Polypipe UFH

Hi. Strange one here.

Polypipe UFH system using the polypipe overlay system, then covered by 6mm ply. 10mm carpet underlay and 10mm carpet. Obviously not much heat. I know that carpet needs to be a low tog value (I doubt this is) but the ply had me stumped with wood being an insulator. Its like its heating the ground and not the room. totally pointless.

Ive read the documentation and was surprised to read;
"17.16 It is recommended that a 6 mm thick waterproof plywood cover is installed over the overlay panels and pipes when carpet is to be fitted as the floor finish. The plywood can be retained with staples or screws with overlay panels, and with adhesive with Overlay Lite panels."

So it is correct as per polypipe's doc. Does anyone have any suggestions as to what to do? I dont see any reason why the carpet couldn't be laid directly over the overlay system. perhaps even with a thin screed. I presume the ply must be to prevent the pipes crushing. Obviously clients floor covering was a bad choice but ...

Yes, the plywood needs to be there to provide support and spread the load. Both the underlay and the carpet need to be low tog - below 3 in total. I'd check with the client that they ensured it was.

Is the UFH just in the room with the carpet or in other rooms with different floor coverings that restricts the UFH water temp i.e - engineered wood?

Thanks for the reply. The house has same system on both floors and is carpeted throughout with the exceptions of the kitchen, toilets and hallway which is engineered wood/laminate

The carpets are all decent pile wool carpets with standard recycled foam underlay. The only rad in the house is the bathroom towel rail.

I can understand the ply for stability but the whole notion of it above ufh seems idiotic.

what about cement boards over the top instead of ply? Something that will conduct and store heat. That’s said I’m also thinking it’s just going to be more worth while to switch to tiles

Not at all, if it's an Fibre/EPS overlay system then you need to protect the pipework and panels from point loading from shoes, furniture etc when a soft flooring is to be used. Using a 6/8mm plywood would be the norm.

Harder/hard flooring is fine as there isn't the same point loading

If it's not warming up properly then it sounds like the main problem is the standard recycled underlay and the wool carpet. A standard 10/12mm recycled underlay has a TOG rating of more than 2.5TOG, add that to the carpet which may be around the same then that's around double the recommended insulation rating on top of the UFH. Ideally the total TOG rating should be 2.5TOG or lower, especially if the UFH is running a little cooler if it's been set up correctly for the engineered wood/laminate.

It's a bit counter intuitive as everyone is used to buying the warmest underlay/carpet, it's in reverse with UFH for obvious reasons.

Excellent. Yes that all makes sense. I think we will start with the underlay first. The client may be ok in the short term with the compromise of no underlay in exchange for a warmer house. Tiling as a best solution since it will also store the heat to a degree and radiate it back to the room better. Though I suspect carpet will still be a preference. So a low tog alternative… that or include some rads.

Carpet and underlay can be used as long as it's tailored specifically to the UFH. The client needs to find out what TOG their carpet is, if it's new. Then couple that with a low TOG underlay.

If the client asks at the carpet shop/fitter they can specify the low TOG rated carpets that they supply.

Duralay King is about the best underlay as far as comfort and low TOG (0.8) rating is concerned. That coupled with a carpet of between 1>1.5TOG then maximises the thermal transfer and keeps it all below the 2.5TOG recommendations for UFH.

It'll never be as efficient as tile would be of course.