A sufficient PAR level is critical to maintain healthy plants.
It is ideal to place rows of lights along the ceiling at different angles, as this provides an even light distribution. In addition, plants grow towards the light, and green walls look better with plants growing upwards. Lights along the floor may lead to plants growing “downward” towards the light and eventually even covering the floor lights.
For very tall green walls, fixtures may need to be installed along the bottom to provide even light coverage and reduce total fixtures required. When the fixtures are installed along the bottom, they need to be at least 1.5ft away from wall. If the fixtures are installed along the base of a green wall, they should be water proof as they are prone to get dirty or wet.
Case Study – KU Center for Design Research (CDR)
In 2010, this 34ft x 12ft Green wall was originally designed with 32 pieces of LED lights output around 900 lumens. With the sky lights designed above the plants, the designers thought the lighting was enough to maintain the green wall. But it turns out that the plants were not healthy.
In 2011, Sunlite got involved in designing the lighting for this wall. After simulating the PAR value across the wall, we suggested a top row of eight 4ft ST40 Greenwall strips and a bottom row of eight 4ft ST40 Greenwall Strips to provide even lighting to the entire wall. Below is a picture of this setting. The top row was placed 1.5 ft away from the wall, the bottom row was placed 1ft away from the wall. The bottom row fixtures are waterproof fixtures.
The plants were healthy and were growing. Plants at the bottom end up covering the bottom fixtures quickly, they need to be trimmed often. In 2014, CDR decided to take off the bottom row and add another row of 8 fixtures on the top, 3ft away from the wall. Below is the picture with two rows on the top. The lighting are more even. The wall looks better because plants grow towards the lights, and waterproof fixtures (which costs more than regular fixtures) are no longer needed.
Case Study – Johnson County Community College (JCCC)
The three green walls at JCCC are success installs with top and bottom row. The lighting was designed together with the 20ft X 10ft green walls in 2012. The fixtures at the bottom were at 1.5ft away from the wall. Plants are healthy, the bottom plants don’t cover the bottom easily. The maintenance was manageable.
Case Study – EnviroZone Design Rock Wall
In general, one row of ST40 fixtures are recommended for a green wall shorter than 6ft and two rows of ST40 fixtures are recommended for a green wall between 6 and 12 ft. In the case where very low light plants are planted, or with good daylight, less fixtures may be needed. With just one fixture, this plants on the rock below grow bigger in one year.
To see details of our four standard green wall lighting layouts click here!