check your builder's spec first. they should state what kind of material they will use for your house.
when you visit their model home, please ask the sales for a upgrade list for the model home, so you will know what they had done for their own model home to make it more attractive to you
this site has lots of discussion about upgrading for different builders in ottawa area.
http://www.buildinghomes.ca/community/forums/forumdisplay.php?f=35