How to install the roof mounted exhaust fan With back draft damper & What should be the recommended height after the backdraft damper?

To install the roof mounted exhaust, you need to see whether the exhaust fan is needed in roof only or in a chimney, if it is chimney, then you will have to see the size of chimney, then you will buy exhaust fan according to the size. To install the fan, you need to have electical wires on the spot, an open space for ventilation on the roof. You need to drill four holes and then fix the fan with the help of screws. Then connect with the wires. After doing that you will have to install draft damper above the roof, if the draft damper is available then you will fix as it is, and if not, then you will have to make one.

You can make it either by wood or PVC pipes and fittings. You can use wooden box of similar size of exhaust fan, but if you are using PVC pipes, then you can use6 inches to8 inches pipe with the length of3 feet and an elbow with similar diameter, after installing that, you can use grill at the end of that elbow, so that birds and other animals prevent to enter.