AC room will definitely have considerable effect on the welding process. AC includes cooling, De/Humidification, and controlling of air motion inside the closed space it affect the welding process.

        The temperature plays a major role. As air around welding material is tool cold it may affect the material properties as like the effects of quenching, hardening effects may be felt.

AC room have effect on thermal history / cooling rate of welding. But the effect is not so  significant. Because the AC room generally the minimum temperature is around 15 Deg. Centigrade where as  in normal room temperature is around 25 Deg. Centigrade. So, this 10 Deg. does not have much effect on weld quality.