In-Slab central heat and air ducts?

[SouthernThunder]

I will be constructing a small two story cabin that necessitates running the central heat and air ducts as well as some of the wastewater plumbing under the slab. There is no crawl space. Solid concrete.

I have been told by a couple of heating and air folks that the standard ductwork will eventually rust out and collaspe and then you have to bust up the slab to fix it.

Does anyone have a solution to the problem of the air ducts eventually going bad? Is there a plastic equivalent to the standard ductwork that is legit?

[mtman]

roughing in under the slab i can see everybody does that but the duct work in the slab i never heard of that

[fordy]

...............My uncle had his builder run all of his duct work out of PVC in the slab. Get your local tin shop to build the main Plenum out of stainless sheet then all the other "runs" can be hooked to the main plenum and then you won't have to worry about a rust problem. fordy...

[SouthernThunder]

Thanks fordy. Sounds like a plan.

[fordy]

Originally Posted by SouthernThunder

Thanks fordy. Sounds like a plan.

............One other point.....Once they had all their concrete forms up and the beams dug the builder had the concrete guy pour a 4 sided protective wall around the plenum with 1 piece of each of the PVC runs projected Thru the protective wall and hooked to the plenum . This way when they actually poured the slab the weight of the concrete would NOT displace the plenum from it's designated position . Then , after the protective wall cured they finished running the PVC ducts and then they were able to tie all their steel as the PVC was set deep enough that only the vertical portions of the ducts were sticking up above grade . I've never seen anyone do this but it works very well . ..fordy...

[DrippingSprings]

have seen it run between the 2x4 studs in the walls. filled the space between two studs. it was run through the ceiling and down the walls needed for each rook. Looked like regular square in the ceiling then it branched off left and right and down through the wall from second to first floors. the vents were right above the trim at the floor levels and was about 3wide and 12wide.