the roots wont be boiled... because

1) the water isn't being boiled.. its just being heated to the point of evaporation..
just like when its humid outside... the rainwater that escaped into the dirt n ground, evaporates n humidifies the country lol.. applyin the same effect

i'm using a heating blanket, which ppl use to heat their beds in the winter, get warm n comfy, etc... which will cover the bottle, which will thus warm the bottle up until the water begins to evaporate.. and it will trace thru the tube into the grow environment..

this water will make no contact with the roots.. its not going to be real steam, just evaporating the water..