We have tons of info but will try to keep this shorter to encourage replies. We purchased a 12 yr. old home last month in Tennessee. Has crawlspace, first floor living space, second floor unfinished walk-in attic, roughly 1600 sq ft footprint with brick foundation and vinyl siding. House is on a sloped hill with crawlspace 6'-10' high, great access with lighting and electric down there.
HVAC is all electric with air handler inside crawlspace, same age as house. Home smelled musty when we purchased but it was vacant and carpets were dirty so we assumed it was just from being closed up for a few months. We had carpet and pad replaced in whole house, and also installed vinyl in bathrooms which were previously carpeted. We then moved in, aired the house out with windows open and fans on for a few days, and then closed up the house and ran the AC for a week or so. The musty smell returned and I had breathing trouble when home, possibly from an allergy to mold.
Inspected the crawlspace and found that clothes dryer was vented to crawlspace and also no vapor barrier at all. All vents were open year round. Ducts were reasonably clean inside and out but return ducts are interior lined with fiberglass and appeared dirty, hard to tell without removing. Not much mold visible in crawlspace but some white powdery mold sprinkled on joists near dryer vent and surrounding area. We cleaned all debris from crawlspace, vented dryer to outside, sprayed joists with 50% bleach and water mist, then dried out with fans. Recently shut all vents and installed dehumidifier down there with moisture outlet discharged to outside. Is much dryer down there already after just a few days, but we still have the smell when we run AC unit. Had numerous HVAC contractors and mold contractors inspect and make recommendations. Solutions were many but fall into three main categories:
1 - install sealed vapor barrier to crawlspace floor and walls, clean out existing air handler with biocide
2 - all of 1 plus clean and seal supply ducts, replace the interior lined returns with exterior lined ducts to remove potential mold build up or moisture in returns, install a UV light and filter kit at the air handler to kill future mold spores
3 - all of 1 with option for 2, plus connect a new exterior air vent and filter to the return line to supply some fresh air mixed with house air, seal the leaks in the house such as plumbing, door, and register openings, and create a positive pressure in the home to prevent mold, dirt, or other items from entering the home
Total project costs range from $3,000 to $10,000 depending on the contractors and options selected. I have done a TON of research and reading plus spoken to many contractors but am still at a loss for which option is best. Am leaning toward item 1 and 3 right now, then could possibly do 2 later if problem is still not solved. Any ideas or recommendations? I can supply more detail if needed, just let me know your questions.
read several of the threads herein-- & for RH in Residential threads.
have a/c coil in air handler cleaned -- an access hole may need to be cut into the plenum, then cover made & installed for future. have blower fan cleaned.
look for mold behind paneling, wall paper! esp if any water leaks evident -- under | in carpeting.
measure your house, including all exterior openings, run the load calc at this site! Your a/c is probably too big, so you will need a dehum upstairs!
get duct mastic and seal ALL joints, cracks of ducts and plenums -- use duct tape on access door cracks.
redirect water away from house, extend downspouts 10ft out, with but one elbow in piping -- dirt to slope away from house 6" in 10ft. intercept any water with ditching & gutters.
put down layer of sand over earth, then 0.006" tk pvc over earth. sand keeps termites from tunneling. overlap pvc up foundation, but leave 4" exposed masonry to be able to look for termites, etc. tape joints. white pool cover material is thick & helps lighting.
insulate upper part of crawl walls with glued on 2" tk Styrofoam | Foamboard. insulate joist band space with unfaced insulation, or Styrofoam pieces.
be sure brick has weep holes near bottom, say 0.375" about 2ft apart.
For a simular house in Lewisburg TN, I had to put in a 3" drain on the lower side to be below the foundation to allow ground water to get out from under the bsmt floor! else would have 0.5" stream across whole bsmt, squirting in beside columns, pipes, floor cracks.
Keep all areas below 50%RH including the crawlspace. Requires earth covered and vents closed. Takes a good dehumidifier when crawl is cool, <60^F spring & fall. Discharge some of the dehumidified air into the a/c ducts for distribution throughout the home and to dry out the a/c ducts when not cooling. A small amount of fresh make-up air with good filter is also suggested for postive pressure to stop humid air from being sucked into walls. "cem-bsee" covers all the bases but did not mention real humidity control. Keeping all the space and ducts dry will eliminate most of the odor problems. This takes 100 pints of dehumidification for 2,500 sq.ft. of house and will also handle the crawlspace. Check out http://www.thermastor.com/DesktopDefault.aspx?tabid=245
return air leak
Hi Bob; I just had the same problem in a friends house.He asked me to stop over and see if I could fiqure out why his house always smelled so musty.At first I thought it was because his duct was wet ( duct board )due to a blow by condition on a horizontal coil mounted in his crawl space so I replaced the plenum with insulated sheetmetal and the problem still was there.Then I discovered that in the real hard to reach spaces on his return air someone did a real half**##* job of insulating and there were some real big gaps between the floor joists and the panning. There was one place where a group of wires passed through the joists,into the return and out the next joist (completely against code)without any insulation,caulk,or anything.In other words,all his musty,nasty smelling air from his crawl was being sucked right into his furnace and supplied to every room in his living space.I sealed everything real good and they haven't had a problem since. Point is,before you go spending a ton of money,make sure the problem isn't a simple one that is easily remedied!! Good luck