I actually have low regard for regular bicycle helmets - I have not had one that I actually liked - and am looking forward to the opportunity of wearing a ski helmet. The downside of a typical ski helmet is poor ventilation. I use max temperature as a guide and wear a ski helmet below ~16C. For cycling, I have a visor attached by velcro that I take off for skiing. Like another poster, I use Giro. The helmet has attachable earmuffs that I might put on below -20C. I do not like, though, how they muff the sound.