Hi. I've been working on a house project for a long time now and just now it occurred to me that I haven't seen a single window in the CS. I wonder if there are any modders ressources or workarounds to make my estate a bit less gloomy place to live at?

Windows are built in to all the interior and exterior building models, there is no need to add them. You'll only find window texture assets.

Another thing to note is that windows don't let in any light. You'll need to separately place a light source next to the window in order to get that effect. The more sophisticated house mods have scripts that adjust the light from the window area to match the time of day, and frequently do the inverse to light up the candles in the process.

Guess I have to bid farewell to the windows then because I used a custom tileset and they didn't come with windows. Thanks for the replies.

There are a number of window resource at http://oblivionsrealestate.com/Resources/resources.html that can be placed on any blank piece of wall. You may not find all the styles you're looking for, but some are plain enough.

I have made windows on http://tesnexus.com/downloads/file.php?id=36886 separate, but they are rather simple and bulky.