Water can enter into a wall cavity from water leaks, vapor leaks, and condensation in the wall caused by the dew point inside the wall cavity. To help reduce these conditions we need to make sure our envelope is properly sealed to avoid vapor, and moisture leaks. The best time to do this is during construction. 

 

New Construction? Consider These Moisture Resistant Options.

THERMAX™ (ci) Exterior Insulation

Make sure a vapor barrier is used and all the joints, seams, and penetrations are properly

sealed. For condensation make sure the exterior of the wall is insulated to move the dew point to the wall exterior. The best way to do the above is with a commercial envelope system like Dow's™ Thermax CI system which gives continuous insulation, an air barrier, a moisture barrier and it replaces the standard exterior sheathing with fire rated continuous insulated sheathing.

 

 

Another option is to cover your exterior sheathing with continuous insulation that also is an air and moisture barrier.  Extruded Polystyrene, "xps" can give you great performance as exterior insulation and moisture/vapor/air barrier.

 

In all cases make sure your materials meet the required fire rating, and ASTM performance rating.  Ask for the specifications not just the manufacturers opinion.

 

Again make sure all the joints, seams and penetrations are sealed otherwise you have spent a lot of money on exterior insulation and will not get the performance.

 

 

If you have an existing structure you can add exterior insulation when you re-stucco or apply new exterior facia. House wrap, blown in or batt insulation will not solve these problems no matter how much you put in the wall. You need to move the dew point to the outside and seal the gaps and cracks.