Hi, having seen how many people have had solid replies on here I thought I'd test the waters. I have a 1920s semi detached, solid brick wall and suspended wooden floor with 2x lowered areas (kitchen and downstairs loo) that appear to be concrete (freezing floor in winter). I'm extending the house 4.3m back, the full width of the property and am very keen to install UFH on the ground floor only. Any response to these questions would be greatly appreciated: 1) Trying to decide where I should rip up all the flooring and install 100mm insulation then UFH or use an overboard system. Have heard through forums some people have had good experiences with the Wanda EPS400 overboard system, but will that insulate sufficiently at only 20mm thick? They say the aluminium reflects the heat back up - has anyone installed this and found it does what it says on the tin? 2) Any other overboard systems out there that UFH installers have found has worked well for others in older style houses? 3) As I have an older house with no wall/floor insulation, should I get heating calcs done to confirm if UFH will perform adequately? 4) Anyone have a rough idea of the install cost for ripping up floorboards and installing a 'between joist system' and relaying a chipboard etc... on top - circa 50sqm for old ground floor. I feel it's better, but can't get a handle on the install cost difference between that and an overboard system. Any help would be greatly appreciated.