Building airflow designer
Add every room in the project, pick the calculation method that fits each one, and mark whether it's a supply point, an exhaust point, or balanced. This designer rolls the whole building up into a single supply vs exhaust balance — so you catch a depressurized building before it's built, not after.
1–2. Select method & add rooms
Pick the method family that fits the room you're adding, then fill in its inputs.
3. Results & balance
Total supply vs exhaust across every room, and whether the building pressurizes or depressurizes.
Airflow by room
Air balance summary
Balance indicator
Detailed results
| # | Room | Method | Role | Supply | Exhaust |
|---|
Project information
Shown on the exported report. Optional, but helps identify the project later.
4. Report
Export the full room list and balance results.
How to use this designer
- Pick a method family — Occupancy Based, Residential, Public/Industrial, Kitchen Hood or Manual/Transfer — then click "+ Add Room".
- Fill in that room's inputs and, if the default doesn't fit, override its Supply/Exhaust role chip.
- Repeat for every room in the project — offices, wet rooms, kitchens, corridors, plant rooms.
- Check Results & Balance for the building's total supply vs exhaust and its pressurization status.
- Fill in the project information and export a PDF report or an XLS spreadsheet.
Why supply/exhaust balance matters
Every room's calculated airflow is either a supply point, an exhaust point, or both (balanced ventilation). Summed across the whole building, total supply rarely equals total exhaust exactly by accident — dedicated extraction points like kitchen hoods and wet-room fans pull air out with no matching supply of their own, so unless make-up air is planned for elsewhere, the building runs at a deficit. That deficit shows up as infiltration: unconditioned outdoor air, or air from an adjoining space, gets pulled in through whatever gaps exist, rather than through a filtered, tempered supply path.
Balance = Supply - Exhaust [m³/h]
Balance % = (Supply - Exhaust) / (Supply + Exhaust) × 100
The percentage form is what drives the balance indicator gauge: it stays within ±100% however large the building is, with 0% meaning supply and exhaust are exactly equal.
Choosing each room's role
Occupancy-based rooms (offices, classrooms) and general area/ACH lookups default to balanced, since dilution ventilation needs both a supply path in and a return or exhaust path out. Kitchen hoods, wet-room extraction (bathrooms, toilets, laundries) and other fixed exhaust-rate methods default to exhaust-only, since they model a dedicated extraction point rather than the room's general ventilation. Every default can be overridden — some projects size make-up air separately and want a kitchen counted as balanced, for instance.
A small negative balance is normal, a large one usually isn't. Most real buildings run slightly negative, since a controlled amount of infiltration is often accepted rather than designed for with dedicated make-up air. The balance indicator's colour zones flag when the imbalance has grown large enough to be worth a second look, not any non-zero value.
Per-room calculation methods and reference data are the same verified set used by CloudAir's Ventilation Airflow calculator — PN-83/B-03430 (Az3:2000), PN-EN 16798-1:2019-06, PN-EN 16282-1:2017 and ANSI/ASHRAE 62.1-2019. Supply/exhaust role defaults and the balance calculation are CloudAir's own engineering convention, not a published standard formula — verify against project requirements and local regulations for binding designs.
Frequently asked questions
What does a negative building airflow balance mean?
A negative balance means total exhaust airflow exceeds total supply airflow across the building, which depressurizes the space relative to outdoors or adjoining areas. This can pull in unconditioned air, dust or odours through gaps and openings. A positive balance means supply exceeds exhaust, pressurizing the space.
How is each room's supply/exhaust role decided?
Each calculation method has a sensible default: occupancy-based and general lookup methods default to balanced (the room needs both fresh air supply and a matching return/exhaust path), while kitchen hoods, wet-room extraction and fixed exhaust-rate methods default to exhaust-only, since they represent a dedicated extraction point rather than a ventilated space. Every room's role can be overridden manually.
Which standards does the Building Airflow Designer use?
The same verified reference data as CloudAir's Ventilation Airflow calculator: ASHRAE 62.1-2019 (Tables 6-1 and 6-2), PN-EN 16798-1:2019-06 (occupancy and residential category methods), PN-EN 16282-1:2017 (kitchen hood heat-gain method) and PN-83/B-03430 (Az3:2000) for Polish residential fixed rates and the public/industrial lookup table.
Can I export the building airflow balance as a PDF report?
Yes. The Report step generates a branded PDF with your project information, the full room list, and the supply/exhaust balance including the chart images, or an XLS spreadsheet with the same data for further editing.