I like the stand alone dehumidifers better than ones incorprated in to hvac system. When you place the dehumidiferes in the conditioned space they sense the RH in that space, many central dehumidifiers sense the RH in the area they are located in and do not dehumidify the conditioned space as well. Where are you located? Where are central units located? Have you talked to hvac company about adjusting dip switch settings? Many times they are installed with factory settings and need to be adjusted for your climate. ERV's are usually not for cold climates..that would be an HRV, so I wonder about your location. Also ERV's are for 'tight' houses..with less than .25 air changes per hour. If your house is not at this level of air tightness the ERV can bring in moisture adding to the dehumidification load of hvac. Was the house tested for air tightness with a blower door? To 'see' what is happening behind the walls and between floors of your home would require a thermal scan of your home. This will show you moisture intrustion sites and moisture in walls, ceilings and floors. IMO this will be the way to go to actually KNOW what is happening. Then whatever the IR scan shows will be on you to address. Around here (Louisiana) thermal scan (InfraRed) scans are used often when home owners and builders are seeking solutions. I've even seen them used in court cases. But hopefully...it won't come to that! best of luck.

Since I last posted, I've narrowed a few things down. One of the rooms that was affected (there were 2 rooms total), has been fixed. The french drain I installed around the perimeter of the front of the house, where water was creeping under the foundation, seems to have fixed the issue in the larger room. There is now no more musty smell in there. However, the other room, which is a "closet" that backs up directly to a bathroom, still has the odor, which has actually gotten worse. The smell is definitely partially sweet, and partially musty. I've cut the drywall all the way around the room to see if there is any signs of water damage, dead animals, etc inside of the walls. Interestingly enough, the inside of the walls that butt up to other rooms, smell fine. The walls that have concrete on the other side, have the odor present (perimeter walls). The only two things I haven't addressed yet are the roof (I'd have to cut the ceiling open because there is no attic access at this point for how low the roof pitches). The other thing would be the foundation (slab). I have fairly expensive laminate flooring and underlayment in that room, which would have to be removed, and the floor would have to be inspected for dampness. However, given the circumstances, it's been narrowed down quite a bit. The room has 4 walls (2 butt up to exterior concrete and 2 others butt up to interior rooms), a standard hollow core wood door, a West-facing window, and a drywall knockdown ceiling. There is only two piece of furniture in the room, which are bookcases. One is MDF (still wrapped in plastic to hold it together before I bolt it in), and the other is pine wood, also wrapped in thin plastic to protect it. I've just put two large shop fans, a big air purifier, an ionizer, and ozone generator all in the room with a big bucket of damprid (although humidity levels in that room are only 49% in south florida, which is fairly average). I've also sprayed half a can of lysol air spray into the room. I'll let you guys know how that works out, and hopefully we can figure it out. and ESMAN - let me know your notes as well. Thanks.

I have bad allergies - I've walked into basements that hit me like a wall, instant headaches from mold, and I've turned and walked right out. But there have been others that were just a little musty that weren't as bad. Depends. If it has carpeting, and especially if that carpeting is old, I'd consider it...of course, remove the carpet, install a ceramic tile floor and anything that contributes to the growth of mold, mildew or dust mites. Are the walls exposed? We've got a few areas on the north face of our house that have mold on the cinder blocks behind the paneling, when we purchased the previous owners didn't have proper grading, and there were areas between the house and the concrete terrace that were open allowing water in. We rectified these problems, sealed the openings with concrete, applied a basement paint / sealer to the walls, works wonderfully by the way, filled a step crack with hydraulic cement, and we run a dehumidifier in the basement. Now, no musty smell. It takes work, but well worth it. We also opened up the heating ducts to the basement - previous owner kept them closed to keep heating costs down, I'm assuming. Makes a big difference. Look at the grading of the land - is there proper sloping so that water drains away from the house? We also installed glass block windows with window vents, but kept two original windows in case we needed to run a fan (say if we're painting) for air circulation, and an emergency exit in case of a fire. Good luck. Don't let it pass you by, you'll always wonder, what if? Hopefully the inspection will go well.

Three things that musty old houses have in common: little ventilation, high humidity, and darkness. This is a perfect petri dish for mold to flourish causing the "old house smell".