underfloor heating advice

[slaval]

Looking for some advice on my underfloor heating. It was put in over 10 years ago as part of major renovations to the house. Its a relatively small underfloor system that covers 2 downstairs rooms and 1 upstairs room, the rest of the house being heated with radiators. It might have kind of worked with a gas boiler but now we have an air source heat pump, I need it to perform much better. I think the heat is not being dissipated to the fabric of the house effectively because of how the system has been installed.

I think they did as follows: Laid a membrane over existing slab, built a wooden suspended floor, filled the voids with Cellotex sheet, ran the heating pipes, clipping directly to the Cellotex and cutting notches in the joists as necessary for the pipes. Covered with flooring chipboard and then that was covered with either engineered oak or carpet.

I guess I will have to do some investigation to confirm all this but what would people recommend to make this more efficient, to increase thermal mass and conductivity to the floor surface. The underfloor ought to be a very good emitter of heat but I don't think it is so the heat pump has to run at higher flow temperatures than it otherwise might which is inefficient and costly.

Any opinions would be welcome.

Thanks

 

[Rodders53]

My 2d-worth as owner of oil-fired boiler with UFH, a concrete screed floor and tiles (kitchen/loo) plus engineered wood elsewhere. Rads upstairs.

More info needed on Manifold / Mixer and room stat controls.
Plus other controls for zones / rads vs UFH vs HW storage...
Also what temps are you running (main/setback) and how long for.

You may not be using things correctly.
BUT what does your HP installer advise? What were their heat calculations like room by room? Or did they arrive on horseback?

Carpet needs to be low tog stuff, or it insulates: stopping heat into room. Wooden floor is similar(ish) and more so if underlay is fitted. More heat conducting materials may be better than either (e.g. ceramic tiles).

Only way to significantly increase heat retaining mass is probably to rip up and start again I think.

Wet UFH is not like normal radiator heating. Low and slow - almost continuous running seems to be the ideal way.

 

[slaval]

3 port Emmeti manifold
2 zones coming off heat pump - Mitusbishi Ecodan 11.2 KW
When we moved in the house was heated by oil. We had major works done which included the underfloor and a gas boiler. At this point there was a mixer coming off the underfloor manifold to get the reduce the flow temp for the underfloor I think.

The heat pump is running in what they call "Room Temperature Mode" so it sets the flow temp itself based on outside and inside temps. The temperature it sets itself to seems to be between 40 and 50 degrees. Tried pure weather compensation but that just doesn't get the house warm and causes excessive cycling. I think it basically cycling because the underfloor is so crap. There is literally air surrounding the heating pipes under the floor so therefore a high flow temp is needed for any of that heat to reach the surface of the floor.

I accept what you say about starting again... but I'd like to try to make it better doing something like

The pic above is what I think I have.. bar the screed. If there was some screed like material covering the pipes and contacting the boards above.. I think it would be much better.

I won't say the HP installers were cowboys because they have resolved many issues, although admittedly there shouldn't have been so many issues in the first place. I don't believe they did accurate calculations and I also don't believe they delivered quite what they promised.

 

[Rodders53]

My advice is to go over to MSE Forums as well as here and have a good readof threads on there.

There are a few good and knowledgeable people there with UFH and ASHPs who may be able to better advise than I.

One is in a Bungalow in the Fens (Ely way?) where the UFH is all overlay on existing floors I think. Low and slow running I believe and careful use of weather compensation plus turning off all the immersion heater boost/backups to the HP (except in extreme circumstances) --- from memory. {matelodave rings a bell as the name.}