Façade trees

Façade trees are an alternative to façade greening. They represent a completely new and unconventional form of building greening. Façade trees are trees trimmed on one side (half root space, half crown), which are planted up to 1.50 m close to a building.

Both building greening variants - façade greening and façade trees - are used to shade building envelopes behind them and for local cooling. There is no fundamentally better or worse variant; both types of greening have advantages and disadvantages, which is why it is a question of weighing up (see below) which type of greening is used.

A first pilot project was completed at Walheim elementary school in 2024, which is presented in this article. In future, the concept of façade trees will be tested and varied in other projects.

Façade greening vs. façade trees

In contrast to façade greening with climbing plants, façade trees stand completely independently in front of the façade. The advantage of façade trees is that, when fully grown, they shade the entire façade, including parts of the roof if necessary.
Climbing plants, on the other hand, are only placed directly in front of closed walls or moved away from the actual façade using a more elaborate climbing scaffold construction. Although shading solutions for window areas can also be implemented in this way, they are not as cost-effective as planting façade trees.

The space available in front of the façade plays a decisive role when considering whether green façades or façade trees make more sense. While a façade tree requires four meters of space in front of the façade, façade greening only requires 1.70 meters. If espalier trees are chosen as façade trees, the space required is less, but the growth height of the trees is limited.

Pilot project at Walheim elementary school

Façade trees were planted as a pilot project at Walheim elementary school in 2023. The successful growth of the trees was established in 2024. The project is intended to provide information on whether the façade trees concept can be successful. After just one year, the development is so satisfactory that façade trees are already being considered for other projects.

Existing situation
The classrooms at Walheim elementary school face south and have a very high proportion of glass in the building envelope. This results in extreme heating of the interior rooms due to the so-called greenhouse effect. Other classrooms, which are shaded by the local old trees, do not have this problem and remain noticeably cooler than the sunlit classrooms. This gave rise to the idea of expanding the existing tree population with new plantings.

Example project Bamberg
The study by an interdisciplinary research team on the implementation of a pilot project in Bamberg with tree façades was used in the planning for the implementation of the trees close to the façade envisaged here. The study analyzed how close and under what conditions a tree can be planted to a façade.

Planning
The most important criteria for investigating the feasibility of façade trees relate to an understanding of tree growth and tree statics, particularly in windy conditions. For the project here, it was decided to position the tree free-standing at a distance of 1.5 m from the façade, so that the tree does not need to be supported with façade swords or similar. In addition, after careful consideration, the hornbeam tree species was chosen.

Implementation
The trees are positioned in front of the façade at a suitable and regular distance from each other, depending on the type of tree. Approx. 10 trees are required to shade a façade length of approx. 30m.

At the beginning, the trees are still too small to shade the classrooms behind them. As soon as the trees have reached the height of the façade and close the gaps between them, the canopy will ensure that the hot rays of the sun do not hit the building in summer, thus protecting it from overheating.

At the same time, the view from the classrooms "at the height of the treetop" of the landscape of branches and leaves and their inhabitants should provide an attractive natural experience for the pupils.