Diagnosing a Dark Room Despite Large South-Facing Windows

I’m trying to identify why a small room receives less usable daylight than expected before considering skylights or larger windows.

The room is 11 feet wide by 15 feet deep, with the 11-foot wall facing south. That wall has two windows, each 3 feet wide by 5 feet high, with 30-inch sill heights. The opposite wall is only about 8 feet away from a neighboring house, and a roof overhang extends approximately 24 inches above the windows. There are also deciduous trees near the south property line, although the room remains noticeably dim even when the trees are bare.

The room feels darkest toward the back half, particularly in the morning and late afternoon. The ceiling is white, the walls are a medium warm gray, and the floor is a medium oak tone. The windows have no interior blinds, but the exterior wall and overhang may be limiting the sky view.

For those familiar with small-home daylighting, which factor would you investigate first?

- Is the 15-foot room depth excessive for the window area and sill height?
- Could the overhang, neighboring house, or tree canopy be blocking enough of the visible sky to matter?
- Would lighter wall and flooring finishes improve perceived brightness without substantially increasing actual daylight?
- Is the window placement too concentrated on one wall, even though the total glass area seems reasonable?

I’m especially interested in practical ways to distinguish an exterior-shading problem from an interior-reflectance or room-proportion problem before changing the windows.