Cat-proofing flexible air ducts

Question

I have cats occupying my boiler room. Unfortunately, my cats are climbing all over the place and are often tearing the flexible air ducts which provide the house with fresh air and warmth. Image for reference:

After a while, the holes in the ducts get large enough for them to fit through and the curious critters start exploring the newly found hiding places. I want to keep them from harm's way and I'm also sick and tired of repairing the damage.

Here are a couple of things I have considered/tried:

1. Replacing the flexible ducts with metal ones - not possible, the ducts are running through some tight spaces and bend very often, and I'm on a limited budget
2. Buying a more sturdy duct - the image above shows one which is covered by rubber. This helped to some degree, but the cats are persistent and get through eventually
3. Wrapping the ducts in a hard and slippery plastic foil. Somewhat effective, but also not perfect

How can I prevent the cats from tearing the ducts up?

Answer 1

From a cat's perspective, ductwork is fun! The foil wrap makes cool crinkly sounds when you pounce on it, and it tears easily under the outstretched claws of any cat.

However, cellophane packaging tape is not fun. Booo!!!

Whenever my cats take to scaling or scratching things I'd rather they not (furniture, rugs, door jams, etc), I just cover the spot with a few strips of packaging tape. Something about the plastic-y, smooth membrane seems to really turn them off… and they never touch it again (and I can remove it once they move on to other adventures). I used to wrap things sticky-side out, but that doesn't seem to be necessary — they just hate the stuff as is.

Try wrapping a small section of your ductwork in cellophane packaging tape to see if it deters them. It isn't very expensive, so for a modest investment, I think this has a pretty good chance of deterring the scratching — and will even increase the insulating properties of your ductwork a bit!

Answer 2

You could use chicken wire or some equivalent to wrap the duct work. You can get it with gaps of different sizes and it should be available at most local hardware stores. If the gaps were small enough, that should prevent them from even touching the ducts. With larger gaps, they may be able to scratch the ducts but will not be able to pass through the chicken wire to enter the ducts.

https://en.wikipedia.org/wiki/Chicken_wire

Answer 3

If a solid casing like Robert Cartiano suggested isn't practical, you could enclose the ducts in hardware cloth:

Hardware cloth is flexible enough that you can shape it as you need to, but rigid enough to support cats climbing on it and keep them from tearing the ducts. You can also cut the hardware cloth to whatever odd shapes you need, and use a set of special J-clip pliers and a pack of J-clips to bind the edges/corners. One of the nice things about this is, if your duct goes behind pipes/etc you can cut holes in your "cover" so the pipes can poke through but the duct still gets continuous coverage.

(Note: I do not use or endorse the products I linked here, they were just the first ones I found on Amazon, to give an idea what I'm talking about)

PROS

• Durable, should support cats' weight
• Cats may not want to walk/climb on the mesh in the first place
• Can be cut/bent to fit where and how you need it

CONS

• Expensive (a 10 foot roll of 23-gauge cloth is ~$15, the pliers are $10-20, and clips are a couple bucks)
• While usually made from galvanized steel, in particularly damp environments hardware cloth may rust over time
• Time-consuming initial setup (cutting the hardware cloth to shape, and clipping the parts together)
• Pointy bits won't be fun to brush against; though these might deter cats too

Alternatively, you could combine both methods: use plywood or drywall to protect long and/or relatively straight exposed lengths of duct, and just use the hardware cloth to protect the ducts where they go around/under obstacles or take weird bends. Hardware cloth lends itself pretty well to being stapled to stuff (with a staple gun, not an office stapler!)

Answer 4

You could try semi-rigid dryer ducting:

It's still flexible, more durable, and only slightly more expensive. This is more than just tinfoil. Besides being stronger, it may also deter them due to the harsh tactile nature of it.

In dryer months (no pun intended) this can act as an electrical ground, too. I've seen cats playing on a carpet get statically charges, then go near an outlet to get zapped. Hilarity ensues (for the human).

If there's any significant amount of heat going through these, I'd stay away from the packing tape @Robert Cartaino suggested. The packing tape could melt and/or start a fire. Putting the tape as a barrier (without actually touching) to getting access to these might be an option, though.

Answer 5

Your first (and best) line of defense is physical barriers to encase or block the duct work. The photo above is faux wood made specifically for that purpose, but you can just as easily (and more economically) fashion a simple conduit or barrier out of plywood or even inexpensive drywall sheets — they very easy to cut and finish to blend in with the existing architecture.

Answer 6

There are a lot of products specifically designed to deter cat from climbing, biting, and scratching on the fixtures around your home. Bitter apple is a particularly nasty substance; if you've ever touched it, you'd know what I mean.

For a few dollars, this is an inexpensive way to see if such irritants will (safely) deter your cats from making a playground out of your duct work permanently.

Product Search: Bitter Apple Cat Repellent

Answer 7

Cats like both shelter and warmth.

They are interested in your ductwork because of the heat it provides, and if they have a hole, they also have a shelter.

Place multiple carton boxes around/on top of the ductwork, this gives them an instant shelter that both has heat and protection.

Answer 8

Replace the flexible ducts with insulated flexible ducts. If they rip the outer plastic, they will only hit the insulation and not create an air leak. You can tape up any holes without compromising the integrity of the inner duct. It's essentially a tube inside of a tube with insulation around it.

Answer 9

Plastic trellis from the local hardware store will solve the problem.

It's cheap and easy to use.

It can be easily cut with normal scissors and still sturdy.

We use one with a 10mm square hole to hang flexible duct (donkey dick in the trade) all the time.

Answer 10

There are many good answers here about protecting the ductwork. An alternative would be to make it inaccessible to cats. That is, remove anything around it that would allow them to climb up to it.

Without knowing how your boiler room is set up, I can't be sure this is an option. But if there are ladders, chairs, cabinets, etc. that give the cats access to the ducts, it may be possible to move them away from the ducts and solve the problem.

Answer 11

Revisit what those ducts are doing. You may see a maze of ducts, but generally they are only two ducts: hot air to the rooms, and cold air return. Often the cold air return is absent, or these particualr ones are unnecessary, leaving only the hot air ducting.

Rather than redundant routes back to the furnace, that whole area can be boxed in, creating a plenum, with each branch then tapped off the plenum. A simple rigid duct to the furnace proper and you're done.