The thing about hooped bivvies is that they have ( weather allowing) better ventilation to reduce that issue.(certainly the Snugpak)Gas Permeable Gore Tex fabric allows to close the bivvy bag and actually breath through the fabric.
(What you can NOT do with any other bivvy bag.)
And they told me that if you do that all the night you will get condensation problems.
That means that you will get such problems in every hooped bivvy bag.
If you want to keep your sleeping bag dry you simply need to breath out of the bivvy bag!
Personally I would only be interested in using one in clement conditions as well.........?