I have never thought about it before as I got house with chimney just recently. And I have noticed, that simple metallic fireplace screen (which made as metallic grill/lattice) screens a really significant part of warm. At the same time it doesn't become hot.
I'm wondering, does it because it works as Faraday shield and screens in this way Thermal radiation, which is essentially is electromagnetic radiation, or I'm totally wrong?
UPD: besides simple measurement of temperature in the room, I've made some experiment: I've measured heating of black circle on paper, hanged on same distance from fireplace with screen and without (of course there were two similar papers, not same one). I've measured heating using infrared thermometer. It shown me that with screen heating was only 1 Celsius degree on 2 minutes, while without screen - almost 3.5. Is it because of absorption/reflection?