Purple-Roof

Purple-Roof

Purple-Roof, the definitive Green Roof podcast! Audio articles and interviews with the brightest minds in the field.

For a GREEN future! We are critically investigating all aspects of green roofs ranging from Economy, to Ecology, and Society.

All Episodes

Want to learn more about vegetated roof detention and retention research? We met with Dr. Anna Zakrisson from the green roof laboratory of Green Roof Diagnostics in Culpeper, Virginia. Short version. Full interview: https://youtu.be/qot1KpJIjPc Green Roof Diagnostics: https://www.greenroofdiagnostics.com Dr. Anna Zakrisson, was interviewed for Purple-Roof by Folkert Tempelman from Studio Piso7. These are the latest advancements in green infrastructure stormwater management. Zakrisson is part of a team of green roof researchers investigating and improving green roofs. Their main focus so far has been stormwater management. Detention green roofs can reduce or replace grey infrastructure stormwater management solutions such as tanks and cisterns. _____ Green & Grey Stormwater Management Options https://www.purple-roof.com/post/what-stormwater-management-options-are-there How to Manage Stormwater with Green Infrastructure https://www.purple-roof.com/post/green-infrastructure-stormwater-management _____ Feel free to embed these videos on your website. They are for educational purposes.

Mar 2020

19 min 36 sec

We met with water resilience expert Nanco Dolman in Amsterdam. Nanco Dolman is a leading professional in Water Resilient Cities at Royal HaskoningDHV and has long experience in both disaster water management, for example storm Sandy, as well as in preventative measures. Nanco shares with us a very interesting perspective and some visions of how our future cities could look like and function with regard to water management. The main message is to see water as a resource and work *with it* and not against it. Follow Nanco on LinkedIn https://www.linkedin.com/in/nancodolman/?locale=nl_NL Read about green infrastructure stormwater management: https://www.purple-roof.com/post/green-infrastructure-stormwater-management Visit Purple-Roof HOME: www.purple-roof.com _____ Nanco was interviewed by Folkert Tempelman from Studio Piso7 https://piso7.studio/ Idea & Concept: Anna Zakrisson https://annazakrisson.com/ Jingle: Joa Helgesson http://joahelgesson.net/

Dec 2019

23 min 32 sec

We interviewed Dr. Helen Toxopeus, a researcher at Sustainable Finance Lab, Utrecht University on the importance of green roofs / vegetated roofs as nature-based solutions. Toxopeus is involved in the EU-wide project Naturvation, a project with the aim to assess what nature-based solutions can be achieved in cities, and what tools are required to realize urban sustainability goals. https://naturvation.eu/home Also, we wanted to understand more about the financial aspects of installing green roofs: what financial incentives are there available in the EU region? Folkert Tempelman from Studio Piso7 conducted the interview on behalf of Purple-Roof. Purple-Roof website: https://www.purple-roof.com/

Dec 2019

20 min

What Is A Combined Sewer? written and narrated by Dr. Anna Zakrisson ____ Does your city smell of poo from time to time? It is quite likely that you have felt a whiff of such unpleasant odors after heavy rain events. But, have you ever stopped and asked yourself why this happens? You might not like the answer… The reason is: overflowing combined sewers. Find out how green roofs can help to mitigate this serious problem! ____ ______ Read the full article on the Purple-Roof blog: https://www.purple-roof.com/post/what-is-a-combined-sewer _______ Don't hesitate to contact us if you have any questions at info@purple-roof.com

Apr 2019

9 min 24 sec

What is green roof retention? Written by Brad Garner and narrated by Dr. Anna Zakrisson. _____ Retention is the process of holding water on the green roof, i.e., preventing water from draining off the green roof. Retention has been the focus of the hydrologic design of green roofs over the past few decades. Many people familiar with green roofs but less familiar with other types of stormwater management might not realize that most engineers consider retention the “free gift with purchase” rather than their central stormwater goal. So, what is this odd thing, retention? The secret of green roof water retention is green Retention works like this: rain falls onto a relatively dry green roof, and the green roof absorbs the water, usually in pore spaces. Later, the sun comes out, and the plants use the rainwater to evapotranspire. This means that the water leaves the roof as vapor. Eventually, it rains again, and the process is repeated. A surprising amount is going on there. Let’s unpack it! ______ Read the full article on the Purple-Roof blog: https://www.purple-roof.com/post/green-roof-water-retention _______ Don't hesitate to contact us if you have any questions at info@purple-roof.com

Mar 2019

8 min 33 sec

Green Roof Plants - How do They Survive Written and narrated by Dr. Anna Zakrisson for Purple-Roof. www.purple-roof.com/ _____ Pests and green roof plants During which parts of your life did you get the most infections? If you’d allow me to make a qualified guess, I’d probably say that it has been during times of high stress, mentally and/or physically. If we sleep little, eat poorly, and stress a lot, we tend to get sick. In a way, this is also the case for plants, through their stress looks different. Plant stress can be things like too little (or too much) water, high UV radiation, too much shade, too little (or too much) nutrients, or nutrients in the wrong ratios. Usually, one moderate stressor won’t crash a system, but if several of them come together, well, then you end up with sick plants. Often, we apply pesticides and hope for the best. However, if the stressors aren’t being dealt with, we are just postponing the situation. As an example, we were once asked to remove grubs that were eating up the green roofs in Montgomery County MD. Instead of applying pesticides, we recommended that we needed to remove plant stress. You remove plant stress, and the plants themselves can deal with the grubs. Pesticides fix the system short-term but mess it up even more long-term. Pesticides are not only expensive but end up in downstream water bodies, which may destroy local ecosystems and risk violating local environmental regulations. Furthermore, the symbiotic relationships between the plants and microbes such as mycorrhizae might be killed by broad-spectrum pesticides. Destruction of this type of symbiosis means lower water and nutrient availability for the plants, which in turn means more stress. It is like applying a band-aid on a gaping wound. We are much better off taking a close look at what is stressing the plants in the first place: let’s focus on sustainability. _____ Read the article on the Purple-Roof blog! www.purple-roof.com/post/green-roof…do-they-survive ____ Don't hesitate to contact us if you have any questions or feedback! info@purple-roof.com

Mar 2019

13 min 55 sec

Green Roof Plants - How do They Survive Written and narrated by Dr. Anna Zakrisson for Purple-Roof. www.purple-roof.com/ _____ Do green roof plants matter? Yes, absolutely! The vegetation on a green roof is a central part of the engine that drives evapotranspiration. Evapotranspiration helps to ensure efficient green roof stormwater management. Also, if the roof isn’t covered by a protective layer of vegetation, the soil might simply blow away or even flush away during a rainfall. Selecting green roof plants The choice of green roof plants is important and should be carefully considered. The layer of vegetation should be selected based on climatic region and be well-tailored to the soil. Vegetation and soil are closely linked, and healthy soil biology is essential for happy plants. If the vegetation layer crashes, the functionality of the roof is destroyed. ______ Read the article on the Purple-Roof blog! https://www.purple-roof.com/post/green-roof-plants-how-do-they-survive ____ Don't hesitate to contact us if you have any questions or feedback! info@purple-roof.com

Mar 2019

8 min 34 sec

Green Roof ROI - What's the Deal? Written by Oscar Warmerdam and narrated by Dr. Anna Zakrisson https://www.purple-roof.com/ _____ Almost all green roofs are sold in regulatory environments where there are incentives, and rebates, but mostly requirements to build green roofs. Often, the million-dollar question is dodged: “What is the real economic benefit of building a green roof?” How is it possible that in Washington DC more or less every building has a green roof, but just over the border on the other side of the street in Fairfax County one rarely sees a green roof built voluntarily? We’d like to take a close look at this from a purely economic perspective without the environmental or architectural discussion. Just the pure finance. In the end, most green roof customers are not eccentric billionaires with millions to spend on do-good stuff. Sure, it’s fantastic if we can help the environment, but to be honest, most of us simply can’t save the world on our salaries. We must get something out of the investment. However, it is possible to do good and get a return on your investment when it comes to green roofs. Continue listening to understand how! ____ Read the article on the Purple-Roof blog! https://www.purple-roof.com/post/green-roof-roi ____ Feel free to contact us if you have any questions or feedback! info@purple-roof.com

Mar 2019

11 min 23 sec

Green Roof Soil - Great Opportunities Ahead! Part 2 by Purple-Roof Written and narrated by Dr. Anna Zakrisson _____ Green roofs can retain a lot of rainwater. Small and medium storms are generally not a problem. A roof can retain about 80% of the frequency of all storms, but these storms are routine rain events, and they only make up about 50% of the total rain volume. The remnant 50% is what becomes a flooding risk. This 50% is the Achilles heel of the current green roof industry but is an issue that is intensively researched, and many ingenious solutions are about to hit the market. Extreme storms are expected to become more frequent over the years to come. Thus, if green roofs are to become the best solution for stormwater management, we need to look at these matters from many different perspectives, and that includes the often overlooked, but central, topic of soil biology. ______ Read the full article on the Purple-Roof blog: www.purple-roof.com/post/green-roof…anagement-tools _______ Don't hesitate to contact us if you have any questions at info@purple-roof.com

Mar 2019

10 min 5 sec

Green Roof Soil - Great Opportunities Ahead! Part 1 by Purple-Roof Written and narrated by Dr. Anna Zakrisson _____ Green roof soil biology – why should I care? Traditionally, green roof soil biology (or soil health) has not been considered a central factor for improving stormwater management or nutrient runoff in green roofs. This life-giving layer has merely been viewed as a compartment for water, and the intricacies and complexities of the biological systems have often been ignored. We think that this one-dimensional view results in the loss of great opportunities. We are convinced that improving the roof’s soil biology helps creates a sustainable ecosystem, which can have profound positive impacts on vegetation stability, nutrient runoff, and stormwater retention, all leading to significant cost reductions for the end user. ______ Read the full article on the Purple-Roof blog: www.purple-roof.com/post/green-roof…anagement-tools _______ Don't hesitate to contact us if you have any questions at info@purple-roof.com

Mar 2019

7 min 19 sec

Are Green Roofs True Stormwater Management Tools? Part 3 by Purple-Roof An audio article by Oscar Warmerdam ______ Detention is the process of absorbing or holding water during a storm, then slowly releasing it. Unlike retention, detention works regardless of the weather. When a detention-oriented system drains, it recharges. So, a detention-oriented green roof can recharge quickly, and be ready for the next storm, or the tail end of a large storm. Even in dark and cloudy weather! Retention cannot do this, retention takes weeks to re-charge, and it better otherwise the plants would not have enough water. Detention slows the flow of water, so that the hydrologic characteristics more closely resemble that of a forest, with peak runoff being delayed from peak rainfall. ______ Read the full article on the Purple-Roof blog: https://www.purple-roof.com/post/green-roofs-stormwater-management-tools _______ Don't hesitate to contact us if you have any questions at info@purple-roof.com

Mar 2019

5 min 31 sec

Are Green Roofs True Stormwater Management Tools? Part 2 An audio article by Oscar Warmerdam. ________ Why retention is unreliable for stormwater management at the building scale. Retention can be unreliable because it doesn’t work in repeat storms, large storms, or during cool and cloudy weather. Why? Water that is retained, by definition, leaves the green roof only via evapotranspiration. If there is no time for evaporation, such as during big storms or repeat storms, or if weather conditions do not permit much evaporation, then the retention-oriented green roof sits there like a wet sponge. 2nd-day storms may not be substantial enough on their own to cause trouble but may cause huge problems when combined with the precipitation from the first-day storm. Extra-large storms also often exceed the capacity of the green roof as they outflow with little or no delay. These types of extreme storms happen only a few times a year (5-7), but it is precisely these storms that cause flooding, pollution and river stream erosion. ________ Read the full article on the Purple-Roof blog: https://www.purple-roof.com/post/green-roofs-stormwater-management-tools ________ Don't hesitate to contact us if you have any questions! info@purple-roof.com

Mar 2019

7 min 32 sec

Are Green Roofs True Stormwater Management Tools? - Part 1 An audio article by Oscar Warmerdam. Green roofs are often sold as stormwater management tools. And that is true: green roofs do manage stormwater but mostly as a volume reduction tool. This volume reduction has huge benefits on a city scale. The benefactors are the taxpayers, citizens of what is now a city with cleaner water, and cleaner air. This is why many progressive cities have regulations in place that promote green roofs. But, if that’s the case… If green roofs are an excellent volume reduction tool on a city scale, why don’t civil engineers put one on top of every roof they can? The answer is simple but will be a surprise to most: most green roofs do not detain water well enough. Let us explain. _____ Read the article here: https://www.purple-roof.com/post/green-roofs-stormwater-management-tools _____ Don't hesitate to contact us if you have any questions at info@purple-roof.com

Mar 2019

5 min 47 sec

What is Evapotranspiration Part 2: Green roofs are tricky. On the one hand, we want evapotranspiration to be very high to get rid of stormwater as quickly as possible and prepare to absorb the next storm. On the other hand, we want the plants to conserve water to not dry out in the thin soil media between storms. We also do not want to have to irrigate green roofs to support plants. It is a challenging task to design a plant palette that minimizes the need for additional irrigation. LEED, in particular, is giving the green roof designer a tough time balancing the desire for native plants, in a very shallow soil profile, and yet at the same time forbid irrigation. This shows the importance of using different roof systems for different climates and abandoning the current strategy of one-size-fits-all for soil and vegetation. Read this article on our blog: https://www.purple-roof.com/post/what-is-evapotranspiration Don't hesitate to contact us if you have any questions, suggestions, or comments!

Mar 2019

8 min 12 sec

What is Evapotranspiration Part I: Detailed knowledge of evapotranspiration rates is essential for a successful green roof. In this audio article, we dive into the topic of evapotranspiration. If you would like to read the article, it is available here: https://www.purple-roof.com/post/what-is-evapotranspiration Evapotranspiration is merely a combination of the words: evaporation (evapo-) and transpiration (-transpiration). But what do these two terms mean? Let’s start with evaporation!

Mar 2019

7 min 2 sec