5 ms·
Thermal insulation, whether we're talking about a blanket, a winter jacket, or the foam stuff in your walls, generally involves a layer of some thickness within
by snewman 5y ago
Thermal insulation, whether we're talking about a blanket, a winter jacket, or the foam stuff in your walls, generally involves a layer of some thickness within which there are many tiny spaces full of trapped air. It's difficult for heat to propagate across those spaces. The author's point is that mylar emergency blankets do not provide this thick layer of "trapped air". It's true that they prevent air from crossing, but only for the very thin layer of the blanket.
I'm not sure exactly how effective the mylar blankets are and under what circumstances, but this is what "trapped air" refers to.
- tinus_hn 5y agoHeat is transmitted by radiation, by conduction and by convection. A foam jacket blocks heat transmission by preventing convection. A mylar blanket prevents transmission by radiation and convection. Yes, it still loses heat to transmission but it isolates rather well. Unsurprisingly, that’s why they are used as emergency blankets.
- hypertele-Xii 5y agoYou'd be surprised how hot surrounding oneself with mylar gets. I've been inside a grow tent lined with mylar, and even though it was open on one side, it felt like a sauna within minutes!
- pengaru 5y agoHomeless people use garbage bags to similar effect, you don't even need fancy mylar, it's just an optimization. The main problem with these solutions AIUI is the trapped humidity.