Putting the underground heat resistant after Aquilo foundations seems way too far. I can understand needing another tech, perhaps, but it doesn't add up in my brain. They're pipes covered in dirt. Same as pipes covered in air.

Can you please add an option to move the research earlier?

The undergrounds require foundation to be build, because the crust of Vulcanus is rather thin, you need to support the undergrounds with foundation beneath the surface.

Perhaps this helps with making it work within your brain :-)