When I bake my irradiance volume you can see artifacts (circled in red)
Could you show your irradiance probe placement? I think for your case there shouldn’t be probes places outside of the room (Those are leaking light into the room).
Simply scale down your irradiance volume and make those little “probes” inside your room. Also sun light tends to leak more than other light sources. I suggest trying an area light. Below is a render I took with this setup (I just enabled ambient occlusion and increased render sample count to 512)
You mean make little irradiance volumes for those areas like the window. I made only one vol and made it extrude a bit and this was the result:
I don’t know if this is your case, but I have solved some similar problems in the past by increasing the irradiance volumes’ “clipping start” value. If some of the probes are partially clipping through objects, this can cause artifacts because they have a shadowing system which then goes crazy. By increasing the clipping distance, you make each probe ignore the objects close to itself. Just increase the value little by little and make sure your walls have a good amount of thickness, so you don’t risk catching the sky through the walls.
Apart from this, you can also go into the render settings, in the “indirect lighting” section. The settings that affect irradiance volumes there are “diffuse occlusion” (higher=more quality) and “irradiance smoothing” (it can soften those sharp detail, at the cost of a blurrier result).
After you have checked those settings, an other thing you can try is to increase the resolution of the irradiance volume. Each little probe has its own shadow grid, so more probes=finer artifacts and better response to irradiance smoothing. Of course, you don’t want to go too high either, or you lose the smooth gradients. In a room this size, I would try something like 10x10x8.
By probes, I mean the little dots/spheres. Take a look at this video to better understand irradiance volumes (He also gives tips&tricks for interior spaces): https://youtu.be/9SD0of-mOHo?t=119
I didn’t tell to add probes, I told to place them inside your room and not outside. Also artifacts in your first render probably caused by some of the probes placed inside the objects (pillow, bed etc.).
Above video explains these well.
I would avoid using HDR to enlight the scene because background lighting kind of ignores the objects in Eevee (Use it with very low intensity to give just a slight tint to your space).
