Green profits: how you build a photovoltaic stormwater tool with cooling biodiversity that pays for itself.

Green Roofs Make Solar Panels Work Better

No technology comes without side effects. This is also the case with photovoltaics systems which, in many studies, have been shown to increase urban heat island effects. However, combining photovoltaics with green roofs can alleviate this issue as the green roof evapotranspiration can cool the panels and the surrounding area. Add green roof stormwater detention, and you also have a clear ROI.

R and U-Values are unsuitable for measuring the thermal performance of green roofs. This is what you should do instead!

R and U-Values are Unsuitable for Green Roofs

An R- or U-value is not an optimal way to describe the ability of a green roof to manage heat energy. This is also because R and U-values are static and do not incorporate or describe the heat loss from the living part of the roof: the plants. Hence, the green roof’s capacity to manage heat energy is not so much dependent on the static building components but on the upper part of the profile where water is evapotranspired – especially during wet and hot conditions. The energy lost via evapotranspiration is much more difficult to calculate and describe than the static R and U-values and involves dynamic modeling.

R and U-Values are Unsuitable for Measuring Thermal Performance of Green Roofs

The Purple-Roof concept is a stormwater tool that doubles as a green roof! The concept provides both stormwater retention and detention.

A Stormwater Tool that Doubles as a Green Roof!

The Purple-Roof concept is far from a simple green roof upgrade. It might be clearer to describe the Purple-Roof concept as a stormwater tool that doubles as a green roof. The concept provides both stormwater retention and detention and thus fulfills the civil engineer’s requirements for stormwater management.

Generally, the main reason for installing a Purple-Roof compliant system is that you can reduce or even remove at-grade stormwater solutions and free up floor space for income-generating development. You are managing your stormwater on an otherwise unused and neglected area: the roof. Hence, there is a strong business case in densely populated urban areas where land is expensive.

Then add all the benefits you get from a green roof, such as cooling, reduced energy needs, pollution capture, increased biodiversity, and LEED points, and you also get a much better-looking roof.

Green roof detention can help reduce pressure on at-grade green stormwater solutions preventing blow-outs and increasing performance.

Roof-to-Ground: Green Roof Detention Treatment Train

A treatment train is a sequence of stormwater treatments designed to maximize results in a specific environment. This means that we need to take a step back to get a good overview and see how we can connect different stormwater solutions to reestablish the natural hydrologic cycle. This is especially important for the city/municipality as it will further assist the city in reducing stormwater treated by the sewage treatment plants and reducing combined sewer overflows.
One such example could be to combine detention-type green roofs with bioretention ponds or bioswales to create a green stormwater infrastructure treatment train.

How Green Roof Detention can Improve the Functionality of At-Grade Green Stormwater Infrastructures

Green roofs very rarely get pests and if they do, it is mostly because the roof was in poor shape: a case study.

How to prevent green roof bug infestations

Green roofs rarely get pest and bug infestations and if they do, it is because the vegetation was in bad shape e.g. wrong watering regimes or too little nutrients. Pests on green roofs are avoidable by keeping your vegetation strong and healthy.

A detention-based green roof system can kick out your at-grade stormwater tank and free up space. Learn how!

How Does the Purple-Roof Concept's Detention Layer Work?

A detention-based green/vegetated roof slows the outflow of water also when the green roof is soaked with water from a previous rainfall. This slowing down of water, or stormwater detention, is analogous to the functionality of a bioretention cell where water is collected and the peak outflow is reduced and delayed in order to prevent flooding damages.

By investing $121,500 on green roof stormwater management, the developer was able to sell two additional units for a total of $1,800,000.

Economic Case Study: Vegetated Roof ROI

ECONOMIC CASE STUDY: A project always needs a stormwater plan to protect the property and the city from the devastating effects of flooding. These solutions must work every single time and must be completely independent of the health of the greenery, or the saturation status of the green roof.  By investing $121,500 to manage the stormwater on the roof, the developer was able to sell two additional units for a total of $1,800,000.

Economic Case Study: Green Roof ROI

Detention-type green roofs can replace stormwater tanks and cisterns and ensure that max allowable outflow rates are met. Learn more...

Novel Flooding Prevention using Green Roofs

Water is a precious resource and should be treated as such. In many urban areas, water is merely viewed as a problem, and any precipitation is rapidly expedited out of the city in a gray infrastructure network of pipes and sewers. We can do better! We can also do it cheaper. Green roofs are nature-based solution that can provide this much needed support for urban areas.

Green roof color patterns can look wonderful, but do they last? Learn more about the associated maintenance requirements and costs.

Green Roof Color Patterns: Maintenance & Cost

Green roof color patterns can look amazing, but we need to manage expectations; these are living systems, and as the plants grow, develop, and die back, the designs are bound to change unless we put up a big fight against this natural change.

Urban canyons trap air pollutions at street level causing bad health and exacerbate heat island effects. Green infrastructure is a solution.

How Green Infrastructure Reduce Urban Canyon Effects

Green infrastructure provides a high surface area for pollution deposition, acts as a permeable barrier, and can alter local air dispensation patterns. However, the real impact of green infrastructure on air quality is complex and is depending on a range of parameters such as local meteorological conditions, urban canyon geometry, and vegetation characteristics such as geometry and transpiration rates.

How Green Infrastructure Affects Urban Air Quality

Learn more about vegetated roofs and nutrient leaching: a summary of current research with academic references.

Do Green Roofs Leach Nutrients?

Green roofs are engineered ecosystems with unique nutrient cycling characteristics compared to natural systems. This uniqueness is due to the designed and selected components that have not co-evolved over long periods of time. Hence, direct comparisons with the nutrient dynamics of natural systems can be flawed, which is why green roofs deserve, and require, further dedicated research attention to develop best practices for our current and future cities.

Green Roof Nutrient Leaching

If evapotranspiration is the objective, what plants are the best choice? Evapotranspiration is the amount of water the soil and plants can r

Choosing Plants for a High-Retention Green Roof

Evapotranspiration is the amount of water the soil and plants can release in vapor form. In order to optimize green roof evapotranspiration, which plants are the best choice?

Plant Selection for a High-Retention Green Roof

Learn the basics of a green roof/living roof carbon budget. What items must be considered and how do roof systems differ in their footprint?

Green Roof CO2 Capture Explained

Green roof carbon budgets: vegetated roofs capture CO2. But how much CO2 can they really capture? What numbers do we land on when we do a carbon budget that considers the whole manufacturing and transport chain?

How Much CO2 is Captured by a Green Roof?

This green roof guide focuses on the main functionalities that you need to be aware of before successfully installing a vegetated roof.

Green Roof Guide: How to Select your Vegetated Roof

Guide to green roofs – what is the most optimal type of vegetated roof for your construction project? Living roofs and facades help create a more decent living environment in our present, and future cities. But you need to choose the right roof for the right place.

Urban heat islands linked to the release of air pollutants from asphalt and bare roof coverings. Green roofs are a mitigant.

Heat Islands: Bare Roofs Release Pollutants

Urban Heat Islands can cause asphalt and roof coverings to release more secondary organic aerosols (SOA) than road traffic. Cars still release the most pollutants overall, but the SOA produced from rooftops and asphalt is significant and has, until now, largely gone unreported.
This study is yet another argument for implementing green infrastructure such as vegetated, green roofs to cool our cities, restore the natural water cycle, and improve biodiversity.

Heat Islands Cause Bare Roofs to Release Air Pollutants

The benefits of a green roof are not limited to environmental matters. Living roofs also provide economic, health, and social advantages.

Top 10 Benefits of a Green Roof

It is no surprise that green roofs provide environmental benefits, but did you know they can provide economic, health, and social benefits as well? A green roof is an excellent investment that will ultimately pay for itself. By adding a vegetated roof to the city you are able to cut cost related to energy usage, contribute to the reversal of the urban heat island effect, reduce ambient noise, increase biodiversity, increase your roofing membrane’s lifespan, naturally filter the air, and even find new hobbies to decrease stress. From the well-known benefit of stormwater management to the unfamiliar tax credits, read about all the perks provided by living roofs.

These are the Top Benefits of a Green Roof

These are the main challenges to green roof biodiversity.  Which are the most effective methods to increase urban biodiversity fast?

Top Green Roof Biodiversity Challenges

What about green roof biodiversity? A sedum extensive green roof is much more diverse and brings so many ecological benefits ranging from stormwater to cooling, to pollution capture compared with a black or white roof. Sure, it might not be perfect, but the comparison should not be to that of natural forests, but to a black, virtually sterile roof. If our target is to green our cities quickly, we need to be less stuck in dichotomous thinking and go for the methods that are tried and tested and that we know work. Sometimes this means installing a super diverse intensive green roof, and sometimes, this is a thin extensive sedum roof. Both increase urban biodiversity.

Is Green Roof Biodiversity Important?

Here we compare retention and detention. Dick explains why detention is a more reliable tool for stormwater management.

What is green roof stormwater detention?

Detention is water temporarily held by the green roof that flows out at a later time. Why is this important? This manages stormwater run off by reducing/ delaying peak flow rates. Effects from runoff include infrastructure damage, over flowing pipes and sewers, flooding, and erosion. In this video, Dick and Joep compare and contrast retention and detention strategies for managing stormwater runoff. The models help demonstrate the effects of urban stormwater discharge.

What is Green Roof Stormwater Detention?

How green roof retention is currently tested and how this can be a misrepresentation of real-world retention values.

Best Methods to Test Green Roof Retention

What is retention? It is the process of holding water on the green roof, also known as evapotranspiration.  In this video, Joep and Dick use models to explain how the ASTM-E2399 test is used to measure retention. The ATSM test actually measures the maximum weight of the green roof. Why is this important? This is one way to reduce runoff and increase cooling potential.

Are you considering a green roof? Learn about green roofs, their history, benefits to the environment,  and the installation process.

8 Green Roof Myths Exposed

Whether you know them as green roofs, living roofs vegetated roofs, or eco-roofs they are tied to many misconceptions. Many people worry that intensive and extensive green roofs are too expensive, they have many faults that will cause roof damages, they cannot be protected by a warranty, they can be installed by anyone, and they do not have much research conducted on them. After some analysis, you will realize the idea of green roofs is simpler than the misconceptions lead on.

Learn About the Top 8 Green Roofs Myths

Soil poorly distributes water on green roofs. A combination of needled mineral wool and soil solves this issue and reduces irrigation needs.

How To Minimize Green Roof Irrigation

Green Roof Diagnostics laboratory has tested over 800 different green roof profiles over the last 2 years, and many of them showcase that green roof soil, in particular, is a funny product that is not always very good at managing water, or better said it doesn’t compensate for uneven rainfall distribution very well.

Minimize Green Roof Irrigation

A sustainable city limits urban sprawl and uses green infrastructure to add back green areas needed for air quality and stormwater control.

Green infrastructure for Sustainable Cites

A sustainable city is densely populated. This might appear counterintuitive, but the current urban sprawl weighs heavily on both environment and the economy. A more densely populated city will allow for more effective land use and reduce pressure on surrounding agricultural, recreational, and wild surrounding lands. Green infrastructure can be used to add back green areas to the cityscape in a cost, and space-effective manner.

Green roof spring maintenance - a quick guide for a lush, healthy, and highly functional living roof!

Green Roof Spring Maintenance

An extensive green roof requires very little maintenance, but a green roof is still a living thing in need of some tender loving care, especially after the long and cold winter. Read more in this quick guide!

Spring Maintenance for Green Roofs

Green infrastructure is slowly replacing old and outdated grey stormwater water management and is often the financially sensible solution.

Do you want green stormwater management with an ROI?

Stormwater management is needed to prevent flooding, erosion, pollution of water, to appropriately refill our aquifers, and to reduce habitat degradation. Stormwater management is particularly important in urban areas where most surfaces are impervious and do not absorb much water.  Green infrastructure and green roof stormwater management are replacing old & outdated grey infrastructure.

Green & Grey Stormwater Management Options

How can we mainstream nature-based solutions such as green roofs through economic incentives, communication, and research?

Are Green Roofs Nature-Based Solutions?

Green roofs are a type of nature-based solution as we let nature work for us instead of against us. How can we work on mainstreaming these natural solutions and make them financially attractive and widely accepted? We interviewed Dr. Helen Toxopeus from Utrecht Sustainable Finance Lab.

Green Roofs as Nature-Based Solutions

What is retention? Green roof stormwater management comes in two parts: retention and detention.  Retained water never leaves as runoff...

What is Green Roof Retention and why is it Important?

Green roof stormwater management  is made up of retention and detention. What is vegetated roof retention? Retained water leaves as vapor through evapotranspiration and detained water is slowed down runoff...

What is Green Roof Retention and Why is it Important?

Learn the difference between green roof retention and detention in this article and short explainer video.

What is the Difference Between Retention and Detention?

The difference between green roof retention and detention is the direction of the water. Retained water returns to the air as vapor and detained water is slowing down runoff.  Learn more about these hydrological vegetated roof  terms in this video article!

What is the Difference Between Green Roof Retention and Detention?

Find out when a detention roof, e.g. a Purple-Roof, is a perfect stormwater solution for your project.

Is a Detention Roof a Good Fit for Your Project?

Detention roofs are excellent stormwater management tools and provide all the benefits of a green roof. Purple-Roof also provides a clear green roof ROI. However, not all projects are suitable. Find out more!

Does a Detention Roof Make Sense for Your Project?

Blaue, Blau-Grüne Dächer und Purple-Roof (in Deutschland: Detention Roof) sind Lösungskonzepte zur Detention - Wahre Starkregenmanagement!

Top 3 Detention Roofs auf dem Markt

Wussten Sie, dass Sie mithilfe Ihres Daches Wasser zurückhalten können? Blaue, Blau-Grüne Dächer und Purple-Roofs/Detention Roof sind Lösungskonzepte zur Detention, die auch Ihre Anforderungen ans Regenwassermanagement erfüllen und Grüne Kapitalrendite generieren!

Blaudächer, Blau-Grüne Dächer und Purple-Roof sind alle Detention Roofs

Green roof research is moving fast forward! These are the latest advancements in the field of green stormwater management.

Advancements in Green Roof Research

Green roof research shows that traditional green roofs have many benefits, but they are unreliable stormwater management tools. Detention roofs can provide stormwater management as well as the green benefits of traditional green roofs.

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