Considering a Greenhouse Upgrade: Is Polycarbonate Better for house plants?

Hello,

I built a small greenhouse(440sf ft) in our backyard in Los Angeles California a few years ago using regular greenhouse film to grow houseplants.

However, I quickly found that it became too hot and too bright inside—especially during the summer—for most houseplants. So, I applied shading compound to the plastic film and made other adjustments.

Over time, I noticed that cats were walking across the greenhouse, which caused small holes in the film. As a result, it started leaking during winter.

Now, we’re considering growing rare anthuriums in the greenhouse. Because of that, we’re thinking about upgrading it with polycarbonate panels as we’ve heard good things about them. (—6mm for the roof and 8mm for the sides—)

Could you let me know if upgrading to polycarbonate panels will significantly improve the greenhouse environment?
The product description says it has 89% light transmission and blocks 99% of UV rays.
Do we still need to install shade cloth?

Thank you!

Hello Kevin, welcome to permies!

Polycarbonate comes in a variety of types.  For your purposes, I'm assuming that you're looking at single wall poly.  (double wall or triple wall are used for insulation.)

Even single-wall poly will hold in more heat than you'll want for summers in LA.  However, with the firmer structure to work with you can go look at intake shutters (louvres) and fans.  They detect the temperature in your greenhouse to open and close the louvres.  There are a wide variety depending on what you want, that could be a whole thread unto itself.  If your greenhouse has power then the powered shutter pistons are the easiest, in my opinion.  There are unpowered ones that use paraffin, but they take a bit of fiddling to get them to behave properly.

Alternatively, if you want to continue to shade, look at shade-cloth.  It's nice because it is mobile.  You can cover all or part of your greenhouse, and when things cool down you can remove it, so you get more heat in the winter.  Nursery suppliers carry it and they come in everything from 10% to 90% shading.  I've used shade cloth with plastic film greenhouses as well.

Thank you for the replies.
I’m planning to buy double-wall polycarbonate panels, either 6mm or 8mm. I’m also thinking of installing a water wall with an exhaust fan to keep the greenhouse cooler in the summer, and add heating for the winter. I plan to install an automatic roof vent opener as well.

I’ll be growing rare anthuriums and would like to maintain the temperature between 60°F and 85°F, and humidity around 65 to 75%

A nursery owner mentioned that polycarbonate panels provide excellent conditions for plants
However, I’m a bit hesitant because it will cost me a couple of thousand dollars.

Well, local advice is always key there, I'm hoping that other folks from LA can weigh in there.

It sounds like you've got a good plan there.  I'd love to hear how the water wall works out for you.  My only other experience with them was a friend's house in Provo, UT.  It was about 10,000 gallons to moderate the house temperature.  Really impressive.

You might consider this stuff. Solexx It comes on a roll and is easy to work with. I don't think it as robust as the other polycarbonate but is considerably less expensive.