Living Wall Lighting Considerations and Trends
Lighting is perhaps the most essential design consideration for an interior green wall. Light is crucial to plant health indoors and adds to the aesthetic of the green wall.
Once adequate lighting is established, generating plant choices and a planting design becomes much easier. So, it’s important to enlighten your client about lighting needs and natural or artificial design solutions early in the planning process.
As an interiorscape professional, you’re already keenly aware that available light dictates the diversity of usable plants and impacts plant health. But be aware that a living wall may have specific lighting needs. Why? Well, first, consider that a large living wall can comprise hundreds or thousands of plants. One system I’ve used has 8 cells per module – that’s 8 plants per sf! That’s a lot of competition for light. Second, consider that a living wall is a vertical array of plants. The position and angle of available light source(s) may result in uneven or inadequate lighting.
Be prepared to 1) assess the available light, 2) correct the natural lighting (if possible), and 3) plan for supplemental artificial lighting (probably).
1. Assessing Available Light
It’s important to consider light intensity, duration, angle, and spectrum for your green wall. During the site assessment (See Planning Tip #2), I recommend a digital light meter to evaluate light levels. A light meter, which measures light intensity in Foot-Candles or Lux, eliminates the guesswork and reduces human error from eye-balling a project space. Many green wall manufacturers recommend at least 150 FC for the lowest-light tolerant plants to survive. Tips on assessing light:
- Take readings at multiple points along the proposed wall space (create a grid)
- Take readings throughout the day, if possible
- Consider seasonal variances in light
- Consider orientation of light sources and the proposed living wall
- Consider shade sources (exterior: buildings, trees, awnings; interior: blinds/tint)
- For existing buildings, document natural light sources and alternate green wall locations
- For existing buildings, document existing artificial light sources
- For new construction, consider computer models to anticipate daylighting
The data you collect is valuable as you consider green wall placement and planting options. If your client is reluctant to install supplemental lighting, the data is also useful as supporting evidence. Make them see the light!
2. Correcting Natural Lighting
To improve the light environment for an interior living wall, utilize or introduce sources of natural light. If this is a component of a new construction, be adamant about designing for natural light (Daylighting contributes to LEED certification, too). If this is a part of a renovation, see if the client is willing or able to introduce more natural lighting. Natural lighting tips:
- Re-locate or re-orient the living wall to optimize uptake of natural light
- Enlarge window(s) and adjust awnings and other shade sources
- Install sky lighting or solar lighting tubes (e.g. Solatube)
3. Planning for Artificial Lighting
While knocking a hole in the roof sounds great for lighting a green wall project, it may be impossible or cost-prohibitive for the client. Even when natural light is available, it might be inadequate in intensity, spectrum, or duration to guarantee plant survival. Artificial lighting, consequently, can serve as a primary or secondary light source. Regardless of the type specified, be certain to use an adjustable timer to moderate lighting duration.
During my research, I’ve seen many opinions about the ‘best’ grow lighting for green walls. Nonetheless, I’ve noticed a few trends:
- High Intensity Discharge (HID) lamps can emit light effectively over a large area and are specified often for green walls. There are two types of HID lights. Metal Halide (MH) lights produce light in the blue spectrum and promote leafy growth. High Pressure Sodium (HPS) lights produce orange-red light and encourage flowering. HID Cons: excessive heat production, bulky fixtures/ballasts required, energy cost, regular bulb changing required.
- Light Emitting Diode (LED) technology has improved dramatically in recent years and there are now living wall-specific LED lighting solutions on the market (e.g. Sunlite Science and Tech). Apparently, LEDs can be tailored to specific light spectrums, produce little heat, require very little energy, and last a VERY long time. LED Con: initial expense, bright enough?
- Other lighting types discussed include fluorescent tube lighting and halogen lighting. I’m interested in arguments for these types, but I’m skeptical they can provide adequate and efficient light per square foot.
Overall, MH lighting seems to be most frequently recommended for interior green walls thus far. But I predict that LED lighting will soon gain a strong foothold in the green wall industry.
Living walls are highly visible examples of your work and proud examples of your client’s aspirations to appear ‘green.’ Successful green wall projects rely on careful planning and investment in lighting solutions, so it’s imperative that you shed some light on the subject early in the planning phase!
Featured image by GSky