WHAT IS A BUILDING ENVELOPE?

A buildings envelope is what separates the transition between the inner and outside wall, it is also what protects the sheathing from the elements of weather. The windows are the first to be installed and prepared for a building envelope to be successful in redirecting and water even if there is a breach or a leak, the industry call this  a drainage dam. It is constructed by installing a strip of sloped wood on the bottom sill situated on the inside of the window rough opening ledge. This area then gets a primer application and wrapped with a rubber like membrane material called Soprema, on the outside of the bottom of the windows rough opening, a cut section of building paper is attached to an extended flap of Soprema making it look at the base of the window like its an apron somewhat. After this the window is installed into the rough opening on top of the newly built drainage dam and fastened to the building, then the sides and top of the window receive primmer and Soprema placed on top of and surrounding the nailing flange of the window should water ever get in the window area it will drain down to the bottom of the window onto the drainage dam out onto the apron. After the double layer of building paper has been applied to the buildings exterior the apron is placed on top allowing the water to now naturally drain onto the drainage plain. The double papering of your building believe it or not is the single most important part of a building envelope being successful. Often this part of the construction is done by the least experienced workers and is the single largest reason for building envelope failure we call this reverse lapping.