Our local CERT organization was considering a bulk buy of these, to hand out in the event of the Big Shake that takes out most shelters. We trialed it at an annual drill, and decided against. Not to be crass, but we thought the mylar blankets would end up best used as temporary body wraps, for corpses, which is what alot of disaster survivors might end up if this was their only shelter for a 40 degree night with rain. For personal protection, for a few dollars more you get a reusable AMK bivvy or heetsheet, which doesn't rip or crinkle nearly as much. For a mass casualty situation, I would recommend an up front investment in group shelters of almost any type besides these mylar sleeping bags, which will rip and be fairly useless even after the first night.

Your mileage may vary in Texas of course - we tend to have colder and wet weather even in summertime in the Pacific Northwest, so we can't really afford to trust to mylar, not with other options available. I will be elated if after the Seattle Fault rips the biggest complaint from survivors is their tent shelter was too warm.