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Building Code Reference

Got a ASHRAE 62.2 correction?

Whole-house ventilation standard

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

ASHRAE 62.2 is the ventilation standard that California’s Title 24 building code adopts to require a whole-house mechanical ventilation system in every new residence. The standard sets the minimum continuous or intermittent airflow rate your house needs to maintain acceptable indoor air quality, calculated based on floor area and number of bedrooms. Vented kitchen hoods must meet the airflow or capture efficiency in Energy Code Table 150.0-G (110 to 280 CFM by home size and range fuel), and each bathroom needs 50 CFM of on-demand exhaust or 20 CFM continuous. New single-family homes, ADUs, and multi-unit residential projects all fall under this requirement.

How to fix it

  1. Calculate the required whole-house CFM

    Use the total required ventilation rate formula in the 2025 Energy Code (Equation 150.0-B): required CFM = 7.5 × (number of bedrooms + 1) + 0.03 × dwelling-unit floor area in square feet, counting at least 1 bedroom. For a 3-bedroom, 1,500 sq ft home: 7.5 × (3 + 1) + 0.03 × 1,500 = 30 + 45 = 75 CFM. Write this calculation out on your M-sheets — showing your inputs and result makes the plan-checker's job easy and speeds approval.

  2. Choose a whole-house ventilation strategy

    ASHRAE 62.2 allows several approaches: a dedicated supply fan (pulls outside air into the return plenum), a dedicated exhaust fan (draws stale air out continuously), or a balanced system like an ERV or HRV. For most California climates, exhaust-only or supply-only systems are the simplest. Balanced ERV/HRV systems cost more upfront but recover energy and are often the better choice in tight, well-insulated homes. Pick your strategy before sizing equipment.

  3. Specify the fan model, CFM, and sone rating on the M-sheets

    List the manufacturer name, model number, rated CFM at the system's design static pressure, and sone rating. California's energy code limits bath fans used as the whole-house ventilator to 1.0 sone or less when running continuously. Bath fans used only for demand-controlled spot exhaust are allowed up to 3.0 sones. If your whole-house strategy uses a bath fan running on a timer, make sure it's rated at 1.0 sone or less — and call that out explicitly.

  4. Show vented kitchen exhaust sized to Table 150.0-G

    Vented range hoods must meet the airflow or capture efficiency in Energy Code Table 150.0-G, from 110 CFM (electric range, home over 1,000 sq ft) to 280 CFM (gas range, home under 1,000 sq ft); other kitchen exhaust fans, including downdrafts, need 300 CFM. Recirculating hoods that filter and return air to the kitchen don't meet this requirement — the air has to go outside. Note the duct size, termination point, and fan CFM on both the floor plan and M-sheets. If the kitchen is in an interior location with a long duct run, confirm the fan's rated CFM accounts for static pressure loss.

  5. Confirm each bathroom has 50 CFM on-demand or 20 CFM continuous exhaust

    Every bathroom (including half-baths) needs an exhaust fan ducted to the exterior: 50 CFM minimum if it runs on demand, or 20 CFM if it runs continuously. Show the fan location on the floor plan and list the model and CFM on the mechanical schedule. Confirm the duct terminates at an exterior wall cap or roof jack — not into an attic space, which is both a code violation and a moisture problem.

  6. Add a ventilation controls note

    ASHRAE 62.2 requires the whole-house system to run continuously or on a timer that provides the equivalent average airflow. If your system runs intermittently (e.g., a bath fan on a 20-minutes-per-hour timer), note on the drawings how the total run time produces the required average CFM. Many plan-checkers want to see this math spelled out, especially for timer-based strategies.

  7. Cross-reference the Title 24 compliance documents

    California requires Title 24, Part 6 compliance documents for the ventilation design as part of the permit submittal, and the whole-house airflow must later pass field verification under 150.0(o)2. Make sure the form lists the whole-house fan model, CFM, and sone rating, and that the numbers on the form match what's on your M-sheets. Discrepancies between the compliance form and the drawings are a common cause of back-and-forth with the plan-checker.

  8. Double-check duct sealing requirements

    Exhaust ducts for ASHRAE 62.2 systems must be sealed per California's energy code — all joints and connections need mastic or approved tape. Call out the duct sealing method on your drawings. If you're using a supply-fan approach pulling exterior air through the HVAC return, note how the supply-air duct connection is made airtight where it connects to the existing duct system.

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Why you got flagged

Most ASHRAE 62.2 corrections come down to one of four things: the system isn’t shown on the plans at all, the CFM rates aren’t specified, the wrong type of fan is called out, or the plans say “ventilation per code” without the actual design numbers.

The most common miss is simply not designing the whole-house system. Kitchen range hoods and bath fans handle spot ventilation; they’re not a substitute for the continuous whole-house system the standard requires. Many contractors assume bath fans cover it. They don’t. ASHRAE 62.2 treats spot and whole-house ventilation as separate systems. If your M-sheets only show a range hood and bath fans with no dedicated whole-house ERV, HRV, or supply/exhaust fan strategy, you’re getting a correction.

The second scenario is sizing. The whole-house rate is calculated from floor area and number of bedrooms. California’s energy code uses a formula based on these inputs — roughly 7.5 CFM per occupant plus a floor-area component. If your drawings call out a 50 CFM bath fan as the whole-house solution without showing the number was derived from the formula, the plan-checker will flag it. They can’t give credit for a system that isn’t documented.

Bathroom exhaust is the third trigger. ASHRAE 62.2 sets a minimum 50 CFM for bath exhaust fans, but plans also need to show sone ratings. California’s energy code, through ASHRAE 62.2, limits whole-house and continuous fans to 1 sone and demand-controlled spot exhaust to 3 sones. If the sone rating isn’t on your drawings, the plan-checker can’t verify compliance.

The fourth scenario shows up on remodel permits most often: notes say “ventilation per ASHRAE 62.2” without specifying the fan model, CFM, or sone rating. That reads as a placeholder, not a design. Plan-checkers routinely reject it and ask for the actual numbers.

The official code

ANSI/ASHRAE Standard 62.2-2022, Ventilation and Acceptable Indoor Air Quality in Residential Buildings, as adopted by 2025 Energy Code Section 150.0(o)

Read the source →

Common questions

Does ASHRAE 62.2 apply to ADUs in California?
Yes. Every new ADU is a new dwelling unit, and California's energy code requires ASHRAE 62.2 whole-house ventilation compliance for all new residential construction — ADUs included. The required CFM is calculated the same way: 7.5 × (bedrooms + 1) + 0.03 × conditioned floor area. A 500 sq ft studio ADU counts as 1 bedroom, because the formula sets bedrooms at not less than 1, so it needs at minimum 7.5 × (1 + 1) + 0.03 × 500 = 30 CFM — round up to the next standard fan size. Document the calculation on your M-sheets.
Can a recirculating kitchen hood satisfy the ASHRAE 62.2 kitchen exhaust requirement?
No. Recirculating hoods filter the air and return it to the kitchen — they don't remove moisture, combustion byproducts, or pollutants from the building. The 2025 Energy Code requires a vented range hood meeting Table 150.0-G (110 to 280 CFM, or a rated capture efficiency), a 300 CFM kitchen exhaust fan, or 5 air changes per hour of continuous exhaust in an enclosed kitchen. If your plans show a recirculating hood, you'll get a correction. You need a duct that runs through the wall or ceiling and terminates outside.
What's the sone rating limit for bathroom exhaust fans in California?
It depends on how the fan is being used. If the bath fan is part of your whole-house ventilation strategy and runs continuously or on a timer, the current California energy code limits it to 1.0 sone or less. If the fan is demand-controlled spot exhaust only, not counted toward the whole-house requirement, the limit is 3.0 sones. Either way, the sone rating needs to be called out on your drawings. Many plan-check corrections come back specifically because the fan model is listed but the sone rating isn't.
Can a bath fan running on a timer count as the whole-house ventilation system?
Yes, if it's sized correctly and the timer is set to provide equivalent average airflow. This is called an intermittent ventilation strategy. The fan needs to run enough hours per day to deliver the same total airflow as if it were running continuously at the required CFM. You need to document the timer schedule and show the math on your plans: for example, if the required rate is 50 CFM continuous and the fan runs at 150 CFM, it needs to run at least one-third of each hour. The plan-checker will want to see this spelled out.
Does adding a whole-house ventilation system mean I need a heat recovery ventilator?
No. An HRV or ERV is one option, not a requirement. Simple supply fans, exhaust fans, or a combination of the two can satisfy ASHRAE 62.2 as long as the CFM is right. HRVs and ERVs are popular in energy-efficient builds because they recover heat from outgoing air before it leaves the building, but they're not mandated by the standard itself. For most straightforward projects, a properly sized and documented exhaust fan or supply fan strategy is the simplest path to plan-check approval.
How is the required whole-house ventilation CFM calculated for a 4-bedroom house?
Use the formula in the current adopted edition of California's energy code: required CFM = 7.5 × (bedrooms + 1) + 0.03 × conditioned floor area. For a 4-bedroom, 2,000 sq ft home: 7.5 × (4 + 1) + 0.03 × 2,000 = 37.5 + 60 = 97.5 CFM — round up to 100 CFM when selecting equipment. Write the inputs and result on your M-sheets so the plan-checker doesn't have to back-calculate it themselves.
What happens if my plans say 'ventilation per ASHRAE 62.2' without specific fan specs?
You'll get a correction. Blanket code-compliance notes like 'per ASHRAE 62.2' or 'fans per Title 24' are placeholders — they don't tell the plan-checker anything about the actual system design. The correction will ask you to provide the fan model, rated CFM, sone rating, and the calculation showing how the whole-house ventilation rate was derived. It's a common and completely avoidable back-and-forth. Put the numbers on the drawings before you submit.
Does ASHRAE 62.2 apply to remodels or only new construction?
California's energy code applies the ASHRAE 62.2 whole-house ventilation rate to new dwellings and to additions that add more than 1,000 sq ft of conditioned area, sized on the whole home; smaller additions and JADU additions are exempt from the whole-house rate but still need local kitchen and bath exhaust. Simple remodels that don't add conditioned area typically don't trigger a full ASHRAE 62.2 compliance review — but they do need to show that the existing ventilation isn't being degraded. If your remodel involves tightening the building envelope (new windows, insulation, air sealing), a plan-checker may require you to document the existing whole-house ventilation rate. When in doubt, include it.

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