In reply to geordiepie:
Hi Martin,
I happen to work for Eureka, so I could tell you quite a bit on the fabrics/construction etc.
The BTC is a non-coated fabric, which means that its waterproofness comes from the cotton fibers swelling when they get wet. When dry, you can literally breathe trough the fabric if you press your mouth against it, and condensation is not an issue.