Sounds like the house could benefit from a bit of air circulation. If it's a 2-story house, it might help to crack a window open just slightly. I say 2nd story for security reasons. If you have a programmable thermostat or one you can access with an app, you can periodically turn on the fan to circulate air too. All of this assumes there is no offending smell in the house that you have to search for and obliterate.