I want to get rid of the noise but I can't for the sake of god find out what is causing it. I am using an HDRI. I am not using glass materials. I blocked all the HDRI light with objects apart from 2 windows (no glass, no geometry, just 2 big openings). Here is a picture (32 samples) : (I am new to blender but I am very familiar with 3d environments) (HDRI is hidden by ''world-> ray visibility-> camera (uncheck)'' but checking it doesnt make any difference anyways)
EDIT: My question here lies on, why does this happen? The problem is solved, I can just increase the samples and activate the denoiser. The problem I have with this is that previewing with 32 samples is different than previewing with 100 or 500 samples. At one point I added a glass material and it acted as a noise trap and after removing the material, the noise trap persisted. I want to know why that happened.