This post is intended to be a broad overview and summary of my bedroom greenwall. I'll try to interweave information about its actual design with lessons learned and speculation on how I would build another if I started over from scratch.
Step 1 of building a greenwall is protecting the room that it's built in from the greenwall. You really, really don't want to take down a several-years-old greenwall and find that the building wall behind it is moldy and rotten. I quickly built a wooden frame, covered that with plastic siding, and covered that with felt pockets that hold plants. My current wall spaces the siding about two inches away from the bedroom wall, and I haven't had any problems with humidity or mold, but if I built a new wall today I would definitely line the building wall with a large single-piece plastic sheet before anything else.
I built a very simple rectangular frame to support my wall. It's just a rectangle of 2x3 Douglas Fir lumber, held together with metal brackets at the corners and held rectilinear with wire rope in an "X" arrangement. Plastic siding is screwed onto this frame, supported at the ends, and plants are mounted onto the siding. The weight of the plants is transferred to the siding, which transfer load to the vertical boards, which transfer load directly to the floor. The entire structure leans against the wall a few inches short of the ceiling and is kept from falling over by a few hooked brackets that screw into the wall at the top. So no vertical loading goes into the wall at all. If I built a new support structure today I would probably do it the same way. I've had no problems.
I purchased felt curtains from Amazon. Each curtain is about one meter square and has pockets about 200mm square. I just stapled them onto the plastic siding. I've had no major problems with these, aside from occasionally a staple popping out of place. If I built a new wall I would definitely investigate stackable plastic cups. I've seen several different designs on Alibaba. They stack together into a grid. They have drainage holes built into the bottom. They have rigid wall-mount points designed in. Some even have clips for irrigation lines built in. When purchased in bulk I'd guess they would be only slightly more expensive than the felt curtains that I used.
I installed four T5 LED growlights on my ceiling. I bought them through Amazon for ~$25/each and they've worked perfectly for the past two years. No complaints. If I started over today, I would probably used more, maybe six or nine lights instead of four. I might also buy lights that could be powered by DC. The ones I purchased have AC->DC converters built in and I didn't want to hack them to make them dimmable. I'd like the lights to turn on and off slowly over the course of several minutes instead of turning on and off abruptly.
This was the biggest problem and the biggest consumer of time BY FAR. When I first started the project I didn't even think about irrigation. I just started watering everything by hand every day. That's fine for a dozen plants for a few weeks, but not feasible for 200 plants for years. I went through several different designs, but ended up buying almost everything commercial off the shelf. My ~100 plants currently are watered automatically twice a day, consume about one gallon of water per day, and seem to be very happy. Automation was key. The felt pockets do not retain any water at all so if I skip a day or two of watering many of the plants immediately start to turn brown and it will take months for them to recover.
Everything starts with the reservoir. I haven't been able to find a tank that fits into the long, narrow space underneath the greenwall and against the bedroom wall, so I built one. 8ft long, 6in wide, and 9in tall gives me about 15gal, which allows me to leave home for a week or two without having to worry about my plants. I built a box by gluing together plywood, coating it in many layers of epoxy, and reinforcing the seams with fiberglass. Water is pumped from the tank up to the plants by a 12VDC electric pump that I believe is intended for RV or boat use. I found that small membrane pumps rated for 30psi and 1-2gal/min are perfect for the job. Larger pumps tend to be very, very loud. I put a cloth filter on the pump inlet to protect the whole irrigation system from mold or debris. The irrigation system waters one row of plants at a time, with 13 rows of plants in the wall. Water is distributed through 13 solenoid valves that cost ~$5/each. (A pump powerful enough to water all the plants at once would be enormous, expensive, and very loud.) Water is sprayed onto each individual plant through commercial irrigation tubing and spray nozzles which can be bought in bulk for very low prices. This allows me to tune the amount of water delivered to each and every plant for a pretty low price. It is a good idea to choose soil that retains the right amount of water for each plant because the felt pockets are not going to help you here. Excess water drips through the felt pockets, down the wall, and back into the tank at the bottom. I made a cover for the tank out of PVC project board glued together. It allows water to drip back in through the top while keeping light out, which prevents the growth of algae. My wonderful girlfriend painted a mural on the front so it wouldn't just be a big white box.
For the water itself, the tap water in my town is extremely variable. It'll be visibly brown for a few days and then it'll be incredibly excessively chlorinated for a few days, so I always filter it. Filtering ten gallons of water at a time is a bit of a pain so I turned some 5gal buckets into giant Brita filters. I printed a ring that holds a filter and I can filter 5gal at a time. I could probably just put 5gal of tap water into a bucket and let it sit for a day or two and the chlorine would evaporate out that way, but I've already made the filter so I'll just keep using that. The plants are happy.
Lights and irrigation are controlled by a system I threw together myself. It's fairly simple, just some MOSFETs to control the pump and solenoids and a TRIAC to control the LED lights, all controlled by a Raspberry Pi Pico. Everything runs on a 24hr schedule. At 7am every day, lights turn on and the pump runs, switching through all the solenoid valves to water each row for 12sec. At 7pm the lights turn off and the pump runs through another watering cycle.
I figured out what did and didn't work in my wall largely through trial and error. Some were obvious. Pothoses, Philodendrons, spider plants, and various ivies are very happy in the wall. Some were harder to figure out. Maiden hair ferns, asparagus ferns, and fluffy ruffle ferns are all happy in the wall but silver lady ferns, Alaska ferns, dear tongue ferns, and Japanese painted ferns didn't last very long. Antarctica ferns are happy as long as they don't go a single day without water. ZZ plants are fine as long as they don't get too much water. The felt wicks water down, but the bottom row of pockets tend to retain a lot of water, so ZZ plants get root rot very quickly there. Fuschias survive and grow in the wall, but haven't been producing any flowers. Selaginellas also seem to be happy.
Many plants, including long grasses, are very happy in the wall but seem to bring in or attract lots of insects, so I got rid of those. Some of my ferns seem to attract midges and I haven't found a good way to get rid of them yet. I read lots of places that low-concentration hydrogen peroxide would kill the midges without harming the ferns, but I found the opposite to be true.
Initially I spaced plants much too close together. Eventually I started planting every other pocket in a checkerboard pattern for very bushy plants like ivy, philodendron, and ferns.
I love my greenwall. It's the first thing I see when I open my eyes each morning. It's beautiful. At this point I'm just letting it grow. I still have plenty of empty pockets that I can plant in if I find a new plant that I like. Getting the irrigation 100% automated was the biggest unexpected hurdle, and ever since that's done it's extremely easy to maintain. There are plenty of things I will do differently if I ever build another one, but this one's good as it is. I bought plenty of spare parts and I think I could repair any part of it in a day or two if it breaks.