floating menu, lags during page scroll

floating menu, lags during page scroll

Hi guys, 

I have a floating menu moves together with the page scrolll.

Here is my code.

$(window).scroll(function() {
   var bottomHeight = $(window).height()/100*35;
   $('.logo').css('bottom',parseInt(bottomHeight) - parseInt($(document).scrollTop()));
});

Problem is when i scroll move then one frame a time, the menu will look like its lagging.

Does anyone know how to fix this? 

Thanks in advance. 

Cheers,
Thomas