Ivan is correct, marine epoxy or spar urethane would keep moisture out of the wood. silicone will only cover the surface of the wood. either of the two i mentioned will actually penetrate the wood and seal it from any humidity/moisture. that's the difference between a sealer and a sealant. a sealant will only seal a surface, but a sealant penetrates. if a sealant gets a small nick in it, all bets are off. i would definitely seal the edges of the glass with silicone, but any and all wood surfaces, i would seal with marine epoxy reinforced with fiberglass mesh between the first and second layers.