Kalkulator ventilasi alami gratis: atur dimensi ruang, tipe bukaan, iklim, dan angin untuk menghitung laju aliran udara serta luas bukaan yang dibutuhkan.
This natural ventilation calculator is free to use, with no account and no password. It runs entirely in your browser; enter your name and email to reveal your result, and we can send you a copy.
The tool sizes natural ventilation in either direction. Set it to Opening area and it returns the openable area a room needs to reach a target air change rate. Set it to Air changes and it returns the air change rate the openings you already have will actually deliver. Both directions run on the same single-zone envelope-flow model, in metric or imperial units.
It is built for the stage where the plan exists but the facade does not. A width, a depth, a ceiling height, a ventilation strategy and a climate are enough to get a defensible number, which is what makes it useful before window schedules are frozen and while the strategy can still change.
Five ventilation regimes are modelled: cross ventilation driven by wind, stack effect driven by temperature, the two combined, single-sided ventilation from one facade, and a stack device such as a chimney or an atrium. There is a step by step walkthrough of every field in the natural ventilation calculator guide.
Air moves through a building envelope for two reasons, and the calculator models both.
The first is buoyancy, the stack effect. Warm indoor air is less dense than cooler outdoor air, so it rises and escapes through high openings while cooler air is drawn in low. The driver is the indoor to outdoor temperature difference, amplified by the vertical distance between the inlet and the outlet. That distance is the stack height, and it is why an atrium or a chimney shaft ventilates a building that a row of windows cannot.
The second is wind. Wind creates positive pressure on the windward face and negative pressure on the leeward face, and air flows across the building between them. The driver is the local wind speed and the pressure coefficient difference across the envelope.
Where both act together the calculator adds them in quadrature rather than arithmetically, because two independent driving pressures do not simply sum. That combined mode is the tool’s own stated realistic default and the right starting point for most rooms.
Every regime then passes through the same aperture model. Flow depends on the effective free area of the openings, not their frame area, so the calculator applies a free area fraction for the opening type and an additional factor for any insect screen before it computes anything. A ventilation effectiveness term accounts for incoming air that short circuits to the outlet without reaching the occupied zone.
Four groups of inputs carry the result, and they do not carry it equally.
The ventilation regime changes the answer more than any other single field, because it decides which physics runs at all. Choose stack effect and the wind term is switched off entirely; choose cross ventilation and buoyancy is. Single-sided ventilation additionally reduces wind effectiveness to roughly a third and applies a room depth limit of 2.5 times the ceiling height, which is the honest constraint on ventilating a deep plan from one facade.
Room dimensions set the volume that the air change rate is measured against, and the floor area that the prescriptive area thresholds are taken from. A taller ceiling raises the volume to be flushed, so it raises the flow required for the same air change rate.
Opening type and screen convert frame area into effective free area. A sliding or double-hung window delivers roughly half the free area of its frame because only one leaf ever opens, while a permanent open aperture delivers nearly all of it. A standard insect screen then removes a further share, and a dense or dirty screen removes considerably more. This pair of fields is the most common source of a calculation that looks right and a room that underperforms.
Climate, terrain and shielding decide the driving forces. The wind speed field wants the meteorological value at the standard 10 m reference height; terrain roughness, surrounding shielding and the opening height above ground are what bring that down to the speed actually arriving at the window. Five Indonesian climate presets are built in, covering Jakarta, Surabaya, Bandung, Medan and Denpasar, alongside a manual mode.
The built-in example is a 12 by 10 by 4 metre space in Jakarta, ventilated by combined stack and wind, with louvre openings carrying a standard insect screen, 6 square metres of frame area at both inlet and outlet, a 3 metre stack height, suburban terrain, partial shielding, 80 occupants and a target of 6 air changes per hour.
Loading it populates the inputs only. You still press Generate result, which is the point at which the tool asks who you are and then returns the answer.
What the result shows is the useful part. The headline is the required openable area, expressed both as a total free area and as a percentage of floor area. Beneath it the calculator separates Physics area, the area the airflow calculation demands, from Code minimum, the area a prescriptive percentage rule demands. These are independent numbers and the larger one governs. A Governing rule line names which of the two is deciding your result, which saves the common error of quoting the airflow figure when the prescriptive rule is actually the binding constraint.
A Frame area to build figure converts the required free area back up through the opening type and screen factors, so the number that reaches the window schedule is a real frame dimension rather than a theoretical aperture.
The results panel includes a compliance check that sets your provided or required area against two prescriptive thresholds expressed as a percentage of floor area: the SNI 5 percent figure used in Indonesian practice and the ASHRAE 4 percent figure. Each row is tagged as passing or failing.
Reading them together with the physics figure is the point. A room can satisfy the prescriptive percentage and still fail to move enough air, if the openings face the wrong way or the stack height is negligible. It can equally exceed the airflow requirement and still fall short of the prescriptive minimum, in which case the code governs regardless of the physics.
The panel also raises warnings where the model is being pushed outside its range. The reverse buoyancy warning is the one that matters most in a tropical climate: when outdoor air is warmer than indoor air, the stack runs backwards, warm air enters through the high openings, and the ventilation imports heat instead of removing it.
A standing note covers the acoustic consequence, because it is a real trade rather than a footnote. An opening of this size held open through occupied hours gives roughly 10 to 15 dB of facade sound reduction, against 30 to 40 dB with the facade closed. On a traffic exposed site that difference decides whether natural ventilation is viable at all, and an acoustic louvre has a smaller free area than its frame, so the calculation has to be run again with the attenuator’s own free area.
The tool states its scope in its own disclaimer: a single-zone steady-state envelope-flow model following ASHRAE Fundamentals and CIBSE AM10, intended as a sizing and feasibility instrument rather than a compliance simulation.
Three limits follow from that. It treats the room as one well mixed volume, so it does not model air moving between rooms, corridors acting as flow paths, or the vertical coupling of a multi-storey space. It uses one steady wind speed and one steady temperature difference, where a real day is a distribution of both and the worst hour is usually the one that decides the design. And it says nothing about where air goes once it is inside, which is exactly what determines whether an occupant at the back of a deep plan feels any benefit.
For early sizing and for testing whether a natural ventilation strategy is viable before the facade is committed, that scope is the right one. Once the scheme carries real weight, a multi-zone airflow network model or CFD with measured local wind data is the next step. Envelope heat gain is a separate question, handled by the OTTV calculator, and the two are usually read together on a tropical project.
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