Wood

I was off to walk the dog this morning and I walked past this garage door and was struck by the pattern on it. The garage is within the structure of the house and you can clearly see that there is a temperature difference in the wood where there is a reinforcing bar behind it. I think that where we see the spot in the "bars" are probably where there are nails or screws which being made from metal are much better conductors of heat that the wood.

My theory is that the dark areas are where the extra wood has slowed the cooling of the exterior down a fraction, and the result is that the cold wet air has only condensed on the other sections, coating it in a fine layer of water droplets which give it the lighter colour.

I didn't go and touch it to see which part is wet and which is dry, so I could be wrong...