[jeroen94704]

I am somewhat skeptical about this.

It sounds like they tried to apply thin-film optics for this material, given their talk of layers that are both extremely thin and precisely defined. Thin-film optics relies on interference effects between transmitted and reflected light, and enables very specific optical behavior. For example, using thin films it is possible to make a stack of layers that reflects a very specific, narrow band of wavelenghts, while transmitting everything else. In real-life, rewritable optical media such as CD-RW and DVD-RW make use of thin-film optics.

The point though is that thin-film optics only works for coherent light, such as laser light. Sunlight is not coherent, and you will not get the desired interference effects, because the light waves are not "synchronized", as it were.

So while I could be wrong, I wouldn't be surprised if the performance of this reflective sheet is very low, and nowhere near what would be required to replace air-con.

[gallamine]

Layers of films can be stacked to produce a broader absorption band. Since they aren't concerned with transmission then essentially they can build as many layers as they want to block the spectrum of interest (ignoring cost, of course). Perhaps a larger concern is the dependence on thin-film interference to the incident angle of the light.

[sunsu]

I don't think the article ever implies that this would REPLACE air conditioning.

Last sentence: "But the idea of even part of a building’s cooling system being electricity-free is an attractive one, so this may be the start of something really cool."