We were approached by a client at the 11th hour(!) to help introduce underfloor heating to a suspended timber floor. The rest of the project was nearing completion and despite our initial suggestion to insulate the existing timber ground floor,the client felt that their budget did not allow this.You cannot introduce underfloor heating without first adding floor insulation (where none is present!)
The floor joists were only 100mm thick, supported on sleeper walls, so space to accommodate insulation and heating pipes, was tight!
You might be interested of this underfloor heating system from Nu-Heat. This solution requires only 15mm of floor build up to accommodate the warm water pipework. It is ideal where floor depth is limited.
For more details refer to Nu-Heat’s website