User Manual

HVAC Engineering Calc — hvacengineeringcalc.com
Operated by Woodrow Engineering AI LLC · This manual matches the current release.

1. Getting started

• Free account — full features, your first 5 projects are on us. No card required.
• Guest mode — try every tool without an account; work is not saved between visits.
• Pro — unlimited projects, CSV/print exports, Advanced Analysis tools, and the account library (save assemblies, templates and equipment across projects).

After signing in you land on the Projects dashboard. Open a project (or create one) and pick a tool suite: Quick Tools (single-purpose calculators), Load Calcs (the full room-by-room workflow), or Advanced Analysis (Pro).

2. The 5-step project workflow

Project Setup shows this same guide in-app. The green buttons are the big time savers.

1. Name your project and set the building type.
2. Pick your location AND draw your building on the satellite map (green 🛰 Map: Location + Rooms button) — one screen does site + geometry. Details in §3.
3. Design conditions — choose your city and ASHRAE design temperatures fill in automatically; type your own to override.
4. Default construction — pick your typical wall / roof / window assemblies once. Every new room (including map-created rooms) starts with them.
5. Review rooms → size equipment → print the report. Loads update as you edit.

3. The Site Map — location, rooms, walls & shading in one place

3a. Location

• Search an address (OpenStreetMap geocoding), drag or double-click the pin, use 📍 My Location (device GPS — great for field surveys), or type lat/long manually.
• Every method sets one canonical project location and fetches the site elevation automatically (elevation drives barometric-pressure corrections).
• Layers: Esri satellite imagery, OpenStreetMap streets, place labels, and NYS Tax Parcels — real property lines over the imagery for New York State.

3b. Trace the building & rooms

• ▱ Trace Building — outline the roof. You get footprint area (sanity-checked against your room total), edge lengths with true compass bearings, and a centroid you can adopt as the site point.
• ▢ Trace Rooms (green) — outline each room on the roof and name it. The side panel lists each traced room with its measured area.
• Set the Glazing % (default 15%) and press ➕ Create rooms in project. Each traced room becomes a real Room Manager room:
  • exterior walls auto-generated with real lengths, gross areas, and true compass orientations (satellite imagery is already true north — no correction needed);
  • shared walls between adjacent rooms are detected and excluded from the envelope automatically;
  • each exterior wall gets a window sized to your glazing % using the project's default window type.
• Refine anything afterwards in Room Manager (window sizes, per-wall edits, internal gains).

3c. Orientation

Plan north (north_deg) can be typed directly, or solved exactly from a traced footprint edge: pick the edge in the side panel, tell the app which side of your floor plan it is (top/right/bottom/left), and press Solve.

3d. Site shading & sun path

• ▲ Obstruction — trace neighboring buildings or tree lines and enter their height. The engine builds a sky-obstruction profile around your building.
• In the RTS engine, obstructions block direct (beam) solar whenever the sun is behind them and reduce diffuse sky radiation by the computed sky-view factor. Ground-reflected solar and heating loads are intentionally unaffected.
• The side panel draws a sun-path diagram (June and December arcs at your latitude) with the obstruction silhouette in red — a wrong bearing is obvious at a glance.

4. Floor Plan designer (PDF / image)

1. Open Floor Plan and press the green ⬆ Load PDF / Image button.
2. Calibrate the scale (click two points of a known dimension and enter its length).
3. Trace rooms on the drawing; areas and perimeters are measured for you. Group rooms into zones, set the north arrow, and push everything into Room Manager.

5. Room Manager

• Per room: dimensions, ceiling height, individual wall rows (orientation, gross area or length×height, assembly/U-value) with nested windows per wall.
• Internal gains: occupants, lighting and equipment (W/ft², watts, or BTU/hr).
• Infiltration (ACH) and mechanical ventilation per ASHRAE 62.1 / 62.2 space types.
• Heating and cooling loads compute on save and roll up to zones, systems and the report.

6. Quick Tools reference

7. RTS Cooling Analysis (Equipment Sizing page)

The RTS engine computes a true 24-hour design-day cooling profile per room using the ASHRAE Radiant Time Series method (Handbook of Fundamentals, Ch. 18):

• Real conduction time series for 66 wall and 37 roof constructions, radiant time factors by zone weight / floor covering / glazing fraction, and a clear-sky solar model validated against published ASHRAE values.
• Station climate data (monthly clear-sky optical depths and daily range) applies automatically when your project city has it; otherwise enter values manually.
• Site obstructions from the map (§3d) are applied hour by hour.
• Output: building peak with its hour, per-room peaks, a 24-hour profile chart, and a comparison against the classic peak-ΔT estimate. Results are sensible-only and save with the project.

8. Zones, Equipment Sizing & the Report

• Zone Manager — group rooms into zones and systems.
• Equipment Sizing — system capacities from the calculated loads, in tons and nominal sizes, plus the RTS card (§7).
• Summary Report — project header, design conditions, room-by-room table, zone and system rollups, and print/CSV export (Pro).

9. Saving, accounts & mobile

• Projects save to your account with 💾 Save; the dashboard shows "N of 5 free projects used" on the free tier. Deleting a project frees a slot.
• Assemblies, templates and (soon) equipment can be saved to your account library (Pro) and reused across projects.
• The whole app works on phones and tablets — the sidebar becomes a ☰ drawer, tables scroll sideways, and the site map stacks vertically. Field surveys with 📍 GPS + map tracing work great from a phone.

10. FAQ

Which load method does the app use? The classic peak-ΔT method drives the room-by-room workflow; the RTS design-day engine (§7) provides hourly analysis on the Equipment page. Method details are printed with every report.

Why don't obstructions reduce my heating load? Heating design deliberately assumes no sun — shading credit would be unconservative. This is by design.

Where do the ventilation numbers come from? ASHRAE 62.1/62.2 space types in Room Manager, and the 2025 NYS Mechanical Code tables in the NYS Vent 403 tool.

My map-created rooms have no loads yet. Open each room in Room Manager and press save — loads compute per room and update all rollups.

Something looks wrong. Email support@hvacengineeringcalc.com with your project name and what you expected.