Paper or Plastic?

We’ve moved on to the next step- to wrap the house in building paper and to install the required screeds and flashings. There are a myriad of different products on the market- each promising to be better than the other one. There’s Tyvek and Typar, which both are in an advertising war against each other (the concept is pretty interesting and we had looked into Tyvek for a bit (Tyvek has a pretty high UV resistance which allows it to be exposed to the sun for an extended period of time)- but since the code requires a 2-layer weather resistive barrier system- so we would have had to have either 2 layers of Tyvek or one layer of Tyvek and one layer of regular paper. We finally decided to go with paper and not plastic- Since the code requires that 2 layers of building paper are being used, some manufacturers offer paper with a double-thickness (theoretically the strength of 2 layers of paper, but the reason why 2 separate sheets should be used lies elsewhere- The tiny gap between the 2 layers functions as a drainage plain- a micro channel where water, which manages to get through the first layer can drain vertically down to the weep screed. Sound pretty simple- and yet, you see the double-layer strength paper being used all the time. The photo shows the South- west corner of the building being wrapped already.