Thanks very much for your feedback. I'll check what I can do regarding ventilation.
Still I will check if I can do minimal monitoring (and easy) of the condensation.

Hi all

I am a complete newby concerning sensors and this site. I hope this post is at the appropriate location.
First a short introduction:
I have condensation trouble under the roof of my house, just under the waterproof layer on top of the insulation layer. I plan to add some king of vapor barrier to avoid that the water vapor reaches the waterproof layer, but I am not sure that this will avoid condensation.

Once the vapor barrier has been built, I will not be able to measure condensation any longer, and I don't want to break my ceiling for that. According to you, is it possible to put some humidity/temperature sensors (typically DTH22), so that I am still able to monitor humidity/detect condensation between the vapor barrier and the waterproof layer? I guess this would require not to have a wireless connection (I will not be able to change the batteries easily)?
Does it seem feasible to you?
Thanks.