If the white pixels are on the floor I think they might be caused by the glossy shader of the wood floor. I admit that the glossy shader, in some points turned out very sharp, and with low sampling and no clamp it cause some burned white pixel to me too. I've resolved the problem by rising the sampling value to 450 and clamp to 5 ( in the files I upload, usually I reset the sampling to 10 and clamp to 0 in order to not cause problems to users with less powerful pc ). If the white pixels appear in other areas, such as the roof, I can't explain the cause, since to me it doesn't happen. I'm very sorry.

Thanks for letting me know. I'm very happy when I see how my work are used. p.s. I like very much your blend "12 buildings" good job !

Thank you ! I plan to update this file in the near future, I hope you will like it as well

Hi I'm very sorry for answering this late. Maybe you don't need anymore an answer at all, however I wanted to help you anyway... I usually close the timline and other windows since I don't need them, and it's very easy to grasp how to edit the quantity and type of panels on screen but it's pretty difficult to explain it by words alone... I give you the link to a very interesting tutorial on how to get started in blender: https://cgcookie.com/blender/lessons/using-customizing-interface/ this specific lesson by Jonathan Williamson should teach you everything you need to know about how to edit the interface.