In article , Christian McArdle writes
I went to the Homebuilding and Renovation show at the Bath & West showground yesterday and Polyplumb had a working demo of this overlay system. The striping effect (caused by lack of a 65 mm screed) was very noticeable but not in a bothersome way. What worried me was the salesman's insistence that there was no need to put any additional insulation under it, because the heat could only come upwards - Oops. It's a lot more expensive than radiators, so I'll stick to the latter (with 15 mm copper piping). Polyplumb overlay prices :-
Barrier pipe (80 mtrs * 12mm) £84.00 Overlay floor panel 800mm * 600mm * 18mm £128.70 for pack of 10 (4.8m2) for straight runs only. Overlay end returns (provides the U bend at the end of an 800*600 panel) £20.20 for pack of ten DPM 25 mtr * 4 mtr £57.00
15mm manifold 2 port £108.00 3 port £130 4 port £160 (extrapolate for 5 to 11 port) 12 port £345 UFCH control pack (pump+2 port motor valve+mixwer valve + isolating valve) £315 Modulating pump unit (Pump+UFCH mixer valve+thermometer) £315UFCH mixer valve 22mm £92 28mm £103 I reckon it would be possible to make ones own floor panels using 18 mm chipboard suitable routed to make the 12mm channels, and these would spread the heat better than the fibre-board stuff that IMI use.