thank you very much for replying. Noted on the wall temperature. I am still not sure if it is the removing of the pipe studs itself that did the trick but I kept the boundary conditions the same. So i guess it is not the boundary conditions that fixed it. Anyways, I will try modelling with pipe studs again and see. nAlso noted on the residuals. But if the residuals start rising significantly then there is definitely a problem yes? Like below in the first time I modelled - that rise is too much and I should realize there is a problem right?nn