I second the post from dry dog. I had to install a Sante Fe unit into our new home to get rid the the very smell you mentioned. The problem is that with a tight house and a basement that is 3/4 below grade, the moisture coming through the foundation walls and concrete floors has no place to go. We noticed the problem on days when the humidity was very high outside but the temps were too low for the Ac to come on. I bought a humidistat and measured the basement humidity was abobe 70% on some days which is not good. Started to notice wet spots on the concrete floor and the musty smell. For a short term fix I just ran the AC way below the set point and presto - smell and spots went away. I then ordered the Sante Fe unit and that has been a great permanent solution. I bought mine from iaqsourrce.com. If you get one of these, you will need a drain because it sucks out a lot of water. I installed mine of top of 4" solid conderblocks to elevate it for drainage and the drain dumps into the sump pump basin. The air output directlty in front of the Sante Fe output vent feels dry and warm but once the basement gets down to a decent humidity - say 50% - it actually feels cool and crisp. You can hook up your DH in a variety of ways. I chose the standalone configuration which sucks air from one side of the basement and dumps it at the other end. I then use my HVAC fans to circulate air from the basement to the rest of the house and back. My HVAC unit is in the basement, and there are large air intake vents in the basement and upstairs that feed the main input duct so I get good air circulation between the floors. I bought an IAQ thermostat (Honeywell Vision Pro) that allows me to program the HVAC system fan to turn on for up to 20 minutes every hour to circulate the air even if the HVAC is not running for AC or heat. The Vision Pro also has it's own built in humidistat and can be programmed to use the AC as a dehumidifier if the humidity detected at the tstat is above a programmable amount. The combination of the two features - the whole house DH in the basement and the ability to automatically run the AC below the set point when humidity is too high upstairs - has been a terrific solution to our moisture problems. One thing to note - my Sante Fe unit has an anolog knob for setting the humidity level (no digital output). To get the humidity just right in the basement, I used a battery operated humidistat and kept adjusting the knob until I found the spot where it would keep the basement at a 50% humidity level. I also have a separate Energy Recovery Vent system in my house which I use to bring fresh air in and exhiust stale air from the house. I am very careful with this unit and only turn it on when the humidity outside is low because I don't want to suck in fresh moist air. That would only make the Sante Fe unit run more. I learned that through trial and error - mostly error. If I were in your shoes, i would first fix the humidity issue with a whole house DH. Put one in the basement and then manually turn on the HVAC fan when you want to circulate air between floors. If you get tired on the manual switching of the fan ON, you can add a tstat that provides an automatic air circ feature. After that, then decide if you want to add a seperate air ventilation system in. These are recommended for very tightly sealed houses. If the house is older, you may get enough air infiltration through the walls already. You can fix your issue for a lot less than 2300 dollars. I think the Sante Fe runs around 1100 or so but deals can be found. BTW - don't go cheap on the DH unit becuase you really get what you pay for with these things. Do searches and read reviews. Check the specs and see how many pints of water per 24 hours the thing is rated to extract. Check the air flow rate (usually a CFM number) to see how much air it pushes. Beware of systems that don't have a drain (they use a pan instead) unless you plan on dumping the pan every day or more depending on your humidity problem. Good luck.

Iv been looking at whole house fans and would like to replace my old blower with a more efficient one like this after realizing how much power it consumes thanks to zl700. http://www.atrendyhome.com/qcwhhofan.html?productid=qcwhhofan&channelid=FROOG Since I have the grill and flex already installed all I need would be a fan and damper set up. Can anyone recommend where I could buy one? Or what specifications I should look for? Also.. Is my guess at 1600 to 2000 cfm for my old blower close since a 4 ton AC used to be with it? Thanks

"We have no vents in place leading from the attic to the second floor" The whole house fan would go in the attic and draw air from the second floor. Our fan draws air from the hallway centrally located on the second floor but there are options for fans in each room. The installer would determine whether you need more attic venting to the outside of the house. We have a 2700 cfm whole house fan and LOVE it. When it cools down in the evening we open the windows on our 2nd floor and turn the fan on. It's amazing how fast is cools the home. Since the whole house fan vents to the attic it also turns the air over in the attic helping to cool the attic. We have been very happy with our whole house fan. There are some things to consider though. I've read comments from experts on here about fire hazards due to the suction from the fan. I believe this is primarily a concern for those with water heaters in the home. Our water heater is in our garage and so the flame is not subject to the pressure variation caused by the fan. Hopefully some experts will chime in on the things to look out for.

You could have something building on the roof to house a whole-house fan.