[JRTJH]

I would not use KILZ. It should work OK for visible mold, to seal it and contain it, but it isn't effective on the mold root system and the mold will continue to grow under the KILZ because the back side of that 2x2 is still exposed to the exterior metal sheeting and moisture will wick into the wood from that area. So KILZ will "hide it so you can't see it but not kill it"....

Clorox will kill the mold on contact, but doesn't saturate the surface, so it will destroy the "VISIBLE" mold, bleach it white and make it easy to "brush away/break off" of the surface. BUT Clorox will not kill the mold root structure.

Hydrogen Peroxide 3% will also saturate the wood surface and destroy the mold root system, but it will take multiple spraying to work effectively because what it does is remove the oxygen from the mold root structure, drying it out. As long as there is moisture coming into the back side of the wood, the mold can "survive the treatment".

I'd suggest you buy a half gallon of White Distilled Vinegar and a spray bottle and spray the undiluted vinegar on the entire surface. Vinegar (acetic acid) will saturate the wood and destroy the mold root system.

There are many "mold treatment products" on the market, but few are as cost effective and long lasting as "plain old white distilled vinegar".....