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Glass, Polycarbonate or sheet?

Discussion in 'Greenhouse - Shade house.' started by koosjr, Oct 6, 2012.

  1. koosjr

    koosjr New Member

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    It seems the choice is a lot more difficult than what I have thought...

    As I am progressing through all the planning, I found that there are more reasons for using greenhouse plastic than what I had thought.

    Due to our harsh sunlight, it is recommended that a diffused sheet be used, but another interesting thing is that the good greenhouse sheet apparently filters out UV rays up to 380 nm exactly. This cause insect to be unable to navigate inside the tunnel, and if UV is blocked beyond 380 nm it is not good for plant growth.

    If this is true, it means that polycarbonate sheets that blocks 99.9% of UV rays is not a good idea at all.

    Could any experts here perhaps elaborate on this?
     
  2. koosjr

    koosjr New Member

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    Anyone who knows?
     
  3. Jislizard

    Jislizard Member

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    Apparently not!

    I have been looking into the same thing. The double wall polycarbonate seems to be the best bet in the greenhouses I have been looking at.

    It diffuses the light.
    It won't deteriorate under UV (It takes about 10 years to yellow apparently.
    It is lightweight.
    It has better insulation properties.

    I like the acrylic sheeting but it is not cheap either.

    I got most of my info from http://www.domerama.com/coverings/polycarbonate-panels/

    I will be using a mixture!

    Acrylic around head hieght so you can see out (and in), Polycarbonate double walled at the top to diffuse the light and to trap the hot air in winter and stop the greenhouse getting too hot in the summer.
     
  4. koosjr

    koosjr New Member

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    Thing is, I can now get a large amount of 6.5mm laminated glass for absolutely free.

    Yes, the glass is very heavy, but will last forever and if I can get it free, I can spend the cost to have it sand blasted to get the light diffusion.

    I can then only make a second layer from greenhouse plastic, which will then add the thermal barrier.

    That said, the multiwall poly-carbonate seems to be a great product in many aspects.

    I am worried though that it apparently blocks 100% UV and I cannot yet get confirmation if that is bad for plant development.
     
  5. Roark

    Roark New Member

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    Lots'a good stuff here (free trial available)

    http://www.sciencemag.org/content/335/6075/1451.summary


    Some interesting effects of UV, or the absence of.

    http://www.ehow.com/list_6690390_effects-ultraviolet-light-plant_s-growth.html


    Using this on a new house. They curiously don't include the "R" value of a double wall poly house in their comparison chart, which I believe is about 1.62 -1.68 variously, depending on the air space and fan velocity. Two layers of poly is still a lot cheaper, but of course it also doesn't last as long.

    http://www.solexx.com/why-solexx.html

    When buying or installing I wouldn't bother with the 'H' moldings between each piece, just overlap for a stronger, easier, and cheaper install. The diffusion is excellent - no hot spots - which I have had with polycarbonate, but no experience with glass.

    I'd like to read more about the reference to the absence of UV disorienting insects 'cuz the bumble bees don't seem to be effected, but they don't communicate the same way that honey bees do, so I'm not sure what that may all mean w/ or w/o UV. UV can cause a lessening or lack of carb development, which will leave the plant more vulnerable to pests and mold, just as a perfectly healthy plant is frequently indigestible to its common pests. A lot seems to also be plant species specific, so for a large commercial application it seems that more research would prove prudent.

    Me thinks I've got a lot more reading to do.
     
  6. Jislizard

    Jislizard Member

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    Would acid etching be cheaper or easier? Can you buy hydrofluoric acid and do it yourself?

    As to the UV thing, I would like to keep the internal as close to the external environment as possible, with the exception of the heat. Anything else and it starts to get too complicated with too many variables.
     
  7. Richo27

    Richo27 New Member

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    I used standard suntuf on my hot house. This allows pretty much all light to pass through and doesnt block UV. I had considered the multi-wall polycarbonate but determined it wasnt worth the extra expense as winters in my area are not that cold and therefore dont require the additional insulation. I dont have thermometers inside and out yet but it has gotten bloody hot in there already. I could get glass relatively cheap as well, but its heavy and brittle, one hail storm and you've got got yourself a nice mess to clean up.
     
  8. Murray

    Murray Site Admin Staff Member

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    Had a talk today with a company that has a revolutionary greenhouse material that will outlast conventional plastics by three times. Interestingly it allows all UV through and also is actually self cleaning. It is more expensive as one might expect . I have a PDF file but it is too large to upload.

    I will attempt to cut it in half.
     
  9. go4thetop

    go4thetop New Member

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    Hi Murray, any luck with that PDF as I'd be interested in having a read?

    Cheers
     
  10. magoo

    magoo New Member

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    Sounds like you are using a truss for the roof ?


    If so, I'd go acrylic or single layer polycarb sheet for the roof (hard sheet stuff not roll material).
    Design the truss so it has at least 2' of space between the top of the roof rafter and the bottom of the ceiling rafter.
    Put up roll greenhouse plastic on the ceiling. Keep the ends of the roof open.
    What you have created is an attic space or an airspace between the roof top and inside the gh and your allowing the heat to roll out the open ends. It's the same theory as the sheets of material with a small airspace inside,, which by the way costs allot of clams.

    I do the above method but for the opposite reason. We have cold winters and each layer of plastic is about the equivalent of going 500miles south.
    The key ingredient in insulation is air. That's why we are not supposed to compress fiberglass insulation because it removes the airspace.
    Well that's enough coffee for me this morn.

    No way I'd put glass overhead.
    Maybe use it for the south wall? or for end walls?
    Also if its insulated 2 ply with an airspace,, seperate the 2 sheets and use them single. Because soon the vacuum between the 2 sheets will be broken and you will have condensation between the sheets

    I have this glass. Its 4.5' x 9' 1/2" tempered.
    I'll install it on an angle on the south face.
    The head height in the gh at the low end is 6.5'
    The glass has aluminum frames that I won't use,, they have a recycle value of $10ea. I paid $25ea for the glass/frame
    The winter came so we hillbilly wrapped the sides till spring.

    jim
     

    Attached Files:

  11. Murray

    Murray Site Admin Staff Member

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    Sorry Goforthetop,
    I should have got back to you. The owner of the document is not happy for me to publicly distribute the document...just yet. I will be meeting with the CEO of the company next week in California.....so I will have more info then. The film will be released for sale in the US very soon and I am talking with the guy about an arrangement for Australia and the S Pacific.....
     
  12. koosjr

    koosjr New Member

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    Not reading here too often, but thanks for the eventual responses.

    After planning what I could in my free time, I finally realised the the glass is not going to work for me - primarily because of the weight issue. It just makes it overall very difficult to work with.

    My choice therefore fell on greenhouse film and I am currently designing a greenhouse with a wood construction that will enable me to use a double film. It will be done so that replacement of the film every few years, will not be too much of a chore.

    Basically, the size of the greenhouse will be 12mx5.6m. The position in my backyard where I need to put it, is sloped in two directions and I will have to level the area and raise it a bit to prevent rain from running it. Since I need over 20m³ of gravel for filling, it is a viable option to consider a wooden deck instead. Hopefully I get that finalised soon to start with construction.
     
  13. Justenufffarm

    Justenufffarm New Member

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    Any news on the new covering?
    I have several customers that are ready to get some!
     
  14. Yabbies4me

    Yabbies4me Administrator Staff Member

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    ...
    Glass, Polycarbonate or sheet?... Why not plastic bottles?... help the environment by recycling.

    The link doesn't go directly to the post, the code Facebook gives me to embed the post won't link, but the bottle greenhouse is one of the top two posts on my timeline, you'll see it as soon as you start scrolling down.

    I think it's a brilliant idea for a small backyard greenhouse.

    Cheers.
     
  15. Peter the Greek

    Peter the Greek Member

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    Murray,

    Getting a little ahead of myself. I am planning my "MKII" system, which will like go in a greenhouse or glasshouse. Did this product get off the ground? what's your general recommendation these days (given I'm in Sydney?)

    It'll be a 4m x 3m - big tank and filers at one end, possibly a DWC bed and towers for the rest
     
  16. Abhishek Kapoor

    Abhishek Kapoor New Member

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    I prefer polycarbonate as it is a lot safer, harder and easier to keep clean. but like Rainy days says it can break at the edges where the clips go, but this problem can be resolved by moving the clips to some other position. My greenhouse is now six years old and still has all the original poly sheets.
     
  17. Jayant Bhavsar

    Jayant Bhavsar New Member

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    We can supply laminated woven Plastic which last for 10 years as covering material for greenhouses.
     

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