[zwp]

A long time ago I similarly tested a (non-heat-reflective) orange plastic survival bag, sleeping overnight behind some rocks on exposed moorland (something like https://www.military1st.eu/cs037-highlander-emergency-surviv...).

The poor thermal insulation and condensation were predictable. I hadn't predicted the shifting wind which chose to balloon my orange cocoon with cold air every 20 mins no matter which orientation I chose to lie in. I finished the night with a bungie cord around the sack, under my armpits. That of course left my head, shoulders and arms exposed but kept the wind out. Not recommended.

After this experience I upgraded to reflective mylar survival bags. NB "bag". These are a little harder to find than survival blankets but if a bag can be so badly affected by moderate wind, a blanket would be so much worse.