The technical aspects of green renovation: flat roofs

Architects, gardeners, landscapers, and roofers from all over the world know how to find Sempergreen for greening buildings. Fortunately, they involve us earlier and earlier in the renovation or design process. After all, there are several factors to consider when installing a green roof or living wall. The earlier this is done in the design phase, the easier it is to install the greenery later in the project.

Max de Vos, working in Research & Development at Sempergreen, is a specialist in the technical aspects of green renovation. In a series of articles, Max shares his knowledge. In this article, Max talks more about renovating flat roofs.

Early collaboration leads to best results!

Green renovation on flat roofs offers huge benefits but also challenges that are crucial for architects, landscapers, and roofers to consider at an early stage. Avoiding surprises later in the process is best achieved by seeking collaboration early on. Our experienced specialists can help find solutions to challenges you may encounter on your project. This article highlights the technical aspects of green renovation on flat roofs and shows why it can be valuable to work closely with our experts from the start.

What questions are important in the design phase?

How strong is the flat roof to be renovated? Will the entire roof be renovated or built on an existing structure? Of course, it is very important to know how much weight the flat roof can handle. But the very first question is obviously ‘what will be the functions of the flat roof to be renovated?’. Is the roof going to be used intensively? Will it be a so-called living roof or will it be used for water storage, for example? Will the roof be visible and from where? What is the role of sustainability and, last but not least, what is the financial scope for the flat roof to be renovated?

All these questions lead to the best possible solution. For this reason, our Sempergreen specialists like to get involved early in the design phase. Together, we will create a beautiful green roof that will last for years and years.

Bearing capacity: how much weight can my flat roof support?

Sempergreen has many different green roof solutions in its portfolio and these also have different weights. When it comes to a water-storing green roof system, a fully water-saturated roof will have a large weight, which obviously needs to be taken into account in the design phase. If there is a need to collect water for sustainability purposes, we can provide several solutions to meet this demand, like the Purple-Roof. Want to know more about roof water storage? We will soon discuss this subject of water retention in a new article. So keep an eye on the news on our website!

Irrigation: easy construction and management on flat roofs

Naturally, you desire your flat green roof to remain beautiful at all times. By nature, Sedum plants are quite resilient in prolonged dry conditions. However, sometimes architects, landscapers, gardeners, or roofers opt to install an irrigation system regardless. This could be due to the size of the flat roof. It might also be pertinent for housing associations where the question ‘who is responsible and where does the water come from?’ frequently arises. A significant advantage of flat roofs over pitched roofs is the simplicity of constructing and managing irrigation systems. While irrigation on sloping roofs can be somewhat more complex, flat roofs allow for more efficient and straightforward independent management. For large projects, it is thus crucial to decide in advance whether an irrigation system should be directly incorporated into the design and construction.

Maintenance: twice a year in spring and fall

Maintenance is also straightforward with a Sempergreen flat green roof. Most flat green roofs are accessible by foot, making them easy to maintain. We recommend maintenance twice a year, in both spring and fall. This maintenance involves removing unwanted vegetation that birds or wind have carried onto the roof, fertilizing the vegetation to ensure the plants are robust and healthy and to minimize the opportunity for grasses, and addressing any areas where plant growth has been less successful. Interested in learning more about flat green roof maintenance? Contact us!

Vegetation choice: consider the load-bearing capacity of the roof

The load-bearing capacity of flat roofs is, as mentioned, a critical factor. The choice of vegetation impacts the weight of the green roof. The general rule is: the greater the diversity and growth height of the plants, the higher the weight per square foot.

Hail and snow, thunderstorms, wind, rain, and heat

No worries! All Sempergreen products designed for greening flat roofs can withstand nearly all types of weather. Because we cultivate globally, this applies to all weather conditions we encounter. Due to climate change, extreme rain showers are becoming more common. Heavy rainfall that previously occurred only once every 50 or 100 years is now happening more frequently. These large volumes of water create peak loads on sewers and drainage systems, and this issue is only expected to increase in the future. To prevent flooding from excess rainwater, green roofs are an ideal solution. You will soon read more about the solutions we offer for collecting and channeling large amounts of water.

Regarding wind, Sempergreen’s products are also highly resistant. When a green roof covers a very large area (e.g., in large shopping centers, sports arenas, or conference centers), it is wise to consult our specialists on this matter well in advance. There are effective solutions for eliminating any risk of wind uplift, and the earlier these are considered in the process, the simpler they will be to implement.

Lastly, a green roof also significantly reduces the ambient temperature. Large cities and densely built-up areas suffer from the so-called urban heat-island effect, ‘islands’ where the temperature is considerably higher due to the abundance of buildings and the severe lack of cooling nature. The more green roofs we can establish together, the greater our impact on urban temperatures. All the small, green islands combined are a formidable combatant in the climate crisis.

So what are the technical advantages of a flat green roof?

As you have read above, green roofs have a positive impact on the urban heat-island effect. But green roofs also positively affect the thermal regulation of buildings. The additional layer of greenery can provide cooling in summer. Moreover, green roofs can extend the lifespan of the roof by up to 60 years, which naturally ensures that a renovation incorporating greenery is also technically much more sustainable than one without. Interested in how we can best advise you? Then contact us here without any obligation.

Green, greener, greenest.

Integrating solar energy with green roofs is an emerging trend that we at Sempergreen lovingly embrace. After all, we aim to green our beautiful planet, and that means more than just making roofs and facades literally green. We believe sustainable energy is also very important. Do not hesitate to contact us if you want to know more about these kinds of solutions.

Conclusion

Green renovation of flat roofs requires a detailed approach and early cooperation between architects, landscapers, roofers, gardeners, and our Sempergreen specialists. By paying attention to bearing capacity, technical details, water management, irrigation, maintenance, vegetation choice, solar energy, and financial aspects, surprises can be avoided and sustainable, (multi-)functional green roofs can be realized. Renovation with a flat green roof is an investment in the future that will pay off in many ways. Find out who all actually benefits from a green roof or green facade here.