So I've been reading a lot about PSP structures and I just finished watching six hours of video about them. So this is an underground structure that is really cheap if you have timber on your land. Basically, you make a wood box out of posts, cover it in black plastic and then bury it. Of course there are lots more details. But my question of the moment is pretty specific. I drew this little picture in my paint program so I can ask this question. So the two black lines represent the black plastic. The teal colored stuff would be soil that is wet. The tan colored stuff would be soil that is dry. Does dry soil insulate?