What are these called?! Moisture/vent/regulator

[Siderealxxx]

I don't know what to search for, they install them in new builds and can be retrofitted in old houses... Some sort of low energy vent that goes into the loft and regulates moisture in the house... We have a condensation problem to tackle but don't know what they're called! Thanks!

 

[flameport]

Nuaire drimaster is the device.

A better option is to identify where the excess moisture is being created and reduce/eliminate it, rather than cover it up with an expensive fan in a box.