Green facades can cool interiors by up to four degrees

Interest in green facades has risen after summer heat records, and measurements show they can lower indoor temperatures by up to four degrees on sunny days, ORF’s Anna Wohlmuth reports.

Martin Haas, a gardener at a business in Aschbach-Markt, in Amstetten district, said inquiries had increased. Plants release water through evaporation, creating a cooler microclimate and shading the building, he said.

Monitoring has recorded surface temperatures of up to 60 degrees on an unshaded, dark facade in midsummer. With greenery, temperatures at the facade surface were measured at up to 30 degrees, Haas said.

Facade greening can be installed as a ground-based or wall-mounted system. In a ground-based system, climbing plants grow in soil at the base of the building and receive water from the ground, reducing the need for watering. Care usually involves one or two visits a year for tasks such as spring fertilising and pruning. Windows and ventilation systems must be kept clear.

Some climbing plants, including kiwi and wisteria, need supports such as wires. Ivy and Virginia creeper can climb directly on walls, but homeowners should first check for cracks or gaps, where the plants could take root. Their strong clinging roots can also dirty the facade.

Wall-mounted systems use planters fixed to the facade, where grasses, herbs and compact perennials can grow in substrate. They can suit buildings with limited ground space or those built right at the property boundary. The systems are more technically complex, require irrigation and cost more to install, but allow a wider choice of plants.

Using cables as climbing supports can cost from about 200 euros, depending on the size of the area, Haas said. The building-greening association Grün statt Grau offers a free initial consultation for projects such as green roofs and facades.