Heating Element Advice

That kind of depends on where you live and how you build it. 

Happy smoken.

David

Well insulated, as it is, 1500 watt will be plenty.....   In a cold/hot smoker like you are building, 2-4 sq. in. air in, and 4-6 sq. in. air out will be plenty also...   I recommend exhausts on the sides of the smoker, as vents on the top, tend to drip condensate on the food...

When you re sheet the door, I recommend removing the door....  lay on the floor with the 4 corners supported and wedged with wood shims available from a box store.....   Drill the 4 corners at the extreme edges and install sheet metal screws.....   tie strings in an X pattern across the door and make them taught....  shim the corners until the strings "just" touch in the center......   lay the new sheeting on the door and secure....   That method will insure the door will be in "plane" with the refer body and close and seal correctly.....

I learned that method when I built my first refer smoker, and after several attempts to install the door sheeting so the door would seal....  The original door seal will have been removed and a new one will be needed....  using the existing hinges, the new seal will have to be the SAME  thickness...   I used 1/4" lath for backing and sisal, manila rope for a seal....  worked very well....  the smoker never went above 170 and was used exclusively for salmon....  Now there are better seal materials....  like pellet stove seal material....  and high temp silicone sealant to secure it...  The sealant in the pic is for high temp smokers like wood fired smokers...