That is the starting point.
Wearing one sewn onto one's jacket would not be the most comfortable experience, thus the need to know about a mesh or a screen layer.
My thought was, that let's say there is a layer of perforated what-ever-emergency-blanket, the small holes, which are not in the radiation wavelength scale, but what is possible to achieve with everyday techniques (about 0,1mm), the layer will breathe in a way, but would collect considerable amount of condensation water, when close to the outside layer of the clothing, in order to not to heat up much and thus radiate heat away. Sounds right?
On the other hand if the holes are larger and the reflective layer covers less area, if I understood correctly earlier posts also point to, the amount of reflection is relative the amount of area covered by the reflective material. The the question is, what is then the optimal hole size - total perforated area relation, where no longer moisture condenses on the reflective material.
I recon the big boys would go with some kind of fabric coating technique in order to achieve breathable yet radiation blocking fabric, like mentioned previously.