Why are you concerned with the humidity of the room?Unless your snakes are free room in the room, the room conditions really mean little.What matters are the conditions inside the enclosure.

In nature, there is never a constant humidity or temperature. Wide ranges of conditions exist. The ideal for a captive reptile is to provide the same wide range of conditions.

For example...

Even though outside humidity is at 30% and the temperature is 95 deg., I can flip over a rock to find condensation(higher humidity) and a cooler tempature . This is one of the reasons why you find alot of animals when 'flipping' things in the wild. Objects layed on the ground outside provide a great range of TEMPERATURE and HUMIDITY. The reptiles know how to find the conditions that they need.

Now take this approach to enclosures.

In my enclosures, I provide 4 "zones". Warm/dry, Warm/damp, Cool/dry, Cool/damp. My animals have the choice to get in the conditions that they desire. I do not make them have a certain temperature by raising the room temp or room humidity. If a reptile needs humidity, it goes into a humid area within the enclosure. If it doesn't need the humidity, it does not go. Pretty simple.

For snakes, this array of conditions is easily provided with the addition of humid hides to the enclosures. Simple solution for the lack of available higher humidity that does not create an overall damp environment that can lead to mold and other nasties that can harm your animals.