This is not exactly on-topic but close enough that I think you all will be interested. I recently learned that one of the big things causing mold is improperly installed house-wrap. It isn't rocket science to put up Tyvek or other air/moisture barriers properly but apparently a lot of builders don't pay any attention to the house-wrap specs. They just slap the stuff up and put siding over it and the owner is no wiser... until they start having mold problems. Dupont - who makes Tyvek - has gone to the effort of making "housewrap specialists" available in all areas who will come out to your build-site for free and advise on exactly HOW to properly install Tyvek. I know this because when my builder's sub put the Tyvek wrap up, it didn't look right to me - way too many staples and those that were used looked too small, lots of patched together pieces, lower sections over the top of upper sections so that water would be funneled between the layers of Tyvek, vertical seams with no taping, etc. etc. etc. So I went to the Dupont website and pulled up the specs for Tyvek house-wrap and read them. Needless to say, this precipitated a major fight between me and my builder who insisted that his sub had put Tyvek on "hundreds of homes" and that "he knows what he is doing" and "there is more than one right way to put it up" and "I'm the builder, you should trust me to know what I'm doing" etc. In desperation, I contacted Dupont and they gave me the phone number of their house-wrap specialist in my area. I called him at 4:30 PM and he told me he would meet me at my house at 8:30 the next morning. He arrived and took one look, and immediately told my builder "this will NOT do, your installation voids our warranties and if you slap hardiplank over this mess, it'll be a wonder if the homeowner doesn't have mold problems inside of three years." Since my contract requires my builder to follow the specs of manufactured products so as to not void any manufacturer's warranty, that gave me the clout I needed to get my builder to make his sub do it right! The Dupont house-wrap specialist stayed at my site about 3 hours that morning advising the subcontractor and his workers on exactly what needed to be done to fix the job. He then made 2 more trips to out to inspect and finally sign off on the Tyvek installation. Since he had to travel nearly 40 miles (one way) to reach my house, I figure he put in close to a full day assisting with my build. And it cost me nothing so I know there is no way Dupont could have made any profit whatsoever on the house-wrap that went into my house. On his third trip, I asked him WHY Dupont would bother. His response was that it wasn't just my house that was affected but potentially every house that my builder and that sub and even any of his crew worked on in the future and that Dupont saw educating these people as the only way they could protect the integrity of their product. I have to say, I was impressed and wanted to share the information. I'm now reading the installation specs on every product that goes into my house and watching to see that they are followed and, if they're not, I'm going to be calling the manufacturer pronto.

Has anyone used any of the pre-painted or stained fiber cement products to trim out their porch posts? Our question is whether or not they are finished on both sides?

Just a comment on this 10 year old post, but about 10 years ago, I had the same problem that the OP had - failed drywall causing tiles to fall in. I used cement board around the tub and shower and green board everywhere else. I didn't find the cement board much more difficult to use than the green board (or any other drywall) so I don't see what the OP's objections to it are. An interesting aside, this bathroom was not original to the house. The non-shower side of the room had been a closet wall (not a bathroom wall). I removed the "drywall" which turned out to be a gypsum board based lath 3/4" thick with plaster over it. On the back of the gypsum board was printed "patented 1885". The house was built in 1890. A cross section showed three layers of plaster between thin sheets of paper.

MYSTERY SOLVED - for real this time! Since I last posted, our housekeeper's son washed down the ceiling. Everything looked great! The next day all the spots were back. I called a window washer, thinking he would have better equipment and taller ladders. When he left all of the spots seemed to be gone. The next day they were back! I drew two conclusions from that. Either (1) when the spots are wet, they are the same color as the ceiling, or (2) they are being removed and then replaced quickly. Today, DH caught the head of the golf course's maintenance team (did I tell you we are on a golf course?). He said they are army worm eggs. His advice was to do nothing about it until fall and then get our lawn treated when they treat the golf course. He suggested then power washing the porch ceiling. The number of egg sacs have multiplied dramatically since my first post. My ceiling looks scabrous! I suppose it is foolish to do anything to it until we and the golf course try to eradicate the army worms in the fall. Maybe I'll just put very colorful cushions on the porch chairs and no one will look up!