This design is intended for those who are willing to keep the litter box near a single-hung window with outer screening and no burglary concerns (i.e. probably not on the ground floor in a neighborhood like mine!). I will be following up this post with another version that couples to a bathroom exhaust vent.
This project is designed to cost less than $35 to make, and uses mostly common, recycled and/or re-purposed and cheap materials. It is also quite doable for someone with limited tools. Perfect for apartment dwellers!
* Hot glue gun and roughly 10 hot glue sticks
* Heavy duty poultry shears or tin snips
* Serrated bread knife
* Serrated tomato knife
* Electric drill
* Standard drill bit index (up to 1/2")
* Permanent marker
* Hooded plastic cat litter box with at least 7"x7" of flat surface on the back end
* 12V 120mm CPU fan (smaller sizes may also work...try recycling one from an old desktop computer). I used this one.
* 12V DC power adapter (500ma). I used this one.
* 2 x plastic food storage containers (25oz, 740ml - 6-3/4" x 6-3/4" x 2-1/4") with lids
* 2 x empty, de-labeled 28oz food cans (I used cans from crushed tomatoes) with both ends removed.
* approx. 10 hot glue sticks
* 5-25' (location dependent) of 4" dryer duct, aluminum or plastic
* electrical tape
* 2 x 16" long zip ties
* 2 small zip ties
* 8" x 36" rectangle of Owens-Corning Foamular(R) 250 or comparable (pink foundation insulation) or 3/4" plywood (if you have a jigsaw or sawzall).
Step 1: Replace Catbox Air Filters With Cardboard
Step 2: Build duct flanges from empty food cans and leftover containers!
Step 3: Mount the Fan and Attach the Power Adapter
Step 4: Seal Container Lid to Back of Catbox Hood
Step 5: Drill Vent Holes in Litter Box Hood
Step 6: Measure and Cut Foam Rectangle for Window
Use a tape measure to to get the inside dimensions of the track that your lower double-hung window slides in. Use a straight edge to mark a rectangle 8" by the width of your window frame. Use a large, serrated knife to cut the rectangle from the stock. Be sure to support the material as you cut, as it cracks somewhat easily.
Test the fit of the foam in the window and trim accordingly. I had to compress the foam some with the palm of my hand to get it to fit in the window track, but it's going to make a really tight seal against the cold NYC winters as a result! I also found that the seal with the window was improved by using the tongue side of the tongue-and groove as the top edge of the window insert.
Step 7: Build the Exhaust Vent Fixture
Nevertheless, you want the affordability, challenge and fun of re-making this with tin cans and tupperware, read on! It's important that our design keep out the rain and wind, so we're going to use a 2nd leftover container and lid to build a rain/weather hood, with a backdraft-preventer flap made from the extra center stock we cut earlier while making the fan housing. To connect the flap with small zip-ties, drill two small holes per side in the lid and one larger hole per side in the flap and pass the zip-ties through as shown in the photos. The zip ties should pass easily through the flap, allowing it to hang and swing freely.
Note that the container bottom is going to serve as a rain hood on the outside of the window divider. Cut a rectangular portion out of one side of the container, which will face downwards, allowing air to escape. (See last several photos for detail)
Step 8: Cut Through Window Insert and Mount the Vent
Plug in, kick back, and enjoy an odorless litter box! I enjoyed creating some smoke with burning paper just to observe the draft of air passing through the mouth of the litter box hood and out the window.
Step 9: Arduino Extension and a Bathroom Vent Version
If you prefer to have the litter box in a bathroom, you can build a homemade hose coupling that fits over the bathroom exhaust fan / vent. Because 4" duct is a bit unsightly snaking up to the ceiling, it's probably worth using a design with smaller diameter hose, like 2.5" sump pump hose. Smaller cans, like those used for tomato paste, could provide the way here...