Choosing a calculation tool comes down to two questions no feature list answers: what exactly does it compute, and where does it stop. Both are below, along with the standards behind the numbers and what you can hand off at the end. Operating instructions are a separate document, the user manual.
The shape of the tool
PsychroView is a steady-state psychrometric calculator built around a live psychrometric chart. You set an air condition, attach air- treatment processes to it, and each step is solved, plotted, and reported with its heat and mass flows.
Work is organized as a chain. Outside air enters at one end, moves through energy recovery, a heating coil, a humidifier, a cooling coil, whatever the design calls for, and arrives at the space. Every node carries the full state: dry-bulb temperature, humidity ratio in gr/lb, [relative humidity](/glossary/relative- humidity/), enthalpy in Btu/lb, [dew point](/glossary/dew- point/), wet-bulb temperature, specific volume and density.
Units switch between I-P and SI throughout, so the same project can be read by a design team in Ohio and a manufacturer in Germany without anyone retyping numbers.
“Steady-state” is the word that decides most comparisons. It solves design conditions, not a year of operation, and it solves air, not the building wrapped around it. Loads go in; they do not come out.
Air-treatment processes
Thirteen processes, each taking the leaving condition of the node before it as its entering condition.
| Process | What it solves | Primary input |
|---|---|---|
| Air point | Chain starting condition from any valid pair of properties | two of , RH, , , , |
| Air heating | Sensible heating at constant humidity ratio, plus coil capacity | leaving temperature or Btu/h |
| Cooling and dehumidification | Coil performance with condensation — apparatus dew point (ADP), bypass factor, condensate rate, sensible heat ratio (SHR) | leaving condition, capacity, or chilled-water temperatures |
| Energy recovery (ERV/HRV) | Sensible transfer, and latent as well for enthalpy wheels, with effectiveness | effectiveness or leaving temperature |
| Evaporative cooling | Adiabatic cooling along a constant wet-bulb line, with saturation effectiveness | saturation effectiveness or leaving condition |
| Heat gain | Internal sensible gain from people, lighting and equipment, applied at constant humidity ratio | sensible gain [Btu/h] |
| Heat loss | Dry sensible loss through the envelope, flagged if the leaving condition drops below the entering dew point | capacity [Btu/h] |
| Humidification | Water (adiabatic), wet steam or saturated steam, with the water or steam rate | leaving humidity or lb/h |
| Moisture gain | Latent load released into the space, applied at constant temperature | moisture rate [gr/h or lb/h] |
| Desiccant dehumidification | Sorbent drying without condensation, including the temperature rise it produces | leaving humidity ratio |
| Mixing, 2 streams | Resulting condition of two streams combined, weighted by mass flow | airflows and both entering conditions |
| Mixing, 3 streams | The same for three streams | airflows and three entering conditions |
| Airflow split | Dividing one stream into two branches for separate treatment | split ratio or branch airflow |
Split and mixing are a matched pair, and that pairing is what makes return-air recirculation work: split the return, mix a fraction back into the outside air, then condition the blend.
Space balance solvers
Three process cards carry deterministic solvers. They run the calculation backward — from the condition you want in the space to the supply condition and equipment capacity that will produce it — without hand iteration.
- Space load solver (cooling). Give it the target band for the space, the heat gain as either a total or a sensible/latent split, the moisture load, the allowable supply air ΔT and the chilled-water range. It returns the required supply condition, the water temperature rise /, the cooling capacity, the condensate rate, the SHR and any reheat the design needs.
- Space balance solver (heating). From heat loss, moisture load and target band it returns the supply condition, the heating capacity and any humidification required, steam or water rate included.
- Heat and humidify. From a target dry-bulb and relative humidity it returns the heating capacity, the steam rate and the intermediate condition after the coil.
When the request is not physically achievable — saturation exceeded, airflow too low, chilled water that cannot reach the required ADP — the solver says so in plain language and points at what to change, instead of returning a number that merely looks valid.
Design climate data
Outdoor design conditions come from published datasets rather than manual entry. Winter and summer conditions are offered at several severity levels, with coincident humidity or enthalpy wherever the source publishes it.
| Source | Coverage |
|---|---|
| Location search | Worldwide, via Open-Meteo geocoding, with percentiles from JRC PVGIS TMY or the ERA5 1994–2023 reanalysis |
| EPW file | Upload any EnergyPlus Weather file — design conditions derived from all 8,760 hourly records |
| DWD CDC | Germany, design temperature by the DIN/TS 12831-1 method, two climate periods |
| GeoSphere | Austria, NAT-13 with summer percentiles |
| German postal code | Conditions from the nearest DWD station |
| Your own dataset | JSON or CSV import, validated with a preview and stored on your account |
For US projects the EPW route is usually the direct one: drop in the TMY3 file for the station you already use and the design conditions follow from it. Locations can be compared side by side, which is how you find out whether a design is driven by the site or by the equipment selection.
The chart
The chart is the work surface, not a picture generated at the end.
Both conventions ship: the Carrier T-x psychrometric chart standard in North American practice, and the Mollier h-x chart used across continental Europe. It is the same data with the axes exchanged, switchable per project. Barometric pressure is an explicit input, so a job in Denver is calculated at Denver’s pressure rather than approximated at sea level. Chart range, comfort and working zones, SHR and dh/dx protractor lines, legend, info panel and a dark mode are all configurable, and points can be dragged directly on the chart with the calculation tracking the cursor.
Deliverables
| Format | Contents |
|---|---|
| Multi-page letter/A4: project header with chart, summary table, per-process detail | |
| PNG | High-resolution raster of the chart |
| SVG | Vector chart, editable in Illustrator or Inkscape |
| DXF | CAD linework for AutoCAD or BricsCAD |
| XLSX (beta) | Numeric data for every process, with the chart as an embedded image |
| DOCX (beta) | Formatted document with chart and process tables, ready for a submittal |
| HTML (beta) | Self-contained page with chart and tables embedded |
| Clipboard | Chart or summary table, for dropping into an email |
| Animation (beta) | WebM or GIF building the process points one at a time, for teaching |
Blank psychrometric charts for printing are published separately on the downloads page, DXF for CAD included.
Calculation core and standards
The core implements Chapter 1 of the ASHRAE Handbook — Fundamentals 2021, including the real-gas enhancement factor, with saturation pressure from the Hyland-Wexler correlations. Every property has been checked numerically against the ASHRAE reference tables across the HVAC range; the measured deviations are published on the ASHRAE conformance page.
Constants and correlations from Czech technical literature are available as an alternative for projects that have to follow a European national convention instead.
How it runs
Browser-based, on desktop and mobile, with nothing to install and no license server. Calculations start without an account; an account adds saved projects, your own climate datasets and share links. Any project can be published as a read-only link or embedded in another page as a widget. The interface is fully localized into English, German, French, Czech and Slovak.
What PsychroView does not do
This list decides fit more often than the capability list above it does.
- No annual simulation. Calculations are steady-state design points. There is no 8,760-hour run, no seasonal energy consumption and no part-load modeling. It is not a replacement for an energy model.
- No building load calculation. Heat gain, heat loss and moisture load are inputs you supply, from your own load calculation or from dedicated software. The application applies them to the air; it does not derive them from geometry, envelope construction or occupancy schedules.
- No duct design. Pressure drop is tracked for components placed inside a unit, but there is no duct sizing, no fan curve matching and no hydronic calculation.
- No equipment selection. You get capacities and state points; picking a specific coil, AHU or rooftop unit from a manufacturer’s catalog remains a separate step.
- Not CFD. Air distribution, throw and velocity fields, and comfort mapping within a space are outside the scope.
In development
Several modules are built but not yet released: the Builder for laying out an air handler visually, Autopilot for deriving a process sequence automatically, a Sankey diagram of energy flows, WBGT heat stress, a toolbox of quick calculators, and PMV/PPD comfort analysis to ANSI/ASHRAE 55, ISO 7730 and EN 16798-1. They are labeled as in development inside the interface, so what is coming is visible without being mistaken for a shipped feature.