CactiGuide.com

Posted: **Fri Aug 24, 2018 1:56 am**

Is that clear polycarbonate or the white opaque kind? they sell both types at a Home depot a building materials chain store in Town. I was afraid clear would need shading and the white might be OK ?

Posted: **Sun Sep 02, 2018 2:10 pm**

keith wrote: ↑Fri Aug 24, 2018 1:56 am Is that clear polycarbonate or the white opaque kind? they sell both types at a Home depot a building materials chain store in Town. I was afraid clear would need shading and the white might be OK ?

Hi, Keith, I'm using the white opaque kind. Lots of light pass through and now that spring is coming I may consider using a shade cloth. But I 'll not do it unless really necessary. I will keep this post updated.

Posted: **Thu Sep 13, 2018 4:40 pm**

Thanks let me know how it works

Posted: **Thu Sep 13, 2018 5:35 pm**

Not a complete description, but only a picture of a young E. fitchii under the opaque polycarbonate, without shade cloth, taken this week....

: IMG_20180912_072350528-768x1024.jpg (81.5 KiB) Viewed 13380 times

Posted: **Wed Sep 19, 2018 9:12 pm**

Looks good to me

Posted: **Sat Nov 17, 2018 12:25 am**

keith wrote: ↑Wed Sep 19, 2018 9:12 pm Looks good to me

Here it is an update. Five months (winter and spring) after the beginning of the experiment I can say that:
1. All plants look very healthy under the polypropylene roof
2. Mesembs seemed to love it
3. Despite the good looking of the cacti, when they are compared side by side with the control plants of the same species kept in the greenhouse (plastic + very light shade cloth), they are less spined and less compacted.

Here are some pictures.
The plants in the left row were kept in the greenhouse. The plants in the right row were tested under polypropylene roof:

: IMG_20181116_164106764-768x1024.jpg (139.31 KiB) Viewed 12978 times

Note the spination in the Pachycereus and Echinocereus. In the plants grown under polypropylene you can see the body of the plant.

The Mammillarias are clearly more compact when kept in the greenhouse (now at the right side in the pictures):

: IMG_20181115_183126875-768x1024.jpg (115.14 KiB) Viewed 12978 times

: IMG_20181115_183510254-768x1024.jpg (112.63 KiB) Viewed 12978 times

I prefer compact and more spined plants, so now I am not sure about building a greenhouse with polypropylene. But despite this the plants are very beautiful .

Please note that despite of the title of the thread, I am testing polypropylene!

Posted: **Sat Mar 30, 2019 2:04 am**

The roof of a GH has to be rounded and smooth if it is in a cold place. Here is a short video of my friends', their hardiness zone is ~ 6 I think.

One winter day in our greenhouse

Posted: **Thu Apr 30, 2020 1:54 pm**

Hi Spence, I also live in England and have a PCB GH and was recently looking into sheets of it online ( I really need/ want a bigger GH), you can get different thickness and double/triple walled sheets in many sizes you can even get shapes cut for apex end panel and all sorts of shapes for slopes in the end walls panels etc obviously the thicker and extra walled sheets cost more than the thinner stuff... anyway We have a Pergola with a roof that's made of corrugated plastic and when it got really stormy one year the roof just got ripped off in places, whereas I have a flat un-corrugated roof on my GH made of polycarbonate the greenhouse is in a corner so it doesn't get as much wind but you can see my point.. if you get a PCB sheet roof then just make sure the sheets are jointed together with something that wont let the wind (or rain) under the joins so it doest lift in any gales etc. As the other members stated the sheet are (usually) UV stabilised and come with 10year warranty and are just as good for light penetration and if used in a enclosed gardenroom such as a greenhouse actually retain the heat more efficiently than glass and are impact resistant (smash-proof, supposedly) just search online for pcb sheeting and you will find lots of companies willing to supply. Hope you find something to suit your needs, Happy Growing

Dave

Posted: **Mon Aug 10, 2020 4:03 pm**

Dave Adams wrote: ↑Thu Apr 30, 2020 1:54 pm Hi Spence, I also live in England and have a PCB GH and was recently looking into sheets of it online ( I really need/ want a bigger GH), you can get different thickness and double/triple walled sheets in many sizes you can even get shapes cut for apex end panel and all sorts of shapes for slopes in the end walls panels etc obviously the thicker and extra walled sheets cost more than the thinner stuff... anyway We have a Pergola with a roof that's made of corrugated plastic and when it got really stormy one year the roof just got ripped off in places, whereas I have a flat un-corrugated roof on my GH made of polycarbonate the greenhouse is in a corner so it doesn't get as much wind but you can see my point.. if you get a PCB sheet roof then just make sure the sheets are jointed together with something that wont let the wind (or rain) under the joins so it doest lift in any gales etc. As the other members stated the sheet are (usually) UV stabilised and come with 10year warranty and are just as good for light penetration and if used in a enclosed gardenroom such as a greenhouse actually retain the heat more efficiently than glass and are impact resistant (smash-proof, supposedly) just search online for pcb sheeting and you will find lots of companies willing to supply. Hope you find something to suit your needs, Happy Growing
Dave

The post is 2 years old, Dave! No worries I assume, you have some good info. One thing I will say about pcb is that its far harder to keep clean than glass. Mine is a few years old and doesn't allow light to full penetrate at certain angles due to dust etc... between the layers.

Posted: **Mon Aug 10, 2020 5:06 pm**

You are supposed to seal the ends of the sheets with tape and often a capping section to prevent water and dust getting in. However how long the tape actually lasts I do not know:-

https://www.bing.com/videos/search?q=ho ... &FORM=VIRE

Also the sheets usually have a UV resistant coating only on one side which goes upwards towards the sun and this side is usually marked on the peel off protective coating. Peel this off not too fast since a friend of mine ripped it off very quickly and got a static shock that threw him backwards and sat him on his backside on the yard.

Also a flat roof or too low a pitch on the roof can lead to water being pulled up between the sheets at the gutter end if the seals deteriorate.

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