Gp - do NOT assume your property taxes will remain the same. It's not going to happen.
Your assessment will indeed increase due to your improvement of the home.
Unless the town's tax rate goes down (which is highly doubtful)..... your taxes will increase based on the improvement.
Sorry- but that's just the way it is.
Capital improvements result in higher valuation which result in higher property taxes.
You might want to call the tax assessor's office to see if they can give you an approximante idea of how your taxes will be affected.