Duct parts list

Generated from the model. Every figure below is read from the drawn objects — run membership from the object names, lengths and sections from the geometry, register faces from the frame objects. Regenerate it rather than editing it.

Fittings are not in this list. No elbows, tees, takeoffs, boots, transitions or hangers are modelled, and the bend counts below are inferred from segment-to-segment direction changes rather than drawn. A parts list that silently omitted fittings would read as complete when it is not — treat this as the straight-duct schedule and the fitting count as the contractor’s to supply. That is work they are better placed to do anyway, and asking for it is how the effective-length question gets answered.

Lengths are centre-line and do not deduct for fittings, so they run long at every junction. Runs marked future are drawn but out of scope, and are excluded from the material totals.

Supply runs

Return runs

Registers and grilles

Materials summary

Future runs excluded. Round sizes are airway — confirm whether a supplier quotes inner or outer diameter on double-wall before ordering, because getting it backwards costs two inches of diameter on every round run at once.

Where the round duct comes from

Double-wall spiral is fabricator-made rather than a stocked wholesale item, and two shops within reach of the house make it. Both confirmed from their own published pages; neither has been quoted.

Fairfield is the near one and covers every size on this job. Andover is the larger shop and the one more likely to have odd sizes on the floor.

The question to settle on the first call is inner versus outer diameter. Everything above is sized by airway, and on double-wall the insulation sits inside the shell — so a supplier quoting outer diameter delivers roughly two inches less airway than the schedule assumes, on every round run at once.

Two smaller things worth raising at the same time: this job totals under 100 ft of round across four diameters, which is a small order for a commercial shop and may run into a minimum; and 9″ is the least common of the four sizes here, so it is the one most likely to be a special run rather than something on the rack.

An oval section is the box it must fit inside, not its airway. A flat oval turns each corner into a semicircular end, so a run listed 14x18 carries about 210 in² against the 252 the two numbers multiply to — roughly 20% less on every oval run here. The box is what is printed because the box is what has to clear the framing; size the airflow off the airway.

Cost — planning grade only

Every figure here is a band, and the bands are wide on purpose. Fabrication, access and region move installed duct pricing more than size does, so a single number would imply a precision this does not have. Use it to compare options against each other, not to budget.

All figures are pre-incentive. No rebate, tax credit or utility programme is netted off anywhere in this document. Incentives change by year, by model and by jurisdiction, and a quote that quietly assumes one is a quote that cannot be compared against another.

Fittings are missing from that subtotal and they are not a rounding error. Elbows, tees, takeoffs, boots and transitions commonly run 30–50% of a duct job’s material cost, and none of them are modelled here — so treat the straight-duct figure as roughly two thirds of the real material story.

Labour is already inside those bands

The $/ft figures above are installed, not material-only, so labour is not a line to add — it is most of what the band’s width represents. For sanity-checking a quote that separates them: duct labour alone runs roughly $5–15 per linear foot, and HVAC labour is $75–150 per hour per technician.

Published estimates of labour’s share of a duct job disagree sharply — one puts it near 22% of a whole-house replacement, another at 60%. That spread is a signal, not noise: it is the difference between duct run through open basement joists and duct fished through finished walls. This house is both, which is why the bands here are wide and why a walkthrough quote will beat any figure on this page.

Ducted extras, priced separately

A media cleaner has a real interaction with this design and the others do not. A deep filter adds static pressure to the return side, and the return side is already this system’s constraint — see the main-floor return path above. Size the filter cabinet generously and account for its pressure drop in the same breath as the return trunk, rather than adding it afterwards. The others are additions to the system; filtration is a change to it.

Equipment, and why the number to quote is 4 tons

Manual S on the current model recommends 3.5 tons — 40,331 BTU/hr is 3.4 tons of load. The figure worth quoting against is 4.0, and the reason is the state of the model rather than a preference for headroom.

The load calculation runs against geometry that is knowingly incomplete, and every gap in it points the same way:

• No grade line. Basement walls are classed below-grade over their whole height. Taking the professionals’ measured U-value alone moves the load to roughly 45,600 BTU/hr — 3.8 tons.
• The second-floor roof is not drawn. Ceiling area is modelled at 984 ft² against a professional report’s 1,547 — a third of that surface is missing, and it is the hot side of the house.
• Corrections to the model have tended to raise the load, not lower it, and every gap still open points the same way. Today’s figure reads as a floor rather than a midpoint.

The sizing verdict is one to hold loosely. 3.5 tons is what today’s model says; 3.8 is what one known-missing input alone would make it; and the remaining gaps have not been priced at all. Rounding to the next tier is the cheap direction to be wrong in — an oversized heat pump with inverter turndown short-cycles far less than a single-stage unit would, while an undersized one has no remedy short of replacement.

That is a load figure, not an equipment selection. Manual S finishes only once a specific matched indoor/outdoor pair is picked and its published capacities — minimum and maximum, at this climate’s design temperatures — are checked against the loads above. Nominal tonnage is shorthand for a capacity curve, and two units of the same nominal size need not deliver the same thing at 14°F. The candidate on file below is a candidate.

The Bosch IDS Ultra is the candidate on file. Treat both rows as placeholders until a dealer quotes the specific model: published pricing for this equipment comes largely from aggregator sites rather than distributors.

Whole-job estimate

Centre of mass is around $20,658, and the upper band is what you get if every constrained thing turns out to be the hard version — duct fished through finished walls rather than run through open joists, the kitchen cabinetry modified rather than worked around, the high-end UV rather than coil lamps. A realistic landing spot sits below the top of the range rather than at it.

Pre-incentive throughout. Nothing here is netted against a rebate, credit or utility programme, so it can be compared against a quote line for line — and whatever incentives apply come off afterwards rather than being baked into a number nobody can reconcile.

One caveat on the whole table: the fittings allowance is the weakest number in it. It is a percentage standing in for a count not yet made, on the one quantity this model explicitly cannot derive. It is also, not coincidentally, the same count that settles the one-unit-versus-two question — so asking for it buys an answer twice.

What this is for: one air handler or two

The number that matters is not the total, it is the delta between one unit and two. The proposal is a second ducted handler in the north knee-wall attic, reached through the wall at the top of the stairs — so it is attic equipment, in a space our own model puts near 133°F on a summer design day. It is argued with on its merits in ducting-scheme.md.

On cost alone, the delta is a second indoor unit, a second filter, a second condensate path — over a finished ceiling — a second service point reached through a knee-wall hatch, and a second maintenance schedule for as long as the house stands. Against a riser that has to be built anyway for the main floor.

But cost is not what decides it, and neither is static pressure alone. A north knee-wall unit does not reach the south side of those rooms, and the suggested remedy — a duct channel along the office wall — is itself a chase. Ask which registers the second unit can reach before asking whether one unit runs out of static pressure. The fitting counts settle the second question; only a site visit settles the first.

Counts

Every takeoff wants a balancing damper, whatever the balance calculation says. A branch without one cannot be adjusted after the fact, and the first season in a house is when the balance is discovered.