Interview with Joost de Gier - our long-term business partner

Posted by Ana Obreza on Apr 5, 2022 9:08:35 AM


Joost de Gier is our long-term and very valuable business partner, who has been involved with Urbanscape® from the beginning. He has been in the industry since he was 14 years, active in sales of green roofs in Europe for the last 12 years. He says that every green roof is different, but things which are often taken into account are: weight, angle, water retention and plant selection.  

1. Sempergreen has its focus on Green Roof Industry. How would you describe your experiences in that sector? (years, special experiences, educated staff etc.)
Sempergreen itself is family-owned company, just like Knauf. The company was founded in 1996 and has been 26 years active in the market. I’ve been involved with Sempergreen since I was 14 years old. At that time I worked here on Saturdays and Holidays to earn some extra pocket money. After I finished my studies I worked somewhere else, but it didn’t take long before I ended up working with Sempergreen again. It’s just a really great company to work at, with products I can 100% stand behind. By now I’ve been 12 years active in the sales of green roofs in Europe.

2. Out of your perspective, what is the most important in the area of Green Roofing Industry?
When I just started working at Sempergreen, people frowned when I explained I was working in the green roof industry. They didn’t know what it was and were quite sceptical about the product. Nowadays green roofs are well known and very much accepted. People now realise how important it is to improve the biodiversity in our living environment.

Joost de Gier, Sempergreen

3. When selecting the type of green roof to be installed to a specific object, what are the most important criteria for selection?
Every roof and project is different, but things which are often taken into account are: weight, angle, water retention and plant selection. The load baring capacity and angle of a roof determines what kind of green roof can be placed on the building. The type of plants that you wish to place on the roof also determine the weight of the whole green roof system. And you also need to take into consideration what amount of rainwater your roof project is obliged to buffer in compliance with the local stormwater ordinance.

4. What needs to be taken into consideration when trying to establish a Green Roof which will perform well, look nice, do its job also after 5-10 years?
You need to understand that a roof is not a natural environment. The climate there is more harsh than on ground level. Its hotter, dryer, windier and often you have less growing medium in place compared to normal soil in, let’s say, a garden. This means that the plants that live on the roof develop shorter root systems. That is why you need to select plants that naturally have shallow rooting and are still capable of surviving such harsh conditions. If you take this fact into account and you take care of your roof with proper and regular maintenance (fertilizing, removing unwanted plants, like in blown saplings or weeds, and cleaning the water runoff points), your green roof is going to last for more than 40 years.

5. One of the most important components of any Green Roof is also the type of substrate / growing media. What are your main decision criteria when choosing the type of growing media?
That is simple: does the plant want to root live and survive in it? Can it store enough water after dry periods and is it light enough to be put on a roof? If the answer is yes to all three questions you have an effective growing medium for green roofs.

6. How / what is your experience with our Urbanscape® Green Roof Systems & Urbanscape® Green Roll Growing Media? Are you regularly using our solutions?
I was involved with Urbanscape® from the beginning. In the beginning I was a bit sceptical, because not all mineral wool had been proven to be the right solution. The Urbanscape® Green Roll proved the opposite. Due to the non-binder and needle-punched mineral wool we’ve achieved stunning performances.

Topics: green roof