The equity in your primary residence does not affect your expected contribution. The calculator at
http://npc.fas.harvard.edu/ has a box for "real estate equity", but the accompanying note says "This should represent the fair market value of your ownership share of any real estate (excluding your primary residence) not already reflected in the Business/Farm section, less your share of any debts."
Harvard says at
http://www.fao.fas.harvard.edu/icb/icb.do that
"We do not consider home equity or retirement accounts as resources in our determination of a family contribution, and aid packages do not include any loans."
