When you find interior products used in an exterior application you had better investigate because it's probably just the tip of the iceberg.
I found a piece of medium density fiberboard (MDF) behind the gutter on the second story. Needless to say it was waterlogged and inhabited by ants. There is also a piece of interior trim running the perimeter of the soffits all the way around the house. I've pulled lots of bright nails out of the fascia board as I've been taking it down, more interior product.
It's hard to see, but there is a piece of romex running on the exterior under the eave to flood lights. This is a code violation. There's a good reason romex has to be enclosed. Squirrels had gnawed the casing off of the wire. A good way to start a fire.
This is where the two sections of the house connect for a split-level.
When the contractor sprayed the foam insulation against the roof deck they did a good job of sealing everything from the inside. But out on the eaves where the angle pinches down it is hard to reach, even with the wand.
I've filled these voids with rigid foam and expanding foam. The rigid insulation adds another R10 to the system. The foam prevents air flow, moisture and bugs moving into the interior.
For new construction all of this can be accomplished during the construction phase with all spray foam insulation and it makes for a nice tight envelope which saves lots of $$$ on heating and cooling.