Hi, Joe P. You definately want to use tongue and groove for this. Wood expands and contracts more across its width than in the other directions, percentagewise. The sliding of the T&G allow the wood to move and still seal the joint from air infiltration, dust, etc. Even if you put a barrier behind the wood, the gaps will show when the wood contracts. A similar approach to solving this problem is board and batten construction, but that is usually used on the outside.