Was your electric floor heating system installed directly on a concrete slab?
Installing any electric radiant floor heating system directly over a concrete slab will affect the heat up time.
Without a thermal break, the concrete acts as a heat sink. Therefore, the heat is drawn first into the slab before your floor covering. This is why Warmup recommends installing Warmup Insulation Boards (hard or soft depending on the floor covering material) over the concrete sub-floor to act as a thermal break. This forces the heat radiate upwards first rather than down into the slab. Warmup insulation boards can increase ramp-up time by over 70% and decrease heat loss by over 90%.
If floor insulation was not installed, there is no need to re-install the floor heating system. It will still function properly and you will still experience all the wonderful benefits of a heated floor. It just might take longer to hit that target temperature.