What Is an Energy Recovery Ventilator?

Call (626) 365-1518 | Alternative Energy Systems

What Is an Energy Recovery Ventilator is an increasingly important question as California buildings become tighter, more energy efficient, and more dependent on planned mechanical ventilation instead of uncontrolled air leakage.

An energy recovery ventilator, commonly abbreviated as ERV, is a mechanical ventilation system that brings outdoor air into a building while exhausting indoor air.

What makes the system different from a basic exhaust fan or supply fan is the energy-recovery core located between the two air streams.

As outgoing indoor air and incoming outdoor air pass through separate pathways in the unit, the ERV can transfer a portion of the energy between them before the outdoor air enters the occupied space.

Depending on the equipment, that transfer can involve:

• Sensible heat associated with air temperature
• Latent energy associated with moisture

This allows the ventilation system to introduce outdoor air without throwing away as much of the heating or cooling energy already used to condition the indoor air.

An ERV can include:

• An outdoor-air intake
• An indoor exhaust-air path
• A heat-and-moisture transfer core or wheel
• Supply and exhaust fans
• Air filters
• Ductwork
• Controls
• Outdoor and indoor air connections

The system is commonly used as a form of balanced mechanical ventilation.

For general background on the technology, review the energy recovery ventilation information on Wikipedia.

Alternative Energy Systems provides professional Title 24 calculations and energy-compliance documentation for residential, multifamily, mixed-use, and commercial projects throughout California.

If your plans include an ERV, HRV, balanced ventilation system, or other mechanical ventilation equipment, call (626) 365-1518 to have the system reviewed as part of the applicable energy-compliance design.

Why Buildings Need Mechanical Ventilation

Buildings need outdoor air.

Historically, some buildings received substantial outdoor air through gaps and leakage around:

• Windows
• Doors
• Walls
• Roofs
• Utility penetrations

Modern energy-efficient construction is generally more airtight.

That reduces uncontrolled air leakage, but it also means ventilation needs to be planned intentionally.

Mechanical ventilation can provide a controlled path for bringing outdoor air into the building while removing indoor air.

The objective is not simply to make a building leakier.

It is to provide outdoor air at a known rate through a designed ventilation system.

What Makes an ERV Different From a Basic Ventilation Fan?

A basic exhaust fan removes indoor air.

A basic supply fan brings outdoor air inside.

An ERV does both while recovering part of the energy that would otherwise leave with the exhaust air.

Consider an air-conditioned building on a hot day.

The indoor exhaust air may be cooler and drier than the outdoor air.

Instead of exhausting that conditioned air directly outdoors without recovering anything from it, an ERV passes the outgoing and incoming air streams through an energy-recovery component.

The incoming air can then be partially preconditioned before it reaches the occupied space or HVAC system.

During cooler weather, the process can work in the opposite direction.

Does the Exhaust Air Mix With the Incoming Air?

The supply and exhaust air streams are designed as separate air paths.

Energy is transferred across or through the recovery medium.

Depending on the ERV technology, a limited amount of air transfer or leakage can occur, which is one reason equipment ratings, installation, pressure relationships, and application matter.

An ERV should not simply be described as mixing stale indoor air with fresh outdoor air.

Its purpose is to exchange energy between separate ventilation air streams.

What Does the Recovery Core Do?

The recovery core is the central component of many ERV systems.

As indoor exhaust air and outdoor supply air pass through the equipment, the core allows energy to move between those air streams.

In an ERV designed for moisture transfer, the core can also allow controlled transfer of water vapor.

Different manufacturers use different recovery technologies.

These can include:

• Fixed-plate enthalpy cores
• Membrane-based cores
• Rotary energy-recovery wheels
• Other approved heat-and-moisture recovery designs

The performance of these technologies is not identical.

Equipment specifications should therefore be reviewed rather than assuming every ERV has the same recovery efficiency.

What Is Sensible Heat Recovery?

Sensible heat relates to air temperature.

If outdoor air is much warmer or colder than indoor air, the ERV can transfer some thermal energy between the two air streams.

This can reduce the temperature difference the HVAC system must handle after ventilation air enters the building.

What Is Latent Energy Recovery?

Latent energy relates to moisture in the air.

Many ERVs are designed to transfer some water vapor between the incoming and outgoing air streams.

This distinguishes an ERV from systems designed primarily for sensible heat recovery.

How much moisture transfer occurs depends on the equipment and operating conditions.

How an Energy Recovery Ventilator Works

Outdoor Air and Exhaust Air Pass Through Separate Recovery Paths

An ERV usually operates two air streams at the same time.

One side brings outdoor air toward the occupied building.

The other side removes indoor air.

The process can be understood as follows.

1. Outdoor Air Enters the ERV

Outdoor air enters through a dedicated intake.

The air normally passes through a filter before or as it enters the recovery section.

2. Indoor Air Is Exhausted

Indoor air is collected from appropriate exhaust locations and routed toward the ERV.

Those locations depend on the building and ventilation design.

3. The Two Air Streams Pass Through the Recovery Component

The incoming and outgoing air remain in separate pathways while energy is transferred between them.

4. Outdoor Air Is Supplied to the Building

The partially conditioned outdoor air is delivered to the occupied building or connected mechanical system.

5. Exhaust Air Leaves the Building

After passing through the recovery section, the exhaust air is discharged outdoors.

What Does Balanced Ventilation Mean?

A balanced ventilation system uses both mechanical supply and mechanical exhaust.

The system is designed so outdoor air entering the building and indoor air leaving the building are controlled together.

An ERV is commonly used in a balanced ventilation configuration.

Balanced ventilation can help designers manage building pressure more intentionally than an exhaust-only or supply-only strategy.

Is an ERV Part of the Heating and Air Conditioning System?

It can be integrated with HVAC equipment, but it is not the same thing as the primary heating or cooling system.

An ERV’s principal function is ventilation and energy recovery.

A furnace, air conditioner, or heat pump provides space conditioning.

Depending on the design, the ERV may:

• Use dedicated ventilation ductwork
• Connect to portions of the central air distribution system
• Operate through a dedicated outdoor-air configuration
• Serve one dwelling unit
• Serve multiple spaces or units through a central system

The correct arrangement depends on the building.

Does an ERV Heat and Cool a House by Itself?

Generally, no.

An ERV can precondition incoming ventilation air, but it should not automatically be treated as a substitute for the building’s heating and cooling equipment.

Its energy-recovery function can reduce ventilation-related heating or cooling demand.

The primary HVAC system still needs to satisfy the applicable building loads.

Does an ERV Run All the Time?

Operation depends on the ventilation design and controls.

A system may operate:

• Continuously
• Intermittently according to a ventilation schedule
• At multiple speeds
• Under automatic controls

The installed controls should provide the ventilation airflow required by the approved design.

What Happens During Mild Weather?

There can be conditions when recovering heat from exhaust air is not useful.

Certain systems therefore include:

• Recovery bypass
• Free-cooling operation
• Economizer-related controls

These features allow outdoor air to be used more directly when recovery would work against the desired indoor condition.

Applicable California requirements depend on building type and system configuration.

What Is Sensible Recovery Efficiency?

Sensible recovery efficiency is one measure used to describe how effectively an HRV or ERV recovers temperature-related energy.

California’s current Energy Code uses sensible recovery efficiency in certain ERV and HRV provisions.

The required value is project-specific and should not be assumed from the letters “ERV” alone.

What Is Fan Efficacy?

Energy recovery is only part of overall system performance.

The fans themselves consume electricity.

Fan efficacy expresses fan electrical power relative to airflow.

A ventilation system therefore should not be evaluated only according to how much energy its core recovers.

The energy required to move the air also matters.

Energy Recovery Ventilator vs. Heat Recovery Ventilator

Both Recover Heat, but Moisture Transfer Is the Important Difference

Energy recovery ventilators and heat recovery ventilators are closely related technologies.

Both use outgoing indoor air to recover energy that can be used to precondition incoming outdoor air.

The major distinction is the type of energy transfer.

What Does an HRV Recover?

A heat recovery ventilator primarily transfers sensible heat.

In other words, it exchanges temperature-related energy between the incoming and outgoing air streams.

Its recovery core is generally not intended to transfer substantial moisture between the two streams.

What Does an ERV Recover?

An energy recovery ventilator generally transfers both:

• Sensible heat
• Latent energy associated with moisture

That moisture-transfer capability can affect indoor humidity conditions and ventilation loads.

The extent of that transfer depends on equipment design and operating conditions.

Is an ERV Always Better Than an HRV?

No.

The right system depends on:

• Climate
• Building type
• Indoor moisture conditions
• Outdoor moisture conditions
• Ventilation airflow
• Mechanical design
• Applicable Energy Code requirements

An ERV should not be selected simply because its name sounds more advanced.

The equipment should fit the building and compliance strategy.

Does an ERV Dehumidify the Building?

An ERV can transfer moisture and may reduce some moisture-related ventilation load under appropriate conditions.

However, it is not automatically a dedicated dehumidifier.

A building with significant humidity-control requirements may still need separate HVAC or dehumidification capacity.

Can an ERV Add Moisture During Cold Weather?

Depending on indoor and outdoor conditions, an ERV can retain a portion of moisture that would otherwise leave with the exhaust air.

That can help reduce excessive drying in some climates.

The actual effect varies with equipment performance, airflow, weather, occupancy, and indoor moisture generation.

Does an HRV Remove More Moisture?

An HRV does not intentionally transfer latent moisture back to the incoming air in the same way as an ERV.

That difference can make HRV and ERV systems behave differently in various climates.

System selection should be based on actual project needs.

Can the Terms ERV and HRV Be Used Interchangeably?

They should not automatically be treated as identical.

Both are heat-recovery ventilation technologies, but an ERV’s ability to transfer latent energy distinguishes it from a sensible-only HRV.

The product specified in the Title 24 calculations should match the equipment intended for installation.

What Does an ERV Do for Indoor Ventilation?

Filtered Outdoor Air Is Supplied While Indoor Air Is Mechanically Exhausted

An ERV can provide controlled whole-building ventilation.

That can help reduce reliance on random air leakage for outdoor-air exchange.

The system can bring outdoor air into areas such as:

• Bedrooms
• Living rooms
• Other occupied spaces

while collecting exhaust air from appropriate locations elsewhere in the building.

The exact supply and exhaust design should follow the approved mechanical plans.

Does an ERV Replace Bathroom Exhaust Fans?

Not automatically.

Some ventilation designs can incorporate bathroom exhaust into a balanced whole-building system.

Other projects use separate local exhaust fans.

California also has local mechanical exhaust requirements for spaces such as bathrooms and kitchens.

The project-specific ventilation design determines how those requirements are satisfied.

Does an ERV Replace a Kitchen Range Hood?

Do not assume so.

Kitchen cooking exhaust has specific requirements and presents grease, moisture, and contaminant issues that are different from general whole-building ventilation.

A required range hood or other local kitchen exhaust system should not simply be eliminated because an ERV is installed.

Does an ERV Filter Outdoor Air?

ERV systems commonly contain filters.

The filtration protects equipment and can reduce particles entering with ventilation air.

The actual filtering performance depends on:

• Filter type
• Filter rating
• Airflow
• System design
• Maintenance

An ERV should not automatically be described as an air purifier.

Can an ERV Improve Indoor Air Quality?

Controlled outdoor-air ventilation can support indoor air quality by replacing indoor air with outdoor air at a designed rate.

An ERV can make that process more energy efficient by recovering energy from the exhaust air.

Indoor air quality still depends on many other factors, including:

• Outdoor-air quality
• Source control
• Filtration
• Moisture control
• Local exhaust
• Building materials
• Occupant activities

What Happens When Outdoor Air Quality Is Poor?

Outdoor air still needs to be considered as part of the ventilation design.

Filtration can reduce certain airborne particles, but filter effectiveness depends on the equipment and filter rating.

The system should be operated and maintained according to applicable requirements and manufacturer instructions.

Does an ERV Control Carbon Dioxide?

An ERV provides outdoor-air ventilation, which can dilute indoor contaminants generated by occupants.

However, the system does not chemically remove carbon dioxide through the recovery core.

The ventilation airflow itself provides the dilution effect.

Does an ERV Remove Odors?

Exhaust ventilation can help remove indoor air containing odors.

However, odor control depends on:

• Exhaust location
• Ventilation rate
• Source strength
• Equipment condition
• Air-transfer characteristics

A ventilation system should be designed around the building rather than expected to eliminate every indoor odor.

Does an ERV Control Indoor Humidity?

An ERV can influence humidity because many models transfer latent energy.

It should not be relied upon as the only humidity-control strategy in every building.

Climate, occupancy, showers, cooking, HVAC operation, infiltration, and other factors also affect indoor moisture.

How Does an Energy Recovery Ventilator Relate to Title 24?

California Requirements Depend on Building Type, Climate Zone and Compliance Path

For applicable permit applications filed on or after January 1, 2026, California uses the 2025 Building Energy Efficiency Standards.

The current Energy Code specifically addresses ERV and HRV systems in several residential, multifamily, and nonresidential ventilation provisions.

This does not mean every California building is required to have an ERV.

Applicability depends on:

• Building type
• Climate zone
• Ventilation strategy
• System configuration
• Prescriptive or performance compliance
• Project scope

For current official HVAC information, review the California Energy Commission HVAC Energy Code Support Center.

Does Every New California Home Need an ERV?

No universal statement should be made that every new California home requires an energy recovery ventilator.

Current requirements vary according to the applicable building category, climate zone, ventilation design, and selected compliance path.

An ERV can be:

• Part of a prescriptive ventilation design
• Part of a performance-based design
• Used voluntarily as an energy-recovery measure
• Unnecessary under another compliant ventilation strategy

The actual project should be reviewed before equipment is specified.

What About Multifamily Buildings?

The 2025 Energy Code contains specific multifamily requirements involving balanced ventilation and energy recovery.

Under the applicable prescriptive provisions, balanced ventilation systems in certain California climate zones must use an ERV or HRV.

Those climate zones include:

• Climate Zone 1
• Climate Zone 2
• Climate Zone 4
• Climate Zones 11 through 14
• Climate Zone 16

For applicable systems serving individual dwelling units under that provision, the current code also establishes requirements involving:

• Sensible recovery efficiency
• Fan efficacy
• Field verification

The project must be evaluated against the complete applicable code provision rather than using the climate-zone list by itself.

What Recovery Efficiency Does the Current Multifamily Prescriptive Path Require?

For the applicable 2025 multifamily balanced ventilation provisions in Climate Zones 1, 2, 4, 11–14, and 16, the current Energy Code establishes a minimum sensible recovery efficiency of 67 percent at the specified rating condition.

Applicable individual dwelling-unit systems also have fan-efficacy requirements.

These requirements apply to specific prescriptive configurations and should not be treated as a universal product specification for every ERV installed in California.

What Is a Fault Indicator Display?

The current California Energy Code includes fault-indicator-display requirements for applicable HRV and ERV systems serving dwelling units.

A fault indicator can alert the occupant or service provider when the ventilation equipment is not operating properly.

The current provisions also include applicable verification requirements.

This is an example of why an ERV selected for a permit project needs to satisfy more than airflow alone.

Does an ERV Require Field Verification?

Certain Title 24 ERV and HRV measures require field verification or acceptance testing.

Depending on building type and system configuration, verification can involve:

• Ventilation airflow
• Fan efficacy or fan power
• Sensible recovery efficiency
• System controls
• Recovery bypass when applicable

The energy report can identify applicable requirements, but preparation of the report does not replace construction-stage testing.

What About Nonresidential Buildings?

The current 2025 Energy Code contains mechanical acceptance procedures involving:

• Dedicated outdoor-air systems
• Heat recovery ventilators
• Energy recovery ventilators

when applicable.

The California Energy Commission publishes dedicated mechanical compliance and acceptance documentation for these systems.

Commercial projects should therefore coordinate ERV equipment with:

• Mechanical plans
• Ventilation calculations
• Controls
• Energy-compliance forms
• Acceptance testing

For broader commercial assistance, review Title 24 compliance services.

Can an ERV Help a Performance Calculation?

Potentially.

Energy recovery can reduce heating or cooling energy associated with mechanical ventilation.

Under an applicable performance approach, the model may account for characteristics such as:

• Ventilation airflow
• Recovery efficiency
• Fan power
• Equipment controls

The benefit depends on the complete building design.

Adding an ERV does not automatically guarantee that a project will comply.

For additional information about the modeling process, review Title 24 energy calculations.

What Should Be Considered When Installing an ERV?

Airflow, Ductwork, Filters, Controls and Service Access All Matter

An ERV is not simply an appliance that can be placed anywhere and expected to perform correctly.

The installation needs to support the ventilation design.

Important considerations can include:

• Equipment airflow capacity
• Supply duct layout
• Exhaust duct layout
• Outdoor-air intake location
• Exhaust-air termination
• Filter access
• Recovery-core access
• Condensate management when applicable
• Fan power
• Controls
• Noise
• Service access

Where Should an ERV Be Installed?

Depending on the equipment and project, a unit might be located in:

• A mechanical room
• A utility room
• A garage
• A mechanical closet
• A basement
• An accessible rooftop location
• Another approved serviceable location

California’s current code includes accessibility requirements for filters and HRV/ERV recovery cores in applicable dwelling-unit systems.

The unit should be serviceable after the building is completed.

Why Is Filter Access Important?

Filters need periodic maintenance.

If access is difficult, maintenance is more likely to be delayed.

Dirty filters can affect:

• Airflow
• Fan energy
• Ventilation performance
• Equipment condition

The ventilation design should therefore consider how the owner or service technician will reach the filters.

Does the Recovery Core Need Maintenance?

Yes.

Maintenance requirements vary by manufacturer.

The recovery core may require:

• Inspection
• Cleaning
• Replacement

depending on the equipment.

Manufacturer instructions should be followed.

Can an ERV Be Installed in an Attic?

Some equipment can be located in an attic when allowed by the applicable code, manufacturer instructions, and project design.

However, service access becomes especially important.

California’s current Energy Code includes specific access provisions for certain HRV/ERV systems that require servicing from within an attic.

The design should therefore address access before construction is completed.

Does an ERV Need Condensate Drainage?

Depending on climate, equipment, and operating conditions, condensation can occur.

Some systems include condensate drainage provisions.

The manufacturer’s installation instructions and mechanical design should determine whether and how drainage is provided.

Where Should Outdoor Air Be Taken From?

The outdoor-air intake needs to be located where it can provide acceptable outdoor ventilation air and comply with applicable mechanical requirements.

It should not simply be placed next to an exhaust termination without considering recirculation.

Intake and exhaust locations should be coordinated on the plans.

Where Does Exhaust Air Come From?

Balanced ventilation systems commonly exhaust air from locations selected to support the ventilation design.

The exact layout varies.

General whole-building exhaust should also be coordinated with separate local exhaust requirements for bathrooms, kitchens, and other spaces where applicable.

Does Duct Sizing Matter?

Yes.

Undersized or poorly designed ducts can create excessive resistance.

That can:

• Reduce airflow
• Increase fan power
• Increase noise
• Prevent the installed system from reaching design ventilation rates

Ventilation ductwork should be sized and installed according to the equipment and design.

Does Balancing Matter?

Yes.

A balanced system should provide the intended relationship between supply and exhaust airflow.

Installation, duct resistance, filters, grilles, and fan settings can all affect the actual result.

This is one reason field verification may be required for applicable Title 24 projects.

Need Help With an ERV in Your Title 24 Design?

Call (626) 365-1518 | Alternative Energy Systems

If your architect, mechanical engineer, contractor, Title 24 report, or building department references an ERV, Alternative Energy Systems can review how the proposed system relates to the energy-compliance design.

Useful information can include:

• Current floor plans
• Mechanical plans
• Ventilation calculations
• ERV manufacturer and model when available
• Design airflow
• Recovery-efficiency information
• Fan-power or fan-efficacy information
• Duct layout
• Controls
• Existing Title 24 calculations
• Building-department correction comments

What if the ERV Model Has Not Been Selected Yet?

Preliminary energy review can sometimes begin before a final model is selected.

However, enough information must eventually be provided to represent the actual proposed system.

The final equipment can affect:

• Airflow
• Recovery efficiency
• Fan power
• Electrical requirements
• Controls
• Physical installation

Final Title 24 documentation should correspond to the equipment intended for construction.

What if the Contractor Changes the ERV?

Send the new equipment specifications for review.

A replacement unit should not automatically be considered equivalent simply because it has the same nominal airflow.

Relevant differences can include:

• Sensible recovery efficiency
• Latent recovery characteristics
• Fan power
• Controls
• Rated airflow
• Bypass capability
• Verification requirements

What if the Plans and Title 24 Report Do Not Match?

Resolve the discrepancy before construction whenever possible.

For example:

• The report may specify an ERV while the mechanical plans show exhaust-only ventilation
• The plans may show an ERV while the calculations assume another ventilation system
• The equipment model may have changed
• The design airflow may differ between documents

The energy documentation and mechanical plans should describe the same ventilation strategy.

What if the Building Department Requests a Correction?

Send AES:

• The complete correction notice
• The latest construction plans
• The mechanical plans
• The existing Title 24 report
• The proposed ERV specifications

AES can determine whether the correction involves:

• Ventilation airflow
• Equipment performance
• Fan efficacy
• Recovery efficiency
• Controls
• Verification documentation
• Plan coordination

What Information Does AES Need to Start?

The complete requirements depend on the project.

A useful starting package can include:

• Floor plans
• Mechanical plans
• Equipment schedules
• Ventilation specifications
• Duct information
• Existing energy calculations
• Correction notices

For a broader intake guide, review what AES will need from you.

Why Choose Alternative Energy Systems?

Alternative Energy Systems provides professional Title 24 calculations, energy-compliance documentation, revisions, and energy-related plan-check support throughout California.

AES brings more than 30 years of California energy-compliance experience to:

• New residential construction
• ADUs
• Additions
• Residential remodels
• Multifamily projects
• Mixed-use projects
• Commercial construction
• Tenant improvements
• HVAC projects
• Ventilation-system projects
• Energy-related plan-check corrections

AES reviews the actual building and ventilation design instead of assuming that every ERV installation has the same California requirements.

Learn more through the About Us page, review company background on the clients page, or explore Title 24 energy analysis.

Understanding What Is an Energy Recovery Ventilator ultimately comes down to controlled ventilation with energy recovery.

The system supplies outdoor air and exhausts indoor air while transferring a portion of the thermal energy between those air streams.

Many ERVs can also transfer latent energy associated with moisture.

For a California Title 24 project, however, the important questions are more specific:

• Is an ERV required or simply proposed?
• What ventilation airflow is required?
• What recovery efficiency is represented?
• What fan power or efficacy applies?
• Does the installed unit match the calculations?
• Is field verification or acceptance testing required?

Alternative Energy Systems can review the project plans, ventilation design, ERV specifications, and existing energy documentation and determine how the equipment should be represented in the applicable compliance package.

Call (626) 365-1518, email info@title24energy.com, or use the contact page.

When service and payment have already been arranged, payment can be completed through the AES payment page.

Frequently Asked Questions: What Is an Energy Recovery Ventilator?

What Is an Energy Recovery Ventilator?

An energy recovery ventilator is a mechanical ventilation system that supplies outdoor air and exhausts indoor air while transferring a portion of sensible and, in many systems, latent energy between the two air streams.

What does ERV stand for?

ERV stands for energy recovery ventilator or energy recovery ventilation, depending on whether the term refers to the equipment or the process.

How does an ERV work?

Outdoor supply air and indoor exhaust air pass through separate paths in a recovery component that transfers energy between the air streams.

Does an ERV mix indoor and outdoor air?

The system is designed with separate supply and exhaust pathways. Energy is transferred through the recovery component rather than intentionally mixing the two air streams.

What is balanced ventilation?

Balanced ventilation uses mechanical supply and mechanical exhaust so incoming and outgoing airflow can be controlled together.

Is an ERV the same as an HRV?

No. Both recover sensible heat, while an ERV generally also transfers latent energy associated with moisture.

What is sensible heat?

Sensible heat is temperature-related thermal energy.

What is latent energy?

Latent energy is associated with moisture or water vapor in the air.

Does an ERV dehumidify a house?

An ERV can reduce some moisture-related ventilation load in appropriate conditions, but it should not automatically be treated as a dedicated dehumidifier.

Does an ERV heat or cool a house?

It preconditions ventilation air but generally does not replace the primary heating and cooling system.

Does an ERV bring fresh air inside?

It provides controlled outdoor-air ventilation. The actual outdoor-air quality and filtration still affect the quality of the supplied air.

Does an ERV filter the air?

ERV systems commonly include filters, but filtration performance depends on the equipment and selected filter.

Does an ERV replace an air purifier?

No. Its primary function is ventilation and energy recovery.

Does an ERV replace bathroom exhaust?

Not automatically. The mechanical design determines how whole-building ventilation and required local exhaust are provided.

Does an ERV replace a kitchen range hood?

Do not assume so. Cooking exhaust has separate requirements and should be evaluated independently.

Does an ERV control humidity?

It can influence humidity by transferring latent energy, but overall indoor humidity depends on many building and climate factors.

Does every California home need an ERV?

No. Applicability depends on building type, climate zone, ventilation strategy, project scope, and compliance path.

Does Title 24 recognize ERVs?

Yes. The 2025 California Energy Code contains specific ERV and HRV provisions for applicable residential, multifamily, and nonresidential systems.

Are ERVs required in multifamily buildings?

The 2025 prescriptive multifamily requirements specify ERV or HRV systems for certain balanced ventilation configurations in Climate Zones 1, 2, 4, 11–14, and 16.

What recovery efficiency is required?

For the applicable 2025 multifamily prescriptive configurations in those climate zones, the code establishes a minimum sensible recovery efficiency of 67 percent at the specified rating condition. Other projects can have different requirements.

Does fan energy matter?

Yes. California compliance can include fan-efficacy or fan-power requirements in addition to recovery efficiency.

Does an ERV require testing?

Applicable systems can require field verification or acceptance testing of airflow, fan performance, recovery performance, controls, or other characteristics.

What is a fault indicator display?

It is a feature used on applicable dwelling-unit HRV/ERV systems to indicate certain equipment faults. Current California requirements include FID provisions for applicable systems.

Where can an ERV be installed?

Depending on the equipment and design, it may be installed in a mechanical room, utility space, garage, mechanical closet, basement, accessible rooftop location, or another approved location.

Can an ERV be installed in an attic?

Some systems can be, but applicable access, service, manufacturer, and Energy Code requirements must be satisfied.

Does an ERV need maintenance?

Yes. Filters, recovery components, fans, intakes, exhausts, and other components require inspection and maintenance according to the manufacturer.

Why is filter access important?

Dirty filters can reduce airflow and increase fan energy, so the filters need to remain accessible for maintenance.

Does duct design matter?

Yes. Duct resistance can affect airflow, fan power, sound, and the ability of the system to deliver the required ventilation rate.

Can I change ERV models after the Title 24 report is complete?

Potentially, but the proposed replacement should be reviewed when its airflow, recovery efficiency, fan power, controls, or other characteristics differ from the analyzed equipment.

Can an ERV improve a Title 24 performance calculation?

Potentially. Energy recovery can reduce ventilation-related heating or cooling loads, but the actual compliance effect depends on the complete building and system design.

What Energy Code applies now?

For applicable permit applications filed on or after January 1, 2026, California uses the 2025 Building Energy Efficiency Standards.

What should I send AES for an ERV review?

Current plans, mechanical drawings, ventilation calculations, equipment specifications, design airflow, recovery-efficiency information, existing Title 24 calculations, and any building-department corrections are useful starting documents.

How do I get help with an ERV and Title 24?

Call Alternative Energy Systems at (626) 365-1518 and provide the current plans and ventilation-system information for review.