Burying Crawlspce AC Ductwork?

[nhurst]

Is it OK to bury AC ductwork in a crawlspace? I need to do some repairs on my ducts because my crawlspace is very narrow (maybe 18-20 inches from dirt to joist in most areas), and the ducts have been beaten up over the years by people scraping over them to get from one place to another.

I was thinking that if, when I replaced the damaged duct, I made a trench in the dirt, lined it with 18mil Visqueen, and put a piece of plywood on top of that, I could both open the crawlspace up some, and lessen the chances of the ducting getting clobbered again.

Has anyone here done such a thing, or am I about to undertake a task fraught with danger and unnecessary expense?

[Doug Kanter]

What are people doing in the crawlspace to begin with, which leads them to damaging the ducts?

[nhurst]

Home inspection is the most recent. We've also had pest control folks under there since we bought the house. Before we bought there were telephone guys, plumbers, cable guys, and electricians.

I've been moving everything I can (like telephone, cable, and some electrical) up to the attic, but I'm still going to want to get around under the house so I can check for problems.

The people under the house haven't been careless, there's just literally no room to get by without scraping past a duct. I've got water pipes going all over the place as well, and that's an added headache when they cross over a duct.

[tbasc]

Sounds like an old house with lots of patch work connections. I know duct gets buried on some slab-on-grade projects, but I don't like it. I've a similar situation and suggest you look at running the ducts above the ceiling. Major change, but better for the ducts and for maintenance. TB

[Doug Kanter]

I think you'd be better off building some sort of wooden fence type of thing to protect the ducts. Could be as simple as frames which run alongside the ducts, strung with chicken wire, just far enough from the ducts to keep tools & feet from touching the ducts. Use lag bolts to hang them from the rafters, and you can remove them easily if necessary, using a ratchet attachment on a drill.

[nhurst]

We thought about this, but the major problem with this is that our attic is small as well. The house was built without air conditioning in

1960, only a furnace. If we were to put the ducting in the attic, we wouldn't be able to do anything up there.

-Nathan

[Joseph Meehan]

Well if you burry them they will likely be better insulated, but it is going to be a lot of work to do that in an area with that little access. I would bet that in the long run, it will be far easier not to do it.

[Frank Boettcher]

When I lived in Tulsa, it was a common practice at that time to put the ducts underground, however they were encased in concrete below a slab. The ducts were set and poured in when the curbwall was put in place and then a slab was poured over them. Good point is good insulation. Bad thing is that occaisonally a water supply pipe would break and invariably the water would permeate and collect in the duct. You would find out when the humidity went way up in the house.

I think it would work if you can keep the water out.

[Doug Kanter]

He didn't mention the size or shape of his ducts (or I missed it). If they're the large-ish rectangular ones like mine, he's gonna have a hell of a time trying to dig trenches for them with the limited movement available in a crawl space. On the other hand, people *did* manage to dig tunnels out of prison camps under worse conditions.

[nhurst]

They're 6 inch round ducts. When you add the insulation to that, they're about 8 inches total across.

Someone I asked locally mentioned that mold might become an issue. Does anyone here have any thoughts on that?

[Doug Kanter]

Well, those ducts aren't exactly sealed at the joints. So, more than mold, I'd wonder about water getting into them if you had odd weather and the ground got soaked.

[nhurst]

I had planned to wrap them in something like Visqueen or perhaps something like a tube similar to what a newspaper comes in. I figure with no sunlight hitting it, it should last a good long time.

[Stretch]

There are companies that make plastic ducts for use underground. Anything not waterproof wouyld be a mistake.

Stretch

[Stretch]

Try This for underground ducts:

Stretch