ᐅ Loose-fill insulation around pipes vs. insulation boards

Hello everyone,

I have a question regarding loose-fill insulation over heating pipes.

On the concrete slab in the ground floor, we have the following 22cm (8.7 inches) floor structure, from bottom to top:

• ~0.5cm (0.2 inches) waterproof membrane
• 6cm (2.4 inches) + 5cm (2 inches) polystyrene insulation boards
• 3cm (1.2 inches) insulated fixing mat
• 6cm (2.4 inches) screed with underfloor heating pipes
• 1.5cm (0.6 inches) floor coverings

The 6cm (2.4 inches) + 5cm (2 inches) insulation boards are used because most of the pipes on the floor slab are 4–6cm (1.6–2.4 inches) high, and we wanted to lay the second layer of insulation boards completely continuous. Water and heating pipes should be leveled with Mehabit-bound loose-fill insulation up to the top edge of the first layer.

However, on the slab, there are also two heating pipes with insulation sleeves that are 8cm (3.1 inches) high. How should we proceed here?

Current plan: We will lay both layers up to the pipes, fill up to 11cm (4.3 inches), and then simply place the fixing mat on top.

Is this okay, or should a more rigid insulation board be installed under the fixing mat in this area?

Good luck