Eldr — Heating Load (Phase 1, whole-house)

• Indoor / 99% outdoor design: 70°F / 14°F (ΔT = 56°F)
• Infiltration: 0.68 ACH
• Design temps from nearest station: Newark, NJ (lat/long from the model — approximate; set your ACCA station for accuracy)

Supply airflow: 1,245 CFM (at 30°F supply-air rise)

Phase 1 whole-house estimate. Not ACCA-certified. Room-by-room to follow.

Assumptions behind these numbers

Level heights

Total conditioned volume 16,859 ft³ — the infiltration basis. Set levels.<name>.height_ft to correct a height Sweet Home 3D defaulted. A level contributing 0 ft³ holds no conditioned rooms: a garage or crawlspace, a level given role: ignore, or a roomless one Eldr treated as joists/duct chase (which warns separately). Walls have nothing to do with it — a level with conditioned rooms drawn on it contributes whether or not any wall is drawn there.

Buffer spaces

A surface facing a buffer space sees the ΔT shown, not the whole design ΔT; the arrow resolves the factor against that season’s own design ΔT. A factor above 1 is not a bug: a sun-heated attic runs hotter than outdoor air, so the ceiling beneath it sees a larger ΔT than an exterior wall does.

Schematic gaps

⚠ 113.0 ft² of conditioned floor has no level drawn beneath it — modeled as buffer_floor over the undrawn space below (crawlspace, unless a level’s below_void names another), at that space’s own fraction of the design ΔT.

• Largest: Main Bed 113.0 ft².
• Draw those spaces in Sweet Home 3D to replace the assumption with geometry.
• Undrawn rooms distort the WALLS too, not just the floor: a wall is on the envelope when a conditioned room sits on exactly one side of it, so floor area left undrawn on a level makes the walls bordering it read as facing outdoors. Every such wall is counted as exterior, which inflates the envelope wall area and the conduction above with it, until the rooms are drawn.

Open questions

Neither errors nor warnings — assumptions in the numbers above that a careful reader should check against their own house before trusting the total.

• Below-grade surfaces (basement_wall, floor) are loaded at the full outdoor design ΔT, the way Manual J loads them. That assumes the U-value declared for them is a Manual J effective below-grade value — the assembly plus the resistance of the path through the soil out to grade. If a bare wall-assembly U was supplied instead, the soil is missing from the calculation entirely and these rows overstate the heat loss.
• One U-value per category, whatever the depth. In Manual J practice the effective below-grade U falls as the average depth below grade rises, because the soil path gets longer — the same construction is tabulated at several U-values for that reason. Eldr applies one assemblies number to every surface in the category, so a wall that is part shallow and part deep gets whichever single value was declared.
• Below-grade surfaces contribute nothing to the cooling load, because soil below the summer setpoint is a heat sink rather than a source. Some Manual J implementations do carry a small below-grade cooling load; against one of those, these rows will read low.
• Eldr has no grade line. Every wall on a basement level is classed basement_wall over its whole height. Manual J practice splits the same physical wall at grade: the buried portion gets the depth-dependent effective U above, and the portion standing proud of grade is an ordinary above-grade wall. If part of this model’s basement wall is above grade, it is currently carrying the below-grade assembly. Eldr cannot make that split — the reader has to, either by drawing the wall as two segments or by declaring a basement_wall U that averages the two.
• A wall’s own height overrides its level’s. Wall AREA comes from each wall’s drawn height, not from the storey height in the Level heights table above — that height sets the volume behind the infiltration term and nothing else. The two can disagree with nothing in the model looking out of place, so it is worth checking whenever a wall row reads larger or smaller than expected.

Eldr — Cooling Load (Manual J 1b, whole-house)

• Indoor / 1% outdoor design: 75°F / 91°F (ΔT = 16°F) · SHGC 0.35 · 5 occupants

Supply airflow: 844 CFM

Sensible heat ratio: 0.79 (sensible ÷ total) — how much of the job is temperature rather than moisture. A standard Manual J figure, directly comparable against any professional report, and an equipment-selection input: the lower it runs, the more of the load is dehumidification, which calls for a coil that stays wet rather than a bigger one.

Those last three rows are not three more components. Every itemised row above them is sensible heat, and they sum to sensible — the heat that has to leave to hold the dry-bulb setpoint. Latent is a separate quantity: moisture, from the occupants and from the humidity the infiltrating air carries in. That is why it has no component breakdown — no wall, window or roof contributes to it. Total is simply the two added — from the unrounded figures, before each row is rounded for display, so the three printed numbers can be off by one against each other without any of them being wrong. Supply airflow is sized on sensible alone, not on the total, which is why the CFM does not come off the bottom line: air carries the sensible load by temperature difference, while the latent load leaves as condensate at the coil rather than by moving more air.

Solar reads each window’s exact bearing (grouped for display by nearest 8-point, e.g. solar-SW), from the model’s compass northDirection.

Manual S — Equipment Sizing

• Design load (heating): 40,331 BTU/hr = 3.4 tons
• Recommended (smallest size that meets the load): 3.5 tons (+4% vs load)
• Next size up: 4.0 tons (+19% vs load)
• Existing unit: 4.0 tons → +19% vs load → oversized ⚠
  • short-cycling, poor humidity control, added wear

Demo estimate, not ACCA-certified. Sized on the larger of heating/cooling (here: heating).

Eldr — Per-Room Loads (Manual J 1c)

Each room’s load is from the exterior walls, windows, doors and ceiling/floor attributed to it, plus infiltration on its own volume; design CFM is the larger of heating/cooling airflow. Served rooms account for the whole-house 1,245 CFM. A further 8 conditioned room(s) carry 8.3 CFM between them, each below the 3-CFM run threshold — closets, chases and voids, served by transfer rather than a duct of their own. That airflow is additional to the served sum, not a remainder within it, so all conditioned rooms together come to 1,254 CFM. Exceeding the whole-house figure is expected: each room takes the larger of its own heating and cooling airflow, and those do not peak in the same rooms. The column totals 1,246 because each row is rounded before summing, while the whole-house figure rounds once at the end.

Manual D — Duct Sizing (round, equal-friction)

• Friction rate: 0.08 in.wc / 100 ft (design rate — not derived from static pressure)
• Air handler: Air Handler — run length = unit → room (Manhattan + vertical) × fitting factor.

Analysis, not a duct schedule. These sizes come from each room’s own load with no trunk hierarchy, no reducing runs and no installed layout — they answer “how big would a dedicated duct to this room have to be”, which is a useful cross-check and not a thing anyone builds. Where a project keeps a hand-authored register schedule, that schedule is the authority for what gets installed.

Round duct, equal-friction, demo-grade. Total effective length uses a fitting fudge factor, not true fitting equivalent lengths; a full Manual D adds those and rectangular/oval sizing via equivalent diameter.