Phalaenopsis roots are thick and fleshy, absorbing moisture directly from humid air . If the air is too dry, your plants will lose water from the leaves faster than they can replace it from the roots. As a result, the plant wilts. Most epiphytic tropical orchids are from humid areas, often thriving in 50 to 90% humidity.

Therefore, for indoor growers relative humidity is probably the most difficult factor to control  as humidity levels in homes tend to be quite low, especially when homes are heated in winter

Try to aim for a humidity of 50% for your phalaenopsis orchids. If you have a greenhouse or dedicated basement grow room, you can use a microfogger or humidifier to do so easily. If you are an indoor or windowsill grower, where the area is not enclosed, there area few tricks:

-Group your orchid plants together so that they create a more humid microclimate around themselves. The more plants you have the better this works(a good excuse to buy more orchids)!

-Use humidity grow trays -this will also collect run-off water when you water your plants. As the water evaporates  from the trays, it provide humidity around your plants. 

-You can also sit your orchid pots in a shallow pebble-filled trays or pot saucers filled with water-just be sure pots are not actually sitting in the water as orchids do not like 'wet feet.'

-Always run a humidifier near your plants in winter when the air is notoriously dry.

AIR MOVEMENT
Air movement is important in orchid cultivation. In the wild, epiphytic orchids, including phals, grow in trees where there is constant air movement. This air movement keeps plants cool, especially during hot weather. When your collection grows to a dozen plants , run a small fan near them to keep the foliage moving, especially in winter when windows are closed and the air is stagnant. The rest of the time, when windows are open and there is plenty of fresh air, your orchids should do fine. 

Whenever the room you are growing orchids in feels closed or stuffy, chances are the air circulation is poor. If the air is light buoyant and moving, the environment will also feel more pleasant to you.

Always make sure your fan is running when humidity is high, both in winter and summer.  This will greatly reduce the incidence of fungal and bacterial infections which can quickly take hold and destroy a collection of phals in a matter of days.