Why have printing on the metal foil of rigid insulation?

[Stephen Tashiro]

If reflective insulation is useful, why does the metal foil face of many rigid foam insulation panels have printing on it?

Does the foil cover ( probably intended as a vapor barrier) not have any value as reflective insulation - even without any printing?

If the foil covering has value as reflective insulation, is this value unaffected by the printing?

(I'm specifically thinking of the case where rigid foam board is used as attic insulation.)

[Jim Becker]

Advertising of course.

[Bruce Wrenn]

Advertising of course.

Advertising of course, along with instructions, including which side out, nailing pattern, combustion risks, plus building standards used in manufacturing product.

[Brian Elfert]

I always thought the foil is more about keeping the sheet of insulation together rather than reflecting heat. I would think they would put the printing elsewhere if the foil was for reflecting heat. Reflectix is all about reflecting heat and they don't print anything really on the reflective sides.

[Mike Soaper]

My understanding is that polyisocyanurate insulation, although relatively high r valve per inch, gives off quite nasty fumes when burned and the foil is also there to stop/retard combustion

[Mark Bolton]

The foil is continuous and the printing has little to no effect in reduction in reflectivity. No different than putting relative uv film under your shingles or inside your attic. The shingles are 900 miles thicker than any printed text on the foil face.

[Stephen Tashiro]

In another forum this link was given:
https://sava.co.uk/news/calculating-...il-insulation/

Effect of Overprinting on Foils

Surface emissivity is not necessarily uniform, as many foil-faced products are overprinted. This can have an enormous effect on the radiated heat flow because the surface becomes more like an ideal black body (which is a perfect emitter) rather than an ideal white body (which is a perfect reflector)

[Mark Bolton]

Seems like obsessively splitting micro hairs to a bit of an unreasonable extent given the application. This is roof/wall/attic/foundation insulation/reflective barrier, not the Parker Solar Probe. Radiant films are put on the internal side of roof systems, below a shingle layer, and so on. Without a doubt building an umbrella of uber reflective satellite foil may ultimately be the best. No empirical data but my guess would be if you were to measure the performance of the low grade foil that is used prior to printing and after printing it would be pretty much moot. I guess then it becomes a conversation about branding.