Green on the roof
A green roof is really just a roof on which plants grow. This can range from sedums, herbs and low plants to shrubs and even small trees. It forms an extra green layer on top of your building that buffers water, protects the roof and adds extra nature to the environment. The green roof system allows the plants to take root properly without damaging the roof.
Green roofs come in different types. On the one hand, you have the light, simple systems with mainly sedum and low vegetation. On the other hand, there are intensive green roofs, true roof gardens. Which direction you can go depends mainly on one factor: your wishes and the load-bearing capacity of the roof. This determines how much build-up height and weight the roof can handle and thus which type of green roof is feasible.
There are different types of green roofs, each with their own construction, weight and planting.
- Extensive green roof
This is the lightest and most low-maintenance form. The roof has a thin substrate layer (about 6 to 8 cm) and is planted with sedums and low vegetation. It requires little maintenance, weighs relatively little and is suitable for most roofs.
- Biodiversity roof or nature roof
Is based on an extensive roof, supplemented with elements that enhance biodiversity: shaggy vegetation, herbal mixtures, micro-relief, open substrate, wood, stones, branches or insect habitats. It is mainly designed to attract as much life as possible.
- Semi-intensive green roof
This is in between a sedum roof and a roof garden. The substrate layer is thicker and allows a mix of sedums, ornamental grasses, herbs and flowers. It looks more natural and offers more biodiversity, without the heavy build-up of a real roof garden.
- Intensive green roof or roof garden
This is a full-fledged garden at height. With a thick substrate layer, you can combine flowers, grasses, shrubs and even small trees.
In most cases, a green roof is perfectly possible.
There are a few basic conditions, though:
1. Sufficient carrying capacity: the roof must be able to cope with the additional weight of the green roof.
2.Good roof waterproofing: the waterproofing should be in good condition. If it is outdated, an additional layer can be provided.
3. Suitable slope: both flat and gently sloping roofs are suitable.
4. Accessibility: the roof should be accessible for installation and maintenance.
Having doubts? No problem. In most cases, a quick check is enough to see what is possible.
A green roof offers many tangible benefits for both the building and the environment:
1. Keeps your building cooler
A green roof protects against the sun and prevents the roof from heating up significantly. This makes for a more pleasant indoor climate.
2. Buffers rainwater
Green roofs absorb rainwater and hold it temporarily. This reduces the burden on the sewer system during peak rainfall.
3. Extends the life of your roof
The roof waterproofing is protected from UV, temperature variations and weathering, making it last longer.
4. Provides better insulation
In winter, a green roof helps to retain heat better.
5. Brings life to your roof
A green roof attracts bees, insects and birds and increases biodiversity.
6. Makes smart use of space
You use your roof as extra green space, without taking up extra space on the ground.
7. increased appearance
A green roof gives your building a stronger look and increases property value.
8. Sustainable and forward-looking
Green roofs contribute to water management, cooling and a healthier living environment. They fit perfectly within the evolution towards more sustainable building.
9. Fully customised for your project
From a simple sedum roof to an intensive roof garden, a green roof can be tailored to your needs and building.
10. Can be used on any type of roof
Existing roof, new roof, a flat roof or a sloping roof. As long as the roof is accessible and has sufficient load-bearing capacity.
Yes, in most cases you can perfectly install a green roof on an existing roof.
There are a few important conditions, though:
1. Load-bearing capacity of the roof
The roof must be able to handle the extra weight of the green roof (substrate, water and plants).
2. Roof waterproofing
The existing roof waterproofing should be in good condition. If it is outdated or questionable, it is often recommended to provide a new waterproofing layer or additional protection first.
3. Root barrier
Not every roof waterproofing is automatically root resistant. If necessary, an additional root-resistant layer is installed.
4. Roof accessibility
The roof should be practically accessible for installation and possible maintenance.
With older roofs, it is often wise to have the roof structure checked first. Often a small adjustment or extra layer is enough to make the roof ready for a green roof.
In principle, a green roof can be installed all year round. The construction of the roof itself does not depend on the season. The planting does.
The best periods to install a green roof are spring (March to June) and autumn (September to November). This is when conditions are ideal and the plants can take root well.
What should you pay attention to?
- No installation in case of frost
- Beware of heat (>25°C) then provide extra water for planting
- Avoid strong winds when applying cuttings or seeds
Sedum mats are more flexible and can be placed almost all year round, as long as they get enough water in warm weather.
In the beginning, a green roof needs some follow-up (especially water in dry weather). Once well-rooted, it requires much less care.
Yes, in most cases you can perfectly reuse the water from a green roof.
Rainwater coming off a green roof may well be slightly discoloured by the substrate. This is normal and not harmful. So you can use this water for applications such as flushing toilets, outdoor tap or watering plants without any problem.
Keep the following in mind, though:
With a limited green roof area then the impact on rainwater is usually minimal. With larger green roofs, discolouration may be slightly more pronounced. In that case, it is not recommended to use this water for e.g. a washing machine.
Green roofs are lightly fertilised with slow-release fertilisers. These are gradually absorbed by the plants and in practice have no significant impact on the rainwater collected.
For applications such as drinking water or intensive domestic use, rainwater in general (not just from green roofs) is not suitable without additional filtration.
Green on the facade
A green facade offers a combination of practical, ecological and visual benefits:
1. Keeps your building cooler
A green facade acts as natural protection from the sun. In summer, the façade stays noticeably cooler, which is also more pleasant inside.
2. Helps during heavy rain Plants absorb rainwater and hold it temporarily. This reduces the burden on the sewer system during peak showers
3. Air purification
Green facades help filter particulates and pollution from the air.
4. Brings life to the city
A green facade attracts birds, bees and insects. They provide extra greenery even where space is at a premium.
5. Protecting your facade
The facade suffers less from sun and rain. As a result, the façade has a longer lifespan.
6. Attenuates noise
Green facades help to dampen ambient noise.
7. Ideal where there is no room for greenery on the ground or roof
No garden or little space? Then a green facade is a smart way to still add greenery. Enjoy a vertical garden.
8. Aesthetic value
A green facade gives your building a strong appearance and increases property value.
9. Sustainable and forward-looking
Green facades contribute to sustainable construction: they buffer rainwater, improve air quality and help keep buildings cooler. By doing so, they also support companies' ESG goals and respond to stricter regulations around climate and water management.
10. Fully flexible in design and planting
A green façade can be freely designed in plant choice, structure and system, and therefore fits virtually any building.
A green facade always requires maintenance, but this remains perfectly manageable and can either be monitored yourself or taken care of by us via a maintenance plan.
The frequency and intensity depend on the type of green facade:
- Living wall system: requires regular and scheduled maintenance (on average 2 to 4 times a year). This includes control of irrigation, fertilisation and pruning. If necessary, plants are adjusted or replenished.
- Ground-level green facade: requires more limited maintenance (once or twice a year). This consists mainly of pruning, fertilising, guiding climbing plants and general monitoring of growth.
With proper maintenance, a green façade will remain beautiful, healthy and performing for years.
Want to know more about maintenance, cost and frequency? Read our blog post: “Maintenance of green walls: the answers to the most frequently asked questions.”
The difference is mainly in where the plants grow and how the system is constructed:
In a ground-based green facade, the plants grow in full soil and climb against the facade via a support structure (such as cables or nets).
In a living wall system (facade-based), the plants do not grow in the ground, but in modules or panels fixed to the facade. This system provides an 100% instant green result with more design freedom.