Bought a 1976 house in good condition and when we viewed it, it wa already empty because the sellers had already moved. We noticed that it had a very particular odor. Not bad just particular. 4 years later, the smell persists. We especially notice it when we get back from vacation.

It’s a bit musty slash “old”. Roof was replaced, no evidence anywhere of any leaks, plumbing repair also done. All carpet removed and replaced with vinyl. House is vacuumed daily, windows opened whenever possible. No incense or candles help long-term. Kitchen is clean and sink is kept clear.

Any thoughts on what causes this odor? Particularly on humid days? Is it in the walls or what?