Do your walls seem to sweat, or are they damp to the touch? Do you have persistent mildew on your walls?
Mildew growth does indicate that there is moisture present in the wall. Obviously, warmer climates will have more mildew and moisture problems. Humid parts of the country, especially in the South, are often besieged with water most of the year.
When your houses were built in the 1950’s, it was not uncommon to leave the house uninsulated. Energy was cheap back in the ’50s, and insulation was not considered mandatory then.
Before air conditioning became widely used, insulation was not considered necessary. Framing in older homes is sometimes a bit different from the classic pattern, lacking complete top plates on studded walls. The open cavities in the walls actually helped to keep a home cooler in the summer. Air could move up through these open spaces where there was no insulation and then out through attic vents.
Attics were the first places in homes of the South that got insulation as a matter of course. There are a couple of reasons for this. First, the majority of heat loss and heat gain occurs through the roof system. And second, attics are the easiest place to put insulation in an existing structure. It’s more work intensive and costs considerably more to put insulation in existing walls.
There are several possible causes to moisture problems, but the lack of insulation in your exterior walls is at the bottom of most of them.
If your attic is insulated, and the insulation is not placed properly, it could have blocked some flow of air from the uninsulated walls and from soffit vents. If this is the case, moisture is being trapped in the wall cavities and could be causing the problem. Or, the furniture may be blocking the flow of air across the uninsulated wall surface.
When an exterior wall has no insulation and gets no sunshine from a window (which would heat and dry the wall surface), the wall can act like a wick, pulling outside moisture to the inside. The moisture, which is the perfect medium for mildew growth, would be concentrated behind furniture, where lack of air circulation and sunlight would protect the mildew growth.
The best solution for such problems would be to insulate the exterior wall. There are some newer methods of insulating existing walls where the wall covering (plaster, drywall or whatever) does not have to be removed.
Here is how one method works: The baseboard is removed, and holes are drilled along the base of the wall. Foam is injected through these holes and expands to completely fill the empty cavity. Foam is an excellent insulation, and injection methodology is great when done properly.
Once the source of the continuing moisture is remedied, you can kill the mildew and clean the walls. This in turn will eliminate the musty smell in your home.