I use a house wrap material that is similar to, but heavier and more sturdy than Tyvek.
It has one white, and one dark-grey side.
The white side always is my clean side, and the dark-grey provides much better drying in the sun.
True, this house wrap material, just like Tyvek, is not absulutely waterproof and will absorb water. In the same way the water will evaporate as soon as exposed to some sun. A short break of 15 minutes, the dark-side up exposed to the sun, will make it perfectly dry.
While my PU-coated Silnylon poncho never seems to dry up completely, there will always be some hidden folds where drops of water gets stuck.