My initial test of the Heatsheet Emergency Bivvy was in less severe conditions then my test of the Thermo-Lite Bivvy. I plan on doing a few more tests in different conditions but the night of this test the temperature dropped only to 52deg F. I used the Bivvy alone with no shelter or fire and I slept in a cotton long-sleeve t-shirt and cotton utility pants as well as wool hiking socks. It was about 58deg F when I went to bed, and dropped to 52deg F in the four hours I was in the Bivvy. While these conditions are far from cold, I was completely warm inside the Bivvy. The Heatsheet Emergency Bivvy was as warm, if not warmer then the Thermo-Lite Bivvy in similar conditions, however it blocked the wind much better!
_________________________
"Trust in God --and press-check. You cannot ignore danger and call it faith." -Duke