Insulating pipes before screed

[baker332]

Hi,

I'm running 15mm PEX pipe under the screed circa 35-40mm in depth, the pipes are laid on a concrete sub base that has 150mm insulation in. My question is what is the best insulation to wrap the pipes in? I'm currently using wool, but is there anything with more performance? Should it even matter?

Pipe run is 3m out and 3m return total 6m will be in the screed without any joins all one run in pex.

Thanks

 

[23vc]

If the pipes are above the insulation they don’t need insulating

 

[robinbanks]

You mean underfloor heating pipes? You don't insulate them from the screed.

on a concrete sub base that has 150mm insulation in

What do you mean by the claim that 150mm insulation is "in" the concrete?

If you meant that the 150mm insulation is on top of the concrete you can chase the pipe into the surface of the insulation and then cover it with another bit of you don't want to buy any ducting (for example like this )

 

[baker332]

Concrete on top of the insulation.

 

[Integrity Repipe]

For PEX pipes under screed, it's best to use a closed-cell foam insulation designed for underground or embedded applications. Wool can provide some insulation, but it doesn’t offer the same level of thermal efficiency or moisture resistance as foam-based options like polyethylene or elastomeric insulation. Proper insulation minimizes heat loss and prevents any unnecessary strain on your system. Since your run is a single 6m length with no joins, you’re already reducing potential weak points—just ensure the insulation you use can handle the screed’s compressive forces.

 

[mrrusty]

In my house I used these https://www.cityplumbing.co.uk/p/ma...0fgtMEzFxZmZsAxPBeMhiyFhqb0R07eVH-zQYF9sVf6mQ

 

[Notch7]

Concrete on top of the insulation.

So the concrete will be part of the thermal mass of the house?

I’m not sure you want to insulate pipework which will help transfer heat into the house thermal mass.

If your central heating is operating on low flow temps there more you can transfer to the building mass the better.

 

[baker332]

So the concrete will be part of the thermal mass of the house?

I’m not sure you want to insulate pipework which will help transfer heat into the house thermal mass.

If your central heating is operating on low flow temps there more you can transfer to the building mass the better.

This was a while back now but the screed went ontop, it's all fine.