Vertical gardens on house walls: do they really keep heat out? Plus what to watch out for before you start

Do vertical gardens really reduce heat in the house?

The short answer is yes, they really do keep heat out! Thai sun beating directly on concrete walls all day makes the walls soak up heat and release it into the house in the evening. A vertical garden (green wall) acts like "natural heat insulation" that shades the wall from direct sunlight.

The natural mechanisms that cool your home

A vertical garden doesn't just give shade — it also has a process called evapotranspiration, the release of water from plants, which lowers the temperature around the wall remarkably. In addition, the air gap between the garden frame and the wall carries heat away so it doesn't build up in the house. Studies show vertical gardens can reduce wall surface temperatures by as much as 10-15°C and room temperatures by around 2-3°C, noticeably saving on air-conditioning costs.

A 4-point checklist before you build a vertical garden

It reduces heat well, but installed incorrectly it can bring damp and termites into the house. Here's what to prepare:

• 1. Waterproof the wall: always apply waterproofing or fix a plastic damp-proof sheet (HDPE sheet) to the concrete wall before installing the frame, to stop moisture seeping into the house and causing black mould
• 2. Sun direction and plant choice: for a west-facing wall in strong sun, choose sun-tolerant plants such as Bryophyllum, moss rose or some ferns; for a wall in dappled light, choose plants like pothos, wild betel or maidenhair fern
• 3. Watering and drainage: install a mini-sprinkler or drip system with a timer, and a drainage channel at the bottom so water doesn't run all over the floor
• 4. Lightweight growing media: avoid dense soil; use chopped coconut husk, coir dust or sphagnum moss to reduce the load on the structure

Important structural and electrical precautions

Large vertical gardens involve the weight of the plants, moisture and water. For large steel structures that must be fixed to the house, consult a specialist or structural engineer to calculate the loads, and if you connect an automatic water pump, call an electrician to install waterproof sockets and switches (IP65) with earth-leakage protection, for the safety of everyone in the house.