Because those other products are much more expensive. I could line my entire home's walls with reg. Al foil for less than the price of Mylar/Poly in one room.
Plenty of successful growers use regular aluminum foil. Look harder. I'm sure if there was less stigma around doing it you might have more people willing to show their foil-lined grow rooms.
Personally I cover cardboard or wood panels with foil, not the walls. I then mount the light panels in ways which are most optimal to utilizing the small amount of light I use. I can see the foil lighting up the plant more optimally when adjusting the panels. It's very obvious when the plants are growing as well.
"How so?" You ask. Simple, they grow out bushier/denser, then don't stretch for the light sources(CFLs, in my case), as they just grow 'normally'(straight-up vertically, without moving lights around to accomplish this).
The thing about a highly specular reflector, reflective Mylar is one of the best surfaces you can get for this & foil isn't nearly as specular, is the amount of throw it has. A mirror is still a mirror and works as one whether 1 foot, 10 feet, or 100 feet away ... mirrors just reflect light
that's their sole purpose! Which is why most professionals use highly polished aluminum reflectors, they are basically mirror surfaces. A highly diffuse reflector can't throw light anywhere near as far, or anywhere near as intensely as a mirror-like(specular) reflector. White paint is less specular than aluminum foil by more of a difference than there is between foil and reflective mylar. Which is somewhat obvious because aluminum foil is still mirror-like(albeit a bad mirror), and matte paint isn't much at all.
Aluminum foil is still highly diffuse, often around 50%(reflective Mylar can be as little as 25%). So the chances of getting hot spots with foil are less than reflective Mylar using both similarly.
Lets see if we're on the same page now....
Here's a challenge for you. Take some highly reflective material(reflective Mylar, aluminum foil, white paint?
you'll likely burn the paint), a magnifying glass, and some paper outside on a really sunny day, and bounce the focused magnifiying glass beam off the reflective material and see if you can ignite paper using only reflected light. If not, use your hand and see how hot it gets, compare between the surfaces.
I'm going to take an educated guess: Mylar or a mirror will allow you to burn something the easiet, and foil will probably work, but not as well as either of the mirror-surfaces.
So, lets see if we take this 'common sense' and apply it to what 'is said'.
Mirrors bad, but Mylar good. There's one contradiction. Some state it's the glass... bulbs are made of glass. Hoods often have a glass door/barrier. Most glass is well over 90% transmissive for a lot of angles.
Foil bad reflector, but also causes hot spots. There's two contradictions.
Foil has [insert obscenely low figure here]% reflectivity. What type of reflectivity, should be your first question. Yes, it's fairly well known reflective Mylar or foil is 95-97% reflective. What type, though? IR, specfically FIR. Oh, that's worthless for plants, but that figure is often used. For plants, Mylar is no more than 92% effective at reflection of the PAR spectrum(it averages around 90%). It's the exact same for an aluminum mirror.
The red-dotted line is reflective Mylar, the blue-dotted line is ESR(enhanced specular reflector, a material from 3M designed to be highly reflector for visible light).
Al is an aluminum mirror, as you can see it conforms with reflective Mylar pretty much identically, and would continue to do so if the Mylar/ESR graph continued. The others are gold(Au) and silver(Ag) mirrors.
I've done measurements with a CFL bulb and an aluminum cardboard reflector, using a camera. The brightness between a bulb and the reflected light of the bulb off aluminum foil is within 3%. Meaning the foil is around 97% reflective.
http://p25ext.lanl.gov/~hubert/phenix/aerogel/talk_1/ said:
The materials used in the system need to be matched to the chosen PMT response spectrum. Just about all papers and plastics cut off around 270 nm, but Aluminum has a flat response all the way across. [5]
One should consider using aluminum foil or aluminized mylar for a reflector, and let the aerogel do the randomizing, since it has reflective properties superior to the best Tyvek (labeled 'total'). Either that or obtain Spectralon.
This guy agrees with my experiment. Sweet.
That's a good term for it. Aluminized mylar, because without aluminum it'd just be transparent plastic.
So I'm going to go around claiming aluminum foil is 97% reflective now.
