Thank you very much for your suggestions and I implemented them incrementally to see which one would make a difference.
Unfortunately none of them did.
Finally thinking more about the shape of the streaks on the wall, I decided to think “out of the box” and insert a plane from the primitive folder above the exterior of the house and that lessened the effects of the streaks. But, that did not adequately explain why the streaks appeared where the boards where perpendicular to the streaks on the right side of the image.
Making the plane even thicker reduced it further until they disappeared completely.
Oddly previous renditions of the model did not present that issue, because the T&G was one solid - in this new rendition I broke the boards into separate solids to enable to have the wood grain appear more random - thereby perhaps light to be able to pass through.
Thanks again for your suggestions