Do windows filter sunlight and is it less optimal for plants?

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Nicotin

Active Member
Hello friends, I'm wondering if glass from a regular thermopanel sliding door (glass-air-glass) will make sunlight less optimal for cannabis by filtering some of the sun's beneficial rays?

I have the option of growing a plant on an apartment's balcony or to put it inside right after the sliding door. I'd rather put it inside because from that angle neighbours can't see it at all, but I'm curious if the plant won't get as strong because of this. It gets direct sunlight in both cases, only that in option 2 it passes through the sliding door.

Thanks!
 
Most new (er/ish?) glass does block at least some light. Could maybe disguise it in some way? Stick a few fake flowers on it, or something like that? Or even shadecloth which would still allow plenty of direct light yet allow some measure of privacy.
 
Glass is a fluid that is frozen at normal temperatures. Look at old glass and you can see that over time it does run. It does restrict some of the light that goes through it, but that depends on the purity of the glass and its thickness. UV however is blocked by the glass. You can not get a suntan from indoors through the glass, so whatever it is that plants need of the UV, it will not get it inside.

I don't think this affects the plant a lot though, other than their ability to get direct light through that little portal through a large portion of the day. The larger the window, the better. Direction also matters a lot. My grandmother had several carts of beautiful plants in her SE facing sunroom as long as I knew her.
 
Nicotin said:
Hello friends, I'm wondering if glass from a regular thermopanel sliding door (glass-air-glass) will make sunlight less optimal for cannabis by filtering some of the sun's beneficial rays?
Click to expand...

That's actually complicated... Depends on factors such as thickness of the glass, refractive index, angle of the light source in relation to the pane of glass... and the attenuation varies across different wavelengths. But generally speaking, the old-school "single strength" panes of glass (which aren't really seen in windows these days, unless it's a really old house that has never had its windows replaced) reduce the light by approximately 9% to 11%. Thicker glass blocks more. That reduction will be for each piece of glass, of course - if two panes of glass each block 9%, for example, then the net amount getting through will be 82.81% of the total (100 - 9% = 91, 91 - 9% = 82.81). In the last 40 years or so, many manufacturers have included some kind of coating on the inner side of one or more pieces of glass in a multi-pane window/door, and these coatings further reduce light transmission (even if the coating is not noticeable by people). Not all of them have such things, but many do.

Furthermore, even a small amount of dirt/etc. on the glass will add to the overall reduction. If you clean both outer surfaces every few days, it's not significant - but most people probably don't. We tend to not notice this reduction because it occurs gradually over time, and because the human eyeball makes a lousy light meter.

Taken all together, and combined with the fact that the majority of light getting through a window is indirect instead of direct... well, it's half the reason why window box planters are installed on the outside of houses instead of the inside ;) .

Greenhouses have glass, some of them - but it's a far higher percentage of the walls/roof than the average home situation.

You can easily grow plants that don't require a lot of light indoors. Unfortunately, cannabis is not such a plant. Nonetheless, people have done this, but (most often) with poor results, unless they supplemented with artificial lighting. Or just wanted to say they've grown a plant, lol.
 
Emilya Green said:
Glass is a fluid that is frozen at normal temperatures. Look at old glass and you can see that over time it does run.
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The old commercial or store windows had that thick plate glass, almost a 1/3 of an inch thick. Over the years it would slowly flow to the bottom of the window frame and even without measuring tools people could see that it was thicker there than at the top. Now-a-days the window glass is not as thick or fluid and has been replaced with stronger glass and the windows themselves are often smaller to reduce the chance of break-ins.

And there is "Slow Glass" as mentioned in by Bob Shaw in the 1966 story "Light of Other Days" (August issue of Analog), where slow-glass scenic windows or "scenedows" allow urban apartments to look out on beautiful scenery that has been stored when the sun light passed through the glass over the years.

That's it for the literary field and back to our scheduled conversation.
 
Nicotin said:
... the angle from the sun will change in a couple of months and there will be no direct sunlight coming through the glass panel, so I guess putting it outside will be a must at some point. I will try to do some mad LST to try keep it stealthy at ground level.
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Sueet said:
Could maybe disguise it in some way? Stick a few fake flowers on it, or something like that?
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Plan now. Sueet's suggestion is a start. I have seen photos of balcony grows that were stealthed with kitchen herbs on the railing and flowers in larger pots spaced out to distract someone on another balcony from noticing the weeds being trained to be kept low.

There was a photo going around years ago showing a balcony grow. The gardener used training and pruning and kept the canopy of the plants below the top edge of the railing. Then some bending over of growing tips once flowering started so that the colas were not growing tall enough to be seen.
 
Here's a "by the window" grow:

Winging It In Winter By The Window: Soil Auto Grow

Greetings friends, I missed the summer season and have been paying dearly for my meds! I have a gap and out of desperation am going to grow some window weed this winter. If I am capable, I will be erecting / hanging a diy led light above the plants to run overnight. I won't run it during the...
www.420magazine.com
 
Emilya Green said:
Glass is a fluid that is frozen at normal temperatures. Look at old glass and you can see that over time it does run.
Click to expand...
SmokingWings said:
The old commercial or store windows had that thick plate glass, almost a 1/3 of an inch thick. Over the years it would slowly flow to the bottom of the window frame and even without measuring tools people could see that it was thicker there than at the top.
Click to expand...

Sorry to burst your bubble but that's an old urban myth. You're not alone, I was taught it was a supercooled liquid, used to believe it and spread it too. 😆 After examining many old window panes they indeed did find some that were thicker at the top, debunking the myth that glass sagged over time.

'ancient Egyptian vessels have none of this sagging, says Robert Brill, an antique glass researcher at the Corning Museum of Glass in Corning, N.Y. Furthermore, cathedral glass should not flow because it is hundreds of degrees below its glass-transition temperature, Ediger adds. A mathematical model shows it would take longer than the universe has existed for room temperature cathedral glass to rearrange itself to appear melted.

Why old European glass is thicker at one end probably depends on how the glass was made. At that time, glassblowers created glass cylinders that were then flattened to make panes of glass. The resulting pieces may never have been uniformly flat and workers installing the windows preferred, for one reason or another, to put the thicker sides of the pane at the bottom. This gives them a melted look but does not mean glass is a true liquid.

Fact or Fiction?: Glass Is a (Supercooled) Liquid

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Nicotin said:
Hello friends, I'm wondering if glass from a regular thermopanel sliding door (glass-air-glass) will make sunlight less optimal for cannabis by filtering some of the sun's beneficial rays?

I have the option of growing a plant on an apartment's balcony or to put it inside right after the sliding door. I'd rather put it inside because from that angle neighbours can't see it at all, but I'm curious if the plant won't get as strong because of this. It gets direct sunlight in both cases, only that in option 2 it passes through the sliding door.

Thanks!
Click to expand...
Simply Yes... Sunlight is filtered through any glass. Usually it be only 70% light Absorption on a plant in a Greenhouse setting of either glass or clear poly... Keep them"Au Natural", if ya can.
 
i have my mothers by an east facing window and they do well. i have a very small, far away cfl that just stops them from flowering but doesnt really give any growth.

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