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The total conditioned floor area of the home.
Use total conditioned square footage across all floors.
ASHRAE 62.2 uses bedroom count as a proxy for expected occupancy.
This follows the same 'bedrooms + 1' occupancy assumption the standard uses, so a 3-bedroom home assumes 4 occupants. The standard treats the bedroom count as never less than one, which is why this field starts at 1: enter 1 for a studio or a one-room flat, not 0.
Required continuous ventilation rate
78.3 CFM (continuous)
This is the standard ASHRAE 62.2 formula for continuous whole-house mechanical ventilation — actual equipment selection should also account for your specific ERV/HRV unit's rated efficiency and any local code amendments to the base ASHRAE formula.
- House area
- 1,610 sq ft
They open the calculator with your figures already in it
ERV/HRV Sizing Calculator: 78.3 CFM (continuous) — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- ASHRAE 62.2 whole-house mechanical ventilation formula: required CFM = 0.03 x floor area (sq ft) + 7.5 x (number of bedrooms + 1)
Inputs used
- Conditioned Floor Area
- 1610 sq ft
- Number of Bedrooms
- 3
Intermediate steps
- House area
- 1,610 sq ft
Confidence note: This is the standard ASHRAE 62.2 formula for continuous whole-house mechanical ventilation — actual equipment selection should also account for your specific ERV/HRV unit's rated efficiency and any local code amendments to the base ASHRAE formula.
What this calculation does not cover
- This is the whole-house rate only. ASHRAE 62.2 also requires local exhaust at kitchens and bathrooms, sized and ducted separately, and nothing here covers range hoods, bath fans or their duct runs.
- No infiltration credit and no envelope input. The figure is the total ventilation rate; current editions of the standard let a balanced system take credit for natural leakage, so the fan flow a leaky house actually needs can be lower than this. Nothing here reads a blower-door result or an air-tightness figure.
- This is a target flow, not an equipment selection. What a core actually delivers depends on external static pressure, duct length and fittings, filter loading, and how well supply and exhaust are balanced against each other, so a unit whose spec sheet lists this flow can fall well short once it is ducted. Commission with measured flows at the grilles.
- No climate adjustment. Defrost strategies that interrupt the supply side — recirculation, exhaust-only operation, or throttling the supply fan — cut the net fresh air delivered over a cold hour, while a preheater keeps outdoor air flowing continuously and pays for it in energy instead. The ERV-versus-HRV choice for humidity control is not modelled at all, and the number is the same in Miami and in Winnipeg.
- Bedroom count is the standard's occupancy proxy, not your occupancy or your pollutant load. A house run above the bedrooms-plus-one assumption, or one with an attached garage, unvented combustion or a workshop, needs more than this. Local codes and programs amend or replace the base ASHRAE rate, and this calculation does not check for that.
Add the equipment this sizes
This result is a specification — 78.3 CFM (continuous) — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- ASHRAE 62.2 whole-house mechanical ventilation formula: required CFM = 0.03 x floor area (sq ft) + 7.5 x (number of bedrooms + 1)
Which documents these citations point at
Standards referenced: ASHRAE 62.2 (American Society of Heating, Refrigerating and Air-Conditioning Engineers, United States).
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