Custom Duct Plenums Made to Order — Any Furnace or Air Handler

Need one built? The full guide, the equipment-to-plenum sizing calculator, and every one of the 288 published sizes with live prices now live on the custom HVAC plenum page. Size it there and it drops straight into the designer.

The plenum sets up the whole system

Everything downstream connects to the plenum: the equipment on one end, the supply or return trunks on the other. If the plenum is the wrong size or out of square, every take-off after it fights to seal. It's the one box worth getting exactly right.

A made-to-order plenum is cut and formed to your measured dimensions so it drops onto the equipment collar and presents square, flat sides for the trunk connections.

What to specify

• Width × depth — the plenum footprint, set by the equipment and cavity
• Height — how tall the box is, set by available headroom
• Equipment opening — the collar size it mounts to
• Gauge and material — heavier gauge (typically 24–20) for a rigid box
• Connection type — slip/drive or flanged edges for the trunk take-offs

Supply plenums and return plenums are ordered the same way; returns are usually larger and lower-pressure.

Square and rigid beats field-bent

A plenum knocked together in the field from flat stock is only as square as the day allowed. A CNC-cut plenum arrives with clean, straight bend lines, so the box is actually square and the sheet metal is rigid enough not to oil-can under the blower. That squareness is what lets the trunk connections and any drop-in take-offs seal without a fight.