Question about reference method in insulated joists unclipped not totally enclosed

[smokeyc]

Hi All

I wanted to ask a question about the reference method.

Passing wiring through holes made at 0.2-0.4 of the joist span.

The cables passes from one side of the house to another. Unfortunately the joists run in the other direction.
The cables pass through 20 joists, the joists are about 35cm apart.
The traditional joists are 200mm and the cable holes located at the centerline of 10cm.

The ceiling is then insulated with 100mm rockwool in one continuous line between the joists. With insulation above the cables roughly leaving a 10cm void below.

My question is based on the reference methods, I don't actually know where this fits in?
By the image, it looks like 103 but without the total enclosing.
Though 100 has 100mm insulation but does not mention passing through the joists, just that it is clipped to the joists or run across a ceiling. (Sort of impossible with 35cm between joists.

What is the appropriate reference method to refer to. 2.3.1 guide to building regs (table 3d5 bs7671).

Thanks
Chris

 

[newfutile]

Reference methods are based on whether the heat from the cables can escape .
if you have cables in a void but surrounded by insulation i count that as totally surrounded , but in real life some heat may dissipate due to the greater area.
if there are only lighting circuits in a loft i would not worry too much about it .
page 85 and 86 osg refers