Author Topic: Upgrading greenhouse policarbonate, what thickness would be the best?  (Read 725 times)

Plantinyum

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Hi, i am planning on changing my greenhouse 4 mm policarbonate sheets with thicker ones. My goal is to have more insulation ability over the winter. My curent setup is a 4 mm poli in summer, on top of which i add a 1 layer of thick bubble wrap and one layer of polyethylene on top, that i do so i have additional insulation in winter. The putting and taking off of the additional layers is not a pleasant experience, so i am looking into more permanent options. In addition to that, the sheets get dirty and can really be cleaned well, so they end up additionally blocking alot of the already weak sun rays in winter.
I am thinking about 8 or 10 mm thick poli, and mostly aiming at the 8 mm one for now. Should i really change the poli and make it thicker, duss sacrificing some of the light passing trough, or should i rather focus on the heating instead?
I have the central home heating system connected in the greenhouse, so i use radiators in there. Last winter i pulled just fine with one 2 m long and two 80 sm long ones, they all are 60 sm in heigh. I have and additional outlet for another 2 m long radiator, which i also have, just didnt used it last year.

So would i be better of to stay with the 4 mm poli, without the additional sheets for insulation over winter, possibly with adding the additional radiator in there, or would it be better to have the 8 mm poli, which would increase the insulation value and lead to a decreased heating cost?

I also want to make the greenhouse frame a bit taller as plants are getting bigger and given that i cant provide additional side space, i could at least provide a bit of a vertical one. Would like to make the changes at one shot.

So what would you do?
« Last Edit: August 10, 2023, 12:38:12 PM by Plantinyum »

Daintree

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Thats tough.

Your greenhouse is fairly small, so upgrading the poly would not be super expensive. However, the thicker stuff is not as flexible as the thinner, and I would worry tht 10 mm would not be able to make the bend from side to side. It will put a lot of pressure at the top. So I would research the minimum bend radius and make sure you can do it.
If you can, I would do it. The difference in light transmission would not make a noticeable impact.

Another thing that would help retention are fans, up high, gently blowing the warm down onto the plants. I have four ceiling fans down the top of my greenhouse, about every ten feet. Even one fan would help a lot.

Or, if the winter covering works,,but is just a pain to install, maybe you could put it on some sort of roller.

Good luck!
Carolyn


Plantinyum

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Thanks Carolyn! I was also going at first towards the 10 mm, but ive red somewhere before, that exactly as you said, it is hard to bend and was prone to deformation when forced to bend. So i think i should be good with the 8 mm ones. They come in the size 2,10m to 6m , so i would need 3 or 4 as the lenght wont suffice if i chanje the metal frame.
I found them, at several places, they are not that expensive, and dudjing by the amount of work it would spare me, regarding the insulating sheets i wont have to add anymore.
The sheets privided an additional 1 to 2 degrees C,when the heating is off, it goes up if the heat is on. I think an 8 mm would beat that, it should theoretically, right?

The big problem is my passion fruit trellis, which is fixed to the top of the greenhouse, the main problem being that the plant is still on it and i cant really lift the metal foundation, until i take it in. Alot of other plants are fixt in some way to the  greenhouse itself, but not as hard to take off.

I would have to think about it, i would like to do this before winter, will have to be done after i prune and take the passion fruit in, and before the weather gets too cold for the plants to be left for one or 2 days without cover.

Regarding theflexability, they dont really provide the maximum bendable angle, just say the sheets of 8 mm are very flexible. My greenhouse is a dome shape.

By the way, the winter blanckets i was fixing via the screws i have fixed the policarbonate, i unscrew about half of them and then srew them on again, with the bubble wrap and nylon added. Very anoying to do, even twise a year...

fruitnut1944

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I've looked into upgrading my endwalls and sides from current corrugated polycarbonate to 8 or 16 mil double or triple wall. Based on my heating cost and cost of materials my conclusion is the added insulation won't cover costs to upgrade in less than 20 years.

But that all depends on your heating cost vs cost to upgrade. You can calculate heating cost with various coverings using one of the greenhouse heat cost calculators. We can't answer your question without knowing those figures and running the calculations.

I am replacing the roof covering using Palring 175 double layer inflated. Current is Solarig double layer. Both are woven poly. Solarig has lasted 10 years under intense west Texas sun with zero issues. Prior to that I used regular 6 mil 4yr poly double layer inflated. The 6 mil lasted 2-3 years before losing inflation and required a lot of upkeep due to holes and leaks.

Palring 175 is less than twice as expensive as 6 mil and lasted what, 3x as long. I think it's amazing material. The 175 is $0.20 per sq ft so $0.40 for two layers. 8 mil double wall is $2.00 per sq ft plus the connectors that go at each seam.

The woven poly double layer inflated has no seams so no heat leaking out there.

A lot depends on your frame as to which would be best, 8 mil double wall vs Palring 175. How would you attach both and how things line up. The woven will fit irregular, curved, or uneven surfaces that won't be suitable for the hard sheets of 8 mil.
« Last Edit: August 09, 2023, 12:52:49 PM by fruitnut1944 »

brian

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If I remember correctly, there isn't a big difference in insulation value between 6mm, 8mm, 10mm, two-layer polycarbonate panels.  There is some, but they all pale in comparison to non-glazing insulation such as foam and fiberglass.  I believe your time and money is better spent eliminating air leaks, insulating the perimeter, and/or covering the whole thing at night. 


Johnny Eat Fruit

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You can choose any polycarbonate thicnkness you like it's up to you.

When I upgraded from the thin 4 mm panels that came from my 6 X 8 Greenhouse I chose the 10mm panels for durability. They are thicker and last much longer than the 8 or 6mm panels. You can choose for your self.

Enclosed it my greenhouse with newly installed 10mm panels.

Johnny






Plantinyum

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The setup that i have now has a good amount of heat retention, i am ultimatetely looking for a material that will teoretically have a better insulation and light transition than the 4mm poli and bubble wrap layer. I am not looking for the cheapest way possible to do it, but also dont want to spend a lot of money either. If i hadn't wanted to rise the heigh of the greenhouse i wouldn't probably mess with a thicker poli, i would have bought a new bubble wrap sheet and worked with that. Since i dont want to mount and take off this sheet 2 times a year, i want to put something new, that will suffice i winter without additions to it.
I am sure that if i place the additional radiator, i will pull tru the winter fine, even without the bubble wrap blancket, but i would want something that will keep the warmth better in the transition seasons when i often do not heat, spring and fall.

Fruitnut1944, havent really done the calculations, even if i change the poli with a thicker one, i would still have to buy firewood each year. I mean, i am not that into calculating which one is the most economic way, i want something at least as good as what i have now, and slightly better.
The frame would suffice for both the 8mm poli and for the material you suggested, i like the poli better thought. The parling 175 i could not find for sale online locally, i found it internationally, but the price is higher than the 8mm poli.
To be fair, i dont really like the look of it, i really like the look of the policarbonate on the contrary. Dont know why, but the price of the parling, at the sites i found it is close to 2x more expensive than the poli.
Didnt know there were seams for the policarbonate sheets, havent found any for sale , will have to find them as they would be needed this time around.


Brian, i hardly have air leaks , infact, i deliberately left one thin and narrow stripe of unsealed gap at my front door, so i have some fresh air going inside ,even in winter, that was originally left from the time i had the wood stove as a heating device in the greenhouse, i left it then so air could go inside and i dont have the fire extinguished. I have since left it and seled it only in the extreme cold spells.
Any tipe of a blancket over the greenhouse is the thing that i shy away from. Too much fuss.

Johnny Eat Fruit, so far ive stopped myself at the 8mm, 10 would also be good, but as discussed above, i dont know if it would be flexiblw enough, 8mm seems to be the middle ground, regarding that 6mm is almost like my 4 mm i have now.

pagnr

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Have you investigated "double glazing". Twin skin / twin wall coverings are used to create a further insulating air layer between the wall sheets. Thee are also IR infra red films that trap heat. Also another factor is how the cover disperses light, to create a better light scatter.

Plantinyum

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Have you investigated "double glazing". Twin skin / twin wall coverings are used to create a further insulating air layer between the wall sheets. Thee are also IR infra red films that trap heat. Also another factor is how the cover disperses light, to create a better light scatter


havent heard of those, are they used with glass windows, like between the 2 layers of glass?
Do the infrared films stop any light spectrum? In any way they are ment for glass aplication

fruitnut1944

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It sounds like you have your mind made up based on appearance. We can't help with that. The 8 mil twin wall polycarbonate can last 30 years so that's a big plus. But if installed improperly you might be very unhappy after a few years. The people I've heard of unhappy have green algae growth between the two walls. If you have humid conditions and algae growth be concerned. To reduce that, tape is applied over the holes top and bottom. Solid tape on top and drainage tape on the bottom.

Installation guide: https://advancegreenhouses.com/wp-content/uploads/2014/08/polycarb-installation.pdf

If I were to use the sheets of polycarb, 8 mil, I'd use one that diffuses the light not clear. That gives better light distribution but drastically alters the look. You can't see in or out.

It looks like this: https://www.greenhousemegastore.com/products/solarsoft-80-twinwall-panel?variant=42701244301511&msclkid=b5c6995a48a01b082468fd8ea3afbe87&utm_source=bing&utm_medium=cpc&utm_campaign=ECI%20-%20Bing%20Shopping%20-%20All%20Products%20%5BHigh%5D&utm_term=4580221858234042&utm_content=All%20Products

Palring 175 is $0.20 per sq ft. The cheapest 8 mil twin wall I can find is $1.69 per sq ft over 8 x as expensive. I don't know what you are looking at but it's unlikely that Palring is 2x as expensive for equal sizes.

It's easy to find poly of all kinds that have the IR, infared, feature. I'm not sure if 8 mil twin wall has that. What it does is somewhat limit transmission of IR, ie heat, thru the material. That reduces heat loss at night and limits heat gain during the day. It's not a huge factor but noticeable. It reduces heating cost in winter and cooling cost in summer. Palring 175 is AFIR. AF reduces condensation on the interior. IR limits heat transfer.

Plantinyum

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #10 on: August 10, 2023, 01:12:26 PM »
Fruitnut , the cheapest i found this material was for 700$ , for a size of 30 by 105 ft.  The 8 mm polly would cost me like 300$. The palrig price may be worth it, but again i dont need so much, cant find it in my country, which means that i would have to include a whatever, probably substancial  shipping cost. I am not saying that the material does not work ,it may be better than the policarbonate by far, but still i have experience with policarbonate, i like that its rigid and yes, the looks of it also wins me. Its the very thin, nylon like nature of the palring that makes me nervous to have it over my gh. I will have to try this material over another greenhouse that does not contain my tropical collection ,and evaluate its characteristics.
 
But doesnt the diffused light poli stop more of the light from passing trough?
I am not sure if there are poli panels with the IR feature, they are only uv resistant.


As for my present poli cover, some of the channels are full halfway with water, that happened in the start, as at the places i cut the windows ,the holes werent sealed properly( some of them,i used silicone ). I poked holes ot the botom of those, so now they drane. It is strange that people have apgae between the layers, i have so much of the channels occasionally having moisture or water, yet no algae in there, i habe alot of algae on the inside of the poli, like the inside of the greenhouse, but that i can clean easily. I'd imagine that an algae growth between the layers would rend the material useles... My 4 mm poli is looking perfect in its third year.
« Last Edit: August 10, 2023, 01:25:29 PM by Plantinyum »

pagnr

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #11 on: August 10, 2023, 04:38:50 PM »
Have you investigated "double glazing". Twin skin / twin wall coverings are used to create a further insulating air layer between the wall sheets. Thee are also IR infra red films that trap heat. Also another factor is how the cover disperses light, to create a better light scatter


havent heard of those, are they used with glass windows, like between the 2 layers of glass?
Do the infrared films stop any light spectrum? In any way they are ment for glass aplication

Not necessarily glass, can be two layers of plastic greenhouse film ( separated ). Some people put bubble wrap on the inside of house windows for privacy and insulation. Some people fix a clear plastic film inside their wooden window to create a still insulating layer over the window.
Woven clear plastic films are an alternative to polycarbonate. they have a good life span, can be used as walls on many structures, or roofs on dome or tunnel structures.
https://redpath.com.au/plastic-films-textiles/greenhouse-films/polyweave-reinforced-greenhouse-film/

fruitnut1944

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #12 on: August 10, 2023, 06:22:42 PM »
OK, I didn't realize your greenhouse was that small. If I could cover mine in 8 mm twin wall for $300 I'd have it ordered in 10 seconds. I got a bid to cover one end and two sides of mine for $11,000. Maybe shipping cost has dropped but I doubt the materials have by much.

drymifolia

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #13 on: August 10, 2023, 08:14:36 PM »
occasionally having moisture or water, yet no algae in there, i habe alot of algae on the inside of the poli, like the inside of the greenhouse, but that i can clean easily. I'd imagine that an algae growth between the layers would rend the material useles

The person who installed my 8mm twin wall polycarbonate did not seal them properly even though I thought he had. Now, about half the panels have turned green from algae inside them in just 2 years. I had to buy extra panels initially because of bulk pricing, and kept the extras, so I'm planning to replace some on the south side of the roof next year to improve light transmission again, but the north side will stay ugly green. You're very lucky if water is getting inside your panels but no algae yet.

Plantinyum

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #14 on: August 11, 2023, 12:52:25 AM »
My greenhouse is 4 by 3 m. Quite small, well the actual price after i searched various sites yesterday, regarding 8mm, will be a bit higher, around 400$.there was a place where the price was substantially lower, but im afraid that the quality of the material may be also.  But again, i will have to take the measurements into account, and i am thinking of evelating the structure with at least 50 sm or 1 m, so that will add more cost. Planning to do this sometime in september, hopefully.
After this elevation of the structure, i will have to place fant on top for air curculation, i imagine most of the heat will be at the ceiling. 

fruitnut1944

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #15 on: August 11, 2023, 09:06:33 AM »
Good luck with your update/remodel. I hope that works out well for you and your plants.

The recommended way to help keep water out of your poly channels is solid aluminum tape on top and ventilated aluminum tape on the bottom. There are many more recommendations for installation that would be worth reading. This material can last a long time but only if properly installed.

I enjoyed discussing this and appreciate that you responded to comments. Often on this forum that's not the case.

Plantinyum

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #16 on: August 11, 2023, 11:26:58 AM »
Here are some pics of the water filled channels, the two lines on both sides of the seam, in one of the pictures, this is water. Some others have condensation in them, but i only have a white limestone deposits, from the times ive washed the greenhouse with my well water. Strangely, on the inside of the greenhouse, i have a ton of green algae ,havent bothered to clean it, which i should have done...
My policarbonate is fixed on the bottom side, directly to the base, very well sealed so that probably prevents the algae from growing inside the channels. I have to punkture the water filled channels on the bottom, so they drain.

Fruitnut, yeah ,thank you for your suggestions! I just really like the estetics and the jeneral performance of the poly , thats why i woudnt trade it for something else. My current setup doesnt have any tapes or sorts, and there is water inside the channels and its probably pure luck that i dont have an algae in there. So this time i will take both the tape and the seam connectors.















« Last Edit: August 11, 2023, 11:33:35 AM by Plantinyum »

drymifolia

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #17 on: August 11, 2023, 06:27:20 PM »
Here's a great example of the difference between a well-sealed panel and one that was poorly sealed (both are dusty and in need of cleaning, though). The left panel is sealed with the tape, the right one they only sealed the top and I guess they thought the flashing for the gutter was enough to seal it, but algae got into it:


Plantinyum

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #18 on: August 12, 2023, 01:08:55 AM »
Here's a great example of the difference between a well-sealed panel and one that was poorly sealed (both are dusty and in need of cleaning, though). The left panel is sealed with the tape, the right one they only sealed the top and I guess they thought the flashing for the gutter was enough to seal it, but algae got into it:



Did you use the same tape both for the top and the bottom? I mean, did you placed a ventilated tipe of tape on the bottom, like Fruitnut suggested,  or are both ends sealed with the non ventilated one?
Nice example, shows that tape realy is needed.

drymifolia

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #19 on: August 12, 2023, 09:21:47 AM »
Did you use the same tape both for the top and the bottom? I mean, did you placed a ventilated tipe of tape on the bottom, like Fruitnut suggested,  or are both ends sealed with the non ventilated one?
Nice example, shows that tape realy is needed.

I provided the contractor with both types of tape and the instructions for installing, but I wasn't closely supervising and I'm not sure what he ended up doing for the top. I was adding some silicone to seal leaks last year and noticed the bottom tape (perforated) was missing from some panels, but not all of them. It was the first time he'd used polycarbonate panels and I was too trusting of his confidence level. I probably should have just done it myself, but I was recovering from neck surgery at the time and didn't want to risk re-injuring it.
« Last Edit: August 12, 2023, 09:27:09 AM by drymifolia »

Plantinyum

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Re: Upgrading greenhouse policarbonate, what thickness would be the best?
« Reply #20 on: August 12, 2023, 10:57:13 AM »
Did you use the same tape both for the top and the bottom? I mean, did you placed a ventilated tipe of tape on the bottom, like Fruitnut suggested,  or are both ends sealed with the non ventilated one?
Nice example, shows that tape realy is needed.

I provided the contractor with both types of tape and the instructions for installing, but I wasn't closely supervising and I'm not sure what he ended up doing for the top. I was adding some silicone to seal leaks last year and noticed the bottom tape (perforated) was missing from some panels, but not all of them. It was the first time he'd used polycarbonate panels and I was too trusting of his confidence level. I probably should have just done it myself, but I was recovering from neck surgery at the time and didn't want to risk re-injuring it.


Thanks! I will search for both types then !