Condensation and bivvy bags?

[Bearbonesnorm]

Anyone else suffer with small amounts of condensation in bivvy bags? I've used various bags over the years from the cheap to the very expensive but 90% of the time there'll always be a small amount of condensation inside by morning ... even with an eVent or Goretex bag.

It's nearly always down towards my feet and nowhere else ... I'm thinking either I always sleep downhill or I have superheated feet during the night.

Anyone else ever notice?

[Matt]

Yep, Hunka XL feet only on this years WRT.

[didnothingfatal]

I've always been led to believe it's due to feet overhanging the mat, and the difference and heat loss to ground temp.

[Ian]

Was out last under just a tarp - got a bit of condensation/dew at the end of the sleeping bag (no bivi bag). Think it was just a problem with a short mat and improvised camelbak/ shoes laid at the foot end. Starting to see the merits of a full length mat over the lighter shorter versions.

[Matt]

Full length NeoAir used. Tested the bivi bag by filling it with water and it was fine so the water came from me.

My top half was under cover and my feet in that Saturday's biblical rain. I just assumed it can't breathe if its wet through on the outside. ?

[didnothingfatal]

Ian, is that an MKettle in the picture, if so opinion?

[Ian]

Yes, it is. Opinion? I'm somewhat unsure at the moment - I'll start a separate thread with more details.

[Bearbonesnorm]

Am I being stupid or is it possible that there maybe some relationship between condensation in bivvy bags and whether or not you're under a tarp?