I have a homemade electric smoker,Next I am going to build a cold smoking unit. Currently I'm trying this theory out with a cardboard box.
It's a box within a box. The outside box has 2" of fiberglass insulation on all sides.
The heating element on the bottom is controlled by the thermocouple located just below the middle shelf.
The wood box sits directly on the heating element. Two cheap disposable foil pans catch all the drippings and grease, and can be used to hold water.
The temperature controller is located in an ammo box (since it's waterproof)along with an extra thermometer.
I added some extra switches to control a light, and shut off the heating element.
Recently I've been toying with the idea of cold smoking. For $20 in copper pipe, I'm testing it out with a cardboard box.
Plenty of smoke inside the box.