If your policy covers the loss but you and the insurer disagree on the dollar amount, most policies let either side send a written 'demand for appraisal.' Each side names its own appraiser, the two appraisers pick a neutral umpire, and any two of the three set the amount. Look in your policy's Conditions section for the exact wording and deadlines — they vary by state and policy — and consider having a licensed public adjuster or attorney review it. This is general information, not legal advice.
After an appraisal demand you usually have a short, policy-set window (often around 20 days) to name your appraiser in writing. Because most states don't license insurance appraisers, look for verifiable credentials — certification from P.L.A.N., the Windstorm Insurance Network, or the IAUA (Insurance Appraisal & Umpire Association), for example. The LossHQ directory lists certified professionals by state and certification so you can find and contact one directly.