What are the prospects for ventile jackets in survival situations? i know that to keep the rain out they work by swelling (the individual fibres) to 'fill the gaps' as it were and prevent rain from further penetrating the fabric, but would it fit the bill in heavy rain when what you need most is not to be wet and weighed down? they are apparently very comfortable in all temperatures in dry weather, which is why they are used in the antarctic as well as much warmer climes.

i have just ordered one through the post, and i want some opinions of personal experience with the fabric, so that i can reasonably assess how far i could rely on the jacket in a variety of situations, other than the usual walking around the countryside and the Highlands.

is it unreasonable to expect to use it wet for extended periods of time? it may replace my nylon jacket as 'main waterproof' if i keep it.

thanks in advance
ian