Have to get humidity down: glass tops or canopy?

[lastlight]

If you have 2 ducts of equal size (makes it easier to assume stuff lol) and both are equal length (again why not?) and one runs outside and passively lets fresh air in directly into a canopy and the other pulls or blows air out of the canopy and house then I don't see where the dangers apply. That's what I intend to do when I get the boot to the basement someday. Canopy will be tightly sealed to the top of the tank.