Owain wrote:

Even *I* don't like cable tray across the lounge ceiling.

The industrial look let it down for me, but it's not as though they
couldn't plaster the walls and put a false ceiling in later. Turned out
lighter than I expected for an underground cave.

FWIR the solar thermal roof was positioned to catch the best sun, which
seemed to ensure that the PV panels were position to catch the shadows
(as shown during Kevin's final speech).

There's a website here

http://www.aipassivhaus.com/