Home Made Down Draft Kiln Vent

A kiln vent is used to remove not only harmful vapors from your kiln and kiln room, but also to help regulate the heat in the kiln. A down draft kiln vent will pull the air through a hole in the lid of the kiln and out a hole in the bottom of the kiln. This will help to regulate the heat by pulling the hot air down the kiln. Look at the bottom of this page for links to more technical reasons to use the down draft kiln over using the over kiln flu.

You have the option to buy a kiln vent for about $300-450 dollars, or you can make one yourself with some simple tools and time. First you need some Tools: Metal snips (metal scissors), Drill with bits for stone and metal, Rivet gun and rivets, foil tape (metal tape), tape measure, clear silicone caulk, and felt tip pen. Materials that you will need: sheet of thin metal, black stove pipe (Elbows, Caps, Joints and Pipe; I used black stove pipe due to the heat of the kiln) large diameter pipe clamps (I used variable sized PVC clamps) wall anchors (masonry or drywall depending on your wall), an AC powered squirrel cage blower (I unfortunately got a DC powered blower and had a heck of a time getting the adapter), an outside vent housing(one that allows air out but hinders animals coming in), and plywood or some material to fill the window that you will go through to vent the kiln (I used Plexiglas).

Measure the distance from the top of the kiln stand to the floor. This measurement will tell you if you need to cut any metal off the end Cap and Elbow to fit under the kiln stand. First you will need to place an end cap on the pipe elbow. This will act as the first joint from the kiln to the vent system. Once you cut the elbow and cap to fit under the kiln stand, you will need to cut a hole in the center of the sheet
metal so that the end cap can fit into the hole. Make sure that the hole for the end cap only is big enough for the end cap to fit into with the top cap setting on the sheet metal (think of the end cap as a ‘T’ and the top of the ‘T’ will rest on the sheet metal and the bottom shaft of the ‘T’ will fit through the hole). When cutting the sheet metal you should leave several bent down section that you can pop-rivet through to secure the sheet metal, end cap and elbow. This precaution will help the vent to stay in the correct location when you move the kiln and drill the hole in the bottom of the kiln. The cap and the elbow will sandwich around the sheet metal. Do not cut a hole in the end cap, you will do that later.

The sheet metal will lay on the kiln stand and should be placed in the middle of the stand. Make sure that the elbow is facing the window or wall that you will vent the pipe through. Then place the kiln on the stand so that is lays over the sheet metal and end cap. The pipe elbow will rest on the floor.
Measure from the edge of the kiln to the outside edge of the elbow. Use this dimension to measure where the end cap is laying against the bottom of the kiln. Take you drill and drill a 1/2" hole in the bottom of the kiln through to most central point over the end cap. Make sure that you know the location of the end cap under the kiln. You will not want to have to drill two holes. You will easily cut through the fire brick but will find some resistance with the metal on the kiln and end cap.

Now you will connect the elbow under the kiln to pipe and elbow until you get to the window or wall that you are venting through. Once you have the pipe in place you will need to secure it using the PVC anchors.

You will now connect the blower to the end of the black pipe. I used rivets to secure the blower to another end cap. You will need to cut the middle of the end cap out so that the blower will pull air through the pipe. Finally you will need to connect the blower to ventilation to the outside of your room. I used a vent housing that attached to a 3" pipe. I also cut a 3” hole in Plexiglas and silicone caulked the housing to the Plexiglas. You will also want to screw the Plexiglas in place and caulk the Plexiglas to the window frame to prevent drafts.

I used an additional plastic cover over the vent housing in order to ensure that animals didn't want to live there.

The 3" pipe from the outside then connected to the blower with an adapter and foil tape. Cover all seams and joints with foil tape to ensure a good vacuum.