Purple-Roof Concept

12/22/2022

The Purple-Roof concept is 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.

08/25/2022

Does a detention-type green roof make sense for your project?

Detention roofs are incredible workhorses and are excellent stormwater management tools, provide all the other benefits of a green roof, and can provide a clear ROI for a green roof. However, not all projects are suitable.

In this article, we discuss the situations where a detention-type green roof, e.g. a Purple-Roof, is a great solution and where you have a lot to gain from installing one.

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

08/23/2022

Green roofs can make solar panels work better - and create an ROI!

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.

Read more in this article!

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

08/18/2022

Green roof nutrient leaching. A trending topic due to severe algal blooms in many freshwater bodies at the moment.

Should we worry about green roof nutrient runoff and what can be done to reduce leaching?

Generally, green roofs are nutrient sources during the first 6-12months of their lives due to the organic substrate component and that the plants have not yet become fully developed. This leaching is quickly reduced with age.

Good soil quality and immediate soil coverage can help.

A clever and well-thought nutrient addition program should be developed e.g. never fertilize a roof before a rainstorm and avoid adding nutrients that are not needed.

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

08/16/2022

Want to build a high-retention green roof?
Then you need to match your plant selection with your climate (if you want to avoid irrigation) and substrate type and depth.

The plants are the retention engine. If they are not transpiring the held water, it is not retained water, it is just water that doesn't drain.

What is evapotranspiration? It is a combination of the words: ev***ration (evapo -) and transpiration (-transpiration).

08/11/2022

We know that we are in the middle of summer, but here comes some important information that might help you in a few months time!

Many ask us if it is possible to install a sedum green roof in winter.

Most installations of sedum roofs are done in spring and summer, but often there isn’t any reason for this seasonality other than habit as it is possible to install extensive sedum green roofs in winter in most climates.

BUT, there are a few things to consider before you do... learn more in the article!

Winter installations of sedum roofs can be very successful. These are resilient plants. Here are a few things to consider!

08/09/2022

Purple-Roof is 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.

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

08/04/2022

CURIOUSITY 🌱
Always be curious on how to improve a system or a product - and have fun with the science and engineering along the way!

We got curious about irrigation and how to to reduce irrigation needs for green roofs.

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...

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

08/03/2022

How Does the Purple-Roof Concept Work?

As it begins to rain, the Purple-Roof concept profile slowly fills up. First, the water seeps into the soil substrate and then into the mineral wool. Due to the (toxin-free!) needled mineral wool, extra micropore space is available that ensures that more water can be held in the profile compared with substrate-only profiles.

The mineral wool also helps reducing the preferential flow paths, thus increasing the retention capacity of the vegetated roof.

Underneath the mineral wool is a honeycomb-shaped void space that can be adjusted in height depending on project-specific needs. There is no horizontal flow of water between cells. Below the honeycomb detention reservoir, the water reaches the detention layer. This is where the detention magic happens.

Read more...

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

07/28/2022

If evapotranspiration is the objective, what plants are the best choice?

Evapotranspiration is the amount of water the soil and plants can release in v***r form. Which plants are the best choice for a high-retention green roof? This is a complicated question and warrants a complex answer. Not only do your specific local climatic conditions play a role, but the plants also must match the green roof type.

For example, if you have installed a 5cm extensive profile with a highly draining substrate, you would need to go for a different plant palette than if you have installed an intensive Blue-Green roof system. To optimize evapotranspiration, you need to match water availability, local climate, plant resilience, and crop coefficients.

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

07/26/2022

How Does Purple-Roof Green Roof Hydrology Work?

Traditional green roofs capture rainwater and thus reduce runoff. Traditional green roofs work when they are mostly dry. And traditional green roofs are most efficient during warm months due to transpiring vegetation, but they are far less efficient during cool, wet weather, when the plants are dormant.

Purple-Roof is different. Purple-Roof is a concept for a vastly improved green roof that does not have the limitations above.

Fundamental to understanding the differences between Purple-Roof and traditional green roofs is understanding the differences between two common stormwater phenomena:

Retention is capturing stormwater that only leaves the roof through evapotranspiration.
Detention is temporarily holding stormwater and allowing it to flow out at a later time.

Traditional green roofs only provide retention. The Purple-Roof concept and the Blue-Green concept provide both Retention and Detention.

This is how Purple-Roof green roof hydrology works; articles and videos explaining living roof hydrology in an easy way.

07/22/2022

How to determine if a detention-type green roof is a good fit or not!

Detention green roofs are incredible workhorses and are excellent stormwater management tools, provide all the other benefits of a green roof, and can provide a clear ROI for a green roof. However, not all projects are suitable.

In this article, we discuss the situations where a detention roof, e.g. a Purple-Roof, is a great solution and where you have a lot to gain from installing one.

We also discuss where other solutions might be more suitable. In the end, we want every project to be a success and we don’t you to waste your time with technology that is not appropriate for your specific project situation.

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