After ericmark's response to my earlier thread, I read up on Reference Method 101. Never heard of Reference Methods before, being a simple DIY-er!
Apart from learning something new, it's changed my view.
Everything I'd read about loft insulation said that cables must be moved above it. And that 'professional' installers commonly couldn't be bothered to do it.
If I understand things correctly, then as per RM 101, I can safely put the 170mm insulation over the lighting cables, provided:
- I ensure that the load on any of the cables keeps well below 10.5A (by using low-wattage LED bulbs)
- I make sure there aren't other factors, such as cables grouped together, that would reduce heat dissipation further.
I have got a 6A MCB protecting the upstairs lighting.
As mentioned before, I'll move the immersion heater cable above the insulation, as there's enough slack to do it.
Is my understanding correct, and does that sound a sensible plan?
Is it safe and does it comply with wiring and building regulations?