Timing of HVAC Installation:
HVAC installation typically occurs after the roof decking and building shell are completed.
A roughed-in duct system is installed before drywall or sheetrock, along with refrigerant lines and control wiring.
Final HVAC work includes setting up equipment, connecting refrigerant lines, controls, and power wiring after the flooring, ceiling, and walls are finished.
Components and Locations:
Ducting is usually found in basements, attics, walls, floor trusses, and girders.
Joists support floors or ceilings, while girders support joists.
Ductwork running perpendicular to solid joists should be placed below them, or through precut openings in trusses or I-beams.
Always check with manufacturers before making additional openings in structural components.
Duct Placement Challenges:
Ducts may also be buried in the ground, but those placed under slabs can be prone to groundwater intrusion.
Prefabricated roof trusses can make HVAC installation more difficult due to cross bracing.
Rafters can be used for roofing, often 2x6 in size, but this can vary based on roof design and environmental factors.
Chases and Codes:
A chase accommodates pipes or ducts; however, supply air cannot pass through a chase.
Return air chases may still be allowed, but local codes should be consulted for restrictions.
Rooftop Installation:
Some buildings, especially in commercial settings, may have flat roofs, where rooftop HVAC systems are more common.
Equipment is typically placed on a roof curb, which ties into the building frame and allows ducts to pass through.
Sealing the curb to prevent water intrusion is crucial and should be done by a roofing contractor to avoid voiding the roof bond.
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