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design for solex/polycarbonate greenhouse

 
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Hello everyone,I never participated in a forum in my life and english is not my first language so forgive me in advance for any étiquette faux pas I am considering building a couple of passive energy greenhouses here in northern New-Brunswick (cold and huge snow loads). It's gonna be a two step project first part is gonna be a small garden center deal with flowers and plants in the springtime. Second part will be an aquaponic system where I hope to be able to produce fresh vegetables and some fruit year round,the problem is...Canada . I am considering solexx as a material for it but I'm not sure if the diffused light is gonna conteract the natural heat gain I would get from a transparent covering?! I want to use black water barrels as heat sinks to store the sun's energy,I can't seem to find any info about this in particular anywhere,and I can only guess it would still be better to use solexx?! Thanks
 
Alex Thériault
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I know Dillon said something about using different materials for the roof and side of the greenhouse...but what I'mgonna build ( with the hope of keeping operation costs as low as possible) is a passive green house where only the south facing wall is see thru the other three sides are insulated to keep the warmth in.so it's only gonna be solexx or polycarbonate angled up according to my latitude so it gets optimal sunlight in the short winter days.
 
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EDIT: Now that this is a new thread, some references to things above refer instead to things here: https://permies.com/t/44837/greenhouses/Solexx-Polycarbonate

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Hi Alex, welcome to permies.com!

I think the challenge with that design will be getting enough floorspace without the structure becoming unrealistically tall, if I am understanding your design correctly; you will have 3 walls, and then a sloped roof coming to near the ground on the fourth side?

If I am understanding that design right, to get an 8 foot width, using an angle of 65.83(optimal Oct 7th-March 5th solar panel angle for Miramichi, per http://www.solarpaneltilt.com/) you would need a 17.8ft tall building with a 19.5ft span of solexx/polycarb. Yikes!



Interesting question about the light transmittance; I found this additional source which claims 61.5% transmittance on the 5mm Solexx : http://www.adaptiveplastics.com/wp-content/uploads/solexx-technical-guide.pdf

Interestingly, it also has 'shading coefficient' and 'solar heat gain coefficient' values, all different, which suggests this topic is a bit more complicated that it first appears. I do not think that the diffusing effect is significant to heat gain in and of itself; I think the impact of the translucent vs transparent plastic is already accounted for in these numbers.

You'd still need to find matching stats for whatever you are comparing against to have a complete comparison though...

The same .pdf makes the argument for Solexx in cold climates as the superior R-value will be very important; I completely agree with the R-value being key, but would again point out that their comparisons leave out the thicker, many-walled polycarb options I mentioned above, which surpase Solexx in R-value. They also substantially surpass Solexx in price, however...
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