Silica aerogels have a pressure-dependent thermal conductivity, and at atmospheric pressure it is approximately 0.03 W/mK – there are pictures of them on bunsen

Silica aerogels have a pressure-dependent thermal conductivity, and at atmospheric pressure it is approximately 0.03 W/mK – there are pictures of them on bunsen burners with ice-cream or flowers on top. Their "naked" density is on the order of 2 kg/m^3 -- comparable to that of air (~1 kg/m^3), as they are, unsurprisingly, mostly air. The melting point is around 1400 K (either not as high or comparable to the "2200 degrees" mentioned in the article – I'm unsure if that's ºC or ºF). The down side, of course, is the cost: all the "real" providers I can find have a price of "contact us", and on Amazon a ~35x25 cm^2 panel goes for about €30, in comparison to somewhere between half and a tenth the price for bricks or other forms of insulation... [1] https://en.wikipedia.org/wiki/Aerogel#Silica_aerogel https://en.wikipedia.org/wiki/Aerogel#Silica_aerogel