I dont know. Would a mild solution of bleach help maybe. I hope you get some ideas on this. I bet a fan would help. I have three fans going constantly to keep the air movement going. I wish you the best....Barb

You have a lot of humidity in Oregon? I would think (if it's even possible) that if you could wait til summer and get it dried out well, then get some kind of marine paint? This at least would keep (or deter) it from rotting. Just an idea, not sure it's feasible, not knowing exactly how you have it all set up etc.

Is the mold (more likely a form of mildew) having any bad effect on your plants? Are you worried about your health? My greenhouse frame is treated pine and was built in 1992. Our winters here are usually humid due to frequent weather fronts coming in off the Gulf, especially in late January, all of February and March. I haven't had any mildew or mold problems. I suggest you buy some of the bleach solution you can spray on roofing shingles to remove mildew. Empty the greenhouse and spray the wood well. Also, spray everything to kill as many mildew or mold spores as possible. I also suggest your wash the plants with soapy water and wash the pots well. Clay pots are very conducive to growing mold and mildew.

Yes you need fans. Air movement is necessary in good greenhouse culture. Without it plan on loosing plants. Anyone who says otherwise probably has dry air. That is why they do not have your problem. Killing the mold as suggested by others would not be a bad idea.
Try this link for some info.
http://www.essortment.com/all/fungusmoldsind_rhhw.htm

This should also help. It is from ComfortChannel.com
Small pores are also found on the leaves of all plants. These pores act as vents for oxygen, CO2 and water vapor. Water vapor accumulation is called humidity. The relative humidity in a space describes the amount of water vapor present in the air. Knowing the level in your greenhouse is crucial because most plants peak in certain climates. In addition, too much humidity (above 80%) will spur mold growth on your plants and inside your greenhouse. Mold wil destroy plants and wooden structures and cause disease. So the lesson here is to keep your greenhouse humidity between 45 and 60%. To measure the relative humidity in your greenhouse, purchase a hygrometer.

To control high humidity in your greenhouse, you will need to increase the circulation of air. The easiest ways to do this are to install a fan or water earlier in the day and only when your plants need it. To correct low humidity problems simply water more often or purchase a greenhouse humidifier.

A dehumidifier could be useful here also. They make thermostats with hygrometer's you can buy for under $10. Or you can go for a fancy one that will turn misters or electrical equipment on and off.

Roger

Western Oregon is humid though not like I experienced in Atlanta or Miami.

I will put a fan out there and see what happens.

My yard is full of wooden structures that do not grow mold or mildew. There is now fluffy gray mold that looks like what grows on bread in spots on my foundation.

I think getting DH to finally do some weather proofing really made the difference. He caulked and sealed all over and weatherstripped every panel.

I did not have this problem previously.

I'm also heating my greenhouse pond for the first year. That might have something to do with it as well. I have tropical waterlilies and other tropical water plants in it. They died the previous two winters with no heater in the water.