Underfloor Insulation for Wet Heating System

[marktaylor8601]

I am currently experiencing cold floors even though I have a wet under floor heating system. This is a regular coincident and was particularly evident during the recent cold spell, when despite turning the Gas boiler up to its highest setting the floors were still cold. On inspection I found that polystyrene has been used, but at the same time noticed a draft. The underfloor heating pipework was installed in 1987. The system does underperform despite being powerflushed.

On reading various literature, I am now confused as to the best course of action. Do I:

1. Place super foil on top of the polystyrene under the exisiting pipework.
2. Replace polystyrene with a foil backed insulation board under existing pipework
3. Do I leave in place and use a sand mix to existing system
4. Identify and block up where draft are coming in

Any advice would be appreciated