

Green infrastructure or blue-green infrastructure refers to a network that provides the “ingredients” for solving urban and climatic challenges by building with nature. The main components of this approach include stormwater management, climate adaptation, the reduction of heat stress, increasing biodiversity, food production, better air quality, sustainable energy production, clean water, and healthy soils, as well as more anthropocentric functions, such as increased quality of life through recreation and the provision of shade and shelter in and around towns and cities. Green infrastructure also serves to provide an ecological framework for social, economic, and environmental health of the surroundings. More recently scholars and activists have also called for green infrastructure that promotes social inclusion and equity rather than reinforcing pre-existing structures of unequal access to nature-based services.

<span class="mw-page-title-main">Stormwater detention vault</span>

A stormwater detention vault is an underground structure designed to manage excess stormwater runoff on a developed site, often in an urban setting. This type of best management practice may be selected when there is insufficient space on the site to infiltrate the runoff or build a surface facility such as a detention basin or retention basin.

<span class="mw-page-title-main">Rooftop solar power</span> Type of photovoltaic system

A rooftop solar power system, or rooftop PV system, is a photovoltaic (PV) system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various components of such a system include photovoltaic modules, mounting systems, cables, solar inverters battery storage systems, charge controllers, monitoring systems, racking and mounting systems, energy management systems, net metering systems, disconnect switches, grounding equipment, protective devices, combiner boxes, weatherproof enclosures and other electrical accessories.

<span class="mw-page-title-main">Water-sensitive urban design</span> Integrated approach to urban water cycle

Water-sensitive urban design (WSUD) is a land planning and engineering design approach which integrates the urban water cycle, including stormwater, groundwater, and wastewater management and water supply, into urban design to minimise environmental degradation and improve aesthetic and recreational appeal. WSUD is a term used in the Middle East and Australia and is similar to low-impact development (LID), a term used in the United States; and Sustainable Drainage System (SuDS), a term used in the United Kingdom.

<span class="mw-page-title-main">Water storage</span> Storage of water by various means

Water storage is a broad term referring to storage of both potable water for consumption, and non potable water for use in agriculture. In both developing countries and some developed countries found in tropical climates, there is a need to store potable drinking water during the dry season. In agriculture water storage, water is stored for later use in natural water sources, such as groundwater aquifers, soil water, natural wetlands, and small artificial ponds, tanks and reservoirs behind major dams. Storing water invites a host of potential issues regardless of that water's intended purpose, including contamination through organic and inorganic means.

<span class="mw-page-title-main">Low-impact development (U.S. and Canada)</span>

Low-impact development (LID) is a term used in Canada and the United States to describe a land planning and engineering design approach to manage stormwater runoff as part of green infrastructure. LID emphasizes conservation and use of on-site natural features to protect water quality. This approach implements engineered small-scale hydrologic controls to replicate the pre-development hydrologic regime of watersheds through infiltrating, filtering, storing, evaporating, and detaining runoff close to its source. Green infrastructure investments are one approach that often yields multiple benefits and builds city resilience.

Rainwater management is a series of countermeasures to reduce runoff volume and improve water quality by replicating the natural hydrology and water balance of a site, with consideration of rainwater harvesting, urban flood management and rainwater runoff pollution control.

References

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  2. 1 2 "Rooftop Detention (Blue Roofs)". prj.geosyntec.com. Archived from the original on 2016-10-24. Retrieved 2019-12-13.
  3. "Roofing and Plumbing Solutions" . Retrieved October 17, 2014.
  4. "NYC.gov Blue Roof". Archived from the original on February 13, 2013. Retrieved August 20, 2012.
  5. "Roofing Magazine" . Retrieved May 21, 2014.
  6. Nagourney, Adam (2015-04-01). "California Imposes First Mandatory Water Restrictions to Deal With Drought". The New York Times. ISSN   0362-4331 . Retrieved 2019-12-13.
  7. "Blue Roofs". Experiential Design Lab. December 17, 2004.
  8. Quigley, Marcus; Rangarajan, Sri; Pankani, Daniel; Henning, Dawn (2008). "New Directions in Real-Time and Dynamic Control for Stormwater Management and Low Impact Development". World Environmental and Water Resources Congress 2008. pp. 1–7. doi:10.1061/40976(316)29. ISBN   978-0-7844-0976-3 . Retrieved February 17, 2016.
  9. "Boca Raton Roofing Company".
  10. "Egyptian Blue for Energy Efficiency". Lawrence Berkeley Laboratory Heat Island Group. October 9, 2018. Retrieved 2018-10-14.
  11. 1 2 "World's 1st artificially-made pigment Egyptian blue, can help produce solar energy". India Today. October 11, 2018. Retrieved 2018-10-14.
  12. "Scientists give solar PV a paint job". PV magazine USA. October 9, 2018. Retrieved 2018-10-14.