Bivvy/Bivvi/Bivy Thread

[The Heretic]

I have really only used two bivys. The first was the Gortex one I had in the Army, and the other is a high end OR one. Never had an issue with the military Gortex bag, but seem to get some condensation with the OR.

I have a Goretex mountaineering tent (Marmot Taku). It has decent ventilation at the ends of the tent with the large end being much higher than the small end. It is a two person tent, but with two people it is tight quarters.



I have camped in it in all weather conditions, from mild summer to cold snow camping well below freezing to wet and stormy weather.

When it is cold and wet, almost any "breathable" material will become wet to some degree. When this happens, vapor has problems being expelled thru the material. Below freezing it is worse. I have seen this in this tent and others - in very cold temps, the vapor freezes on the inside.

Ventilation helps a lot, but only mitigates the problem. The Taku is design such that warm vapor rises and is at least partially expelled at the upper end of the tent - if you leave the vented areas at least partially open. Proper setup has the lower end towards the prevailing wind direction so that the tent is stable and venting is helped. Many bivys have a similar design concept.