I bought a house jointly with my Pops in 07'. Do we split the deduction? If we don't will I lose big money?

If I don't claim the deduction on my taxes and let my father take full value how will it affect my return? I'm asking does it make a huge difference or small difference. The house was a new build and it finished in July. The equity hasn't climbed much in this current market. Both of our names are on the loan and title. AND if possible anybody got any extra hidden deductions hints I could use?