No, ducts should not be on the ground. The HUD installation requirements [24CFR-3285.606(e)] for manufactured/mobile homes states that the ducts must be installed to manufacturer’s instructions and “ducts must be suspended or supported above the ground by straps or other means that are spaced at a maximum distance not to exceed 4′-0″ or as otherwise permitted by the installation instructions. When straps are used to support a flexible type duct, the straps must be at least 1/2″ wider than the spacing of the metal spirals encasing the duct. The ducts must be installed such that the straps cannot slip between any two spirals and arranged under the floor to prevent compression or kinking in any location."

    Also, here’s several other recommendations from the State of Florida’s installation course for manufactured home installers:

• Ducts may be supported by straps or pads.
• Use long bends to avoid kinks that restrict air flow.
• Limit length of duct to avoid BTU loss.
• All ductwork connections, including duct collars, must be sealed to prevent air leakage.
• If metal straps are used, they must be secured with galvanized sheet metal screws.

    The photo above shows an example of how not to do it.

    Also, see our blog posts Is it safe to go under a mobile home? and What size air conditioner is right for my mobile home?

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Here’s links to a collection of our blog posts about MOBILE/MANUFACTURED HOMES:

• Where can I file a complaint if I have problems with my new or used manufactured/mobile home in Florida?

• What are the most common defects in mobile/manufactured home foundation piers?

• How do I determine the age of a very old mobile home?

• What is a "HUD label verification letter" for a mobile/manufactured home?  

• When did a ground cover vapor barrier (plastic sheet) become required under a mobile/manufactured home?  

• Are older mobile homes unsafe? 

• What do I need to know about buying a foreclosed mobile home? 

• Does it make sense to buy an older mobile home and remodel it? 

• Where do I find the vehicle identification number (VIN) on a mobile home? 

• How do I find out how old a mobile home is and who manufactured it?

• What is the right price for a used mobile home?

• How energy efficient is a mobile home?

• When were the first double-wide mobile homes manufactured?

• Does an addition to a mobile home have to comply with the HUD Code? 

• What walls can I remove in a mobile home?

• What can I do to prevent dampness and mold in my mobile home? 

• How can I tell if a mobile home is well constructed?

• How can I tell the difference between a manufactured home and a modular home?

       Visit our MOBILE/MANUFACTURED HOMES  page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.