To me this room should be much brighter than it is, mid day, high summer,...
Something between sweethome and sunflow isn't right, hence the need for additional lighting...

This is also the case with other 3D software to simulate natural daylight.
Path Tracing rendering is a first approach but it takes a lot of time.

With reference to your posting here what does IBL refer to, i cannot see it in the rendering properties

Cecilia has written an interesting topic about ImageBasedLight rendering (nighttime) and the influence of the sky texture used.
It also works daytime but the result is less obvious than with a sky color (SunSkyLight) for interior rendering.

...but now all the shiny surfaces look a mess

This is normal when using the silk or default (quality 4) shininessShader property because it allows to see the location of the light sources.
To correct this, it is necessary to decrease the shininess of the objects or to use glossy shininessShader but the reflections are different (mirror effect).