Assuming you reported the rental on your 2015 return, you can find that information on your 2015 Form 4562, Depreciation and Amortization (please see the screenshot below-click on the image to enlarge it)
Note that on this report, you would add "Prior Depreciation" and "Current Depreciation" to obtain "Accumulated Depreciation" (not displayed). Your accumulated depreciation would be the number you would enter for the depreciation taken since you began renting your house.
