Jerry:

The point you're missing is that water VAPOUR can pass through Tyvek, but not liquid water.

The reason for this is that the space between the long polyethylene molecules in Tyvek is smaller than the average distance between water molecules in liquid water. In order for liquid water to pass through a film the holes in that film must be large enough for several H2O molecules to pass through the hole simultaneously. Otherwise, NONE of them will pass through the hole. This is because in liquid water, the individual H2O molecules are polar and they attract one another with considerable force. It is this mutual attraction between water molecules that give rise to surface tension in water so that you can "float" a razor blade on the surface of very cold water.

Because the polyethylene molecules in Tyvek are too close together to allow liquid water to pass through the film, but far enough apart to allow individual H2O molecules to pass through relatively easily, Tyvek works to keep walls dry. It allows any humidity that gets into the wall, and even condenses inside the wall to evaporate to the outside through the Tyvek, but won't allow rain to come through the Tyvek from the outside.

So, having Tyvek on your house is not at all like living in a plastic bag. It's like living in a dry house where humidity can escape to the outside, but rain water can't get in.

I don't know if that red Tyvek tape has this same characteristic as Tyvek.