Design it. Solve it. Get it specified.
Draw the machine from typed parts — coils, compressors, fans, packs, pumps — in 3D or as a schematic. Solve the thermodynamic balance. Run it over a year of real weather, then a whole building room by room.
The catalog carries 14 438 compressor maps and the curves behind every listing; 18 worked buildings run on 51 cities' real weather years; 91 anchors hold the physics to published data; the interface reads in 12 languages.
Real physics, no black box
ASHRAE psychrometrics, IAPWS-IF97 water properties, AHRI 540 compressor maps, CoolProp refrigerant data, ε-NTU coil models. The solver reports its convergence — and refuses to hand you a silent partial result. How it reads against published data
Any topology, not templates
DX circuits, water loops, air- and water-cooled chillers, remote condensing units, cooling towers, two-stage evaporative, heat-pipe wraps, heat recovery, face-and-bypass — connect typed air/water/refrigerant ports any way the physics allows, and the graph solver figures out the rest. Every system carries a category — rooftop, split, air handler, chiller, condensing unit, fan coil, evaporative, recovery, plant, unit cooler, or one of your own — and any saved or published system drops into another design as a single block: a system of systems, solved flat.
From design point to 8,760 hours
One click pulls a real typical meteorological year for 51 major cities — measured data from PVGIS, the European Commission's Joint Research Centre. Load-following control staging, compressor modulation, economisers and demand-controlled ventilation, humidity control, VAV terminals, heating and cooling modes — a full annual simulation takes seconds.
How it works
Simulate the whole building
A building tab scales it up: rooms as blocks — floor area, envelope, internal gains, solar aperture — and machines beside them, connected port to port: a machine's outlet to the rooms it serves, their return to its intake, a chiller's water to an air handler's coil, a VAV box on every room. One run solves every machine against the weather year, one hour behind the other where they couple: per-room comfort with unmet hours, humidity and temperature histograms, per-system energy, building totals. Solar gains come straight from the weather data's irradiance. Engineers
Try it before you build anything: the worked example buildings — a mall, an edge data centre, a hotel, an office floor, a primary school, a logistics hall, a telecom shelter, a campus plant, a cleanroom, a supermarket, a hospital suite, a VRF office floor, an apartment block and a clinic: 18 buildings and 51 machines, from a district chiller plant to a cold-store condensing unit — run on every plan including Free, 3 times a day. Cases
Equipment from suppliers
Suppliers publish real machines and components on HVAC Builder — every page carries the manufacturer's own data, solved by the same engine you design with. Browse them, open one in the builder, and request a quote with your design attached.
Chilled-water AHU, 3 m³/s
A chilled-water air handler with reheat and a supply fan, published as an example. The design-point figures below come from the solver, not from a datasheet.
Packaged DX VAV rooftop, 7 m³/s
A packaged rooftop for a VAV floor: outside-air damper with an economiser and demand-controlled ventilation, DX coil on an inverter scroll, an electric heater for morning warm-up, and a supply fan that holds a duct static as the boxes throttle; the boxes themselves live on the building. Published as an example; the figures below are solved from this model.
Air conditioner with a heat-pump hot-water booster on its hot gas
An air conditioner that makes hot water from the heat it would otherwise throw away, the way a hot-water booster does it: a second, R134a heat pump whose evaporator is a plate exchanger on the A/C's hot gas. The A/C is a 20 kW-class split drawn from a supplier's own selection — coil faces, rows, fins, circuits and airflows, 7.5 K superheat and 5 K subcooling — on a Mitsubishi Electric LNB53 inverter rotary at its 60 rps rating speed. Between its compressor and its air condenser sits a **cascade exchanger**: the booster takes what the saturation difference across the plate drives, the air condenser rejects the rest, and the A/C condenses cooler for it. The booster's compressor is a catalog R134a heat-pump water-heater scroll standing in for the Mitsubishi SBB172, whose map is not published; its condenser heats water from 55 to 62 °C. The plate and the water side are an example's, not a maker's.
BITZER 4CDC-9 (R410A semi-hermetic recip, EN 12900)
R410A compressor — 23.7 kW cooling, 9.41 kW input, COP 2.52 at the AHRI 7.2/54.4 °C rating point.
Edwards Coils BEC-5-F coaxial heat-pump evaporator (58.5 MBH, 70 → 62 °F water at 45 °F suction, R-22)
Coaxial evaporator — 17.1 kW from water 21.1 to 16.7 °C, evaporating at 7.2 °C, 0.92 kg/s.
DRI HRW-1000-MS 200 (N) total energy recovery wheel
Sensible-and-latent recovery core, 0.352 m² face a stream, 0.70 / 0.70 m³/s.
Browse all published systems Browse published components Browse suppliers
Ask the suppliers who can actually build it
Once a design solves, request quotes straight from it. HVAC Builder reads the equipment out of the graph — kinds, duties, refrigerants — and matches it against what each supplier has declared it can manufacture, in the regions you pick. Every matched supplier receives one request covering just the parts it can supply, with the specification attached. Quote a whole system, a few selected components, or an entire building in one go — 5 requests a day on every paid plan. Sharing the openable model is opt-in; the written specification always travels with the request.
Let AI do the drafting
HVAC Builder ships an MCP connector: point any AI agent that speaks MCP at hvacbuilder.app/api/mcp as a custom connector — you sign in when it asks, with no key to paste. Describe your requirements and it designs a system, or composes one from published machines and your own; solves it; fetches a real weather year and simulates it; models a building room by room and runs it; saves what it made to your account — and, if you are a supplier, publishes your range and reads your leads.
Prefer to stay in the app? The built-in assistant chats right in the builder — it reads your design, modifies it, solves and simulates on request. Bring your own AI provider key for unlimited chat, or use the platform's, metered in compute tokens.
Pricing
| Free | Starter | Professional | Business | Enterprise | |
|---|---|---|---|---|---|
| Price | $0 | $15/mo First month −15% | $39/mo First month −30% | $79/mo First month −45% | On request |
| Saved systems | 3 | 25 | 100 | 250 | ∞ |
| Annual simulation | examples, 3 a day | ✓ | ✓ | ✓ | ✓ |
| AI assistant | 3 to try | ✓ | ✓ | ✓ | ✓ |
| Building simulation | examples, 3 a day | examples, 3 a day | ✓ | ✓ | ✓ |
| Compute tokens | 250/mo | 1 000/mo | 4 000/mo | 10 000/mo | 30 000/mo |
| Extra tokens | 500 for $10, never expire | ||||
| Reports | watermarked | HTML + PDF | HTML + PDF | HTML + PDF | HTML + PDF |
| API keys + MCP | ✓ | ✓ | ✓ | ✓ | ✓ |
| Workspace seats | — | — | — | 3 included, $15 each | 3 included, $15 each |
| Supplier tier (unlimited listings and leads) | — | — | — | ✓ | ✓ |
Prices are in US dollars. We are not registered for VAT, so no VAT or sales tax is added.
Compute tokens meter everything: a point solve costs one token per ten components, so most machines are one, and a simulated year of that system costs ten times what solving it once does. A report is a solve too: it costs one for each design point it tabulates. No plan caps a system's size — a bigger system costs more tokens rather than being refused — and the engine itself takes up to 500 components. Prices in USD; checkout can present your local currency automatically. Interface in English, Deutsch, Français, Español, Italiano, Polski, Nederlands, Svenska, Norsk, Suomi, 中文 and 日本語.
Start with the machine you have in mind.
No card, no install. If you make the equipment, list it where it is selected.
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