Andy Barber asks about the reference method to use for cables installed flat on a plywood ceiling with loft insulation on top. His question has been answered by the NICEIC (Theme – Cables, Wiring & Wiring Accessories):
Question: What reference method should I apply to cables that are installed laying flat on a plywood ceiling with 150mm of loft insulation layed on top of the cables?
Answer: There is no clear reference method for this situation. However, you refer to the regulations and apply the factors to the closest resembling reference method and apply those deviations to it.
It is usually assumed that cables will be against plasterboard and, therefore, this would be the closest resemblance to your actual electrical installation.
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