We are building a greenhouse structure using used tempered glass from sliding glass doors. The builder is building the wood frames using TimberSIL (a wood/glass composite material). I would like to seal the wood first--I'm asking for recommendations for a good wood sealer that will withstand the hot Arizona sun. Deft and Cabot brands are readily available here. Deft makes a clear water-based polyurethane; Cabot has a clear water-based silicone type waterproof sealer, but their website says recoat every 1 or 2 years. That is too much maintenance for me. Suggestions? The wood will actually not be exposed to the outside since the glass will cover it but there could be humidity build up in the greenhouse (or not--this is Arizona)