Ventilation Rate Calculator
ANA›Life Services Authority›National Calculator Authority›Ventilation Rate Calculator — calculate required fresh air exchange rates per Oregon mechanical code and ASHRAE 62.2
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Ventilation Rate Calculator
Calculate required fresh air exchange rates per Oregon Mechanical Code (OMC) and ASHRAE 62.2-2022 for residential and light commercial spaces.
### Space Information
Space / Occupancy Type
Residential (Single-Family / Multifamily) Office Classroom Retail Restaurant / Dining Gym / Exercise Hotel / Motel Guest Room Conference Room
Floor Area (sq ft)
Number of Bedrooms
Number of Occupants (design)
Ceiling Height (ft)
Calculation Standard
Both (ASHRAE 62.2 + Oregon OMC) ASHRAE 62.2-2022 Only Oregon Mechanical Code Only
Altitude (ft above sea level) — for density correction
Calculate Ventilation Rate
#### Formulas Used
ASHRAE 62.2-2022 — Residential (Section 4.1.2):
Q_fan = 0.01 × A_floor + 7.5 × (N_br + 1) [CFM] Where A_floor = floor area (sq ft), N_br = number of bedrooms.
ASHRAE 62.2-2022 — Commercial (Ventilation Rate Procedure, Section 6):
V_bz = R_p × P_z + R_a × A_z [CFM] Where R_p = people outdoor air rate (CFM/person), P_z = zone population, R_a = area outdoor air rate (CFM/sq ft), A_z = zone floor area.
Oregon Mechanical Code (OMC Table 403.3.1.1) — mirrors ASHRAE 62.1:
V_ot = R_p × P_z + R_a × A_z [CFM]
Air Changes per Hour (ACH):
ACH = (Q_cfm × 60) / V_room V_room = A_floor × H_ceiling [cu ft]
Altitude Density Correction:
CF = 1 / (1 - altitude_ft / 27,000) Q_corrected = Q_cfm × CF
#### Assumptions & References
- Residential rates per ASHRAE 62.2-2022, Section 4.1.2 whole-building ventilation formula.
- Commercial rates per ASHRAE 62.1-2019 Table 6-1 (Ventilation Rate Procedure), which Oregon OMC Table 403.3.1.1 adopts by reference.
- Oregon Mechanical Code (2021 edition) adopts ASHRAE 62.1-2019 for commercial and ASHRAE 62.2-2019 for residential ventilation minimums.
- Results represent minimum outdoor air; actual system design may require more for filtration, pressurization, or energy recovery.
// ── ASHRAE 62.1 / OMC Table 403.3.1.1 space-type parameters ────────────────── // { rp: CFM/person, ra: CFM/sqft, defaultDensity: people/1000sqft } const VEN_SPACE_PARAMS = { office: { rp: 5, ra: 0.06, defaultDensity: 5 }, classroom: { rp: 10, ra: 0.12, defaultDensity: 35 }, retail: { rp: 7.5, ra: 0.06, defaultDensity: 15 }, restaurant: { rp: 7.5, ra: 0.18, defaultDensity: 70 }, gym: { rp: 20, ra: 0.06, defaultDensity: 25 }, hotel: { rp: 5, ra: 0.06, defaultDensity: 10 }, conference: { rp: 5, ra: 0.06, defaultDensity: 50 }, };
function venUpdateFields() { const type = document.getElementById('ven-space-type').value; const resFields = document.getElementById('ven-residential-fields'); const occFields = document.getElementById('ven-occupant-fields'); if (type === 'residential') { resFields.style.display = 'block'; occFields.style.display = 'none'; } else { resFields.style.display = 'none'; occFields.style.display = 'block'; } // Clear previous result const res = document.getElementById('ven-result'); res.style.display = 'none'; res.innerHTML = ''; }
function venAltitudeCF(altFt) { // Density correction factor — only meaningful above ~1000 ft if (altFt 10000) errors.push('Altitude must be between 0 and 10,000 ft.');
let bedrooms = 0, occupants = 0; if (spaceType === 'residential') { bedrooms = parseInt(document.getElementById('ven-bedrooms').value); if (isNaN(bedrooms) || bedrooms 0) { result.className = 'calc-result calc-error'; result.innerHTML = 'Please fix the following:' + errors.map(e => '').join('') + ''; return; }
result.className = 'calc-result';
// ── Core calculations ────────────────────────────────────────────────────── const roomVolume = floorArea * ceilHeight; // cu ft const altCF = venAltitudeCF(altitude);
let html = '';
// ── ASHRAE 62.2 Residential ──────────────────────────────────────────────── if (spaceType === 'residential' && (standard === 'both' || standard === 'ashrae')) { const q622 = 0.01 * floorArea + 7.5 * (bedrooms + 1); const q622corr = q622 * altCF; const ach622 = (q622corr * 60) / roomVolume;
html += ` ### ASHRAE 62.2-2022 — Residential
ParameterValue
Floor Area${floorArea.toLocaleString()} sq ft
Bedrooms${bedrooms}
Formula0.01 × ${floorArea} + 7.5 × (${bedrooms} + 1)
Required CFM (sea level)${q622.toFixed(1)} CFM
${altCF > 1.001 ? Altitude Correction Factor (${altitude} ft)${altCF.toFixed(3)}
Required CFM (altitude-corrected)**${q622corr.toFixed(1)} CFM** : ''}
Air Changes per Hour (ACH)${ach622.toFixed(2)} ACH
Room Volume${roomVolume.toLocaleString()} cu ft
`;
}
// ── Oregon OMC Residential (same formula as 62.2) ───────────────────────── if (spaceType === 'residential' && (standard === 'both' || standard === 'omc')) { const qOmc = 0.01 * floorArea + 7.5 * (bedrooms + 1); const qOmcCorr = qOmc * altCF; const achOmc = (qOmcCorr * 60) / roomVolume;
html += ` ### Oregon Mechanical Code (OMC) — Residential
OMC adopts ASHRAE 62.2-2019 by reference; formula is identical to ASHRAE 62.2.
ParameterValue
Required CFM (sea level)${qOmc.toFixed(1)} CFM
${altCF > 1.001 ? Required CFM (altitude-corrected)**${qOmcCorr.toFixed(1)} CFM** : ''}
Air Changes per Hour (ACH)${achOmc.toFixed(2)} ACH
`;
}
// ── ASHRAE 62.1 / OMC Commercial ────────────────────────────────────────── if (spaceType !== 'residential') { const params = VEN_SPACE_PARAMS[spaceType]; const { rp, ra, defaultDensity } = params;
// Ventilation Rate Procedure: Vbz = Rp × Pz + Ra × Az const vbz = rp * occupants + ra * floorArea; const vbzCorr = vbz * altCF; const achComm = (vbzCorr * 60) / roomVolume; const cfmPerPerson = vbzCorr / occupants; const cfmPerSqft = vbzCorr / floorArea;
const showAshrae = (standard === 'both' || standard === 'ashrae'); const showOmc = (standard === 'both' || standard === 'omc');
- const standardLabel = showAshrae && showOmc
- ? 'ASHRAE 62.1-2019 / Oregon OMC Table 403.3.1.1'
- showAshrae ? 'ASHRAE 62.1-2019' : 'Oregon OMC Table 403.3.1.1';
html += ` ### ${standardLabel} — ${document.getElementById('ven-space-type').options[document.getElementById('ven-space-type').selectedIndex].text}
ParameterValue
Floor Area${floorArea.toLocaleString()} sq ft
Design Occupants${occupants} people
People Rate (R_p)${rp} CFM/person
Area Rate (R_a)${ra} CFM/sq ft
People Component (R_p × P_z)${(rp * occupants).toFixed(1)} CFM
Area Component (R_a × A_z)${(ra * floorArea).toFixed(1)} CFM
Total Required CFM (sea level)${vbz.toFixed(1)} CFM
${altCF > 1.001 ? Altitude Correction Factor (${altitude} ft)${altCF.toFixed(3)}
Total Required CFM (altitude-corrected)**${vbzCorr.toFixed(1)} CFM** : ''}
Air Changes per Hour (ACH)${achComm.toFixed(2)} ACH
CFM per Person${cfmPerPerson.toFixed(1)} CFM/person
CFM per Sq Ft${cfmPerSqft.toFixed(3)} CFM/sq ft
Room Volume${roomVolume.toLocaleString()} cu ft
`;
}
// ── Interpretation ───────────────────────────────────────────────────────── const finalCFM = (() => { if (spaceType === 'residential') { return (0.01 * floorArea + 7.5 * (bedrooms + 1)) * altCF; } else { const p = VEN_SPACE_PARAMS[spaceType]; return (p.rp * occupants + p.ra * floorArea) * altCF; } })(); const finalACH = (finalCFM * 60) / roomVolume;
let achNote = ''; if (finalACH = 0.35 && finalACH = 0.5 && finalACH Summary: Minimum required outdoor airflow = ${finalCFM.toFixed(1)} CFM (${finalACH.toFixed(2)} ACH) ${achNote} `;
result.innerHTML = html; }
// Initialize field visibility on load venUpdateFields();
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