Quote Originally Posted by khronik
For a long time I assumed everyone knew what they were talking about when they said not to use aluminum foil, and to use mylar. Apparently foil can create hot spots. But here's the thing, so can mylar. In fact, it's often used precisely because of its ability to reflect heat!

Anyway, I've heard all sorts of misinformation, like that aluminum foil is only 40% reflective whereas mylar is 98% reflective. So I looked up some data in my thermodynamics textbook from college. Actually, polished aluminum is MORE reflective than mylar! Most mylar has a bit of transparency to it, whereas aluminum is completely opaque. And here's the kicker: mylar is made reflective by depositing aluminum on it!

Aluminum is used because it has a reflectivity of 92-98% depending on the wavelength of the light. Granted, aluminum foil isn't the same as pure aluminum, and isn't optimized for reflectivity, but still, according to its thermodynamic properties, there is NO difference between the way aluminum and mylar reflect light. The only difference seems to be that mylar is much easier to work with, which admittedly, is a major advantage.

So here's my question: is there a reason you guys say not to use foil, or are you just repeating what others have said?
seems like you rebutted your own argument. Aluminum foil is NOT polished aluminum (so why are you quoting this???), and is not optimized for reflectivity. So there IS a difference in the "way" aluminum foil reflects light and the way mylar reflects light.

Who's making walls out of polished aluminum??? That's what someone would have to do to test your ...ummm... "theory"...

There a many more people who have a problem keeping heat down in their growing area than the latter. Mylar instead of foil certainly wouldn't hurt this kind of situation.

Now I have a question. Are you trying to make a point or are you just repeating what other people who don't use mylar say (only a trying to sound a little smarter)?

Just for kicks...

I'd also like an example of an application of mylar "precisely because of its ability to reflect heat!"...