Water should feel warmer than the ambient temperature. Cold water causes stress and cold water standing in the crown causes crown rot and fungus. Be alert for signs of leaves developing a transparent appearance, soft texture, loss of lower leaves, or black in the center leaves and crown. The former are progressive symptoms of damage caused by exposure to cold extremes in air temperature and water. A consideration in the greenhouse is thermal layering or changes in temperature based on distance from the heat source and floor.
All orchids are sensitive to reduced humidity caused by artificial heat.
Electric heat dries the air and reduces the humidity, gas heat can also complicate the dryness by contributing fumes and carbon monoxide. In my own area, this was compounded by using clay pots. Clay pots allowed the mix to dry too quickly and conduct too much cold and heat to the roots. While Phals are relatively simple growers, they have no defense to temperature and humidity extremes. In retrospect, I know that had I taken more precautions and brought my Phals into the house where the climate was more controlled and limited to minimal temperature extremes, I would not have lost as many seedlings this winter.