DENOVA Zone Airflow Lite is a multi-zone HVAC airflow, ventilation and pressurisation summary tool for concept design, feasibility and preliminary equipment sizing. It is part of the DENOVA suite of practical engineering software.
It turns a zone-by-zone schedule of spaces into a coordinated air-side design. For each zone it sizes the supply airflow from sensible load and design ΔT, computes the required outdoor air per the active ventilation standard (ASHRAE 62.1 multi-zone VRP, AS 1668.2, EN 16798), groups zones onto air-handling units with a diversity factor, checks each room’s pressure relationship (positive / balanced / negative), and produces a print-ready A4 engineering report.
Use it for: concept design, feasibility, preliminary AHU and outdoor-air-intake sizing, and a documented basis for early coordination. Not for: construction issue, procurement or detailed design without engineer review.
Workflow: 1 Project → 2 Conditions (climate & setpoints) → 3 Zones (loads & airflow) → 4 Systems (AHU & diversity) → 5 Summary (dashboard) → 6 Report (A4).
Zone Airflow Lite · v1.0 · LITE · Beta
source tag (issuing body short code) and url (official catalogue page). 24 countries · 30 standards · all attributed.No change to the calculation engine, methods or formulas. The Zone-AHU model, ASHRAE 62.1 Ev calculation and pressure-balance logic are unchanged.
30 ventilation standards across 24 countries, grouped by region:
Ventilation rates cited per the issuing technical standard or national code. Each entry’s source tag identifies the body publishing the standard; the url field links to that body’s official catalogue or scheme page. Values shown are widely-published industry reference data; no copyrighted table is reproduced verbatim in this software.
Preliminary design estimates only — not for construction. Suitable for concept design, feasibility and preliminary equipment sizing. All inputs, assumptions and outputs must be reviewed and validated by a qualified mechanical / HVAC engineer (RPEQ / CPEng / PE / PME as applicable to jurisdiction) before incorporation into construction documents, equipment procurement or detailed design.
Verify all ventilation rates against the current edition of the authoritative national standard for your jurisdiction. Standards are updated periodically; this software is a calculation aid, not a substitute for the source document.
On the Conditions tab, Open Climate Library lets you skip manual entry: pick a city and the outdoor design conditions (Summer DB, Summer WB, altitude) auto-fill. Cities are drawn from national met services published under open licences (NOAA, BoM, ECCC, AEMET, DWD, KNMI and Nordic institutes), each shown with a source badge.
For a city not in the library, use Enter custom location with Auto-find geo — it resolves region and elevation from a world gazetteer — then enter design DB/WB. A provenance indicator always shows whether the current climate is filled by library, custom, or engineer-entered.
Library values are indicative design conditions — verify against the ASHRAE Handbook of Fundamentals Ch. 14 for critical projects.
Zone breathing-zone OA is the standard two-term formula used by ASHRAE 62.1 §6.2.2.1, CIBSE Guide A §1.5 and EN 16798-1 §B.6:
Vbz = Rp × Pz + Ra × Az
where Rp is the per-person rate (L/s/person), Pz is design occupancy (persons), Ra is the per-area rate (L/s/m²) and Az is the floor area. Rp / Ra values come from the active ventilation standard (AS 1668.2:2012 by default).
For multiple zones served by one air-handling unit, the system OA intake Vot is reduced by ventilation efficiency Ev per the ASHRAE 62.1 multiple-zone procedure (Normative Appendix A):
Vot = Vou / Ev
where Vou = Σ Voz (uncorrected sum) and Ev is a piecewise function of the critical zone outdoor-air fraction Zp,max:
The picker on the Summary tab shows the AHU’s critical zone (the one driving Zp,max) so the engineer can investigate before sizing the OA intake.
Important: this is an approximate preliminary indicator, not a full ASHRAE 62.1 calculation. The real Appendix A method derives Ev from the system outdoor-air fraction Xs = Vou/Vps (Evz = 1 + Xs − Zpz), which this tool does not compute. Where Xs is low, the true Ev can fall well below 0.50, so this indicator may understate the required outdoor-air intake. Also, Vou here is a simple sum of entered zone OA and omits the occupant-diversity term D. For final design, run the full ASHRAE 62.1 Appendix A procedure.
Each AHU has an engineer-set diversity factor Df applied to the sum of zone supply airflows to obtain the design (sized) AHU supply:
Design supply = Df × Σ zone supply
Default 0.85 (typical for commercial offices with mixed simultaneity). Set per AHU on the Systems tab.
Each zone’s computed L/s/m² is checked against an engineering benchmark envelope for that room type (typical loads / regional practice — not a standard-derived limit; e.g. Office ≈ 2.5–8 L/s/m²). Values outside the envelope trigger a warning chip; cross-check against the actual load calculation.
Per zone: supply − exhaust determines pressure relationship.
A zone with exhaust greater than its own OA but no make-up air path is flagged with an “M-UP” warning.
A common question: on the schematic the outdoor-air (OA) intake is much larger than the exhaust — why don’t they match? They are not meant to. OA and exhaust do different jobs and balance at different levels.
At the zone, supply − exhaust sets the pressure relationship (above). At the whole building, the volume balance is:
OA intake = Σ exhaust + relief (spill) air
Because ventilation OA normally far exceeds the local exhaust, the surplus is discharged as relief (spill) air through relief dampers at each AHU. This keeps the building slightly positively pressurised, resisting infiltration of unconditioned outdoor air. OA equals exhaust only in a fully-extracted space — e.g. a kitchen or laboratory on 100 % OA with no relief.
The schematic shows OA and exhaust explicitly; the relief path is implicit at the AHU. Default core-zone exhaust figures are indicative placeholders — replace them with the project toilet / service exhaust schedule.
SHR = sensible / total. The following are diagnostic engineering sanity-check ranges (typical comfort-cooling values, not standard-mandated limits):
SHR outside the published range is flagged; usually it means the sensible or latent input is wrong, or the room type doesn’t match the actual use.
Implied supply ΔT = sensible / (ρ cp V) using ρ cp = 1.2072 kJ/m³K (air at 20 °C). If the implied ΔT differs from the user-entered design ΔT by more than 1 K, a flag is raised — supply airflow and sensible load are inconsistent. The 1.2072 constant assumes sea-level air density; at ~1000 m elevation sensible capacity per L/s is roughly 10% lower, so high-altitude projects need a density-corrected value.
Measured supply / OA per zone can be recorded against the design value with a configurable tolerance (default ±10%), giving each zone a PASS / FAIL result. These figures feed the commissioning record — commissioning is reported as complete when all zones are tested and pass.
Verify all values against the current edition of the authoritative published standard for your jurisdiction before issue. This software is a calculation aid and audit deliverable, not a substitute for the source document. Standards are updated periodically; the values built into this tool reflect the editions cited in About.
Outdoor-air rate values (Rp / Ra): the per-room-type rates are an ASHRAE 62.1-style two-term structure used as a default engineering placeholder. They are not a verified reproduction of every cited national standard. In particular, AS 1668.2 uses its own outdoor-air method and values (commonly a higher per-person rate) that differ from the ASHRAE-style figures shown — confirm against the current AS 1668.2 edition before any Australian compliance use.
Healthcare spaces: the generic “Healthcare” room type uses placeholder rates and is not sufficient for clinical design. Healthcare ventilation is governed room-by-room by ASHRAE/ASHE Standard 170 (and AS 1668.2 health provisions / FGI / AHJ), with outdoor-air, total air-change, pressure-relationship, exhaust and filtration requirements well above office values. Design healthcare spaces explicitly against those documents.