"Glass House Mods" are used to change some or all of the environmental shaders in a level to a glass shader value, thereby creating nothing but clear walls. This can be accomplished very easily with HMT, or just plain hex editing. EVERY LEVEL has at least one material that can be used to create clear walls. A few levels have one glass shader in particular that is far superior to what is used in other levels. The only true public glasshouse release was for prisoner, using a superior glass element. This file is no longer hosted anywhere to the best of my knowledge. I have managed to make a superior glasshouse mod for several levels containing only inferior glass shaders. Please do not PM me about these mods, as I will most likely just delete them without even reading. There are, however, several other means to contact me. Anyone wanting enough to make these mods could easily figure out how to just by reading this post and playing around with HMT. Simple trial and error.
The reason they are so controversial is that someone wishing to cheat in order to gain an advantage will use these hacks in order to see where other people are in the level by looking through walls and floors. However, there really is no advantage to using these because, no matter what, if they beat you with them off, they'll beat you with them on. This is only really a concern if every game you only lose by a few points. Not enough edge can be gained by cheating. Glass house mods are one of the few mods that work in system link play without causing desync errors. Remember, if you want to make glasshouse mods, do it for the education, the experience, or just the bragging rights, but do not use them online without prior permission of the people you are playing with.