Solar Glass - Pilkington K and plant growing

Discussion in 'General Gardening Discussion' started by JWK, Apr 25, 2009.

  1. JWK

    JWK Gardener Staff Member

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    I wonder if anyone has any experience of growing seedlings behind this new Solar control glass?

    The reason I'm asking is because up to a couple of days ago I was using my half built extension as a nursery, bringing on my tomato & cucumber etc etc seedlings. It was open to the outside and everything was doing really well - I built a small cold frame to help.

    I have just fixed in the windows and doors and they have this Pilkington K solar reflective glass. Its very good at keeping the heat out of the extension, but I'm guessing it might also be cutting out all the solar wavelengths that my plants need to grow. :scratch:

    Anyway, its a bit early to get my seedlings into my greenhouse and I want to keep them growing inside the extension for at least another couple of weeks.

    Anyone got it fitted to their conservatory and found it is OK?
     
  2. PeterS

    PeterS Total Gardener

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    Hi JWK. I have never heard of it until now. So I just had a Google. http://www.lifestylewindowsandconservatories.com/pilkington_glass.asp

    I don't know anything specific about it, but my physics tells me that things that are poor radiators are also poor absorbers of the same radiation. So I suspect that it is a coating that reduces the amount of heat radiation that passes through the window in both directions. This would keep it cool in summer, less radiation coming in from the sun. But also warmer in winter as less heat is lost from the house by radiation. This is exactly the same way that cloud cover in winter reduces the chance of frost. The clouds prevent the radiation from the earth being lost into space, whilst when there is no cloud the heat that is radiated from the earth results in a colder frostier ground. It sounds very sensible. The only downside on the domestic front is that on a sunny day in the winter you won't get the benefit of the sun as some of its radiation will be turned back.

    Your plants don't really want the heat at this time of year. They want the light, which is a different shorter wavelength. The coating on the glass obviously doesn't effect light. It it did the glass would appear darker when you looked at it. So on balance it seems to be good for plants as well as people.
     
  3. pete

    pete Growing a bit of this and a bit of that....

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    I have a feeling it does look darker.

    My windows that are fitted with it have a very subtle greenish tinge, (from the outside), not noticable until you compare it with non K glass.

    Sounds like I read your link first Peter, but I swear I only read it after writing the above.:D
     
  4. Paladin

    Paladin Gardening...A work of Heart

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    I sometimes split Double glazed units and reuse the glass for single glazing...'cos I'm parsimonious not tight:p,but I can't use the treated pane because of the dark tint on it.

     
  5. PeterS

    PeterS Total Gardener

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    I always trust a man of the cloth :D

    I am not surprised that it is a bit darker. Its very difficult to cut out just the heat wavelengths, without effecting the light wavelengths. But I don't think that will be too much of a problem JWK. Some of my seedlings are on the shady side of the house and others on lower tiers in the greenhouse, where it is very dark. Not ideal - but they will still grow. In later months plants will be getting far more light than they can use. But I doubt that we are there now.
     
  6. JWK

    JWK Gardener Staff Member

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    Thanks for the replies guys. The glass has got a slight tint, but hardly noticeable. What is very noticeable is the amount of heat it stops, it will be interesting to see what happens in the middle of summer.

    I'm going to experiment this year I've decided, as I'm sure I will keep more plants in it in the future and I need to know if they are affected. I am hoping your assessment is correct Peter, it make a lot of sense. I will keep a few plants inside this year just to see how they go, and keep the rest in the greenhouse during the day. Then I will be able to compare their growth rates.

    It's a good point Peter, we will not benefit from the winter sun as much as we could. The main issue we were trying to solve was that our previous conservatory overheated very quickly whenever the sun came out, so we fitted blinds which didn't really make any sense to me, we were either in the dark or too hot. This K glass is very effective, the temp measured behind the glass in the full sunshine at midday today was 5 deg C lower than outside.
     
  7. JWK

    JWK Gardener Staff Member

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    Thats reminded me that the office where I work have windows with a very dark tint, and we have plenty of office plants growing in there that don't seem to mind. Maybe thats the proof that it is OK for plants :thumb:
     
  8. Kristen

    Kristen Under gardener

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    "we have plenty of office plants growing"

    If its "office landscaping" (rather than folks own pots along the windowsill) they may have installing growing lights, instead of normal bulbs, above the plants?
     
  9. JWK

    JWK Gardener Staff Member

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    Kristen, its just fluorescent lights in there, nothing special.
     
  10. JWK

    JWK Gardener Staff Member

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    :hehe: I wonder if you should be using the tinted glass for cloches Pal, it would be a shame to waste it :thumb:

    Hmmm, thinking about it, that might be a risk, beacuse if it's this solar reflective stuff I've got you have to have it the right way round to get the effect, if it was the wrong way round you might end up frying your plants!
     
  11. PeterS

    PeterS Total Gardener

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    I doubt that it is directional. The bit that does the work will be a thin film on the surface of the glass. It won't have a back or a front. The only reason that it is on the inside pane of a double glazing unit it to protect the film from the elements and from people cleaning the windows.
     
  12. JWK

    JWK Gardener Staff Member

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    You are right Peter, having checked my glass and talking to Pilkingtons today - its labelled inside/outside and initially I thought that so the reflective coating was the correct way round. But its also got a self cleaning coating as well - and that needs to be on the outside, so the label is for that.

    Pilkingtons weren't very clued up on its effect on plants. They thought the main effect would be UV light reduction, they told me that normal double glazing cuts out some 56% of UV, this K glass coating reduces it by another 10%. A little googling since tells me that too much UV is bad for plants. Also google says that the most important light wavelengths are red and blue and my new glass is not cutting that out. So I reckon it will be OK for plant growth.
     
  13. Kristen

    Kristen Under gardener

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    I did an A level project on the effects of light wavelengths on plant germination and growth (a means of converting Physics to Botany!). But I can't remember the results now ...

    Similar conversion of Chemistry to Botany doing chromatography comparison of the dies in flower petals, and I presume Maths was something to do with statistical analysis of plants, but I can't even remember what the project was now! Or the Biology one for that matter ...

    Anyway, I scraped through but got amazing marks in Computing (which was a subsidiary subject) because I fancied Wendy who drove the ICL 1900 mainframe computer :)
     
  14. pete

    pete Growing a bit of this and a bit of that....

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    As far as I know you always get a label telling you which side should face inwards, even without a self cleaning coating.
    The treated K glass should be on the inside.
     
  15. Kristen

    Kristen Under gardener

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    Would you Adam & Eve it, I fell over this on my travels just now:

    [​IMG]
     
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