We are putting earthtubes and this whole PVC vs Polyethylene debate has been going on in my head for a bit. I stubbed the walls out with PVC (per naturalhome.com) site. Then had some pvc outsided and poly inside pipe i used as well.
However as time goes by I really don,t want the air exchange to be made with pvc. My knowledge of the chemicals is not that good . BUT , when i cut pvc with a skill saw the smell makes me want to puke. When I cut black plastic tubing absolutely no smell. Me thinks pvc is nasty stuff
I think I will use black poly pipe instead. The corrugated stuff has also been used in an earthtube install i have seen online. They ran a circular saw down the bottom of the pipe. This allows any condensation that does occur to drain into surrounding soils. Obviously with a high water table this might not be the best way to go lol.
I do not think that the corrugated black poly is as strong as the pvc (compressive strength) but it would certainly be easier to install vs the 10, sections the pvc pipe comes in and all the elbows that would be to be installed. I would imagine that the flexible pipe would decrease the resistance that air would have coming in, being that there is no hard angles to slow draft.
The corrugated poly pipe also have double the surface area (roughly) of pvc allow more surface area to allow heat exchange. This might allow a shorter distance the pipes would need to be run.