Musty smell - no mold/water/mildew issues
We've lived in our house for just over 1 year and from time to time we get musty/mildew type odors in a few areas of our house (Living Room, 1 Bedroom and that bedroom's closet). The rooms are not next to each other. We have no visible mold/mildew or water damage issues. We've tested the house for mold and it was negative. So why the odor? It only happens when the weather is "in between" - no need for heat or A/C (outside temp 40's to 80's) and has no correlation to rainy weather. Our basement will occasionally get damp in heavy rain (we run a dehumidifier for this), but the basement has NONE of this odor when it's in the rest of the house ......we're stumped.
We only know that the previous owners replaced the subflooring b/c of mildew from the wall-to-wall carpet and padding and then installed laminate floors over the new subflooring in all first floor rooms except the kitchen.
Can't imagine why we'd have this issue?
Has anybody got any ideas - where to look next?