Mildew smell in recently renovated porch
We recently had the three-season porch on our 1936 house converted to a full-year porch. It is a small space (11'x7') that we now use as a playroom. Everything was taken down to studs, windows and door replaced, walls and ceiling insulated, new drywall put in, baseboard heater installed. The only thing that was not replaced was the floor, which is original. The floor is pine and has gaps of a couple of millimeters between the boards. Underneath the porch is a crawl space--just dirt. There was new rigid insulation installed beneath the floor.
Prior to renovating the porch it smelled somewhat mildewy. (We once left the porch closed up during a hot and humid spell, and it got really smelly; it never went away completely.) I had figured that the smell was mostly in the walls, but there is a lingering smell coming from the floor that I notice now that the weather is getting more humid.
Is there anything we can do about this other than keeping the windows open? Would washing the floor with a bleach solution accomplish anything?