It has always been my private conviction that any man who pits his intelligence against a fish and loses has it coming.
To measure resistance to air flow, I attached the hose of a vacuum cleaner to the outlet, and tried holding the three materials tightly over the end of the hose. They all blocked the air so well that I had trouble telling what was happening. To get a more visible result, I took a balloon and stretched it over the fabric on the end of the hose, with interesting results. The CTF3 and the Thermoflect did not let any air through - the balloon stayed flat empty. The aluminized ripstop allowed a very tiny amount of air through, such that the balloon eventually became round, but not inflated. There was not enough pressure to stretch the rubber. In fact, it took several minutes even to fill the unstretched balloon. For comparison, I tried the same test with several samples of 1.1 oz ripstop, 1.9 oz. ripstop, Pertex Microlight, and Momentum 90. All inflated the balloon in seconds, some faster than others.
I started working on moisture tests by spreading Thermoflect over myself recumbent in hammock outside (45° F., rainy) under porch roof. There was no visible condensation. It wasn't as warm as my top quilt, but not bad. In the name of science I was able to tolerate an hour's nap.
Last edited by WV; 02-24-2012 at 19:11. Reason: mixed up my results
But seriously, Corncob, that's a good question. However, I'm going to treat all three of these fabrics as impervious to airflow, especially compared to the non-aluminized ripstops I tested.
Someone probably posted this before but I figure good to repost here. My blanket weighs 125 grams / 4.4 oz. Dave did the math in first post. By weight: Thermoflect 1.5 oz./sq. yd.
Exercise, eat right, die anyway -- Country Roads bumper sticker
Fall seven times, standup eight. -- Japanese Proverb
WV, in your opening post you ask, "What materials will radiant heat pass through easily? (Down, I suspect. How about different synthetic insulations?)".
It's been many years since studying this at school but you can think of radiant heat as you would light. Generally it's not passing through opaque substances. So other than glass or clear plastic film, I wouldn't expect much transmission. I'm trying to find some substantiation but I believe that at the temps we're dealing with for heat sources (our bodies) radiation loss is not too significant. I believe much of the perceived warmth or insulation we sense from reflective blankets and such is due primarily to their vapor barrier characteristics. If you think about it, they're actually made of heat conducting materials and if they make contact with the heat source can actually draw heat away from it.
That brings up another question. Shiny surfaces not only reflect radiant heat, they also emit radiation less than dark layers. Which side of the Thermoflect blanket is intended to be facing the patient? The ad copy says there's "a soft layer" next to the patient. Is that the blue stuff or the very thin layer of clear plastic over the aluminum side?