How long does underfloor heating (water) take to heat up? Is it much slower than normal radiators?

We go out quite a bit so need heating that can warm up rooms in half an hour. We are worried that underfloor heating isn't sufficient and that we would need radiators or extra heaters in addition.

View this post on my blog: http://madeinhome.info/how-long-does-underfloor-heating-water-take-to-heat-up-is-it-much-slower-than-normal-radiators