Perhaps the most important aspect of straw bale building has nothing to do with bales. In fact, it has everything to do with holes in the walls. Windows and doors present the most likely areas for water infiltration and bale damage in the entire house. For this reason it is extremely important to pay extra attention to these areas during construction. For windows, I use two part flashing. The first is called counter flashing and is put in place before the window or door is set in the opening.
Starting at the bottom, a waterproof membrane is applied to the opening and then built towards the top so that each layer overlaps the one below it. In other words, the top of the counter flashing for the bottom window sill is underneath the bottom of the side jamb flashing, and the top of the side jamb flashing is underneath the bottom of the head flashing. In this way, any water that contacts the counter flashing will always be moving down and always end up on top of the counter flashing. I use adhesive flashing for this application.
Once the counter flashing is in place, I install the windows. After the windows are all secured, I wrap them in an adhesive flashing again starting at the bottom and working my way up to the top. The top most piece of flashing must always be above and on top of the layers underneath it. The adhesive flashing works well because it completely seals to the windows and framing. Be careful not to get straw behind it during installation as that will create areas for water to find its way into the building.
I always set my windows flush with the outside plane of the wall, not inset like in adobe houses. The look is a bit more basic than the adobe feel, but the risk for water infiltration is considerably lower. This is just another detail that is something to consider when designing a home. How can I best protect my bales and thus ensure a long life for my home. A simple change in design allows for better protection and a better ability to flash against the elements.
For doors, you can lower the base of the threshold into the floor if you are using concrete by creating a void during the pour. It is also possible to use sill pans underneath the threshold to improve the seal or even use a large bead of high quality caulking beneath the door threshold. These products greatly improve the installation of the door and are worth the extra effort. The side jambs of the door are flashed in the same manner as windows, from bottom to top as is the door head.