Double-line parametric HVAC duct: elbows at 45 and 90 degrees in all four compass turns, plus tees, crosses, caps, transitions and straight runs. The duct width you set is the width that plots, so a run drawn from these blocks is dimensionally honest.
22 blocks in 2 families. DXF R2018, drawn in inches.
Mechanical plans at 1/4 in scale draw supply, return and exhaust ductwork double-line, meaning both walls of the duct are shown so width and clearance can be checked. These 22 fittings build that: 45 and 90 degree elbows in all four quadrants, tees and caps in all four directions, a cross, a transition in each axis, horizontal and vertical straight runs, and a terminal grille. The HVAC engineer or mechanical designer draws them on the M-HVAC layers, typically split into M-HVAC-SUPP, M-HVAC-RETN and M-HVAC-EXHS so each system plots in its own linetype.
Two parameters set every fitting. Width is the duct width that plots, default 10 in and adjustable from 4 to 48 in, so a 14 in duct is drawn 14 in wide. The u value is the leg length from the fitting's origin to its connection port, default 16 in. A straight run ranges from 6 to 480 in. Duct sizes themselves come from a sizing method, ACCA Manual D on residential work or the ASHRAE Fundamentals duct-design procedure on commercial, not from what fits the ceiling.
Origins are chosen so fittings chain. Elbows insert at the bend vertex, tees and the cross at the run center, caps at the open connection end, and transitions at the large end, reducing along +X or +Y. Draw the run centerline first, then drop each fitting at a vertex or junction and set the straight runs between them to the measured length. Because each turn direction is its own block, the orientation is in the name (duct-elbow-90-ne, duct-tee-w) and no mirroring is needed, which keeps the fittings consistent if you later extract a quantity count.
Check clearances where ducts meet structure and other trades. A transition belongs where the duct has to squeeze under a beam or past a pipe, and a double-line run makes that conflict visible in plan. Terminals insert at the grille center at the ceiling, which is also the connection point, so they line up with the reflected ceiling plan grid.
The fittings download free as DXF, DWG or PNG, and in the CADdillo browser editor at app.caddillo.com you can set width and length and assemble a run with no desktop CAD.
Plan-view footprint in inches. Each name opens the block's section on its family page, with DXF, DWG and PNG downloads.
On plans at 1/4 in scale and larger, draw ductwork double-line so the true width is visible and clashes with structure and piping show up. Single-line is reserved for small-scale schematics or small branch ducts. These fittings are double-line, and the width parameter is the width that plots, from 4 to 48 in.
Elbows insert at the bend vertex and tees at the center of the run, with ports at distance u (default 16 in) along each leg. Caps insert at their open end, transitions at the large end. Put the origin on a centerline vertex and the fitting's ports land on the adjoining runs.
Each fitting ships in every compass direction, and the direction is in the name: a 90 degree elbow comes as NE, NW, SE and SW; tees and caps as N, S, E and W. Pick the one that matches the turn instead of mirroring, so geometry and counts stay consistent.
Every category, every MEP orientation, DXF R2018, sorted into folders. Tell us where to send it and the download starts immediately.
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