I wonder if there could be some moisture somewhere that is aggravated by morning sun heating it up. Is there direct sun exposure on the outside of the rooms with the smell that goes away in the afternoon? Any openings in the exterior walls in that area that might be letting in moisture?

The more facts given the better the possibilty your mystery may be solved.

Style of home?

Age of home?

Location, rural, urban, what is in area, such as totally residential to moderate or heavy manufacturing, school, restaurants etc. As much info as possible.

Mechanical system of home, forced air, electric, type of hot water heater and age, AC, age of systems, type of plumbing materials. What is the prevailing winds direction where you are. Have you asked your neighbors if they have noticed anything different .

Has the simplest thing changed since this has started, new appliance, furniture, home project.

Those are a few of many questions that we need to base a theory on.

Can you send a picture of the house, all elevations, and a overhead photo from Google earth.

This can be a simple as a bad hot water heater anode to a drip from a plumbing fitting..

Several of these simple questions can not be answered by some homeowners, it may surprise you as how little residents know about their houses.

The time of day this becomes a problem is good start, what happens at night that changes during the day, opening doors and windows happen, sun comes up, home is warmer, AC goes on, the world wakes up all types of activity comes to life. From factories running to laundry being done.

More info=better solutions.

It's usually the simplest thing that gives us the answer to a problem. As well the smallest thing we overlook as having nothing to do with it.

You have to provide more information.

Someone asked recently to help I.D. a terrible smell, one of those driveway sealing crews did a few homes blocks away.

Is the problem only occuring inside the house? Are neighbors having the same issue?

There is a cardboard mill around here that can smell really wierd around 4am to 7am especially in the summer months.

Is there a bathroom off the master bedroom, is the shower used in the morning?

Glad you got that sorted out!

I as well.