You could always do what a friend of mine did. He cut a hole where he wanted an air intake and grafted an automotive air filter there. His case ended up looking mor car than computer, but it worked.
Ha! When I was an undergraduate, one of my friends was having computer issues. I opened his case and it was literally a block of dust! His family lives on a potato farm, and it had sucked up all the potato dust. It took a vacuum and two full air dusters to clean it out. Surprisingly, the fans still worked and nothing was burned up.
Well that was lucky for him.
Dust happens. Surprisingly some computer manufacturers seem to forget that.
A few times I've considered using air ducting for like dryers or something to go directly out a window. I should probably just do that to stop heating up my room, because I don't live in a frozen wasteland where my computer heat is welcome.