Outdoor air for a house under ASHRAE 62.2 or a commercial space under 62.1, from floor area, bedrooms, occupancy and space type.
The continuous ASHRAE 62.2 rate for a house, with fan airflow, pressure effect and air changes for exhaust-only, supply-only or balanced systems.
Supply air temperature, ventilation heat load and annual heating savings for a heat recovery ventilator, from airflow, efficiency, degree days and fuel price.
Sensible, latent and total energy recovered by an ERV in summer and winter, from airflow, efficiencies and design conditions.
Check whether an HRV or ERV stays balanced once bathroom fans, the range hood and the dryer are running, and whether you need dedicated makeup air.
Heating energy and cost an HRV or ERV recovers compared with exhaust-only ventilation, from airflow, degree days, efficiency and heating cost.
Sensible and latent heating or cooling load of outdoor air, with and without energy recovery, from airflow and design conditions.
Air changes per hour from room size and CFM, or the airflow needed for a target ACH, with a reference table for common space types.
Turn a blower door ACH50 result or a construction-era estimate into natural air changes, infiltration airflow and heating load.
Airflow from wind-driven cross ventilation or stack effect, using opening area, wind speed and indoor to outdoor temperature difference.
Supply airflow and air changes per hour for ISO Class 5 to 8 clean rooms, with the pressure cascade to the corridor.
Supply and outdoor airflow for operating, isolation, patient and procedure rooms from ASHRAE 170 air changes, with the pressure direction for each.
The supply and exhaust offset that holds an isolation, protective or clean room at a target pressure, from door leakage area.
Check whether a door undercut, transfer grille or jump duct can pass the air a bathroom or kitchen fan needs, and whether the donor room can spare it.
Steady-state indoor CO2 in ppm from occupancy, activity and outdoor air, or the airflow needed to hold a target CO2 level.
Outdoor air reduction and annual heating savings from CO2-based demand-controlled ventilation, using ASHRAE 62.1 rates and typical occupancy.
The Canadian Air Quality Health Index from PM2.5, ozone and NO2, with a risk category and HRV or ERV advice for smoky or smoggy days.
Outdoor airflow that holds an indoor contaminant below a target in mg/m3, with Health Canada guideline presets, a mixing factor and ACH.
Outdoor air for a contaminant using the ASHRAE 62.1 IAQ Procedure mass balance, compared with the Ventilation Rate Procedure.
Dilution airflow that keeps an airborne vapour below a target ppm, from its generation rate and a K mixing factor.
Minimum outdoor air for one zone from occupancy and floor area using ASHRAE 62.1 Rp and Ra rates, with office to gym presets.
Breathing zone airflow (Vbz) and zone outdoor airflow (Voz) from occupancy, floor area and air distribution effectiveness.
The outdoor air intake for a multi-zone VAV air handler: enter each zone, find the critical zone and apply system ventilation efficiency per ASHRAE 62.1.
The ASHRAE 62.1 people outdoor air rate (Rp) for offices, classrooms, retail, restaurants and gyms, scaled to a headcount.
Bathroom, kitchen or laundry exhaust fan size in CFM or L/s from room size, duct run and code minimums, with duct size and sone guidance.
Bathroom fan CFM by floor area or fixture count using HVI rules and the Canadian code minimum, with a recommended sone limit.
Commercial Type I hood airflow from hood type, cooking duty and length, with code minimum CFM, makeup air and duct size.
Parking garage exhaust from the code airflow rate or from vehicle CO output and a target ppm, in L/s, CFM and ACH.
Lab exhaust from fume hood face velocity and sash opening, supply air changes, and the offset that holds the lab negative to the corridor.
Local exhaust hood airflow for a point source from capture velocity and distance, for plain, flanged, slot and canopy hoods.
Makeup air for kitchen hoods and other large exhaust, the pressure balance with transfer air, and the winter tempering load.
About Ventilation & IAQ Calculations
Ventilation does three jobs: it dilutes the pollutants that people and materials give off, it supplies fresh air to breathe, and it carries moisture out of the building. The calculators on this page cover those jobs from three directions: how much outdoor air a space needs, what moves it (fans, HRVs, ERVs and transfer paths), and what that air costs in heating and cooling energy.
Houses: ASHRAE 62.2
ASHRAE 62.2 sets the minimum mechanical ventilation for houses and low-rise residential buildings. The rate in CFM is Qtot = 0.03 × A + 7.5 × (N + 1), where A is the floor area in ft² and N is the number of bedrooms. A 180 m² house (about 1,940 ft²) with three bedrooms works out to 88 CFM, or 42 L/s. The Whole-House Ventilation Calculator runs that sum and shows what each fan strategy has to deliver, and the Ventilation Rate Calculator handles both 62.2 and 62.1. Provincial codes can ask for more or less than the standard, so compare the result with the minimums in the Ventilation Code Calculator before it goes on a permit drawing.
Offices, schools and other commercial spaces: ASHRAE 62.1
Commercial and institutional zones follow ASHRAE 62.1. The breathing zone airflow is Vbz = Rp × people + Ra × floor area, and dividing by the zone air distribution effectiveness (Ez) gives the zone outdoor airflow, Voz. A multi-zone air handler then has to cover its critical zone, which is why system ventilation efficiency (Ev) raises the intake above the sum of the zones. Start with the Minimum Ventilation Calculator for one zone, use the ASHRAE 62.1 Calculator for Vbz and Voz, and the Outdoor Air Calculator for the air handler. Hospitals, clean rooms and labs work from their own air change tables, which the Hospital, Clean Room and Laboratory calculators apply.
HRV or ERV
An HRV passes heat from the outgoing air to the incoming air, and an ERV moves moisture as well. Natural Resources Canada advises that the right unit depends on your climate, home and lifestyle, and recommends an ENERGY STAR certified model. As a rule of thumb, an HRV suits a heated house whose winter air is humid and needs drying, while an ERV suits a house that runs dry in winter or carries a large summer humidity load. The HRV Calculator and ERV Calculator size each option, the Ventilation Energy Recovery Calculator compares them with exhaust-only ventilation, and the Ventilation Heat Load Calculator shows the load either one takes off the furnace or air conditioner.
Leaks and exhaust fans
Fan-driven ventilation is only part of the air a house exchanges. Leaks in the envelope add uncontrolled air on top of the fan rate, and the heating load that creates is worked out in the infiltration load calculator, while the Infiltration Calculator here converts a blower door result into air changes. Large exhaust appliances pull the other way: a range hood or dryer running in a tight house depressurizes it, which is the problem the Makeup Air Calculator and Transfer Air Calculator address. The Balanced Ventilation Calculator checks whether an HRV or ERV stays balanced while those fans run.
CO₂ and other contaminants
Carbon dioxide is the usual stand-in for whether an occupied room is getting enough outdoor air. Health Canada's residential guideline sets a long-term limit of 1,000 ppm, based on a 24-hour average. The CO₂ Level Calculator finds the steady-state level for a given occupancy and outdoor airflow, or the airflow that holds a target, and the Demand-Controlled Ventilation Calculator estimates what CO₂ sensors save. For other pollutants, the IAQ Calculator and Dilution Ventilation Calculator size the airflow, and the AQHI Calculator helps decide when outdoor air itself is the problem.
Frequently Asked Questions
ASHRAE 62.2 sets it from floor area and bedrooms: 0.03 CFM per square foot plus 7.5 CFM for each bedroom plus one more. A 180 m² house with three bedrooms needs about 88 CFM (42 L/s), which is 0.35 air changes per hour with 2.4 m ceilings. The Whole-House Ventilation Calculator does the sum for your own numbers.
An HRV recovers heat only, while an ERV recovers heat and moisture. The better fit depends on whether the house needs to shed winter humidity or hold on to it, and on how heavy its summer humidity load is. Compare both with the HRV Calculator and ERV Calculator, then use the Ventilation Energy Recovery Calculator to put a number on the savings.
CFM (or L/s) is an airflow. Air changes per hour divides that airflow by the volume of the space. The same 100 CFM is 6.25 ACH in a 960 ft³ room (10 × 12 × 8 ft) but only 0.375 ACH in a 16,000 ft³ house. The ACH Calculator converts either way.
No. A house gets one whole-building rate from ASHRAE 62.2, driven by floor area and bedroom count. Commercial spaces follow ASHRAE 62.1, which adds a people-based and an area-based part for each zone, then applies zone air distribution effectiveness and, for multi-zone systems, system ventilation efficiency. Use the Minimum Ventilation Calculator for a single zone or the ASHRAE 62.1 Calculator for the zone airflows.