Albert's Greenhouse

I've been working on getting a cooler greenhouse up and running in order to grow some highland tropical plants. It's a very small space, so I took it as an opportunity to try out some new and different construction materials and methods.

This post is about my experiences in using PVC pipe as a framing material, and Solexx corrugated plastic as a covering.


PVC Pipe Greenhouse Framing

There are quite a few plans out there on the internet regarding how to use PVC as a framing material to make a hoop house with a plastic film covering, but I became interested in using it as a more permanent framing material. It's relatively cheap, though it's yet another plastic made from oil, so prices could rise. It's also quite durable, being resistant to sunlight and waterproof. It's very easy to work with - easy to cut and drill and solvent weld or glue.

After some reading up on the matter, I settled on 1" Schedule 40 ( the thick stuff ) PVC pipe as my framing material. Anything larger than this seems to be prohibitively expensive, especially for the fittings, and 1" is quite strong, at least in most directions. I was able to get away with 24" centers in a lot of my construction.

I did not use a primer on the PVC cement - just a thin coating of one of the blue colored cement products at each joint. This greatly speeded construction, and I doubt that there will be an issue with the joint strength because of it. I should note that when you're using such a large quantity of cement in an enclosed garage, ventilation becomes an important consideration.

The main idea was to use the PVC as a framing material - not bending it as in a lot of the plans out there. So I framed walls with the stuff using 90 degree elbows and T joints where necessary. I tried to keep the lengths between the joints between about 2' and 4', which means there is some amount of cross-bracing in the wall panels. Corners were made by simply screwing two wall panels together, and any gaps were filled with silicone caulk ( or one of the cheaper caulks which are available ).

So far, the construction has been plenty strong. The walls are a bit flexible when pressed inward or outward, but they are quite resistant to moving in any other direction. They are supporting fairly heavy metal exhaust fans, light fixtures, and electrical boxes quite firmly.

If I had one complaint about the PVC construction methods I used, it would be that it was exceedingly difficult to keep things square during the construction. The PVC fittings are somewhat variable as to exactly how much of each pipe they accept, and when building boxes for walls, it's often necessary to weld two joints at the same time. All this leads to measurements being a little less than exact. Since I had so much PVC to cut, I used a power compound miter saw to make all the cuts quickly and squarely.

Given the chance, I'd be a little more careful next time with making sure things come out squarely, but I would do it again.

Solexx
Solexx is the brand name of a type of corrugated translucent plastic material sold as a greenhouse covering. What it appears to be is the same corrugated plastic that the post office uses for their mail crates, and various farmers use for packing produce. It's apparently been treated with UV resistant compounds, and it comes in 4 foot wide rolls up to about 1000' long. The good thing about it is that it's shippable by UPS in the roll form.

Solexx comes in two thicknesses: 3.5mm and 5mm. I purchased the thinner one. It seems like it's less than 1/4" thick but more than 1/8" thick. It's substantially cheaper and advertised to let more light through.

Working with Solexx is easy in some ways and difficult in others. It cuts easily with a sharp box cutter, and it's not difficult to get straight cuts if you mark them beforehand with a sharpie and a straight edge. The rolls really need some time on a warm day to flatten out on a lawn or something before they are used. I fastened the material to my PVC greenhouse frame using self-drilling lathe screws from the local hardware store. The manufacturer recommends using screws with neoprene washers for waterproofing, but I did not find this necessary. The extra lip on the head of the lathe screws seems to do the job just fine.

The manufacturer also sells plastic edging strips for joining pieces of material and sealing the ends. I did not use this - I just overlapped the sheets by a small amount and I plan to caulk the ends closed where necessary this summer when things dry out. Meanwhile, I've got some water in the channels, but not much. I imagine that with some caulk, the strips would have made my joints more watertight. The only place that this became an issue is in the roof, where I have a could of overlaps. Caulking between the sheets seems to have sealed them right up without the use of the strips.

If I had to find one fault with the Solexx, it would be the fact that it's a fairly soft plastic. It's never going to shatter, but I have several small holes in the greenhouse ( not worth the trouble to fill, I would think ) that are from times my screwdriver slipped off the head of a screw and punched easily thought the material. It's not a weak material at all, but it is prone to puncture wounds from sharp objects.

Another issue with the Solexx is light transmission. The claim seems to be that it gets about 70% light transmission, which is substantially less than double wall polycarbonate, glass, or even most fiberglass coverings. It's still quite a bit of light, and more than enough light for most plants if the greenhouse is situated in a properly sunny location. Unfortunately, my new greenhouse is not situated very well and doesn't get a lot of light to begin with. I've addressed this with some supplemental lighting rather than worrying about trying to make it work with an ultra-efficient covering.

I think I would also use Solexx again, given the choice. It's a bit cheaper, more conveniently shipped, and easier to work than double wall polycarbonate. On the other hand, I don't really have a good feeling for how long the covering will last, and I would not use it in a place where I needed to capture every last ray of light.

Well, it's been a month at least since I tried to propagate some of my ant ferns ( Lecanopteris sp. ) using spores. And I think I've been successful ... up to this point. These definitely look like prothalli - the intermediate stage in fern reproduction.

I'm happy about it - but what do I do now?