ᐅ Topping layer in screed insulation: yes or no?

Hello everyone,

I have a question again:

It’s soon time to install the floor insulation in our new build. As you know, the pipes from the heating installer and the electrician are laid on the floor. The insulation (bottom layer of 5cm (2 inches) polystyrene foam + a second layer of 4cm (1.5 inches)) will be installed, with the bottom layer extending 5cm (2 inches) around the pipes. I keep reading that the gaps around the pipes should be filled with loose fill material. My question is: can this loose fill be omitted if the polystyrene is already laid up to the pipes and then the second insulation layer is installed on top?

Thanks in advance, Michael

Of course, you can leave them out. Their only purpose is to fill in areas where fixed insulation cannot be installed using loose-fill material.

Bookstar schrieb:
Of course, you can leave them out. The only purpose is to fill areas where rigid insulation cannot be installed with loose fill.

Thank you for your answer...

Could you give me an example of where rigid insulation cannot be installed?

Michael

Right there where pipes cross. That creates voids.

Is there actually any reason not to stuff (torn) insulation wool in instead of loose fill?

I also think that you can skip the (bound!) loose fill if the pipes are going to be covered by a second layer of insulation anyway. However, I would base this decision on the width of the “pipe trenches.”
On the other hand, I don’t really see any benefit in skipping it. A bag of EPS beads (200 liters (53 gallons)) costs less than 15 euros, plus two bags of cement for about five euros, some water, and maybe three hours of work.

On the other hand, using loose fill saves you the hassle of trimming the insulation around the pipes and results in continuous insulation (after all, it was planned with 9cm (3.5 inches) thickness for a reason, right?).
In this context, a note: When using “flowing screed,” be sure no EPS fragments are left floating around. They will rise to the surface later and form lumpy inclusions there.

@denz.: I wouldn’t do that. Mineral wool is not load-bearing and is sensitive to moisture. While neither may be an issue in most cases, I also don’t see any labor savings. Plus, you end up with fibers all over the place.

Yes, I haven’t installed the screed base yet, but I want to. I was ready to start. In the end, the fastening panel will go on top, which will also be sealed, and then the screed will be applied. So, no moisture should pass through. And regarding load-bearing capacity—true. But also not air (because you said small widths can work without a screed base).