No, wheat uses QT framework, which isn't that heavy that .Net. However it's not really .Net what uses so much memory, but its WPF layout, which is the new way that Microsoft made for application layouts. I was searching a lot about how to reduce memory using, but I haven't found any solution for that yet. However I think it's system dependent.. I mean if you have memory enough, then it will use more.
And btw, it's interesting, but when you send the application to the tray, then it will use much less memory.