transite heat problems

[beer batter]

Anyone know of critical issues with running heat/cooling vents under the cement slab, such that it's not recommened to do this any longer?

Looking at doing this on a new build project, but was told to run the vents through the ceiling/walls instead. I'm aware moisture can accumulate inside the pipes, something about radon too? Maybe someone out there can shed more light on it.

[MNice]

If you have ANY moisture concerns, I would run away, far away from in ground ducts. If you have very well drained soil, an all glued system works well. Do not install PVC pipe with PVC coated metal fittings, if you go with PVC, use their PVC fittings that are glued. If you want a product you don't need extra insulation, google akduct.

[Tom7227]

I was out at a lodge that had in the slab duct work and it all rusted out and collapsed. They ended up having to heat the rooms with space heaters. I think the building was 25-30 years old.

[Redlantern]

The pvc used for this stuff isn't very thick, not schedule 40. I've seen a fair amount of it busted. This leads to leaks into the duct and possibly mold issues. Also, the smell of rotting mice in them is never very pleasant. I'd steer clear of this if you can.

[cavalierowner]

I designed a number of commercial buildings with underfloor ductwork. Our engineers always specified PVC with glued fittings. The one thing I remember was that code required that the PVC be sloped to a sump so that if any water did get in, it would drain to a sump and then be pumped out. That was for commercial buildings; I don't know about residential requirements, but it sure sounds like a good idea to me. If you are worried about rodents getting into the system thru the registers, you could put som 1/4" galvanized mesh in the boot, below the register.

[Redlantern]

While it may be code to pitch it, I have yet to see a tinner using a level while installing this stuff. I would also think that an air test would be in order to be sure that there aren't any leaks. Never seen that done, either. I honestly think that this just isn't that good of a system. Might be the only option in some cases but I sure wouldn't want it for myself. I'm not a tinner, though. Maybe one will chime in.

[pureinsanity]

My dad has this in part of his house. No moisture problems at all. works great. PVC. No complaints. house is 20 years old now.