Optimal Glass Selection for Vertical Farming Facades

[zzinfinity]

I'm doing some research on Vertical Farming with the end goal of creating a facade in an existing building. I'm trying to make a recommendation on what sort of glass to use on the exterior to provide light to the crops. Does anyone know of any good resources or glass suppliers?

 

[Bobbywhy]

zzinfinity, I did a Google search using the terms "greenhouse glass" and found lots of choices, including non-glass products specifically for illuminating plants. Why not try a search yourself? If you find a certain product and have doubts about its characteristics, for example, you could return here with the specific product's specifications and ask about your doubt.

Cheers,
Bobbywhy

 

[zzinfinity]

Thanks Bobbywhy, that was helpful.

 

[Straw_Cat]

The answer to what is the best "glass", or glazing, depends on what kind of building you're working with, where and how it is located, and, unfortunately, how deep your project's pockets are.

You have two conditions which work at cross purposes here: You want to allow as much light into the garden space as possible, and you want to lose as little heat as possible. You also don't want it to overheat, which is entirely possible if you have quite clear days in the winter time and a lot of glazing.

In a descending order, the best insulating systems available are:
Vacuum glass windows/ glazing assemblies. I don't know if this is available to any extent yet, but here's and article about it:
http://www.buildinggreen.com/auth/a...olutionary-Vacuum-Glass-Coming-from-Guardian/
I also didn't see any reference here as to how much light passes through the windows. The Guardian company can answer that, if they've made it this far since 2009. But I think these come in at R-20.

The next best choice would be panels containing an aerogel. The draw back with these is that it has a much lower light-transmissivity level than glass.
http://www.kalwall.com/walls.htm
And
http://www.cabot-corp.com/Aerogel/Daylighting
These are apparently upwards to R-13/inch or thereabouts.

The third option is Low-e triple-glazed windows such as offered by the following companies:
http://www.seriouswindows.com/ Claims an R-13 rating.
http://www.floriangreenhouse.com/glass.html Claims an R-10 rating.

Ref: http://www.greenbuildingadvisor.com/blogs/dept/energy-solutions/making-case-triple-glazed-windows

It should be noted that a lot of glazing can lead to overheating, even in the winter time.
http://www.buildingscience.com/documents/insights/bsi-006-can-fully-glazed-curtainwalls-be-green

An overlooked trick to getting more light farther back into a structure is to provide 'ledges on the outside of the building which bounces light off an angled ceiling into the deeper parts of the structure. If the ledges angles can be adjusted, they can be controlled to maximize the bounce during the winter and, handily, to provide shading in the summer.
Here's a small gif showing what I mean:
http://www.wbdg.org/images/daylighting_6.gif

Found at:
http://www.wbdg.org/resources/daylighting.php

The glass which allows the most amount of light to pass, btw, is a low-iron glass.

One thing to keep in mind is that argon-filled windows will lose a percentage of the argon every year, especially at high altitude, so they become less effective at insulating over the years.
Unfortunately. Planning on replacing them in 15-20 years is part of the price of doing business, I guess.

I am highly in favour of vertical farming, and the idea of skyscraper greenhouses occurred to me at least 15-20 years ago.

 

[zzinfinity]

Thanks Straw_Cat, those were some great resources! I was wondering if you had an opinion on polycarbonate panels for use in vertical farming. I know they're used a lot in green houses and seem attractive because of their relatively high PAR transmittance. Not as attractive as glass I guess, though. Just wondering if you had any thoughts. Thanks again!

 

[Straw_Cat]

Thanks Straw_Cat, those were some great resources! I was wondering if you had an opinion on polycarbonate panels for use in vertical farming. I know they're used a lot in green houses and seem attractive because of their relatively high PAR transmittance. Not as attractive as glass I guess, though. Just wondering if you had any thoughts. Thanks again!

I don't have much of an opinion one way or the other about polycarbonate glass panels, other than they won't be all that recyclable when the end of their life comes, (as far as I know at this moment), unlike glass ones. I saw one or two comments which seem to indicate they'll last maybe 15-20 years or whatever.
Not as long as decent glass, but on the other hand, there is a very strong possibility we'll have clear pv panel glass by that time. :-) So polyC could be a bridge until that comes.

I'm an advocate for advanced sustainable building methods, and so-forth, and my ideal goal in that field would be an open plan, net-zero or better, house that can last at 500+ years. That, along with permaculture, living walls and roofs, Vertical Gardens, and so-on.

I have also started helping promote Urban Wildlife Habitats Design, via Facebook. Check it out at:
https://www.facebook.com/UWHDesign
It's a fairly new FB page, so hasn't spread very widely yet. Maybe some kind of dedicated forum like a Yahoo Group or the like might be a good idea if this grows.

 

[Straw_Cat]

@ zzinfinity: How large a Vertical Garden are we talking about, (if you can reveal that)? There are some amazingly tall ones on the drawing boards around the world now. (Do they still use the term 'drawing boards in this digital age...?).