My adviser tends not to answer emails either, and I know (cause he's said so) that if he's rushed or whatever, he deletes things without reading them. What works for me is that if there's something really really important (like, that I need his signature for something) I will put something like URGENT READ THIS in the title. And then he will deal with it. But I am careful not to do that unless he really really needs to be involved.

(My adviser tends not to read my project reports either. But he is very helpful about getting me equipment or whatever if I need it, so I consider him very supportive. ) (Professors are like that, you just have to appreciate whatever they give.)

-Far