We have a 1940s home that still has tongue and groove board on the interior. We decided to keep the tongue and groove instead of drywall because we live a couple miles from the Space X testing facility and I feel the wood is more sound than drywall with 24 oc studs. None of the walls have insulation. We are redoing the exterior down to the studs. The current original wood siding underneath is in bad shape. 

I have been told many contradictory things about spraying foam insulation from the exterior. I’ve been told by some to have rigid board installed against the interior first to keep foam from creeping inside. Is this necessary? Will the foam seep through the space between the T&G? Is it worth spraying the walls vs fiberglass in zone 2A (central TX)? I appreciate your insight.