Ventilation Rate Calculator (ASHRAE 62.2)
ANA›Life Services Authority›National Calculator Authority›Ventilation Rate Calculator (ASHRAE 62.2)
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Ventilation Rate Calculator (ASHRAE 62.2)
Calculate the required whole-building mechanical ventilation rate for residential buildings per ASHRAE Standard 62.2-2022.
Conditioned Floor Area (ft²)
Number of Bedrooms
Number of Occupants (optional — defaults to bedrooms + 1)
Infiltration Credit (CFM) — optional, 0 if unknown
Fan Efficiency (W/CFM) — for power calculation
Calculate
function venCalc() { const resultDiv = document.getElementById('ven-result'); resultDiv.style.display = 'block';
// --- Gather inputs --- const floorArea = parseFloat(document.getElementById('ven-floor-area').value); const bedrooms = parseFloat(document.getElementById('ven-bedrooms').value); const occupInput = document.getElementById('ven-occupants').value.trim(); const infiltration= parseFloat(document.getElementById('ven-infiltration').value) || 0; const efficiency = parseFloat(document.getElementById('ven-efficiency').value);
// --- Validation --- const errors = []; if (isNaN(floorArea) || floorArea 20000) errors.push("Conditioned floor area must be between 100 and 20,000 ft²."); if (isNaN(bedrooms) || bedrooms 20 || !Number.isInteger(bedrooms)) errors.push("Number of bedrooms must be a whole number between 0 and 20."); if (occupInput !== '' && (isNaN(parseFloat(occupInput)) || parseFloat(occupInput) 50)) errors.push("Number of occupants must be between 1 and 50."); if (infiltration 500) errors.push("Infiltration credit must be between 0 and 500 CFM."); if (isNaN(efficiency) || efficiency 5) errors.push("Fan efficiency must be between 0.1 and 5.0 W/CFM.");
if (errors.length > 0) { resultDiv.innerHTML = 'Please fix the following:' + errors.map(e => '').join('') + ''; return; }
// --- ASHRAE 62.2-2022 Formula --- // Qfan = 0.03 × Afloor + 7.5 × (Nbr + 1) // where Afloor = conditioned floor area (ft²), Nbr = number of bedrooms // Occupants default = Nbr + 1 per ASHRAE 62.2 Table 4.1a
const occupants = (occupInput !== '') ? parseFloat(occupInput) : (bedrooms + 1);
// Required ventilation rate (CFM) — ASHRAE 62.2 Equation 4.1a const qRequired = 0.03 * floorArea + 7.5 * (bedrooms + 1);
// Infiltration credit (Section 4.1.3): net required = max(Qfan - 0.5 * Qinf, 0) // Simplified credit: subtract up to 50% of infiltration from required const infiltrationCredit = 0.5 * infiltration; const qNet = Math.max(qRequired - infiltrationCredit, 0);
// Fan power (Watts) const fanPower = qNet * efficiency;
// Annual energy (kWh/yr) assuming continuous operation const annualEnergy = (fanPower * 8760) / 1000;
// Air changes per hour (ACH) — assumes 8 ft ceiling height const assumedCeilingHeight = 8; // ft const volume = floorArea * assumedCeilingHeight; // ft³ const ach = (qNet * 60) / volume;
// CFM per person const cfmPerPerson = qNet / occupants;
// --- Output --- resultDiv.innerHTML = ` ### Results
ParameterValue Conditioned Floor Area${floorArea.toLocaleString()} ft² Bedrooms${bedrooms} Assumed Occupants${occupants} Required Ventilation Rate (Qfan)${qRequired.toFixed(1)} CFM Infiltration Credit (0.5 × ${infiltration} CFM)${infiltrationCredit.toFixed(1)} CFM Net Required Ventilation Rate${qNet.toFixed(1)} CFM CFM per Person${cfmPerPerson.toFixed(1)} CFM/person Estimated ACH (8 ft ceiling)${ach.toFixed(3)} ACH Fan Power (@ ${efficiency} W/CFM)${fanPower.toFixed(1)} W Annual Energy (continuous)${annualEnergy.toFixed(0)} kWh/yr
Note: Net required ventilation = max(Qfan − 0.5 × Qinf, 0). Infiltration credit requires a blower door test per ASHRAE 62.2 Section 4.1.3.
`; }
#### Formula
ASHRAE 62.2-2022, Equation 4.1a — Whole-Building Ventilation Rate:
Qfan = 0.03 × Afloor + 7.5 × (Nbr + 1)
- Qfan — Required mechanical ventilation rate (CFM)
- Afloor — Conditioned floor area (ft²)
- Nbr — Number of bedrooms (occupants default = Nbr + 1)
Infiltration Credit (Section 4.1.3):
Qnet = max(Qfan − 0.5 × Qinf, 0)
Fan Power: P (W) = Qnet × η (W/CFM)
Annual Energy: E (kWh/yr) = P × 8,760 / 1,000
#### Assumptions & References
- Based on ASHRAE Standard 62.2-2022: Ventilation and Acceptable Indoor Air Quality in Residential Buildings.
- Infiltration credit of up to 50% of measured infiltration (Qinf) may be applied when a blower door test is performed per Section 4.1.3.
- This calculator covers whole-building ventilation only; local exhaust (kitchen, bath) requirements are addressed separately in Section 5.
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