# Shade cloth help!



## bullsie (Jun 19, 2016)

I put the orchids out - mostly Cattleya alliance - in the yard every summer. I put a tarp on and off to minimize sun damage - on during dry days off when it rains. I want to invest in shade cloth so I don't have to be spending so much time tarping and untarping and finding I'm too late for sunburn and squashed plants from weighted down rain filled tarps. SOOOOO going to invest in shade cloth. Now, what shade %???

I am in Pennsylvania, the area they are at gets full sun for probably eight hours easy now. Any recommendations for shade percentage.


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## AdamD (Jun 19, 2016)

50 or 60%. I use 50 plus a clear plastic which is itself a 10-15%, but I'm a bit farther south


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## Bob in Albany N.Y. (Jun 19, 2016)

I'm in NY and use 50% shade cloth year round for a mixed collection to include catts. and vandas. I never get sunburn unless it is from the one side of the greenhouse that doesn't have shade cloth.


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## Ray (Jun 19, 2016)

With that much full sun, I would agree at 50%. I am more-or-less directly east of you and used 30%, but my greenhouse is protected by trees. FWIW, Parkside used to use 30% winter and another 30% on top (resulting in the equivalent of 51% shade) in the summer.

I strongly urge you to consider Aluminet, and buy it from Gothic Arch Greenhouses, as they have the best price.


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## AdamD (Jun 19, 2016)

I second the aluminet


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## Stone (Jun 19, 2016)

bullsie said:


> I put the orchids out - mostly Cattleya alliance - in the yard every summer. I put a tarp on and off to minimize sun damage - on during dry days off when it rains. I want to invest in shade cloth so I don't have to be spending so much time tarping and untarping and finding I'm too late for sunburn and squashed plants from weighted down rain filled tarps. SOOOOO going to invest in shade cloth. Now, what shade %???
> 
> I am in Pennsylvania, the area they are at gets full sun for probably eight hours easy now. Any recommendations for shade percentage.



I need to use 75% outside because of the low humidity here in summer. But I agree, over there with summer rain 50 to 60 should be good.


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## abax (Jun 19, 2016)

50% aluminet and the best place is as Ray said...Gothic
Arch. They'll also do the grommets for you if you specify
where and at what intervals you want them. Nice people
too.


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## John M (Jun 20, 2016)

I have 50% shade cloth and it's been fine for years. However, I changed the plastic last fall. That means less green algae inside and dirt/grunge on the plastic, adding to the same percentage. I'm finding that the 50% is NOT enough now. My plants are cooking a bit. No sunburn; but, a lot of yellowing/bleaching. No permanent damage; but, right now, I'd like them to be more green than they are. If I could afford it, I'd get a new 65% shade cloth in a heartbeat. When the plastic gets older and dirty, I could go back to the 50%.


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## gego (Jun 20, 2016)

Distance/height of the shade should be considered. The farther the shade to the plant, the lesser shading you need.Double layering has the advantage of trapping some of the heat and the possibility of removing the second layer during winter. 

I prefer dark/black color nets because it absorbs heats during summer.

Hope this helps.


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## littlefrog (Jun 20, 2016)

When I had a greenhouse... I had two layers of (IIRC) 50% shadecloth. I would remove one layer in the late fall and put it back on in April or so. That was mid Michigan. Aluminet is awesome.

My shade structure now has the same two layers, but only double layered on one half. Cattleyas, aussie dendrobiums, bromeliads get the bright side, everything else gets the shadier side. I have to take all of that down every year or the snow will do that for me and that gets pretty destructive... I am using just regular shadecloth now, the aluminet seemed excessive for my application.


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## Ray (Jun 20, 2016)

gego said:


> I prefer dark/black color nets because it absorbs heats during summer.


Actually, dark shade cloth does not absorb-, but generates heat in the sun.

When the sun hits the cloth, four things happen to it:

some goes straight through unaffected,
some is diffracted and dispersed by the edges of the openings,
some is reflected, and
some is absorbed and turned into heat energy.
All else being equal in the construction of the cloth, the darker the color, the more is turned into heat and less is reflected.


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## gego (Jun 20, 2016)

UV is absorbed. Basically trapped. Heat is generated by the sun not by any material. The shade should absorb the light/ energy that need to be filtered out. If it is reflected, that energy could be reflected towards the plants because not all surfaces of the shade are facing away towards the sky. I expetimented this with the same material but different colors, black color is the coolest. Although the shading are the same, black color filters light more than the light colored. 
Your last sentence says it all, less is reflected. 

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## Ray (Jun 20, 2016)

No offense, but I think you had better refresh your understanding of physics.


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## C. Rothschild (Jun 20, 2016)

I have a screen porch that faces west in Kansas and the green I bought doesn't do much to be honest. It was the cheapest I could find but the good thing is that it supposedly blocks some of the UV. I'm not sure what that would do for plants but I guess if you're going to spend a lot of time in there it's good. Is the UV important for plants? Someone on here probably knows.


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## gego (Jun 20, 2016)

No problem Ray, thats what you think. I dont think its the physics, it your analysis. 
Cloth does not generate geat, it dissipates the heat from light because light is being blocked. Not reflected and reflacted. 
I dont think we differ and you say light is not reflected and so it is absorbed and energy is dissipated on the cloth. If you keep the heat dissipated on the cloth from building up your enclosed gh then gh is cooler. 
You assumption of reflected light is quetionable. Some light get reflected back upwards/ away, some light get reflented down wards towards you gh.And some light passes thru the white cloth. If all lights that hit the cloth are reflected away, then we both agree. But that is not true. You dont need physics for that, its all observation. Thank you. 

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## gonewild (Jun 20, 2016)

C. Rothschild said:


> I have a screen porch that faces west in Kansas and the green I bought doesn't do much to be honest. It was the cheapest I could find but the good thing is that it supposedly blocks some of the UV. I'm not sure what that would do for plants but I guess if you're going to spend a lot of time in there it's good. Is the UV important for plants? Someone on here probably knows.



Are you sure the screen blocks UV or is the plastic just resistant to deterioration by UV?


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## emydura (Jun 20, 2016)

I have always read and been told to use light coloured shade cloth if you want to reduce the build up of heat in your glasshouse, so I use a sandstone colour.

Maybe, the Australian sun is much more intense than growers overseas experience, but I seem to use way more shade cloth for my Paphs than others. In summer I use two layers of 70% around the whole glasshouse plus a layer of aluminet (50%) over the middle section. The polycarbonate and bubble wrap layer would block some light as well (maybe 10%). I find the leaves on my plants are two light with anything less. In winter I remove one of the 70% layers. I have also just removed the aluminet as a trial. In winter the only shade cloth I have on (70%) is fitted inside the house rather than outside so the sunlight hits the polycarbonate walls directly. So even when the temperatures outside are 10oC or less, the temperatures in my greenhouse can go above 30oC.


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## C. Rothschild (Jun 22, 2016)

gonewild said:


> Are you sure the screen blocks UV or is the plastic just resistant to deterioration by UV?



I says it protects against "harmful Ultraviolet something" I looked it up and some research says that Ultraviolet light can damage plant cells.


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## gonewild (Jun 22, 2016)

C. Rothschild said:


> I says it protects against "harmful Ultraviolet something" I looked it up and some research says that Ultraviolet light can damage plant cells.



Keep looking it up and you will also see that UV light benefits plants!
Probably as much benefit as harm.
UV light likely helps to control bad bacteria and fungi that are on the leaf surface.

I was just curious if your shade cloth was designed somehow to specifically block UV rays. it probably just reduced UV along with the other light waves as it makes shade.


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## Ray (Jun 22, 2016)

Gego, it's not my analysis, it's basic science.

Black pigments reflect no visible wavelengths (which is why it looks black), and white pigments reflect all wavelengths. If the light is not reflected, it is absorbed. Energy does not just disappear: if that light energy is absorbed, it is turned into heat.

Put a piece of white paper and one of black paper out in the sun, after a few minutes, if you put your hand over each, you'll note a significant temperature difference, and the white one won't be hotter.


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## Ryan Young (Jun 22, 2016)

Black accumulates and dissipates heat fastest so that heat is going somewhere. If it is outside your greenhouse off of the glass or plastic it will dissipate into the air. If it is touching the surface or inside the greenhouse it will also dissipate / transfer to surface increasing temperature inside. 

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## gego (Jun 22, 2016)

Ray said:


> Gego, it's not my analysis, it's basic science.
> 
> Black pigments reflect no visible wavelengths (which is why it looks black), and white pigments reflect all wavelengths. If the light is not reflected, it is absorbed. Energy does not just disappear: if that light energy is absorbed, it is turned into heat.
> 
> Put a piece of white paper and one of black paper out in the sun, after a few minutes, if you put your hand over each, you'll note a significant temperature difference, and the white one won't be hotter.



Hey Ray, like what I said we are on the same page, black doesn't reflect, so light is absorbed, energy turned to heat and dissipated on the cloth. That's what I said.

I don't what to go deep into it so I just said "heat is absorbed".

I would rather block the light than reflect it if the reflection is a) only partial and b) the direction of the reflection is not totally away from the gh.

My point is if I'm not very clear yet, is that if I have 50% shade, I prefer that I block 100% of that 50% blocked light (if possible) not reflected but blocked. And that black cloth will do a better job.

Then under the black shade add another layer than can insulate and keep that heat absorbed by the cloth from flowing down to your greenhouse. And we know hot air rises. Place some good distance between them so airflow can blow the heat out. This is the trap.

A plastic sheeting is good for the next layer so the 50% light that went thru will be diffused and spread nicely/evenly to the gh. If you still need more shading after this, then add a white cloth below the plastic sheeting.

50% of light is still a lot of light. If the sun is providing 10,000 FC, you will have at least 5000FC (ave) for your plants. If you place a vanda close to the shade you may have a yellow leafed vanda in a short time.

You better read my post again, lol, if there is a shade that will 100% reflect that light away back to the sky then that is my ideal shade.

Better check with your neighbors though,,,,


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