Holdfast Training Services Trial Blog

Hi Ollie
I am assuming that you are asking the question about the roof.
Since earthing metal foil is difficult due to the thickness of the material there has been two recent accidents, one in which a woman was killed.
Accident 1. The walls of the bathroom were insulated with foiled back plaster board, the woman had a towel rail screwed to the board and the locating screws penetrate the foil. Unfortuately, when the board was installed a nail touch the phase conductor, hence the foil became live. Every time she touched the towel rail she got an electric shock, luckily she did not get electrocuted.
Accident 2. The same situation as above, the foil had become live due to faulty installation. In this incident, the cylinder in the airing cupboard leaked and created a large pool of water that went under the plaster board. As you known, water can be a good conductor and as she knelt down to turn the stop cock off (which is earthed) she was electrocuted.
Getting back to your problem, if earthing is not possible, hence an equipotential zone cannot be acheived, then a risk assessment must be carried out to ensure the foil cannot become electrified.
I found on the internet this link which states in 2010 the Aust Gover banned the use of foil in domestic premises.
http://www.theaustralian.com.au/news/nation/garrett-removes-foil-from-roof-scheme/story-e6frg6nf-1225828493309
Hope this is of some help, please let me known the outcome.

Regards John