Alex's House is a major location in MarbleHornets where Alex's old tapes mostly take place. The house is never visited by Jay, nor is it ever shown in present. Alex never states what he did with the house, just that he is leaving, and he never states if he lives by himself, with parents, or with siblings or roommates.
The First Tapes
Entry #1 starts with Jay noting he has noticed something unusual in the tapes. He decided to upload the data online for other opinions. The tape isn't footage of Marble Hornets, but rather is footage of Alex at home. Jay notes the audio in the tape has been cut, so he isn't sure if anything is said during the tape, and isn't entirely positive why Alex would have cut the audio in the first place. Regardless, Alex walks over to the window after killing the lights, and slowly looks out the window. He spots a tall figure standing outside, and dives back behind the curtain quickly to hide. The tape ends there, and Jay notes he may have missed other instances of this. He will be looking back through to see if he finds anything.
Entry #3 also includes Alex's house, but sparingly in a series of other tapes with nothing significant. Entry #4 involves a playground, it is never stated how close the playground is to Alex's house.
Entry #6 is supposedly taking place just right after Entry #1 takes place, and shows Alex wandering his house looking out the windows at the Operator stalks the perimeter outside. Entry #8 may also take place in Alex's house, where he is seen drawing disturbing symbols and imagery repeatedly until he gets up and shuts the light off. With the audio cut and the lights out on the tape, Jay has no idea what else happened.
Alex is running in Entry #10 down a sidewalk, but where he's running from or to is unknown, either he ditched his house and ran, is running to his house, or is in a completely different location altogether.
Entry #11 takes place in Alex's house as well, where he gets up after sleeping to check outside through the windows, then goes back to sleep, only for a shadow to appear on the wall. Who this is (The Operator, Masky, Hoody, or totheark) is never stated, but it's clear that whoever it is has access to Alex's house, and considering the Operator's ability to appear whenever he desires, it is most likely said being wandering his home, although that is speculation. Entry #14 directly implies that the Operator was the entity in Entry #11, where he wanders into Alex's room during his sleep and does something off camera, but never leaves the room. Alex gets up at some point to shut the door, and doesn't see the Operator who is clearly never shown leaving the room, but is now gone. Moments later Alex takes footage of himself covered in blood. The last time the house is shown is in Entry #22, and #22 is referenced in #51. In Entry #22, after Alex is back home from wandering the dilapidated building and losing Seth, Alex is back home saying he is going on the run. A figure's shadow crawls across the wall as the audio distorts, and this is supposedly the last time Alex was ever there.
Jay never goes to investigate the house unlike Brian's house, so it's unknown if Alex left anything behind of importance, although it's more than likely that all traces of evidence were removed.