Ashrae 62.2 Calculator

ASHRAE 62.2 Ventilation Calculator

Determine the required mechanical ventilation rate (CFM) for residential buildings based on the ASHRAE 62.2-2019 standard.

Calculation Results

Total Required Ventilation Rate: 0 CFM

function calculateAshrae() { var area = document.getElementById('floorArea').value; var beds = document.getElementById('numBedrooms').value; if (area === "" || beds === "" || area <= 0 || beds < 0) { alert("Please enter valid positive numbers for Floor Area and Bedrooms."); return; } var fArea = parseFloat(area); var nBeds = parseInt(beds); /* ASHRAE 62.2-2013/2016/2019 Basic Formula: Qtot = 0.03 * Floor Area + 7.5 * (Number of Bedrooms + 1) */ var areaComponent = 0.03 * fArea; var occupantComponent = 7.5 * (nBeds + 1); var totalCFM = areaComponent + occupantComponent; document.getElementById('cfmResult').innerText = Math.ceil(totalCFM); document.getElementById('calcBreakdown').innerText = "Formula: (0.03 × " + fArea + " sq.ft.) + (7.5 × (" + nBeds + " + 1)) = " + totalCFM.toFixed(1) + " CFM"; document.getElementById('resultDisplay').style.display = "block"; }

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Understanding ASHRAE 62.2 Ventilation Standards

ASHRAE 62.2 is the nationally recognized standard for ventilation and indoor air quality in residential buildings. Unlike older construction methods that relied on "natural leakage" through cracks in the building envelope, modern energy-efficient homes are built tight. This requires mechanical ventilation to ensure that moisture, odors, and indoor pollutants (like VOCs and CO2) are properly diluted and removed from the living space.

The Required Ventilation Formula

The calculation for the total required ventilation rate ($Q_{tot}$) is based on two primary factors: the size of the house and the number of potential occupants. The standard assumes the number of occupants is equal to the number of bedrooms plus one.

• Floor Area Factor: 0.03 CFM per square foot of conditioned space.
• Occupant Factor: 7.5 CFM per person (Bedrooms + 1).

This calculator provides the continuous mechanical ventilation rate. If you plan to use intermittent ventilation (fans that turn on and off), you must increase the CFM capacity based on the duty cycle to meet the same daily airflow volume.

Practical Calculation Example

Let's look at a typical 2,500-square-foot home with 4 bedrooms:

1. Step 1 (Area): 2,500 sq. ft. × 0.03 = 75 CFM.
2. Step 2 (Occupants): (4 Bedrooms + 1) × 7.5 = 37.5 CFM.
3. Step 3 (Total): 75 + 37.5 = 112.5 CFM.

In this scenario, the mechanical ventilation system (such as an ERV, HRV, or supply/exhaust fan) must provide at least 113 CFM of continuous airflow to comply with the standard.

Why is Compliance Important?

Adhering to ASHRAE 62.2 is often a requirement for building codes, LEED certification, and ENERGY STAR programs. More importantly, it ensures the health and comfort of occupants. Insufficient ventilation can lead to:

• Accumulation of radon or chemical off-gassing.
• Excess humidity leading to mold and mildew growth.
• High concentrations of CO2, which can impact sleep and cognitive function.
• Lingering household odors.

Pro Tip: This calculator provides the total required airflow. If you are performing a retrofit, you may be eligible for an "Infiltration Credit" if you conduct a Blower Door test, which could reduce the mechanical ventilation requirement. Consult a local HVAC professional for site-specific adjustments.