Hello,
Does anybody have experience in installation new ductwork underground? Could I use galvanized duct pouring concrete directly in an insulation foam trench with vapour barrier, I saw some YouTuber did this way, but I don't know it is ok for Ontario building code.
Thanks!
From the SMACNA Residential Comfort System Installation Standards,
Quote7.7.4 Underground Ducts
The most commonly used material for underground ducts include galvanized steel, vinyl chloride-coated galvanized steel, and stainless steel. Glass fiber reinforced resin, cement, tile, and other nonmetal ducts may also be used. Ducts are not generally required to be waterproof. However, ducts should always be located at an elevation above the water table. The designer should carefully evaluate the exposure to moisture or ground water and require vapor barriers, sumps, porous fill, or subsoil drainage pipe as necessary. See Appendix D for details.
Corrosion resistance is an important characteristic of both in-slab and under-slab ducts. The inherent structural strength of round duct makes them the preferred shape for underground application. Round duct wall thickness in these standards are generally acceptable for below-grade installation. Ribbed or corrugated styles have additional crushing strength. Temporary internal supports can be appropriate at times, especially near duct openings—the ends. Ducts should have continuous bedding support.
Ducts to be embedded in concrete are subject to floating as the concrete is poured and must be restrained.
The first pour should be the base support for the duct and anchors should be included. Ducts buried in sand or pea gravel are not known to float. Porous fill and earth fill should not be dumped directly on ducts in trenches. Fill should be firmly but not heavily tamped under and around the duct. The first layer of fill should be shoveled on top of the duct. Fill should not contain stones larger than 2 in. (50 mm).
APPENDIX D UNDERGROUND AND FLEXIBLE DUCT
D.1 UNDERGROUND DUCT CONSTRUCTION STANDARDS
D1.1 This installation standard is applicable to ducts placed in or beneath concrete floors or in areas free from vehicle traffic.
D1.2 Materials shall conform to the project specifications.
D1.3 Ducts shall be located as shown on the contract drawings.
D1.4 The duct contractor shall provide:
a. Proper assembly of the duct, including connections and sealing as prescribed;
b. Verification of the undamaged condition of the duct before enclosure with fill or encasement;
c. Anchorage for the duct, if any;
d. Notices of requirements for successive placements of fill, if any;
e. Precautions against use of powered vibrators in placing concrete on or around ducts;
f. Witnessing of backfill or encasement; and
g. Temporary protection of openings in ducts.
Thank you Admin, it is really appreciated.