What Is a Cool Roof?

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What Is a Cool Roof is an important question when a California construction project involves new roofing, roof replacement, an addition, new construction, or a Title 24 energy analysis.

A cool roof is a roof designed to reduce the amount of solar heat absorbed by the building.

It does this primarily through roofing materials with properties that can:

• Reflect more incoming solar energy
• Release absorbed heat more effectively
• Reduce roof-surface temperatures compared with less reflective roofing under similar conditions

In California energy compliance, cool-roof performance is commonly described using:

• Solar reflectance
• Thermal emittance
• Solar Reflectance Index

These values allow roofing products to be evaluated by measured performance rather than simply by appearance or color.

A light-colored roof can sometimes have strong cool-roof characteristics, but color alone does not determine compliance.

Likewise, some darker roofing products can be manufactured with solar-reflective characteristics.

For a general background overview, review the cool roof article on Wikipedia.

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

Call (626) 365-1518 if your plans, roofing specifications, Title 24 report, or building-department corrections reference a cool roof and you need help determining how that requirement applies to the project.

A Cool Roof Reduces Solar Heat Gain at the Roof Surface

Roofing receives substantial solar exposure.

When sunlight reaches a conventional roof, part of that solar energy is:

• Reflected away from the roof
• Absorbed by the roofing material
• Transferred into or through the roof assembly
• Released back to the surrounding environment as heat

A cool roof is designed to improve the roof’s response to that solar exposure.

By reflecting a greater portion of incoming solar energy and effectively releasing absorbed heat, the roof can operate at a lower surface temperature than a comparable roof with weaker solar-performance characteristics.

Cool Roof Performance Is About Measured Properties

A roof should not be called code-compliant simply because it looks reflective.

California energy compliance relies on rated roofing-product characteristics.

Relevant information can include:

• Initial solar reflectance
• Aged solar reflectance
• Thermal emittance
• Solar Reflectance Index
• Roof slope
• Product certification

The correct values should correspond to the actual roofing product proposed for the project.

What Is Solar Reflectance?

Solar reflectance describes the portion of incoming solar energy that a surface reflects rather than absorbs.

A roofing material with greater solar reflectance can send more solar energy away from the roof surface.

This characteristic can reduce the amount of solar heat absorbed by the roof.

For California Energy Code purposes, the applicable value may be an aged solar reflectance rather than only the initial value measured when the product is new.

Why Does Aged Solar Reflectance Matter?

Roofing materials can change as they are exposed to:

• Sunlight
• Weather
• Dirt
• Dust
• Other outdoor conditions

Aged solar reflectance provides information about expected reflective performance after weathering rather than relying only on a new product’s initial performance.

This allows energy requirements to consider longer-term roofing characteristics.

What Is Thermal Emittance?

Thermal emittance describes a surface’s ability to release absorbed heat.

This is different from solar reflectance.

Solar reflectance concerns how much incoming solar energy is reflected.

Thermal emittance concerns how effectively absorbed heat can be emitted from the roofing surface.

Both characteristics can influence roof temperature.

What Is Solar Reflectance Index?

Solar Reflectance Index, commonly called SRI, combines solar reflectance and thermal emittance into a single roof-performance indicator.

California allows SRI to be used in applicable situations as an alternative method of demonstrating prescribed roof-surface performance.

This can provide flexibility because different combinations of reflectance and emittance can produce an acceptable SRI.

How Cool Roof Performance Is Measured

Solar Reflectance and Thermal Emittance Work Together

The performance of a cool roof cannot be judged reliably by looking at the material alone.

California uses rated product information so architects, consultants, contractors, building departments, and property owners can identify how a roofing product performs.

Who Rates Cool-Roof Products?

The California Energy Code uses roofing-product ratings associated with the Cool Roof Rating Council, commonly called the CRRC.

Applicable roofing products used for cool-roof compliance are certified and labeled so their rated properties can be identified.

A product label can contain information such as:

• Solar reflectance
• Thermal emittance
• Weathered or aged performance
• Product identification

The roofing material shown in the Title 24 documentation should correspond to the product ultimately installed.

Why Is the Product Label Important?

The label helps distinguish tested roofing performance from advertising claims.

A product may be described using words such as:

• Reflective
• Energy efficient
• Heat resistant
• Solar reflective

Those descriptions alone do not establish the values needed for Energy Code compliance.

The rated information provides measurable data that can be compared with the applicable requirements.

Does a Cool Roof Have to Be White?

No.

White roofing materials are commonly associated with high solar reflectance, especially on low-sloped roofs, but cool-roof products are not limited to white.

Manufacturers can produce roofing materials in a variety of colors and types.

Depending on the product, reflective pigments or other technologies can improve solar performance while maintaining a different appearance.

The important issue for compliance is the rated product performance, not simply whether the roof appears white.

Can a Dark Roof Be a Cool Roof?

Potentially.

A darker roofing product can have solar-performance characteristics that differ substantially from another product of a visually similar color.

That is why the rated solar reflectance, thermal emittance, or SRI should be checked instead of making a decision based entirely on appearance.

What Types of Roofing Can Be Cool Roofs?

Cool-roof characteristics can be available in several roofing categories.

Depending on the building and roof design, products can include:

• Roof membranes
• Roof coatings
• Metal roofing
• Roof tiles
• Shingles
• Other qualifying roofing products

Not every product within these categories automatically qualifies for a particular Energy Code requirement.

The specific rated product should be checked.

Does Roof Slope Matter?

Yes.

California distinguishes between low-sloped and steep-sloped roofs for various Energy Code provisions.

Roof slope can affect:

• Which cool-roof criteria apply
• Applicable reflectance requirements
• Applicable SRI requirements
• Available exceptions
• Prescriptive compliance options

Do not assume that a roofing product appropriate for one roof configuration automatically satisfies the requirements for another.

What Is a Low-Sloped Roof?

California Energy Code provisions define roof-slope categories using the relationship between vertical rise and horizontal run.

Low-sloped roofs are commonly associated with commercial buildings, multifamily buildings, and some residential designs.

They often use:

• Single-ply membranes
• Built-up roofing
• Modified bitumen
• Roof coatings
• Other low-slope roofing systems

The applicable Title 24 requirements depend on the project.

What Is a Steep-Sloped Roof?

Steep-sloped roofs are common on houses and other buildings using pitched roof construction.

Common roofing can include:

• Composition shingles
• Tile
• Metal roofing
• Other pitched-roof products

The cool-roof criteria for steep-sloped construction can differ from those applied to low-sloped roofs.

Cool Roof Ratings Depend on the Actual Roofing Product

Roof Slope, Product Type and Climate Zone Can Change the Requirements

California does not apply one identical cool-roof requirement to every roof.

The project must be evaluated according to the applicable Energy Code provisions.

Factors can include:

• Single-family, multifamily, or nonresidential building type
• New construction
• Addition
• Alteration
• Roof replacement
• Roof slope
• Climate zone
• Prescriptive or performance compliance

How Does Climate Zone Affect Cool-Roof Requirements?

California contains 16 building climate zones.

These zones reflect regional differences in heating, cooling, temperature, and other climate conditions.

Because roof solar performance can have different effects in different climates, cool-roof requirements can vary according to project location.

The same roofing product should therefore not automatically be assumed to satisfy every project in every California climate zone.

For additional information, review why Title 24 standards vary by climate zone.

Does Building Type Matter?

Yes.

California Energy Code requirements distinguish among:

• Single-family buildings
• Multifamily buildings
• Nonresidential buildings

A roofing requirement associated with a commercial building should not automatically be applied to a single-family house without checking the applicable standards.

Likewise, multifamily projects have their own current compliance provisions.

Is a Cool Roof Required on Every California Building?

No.

A universal statement that every California building must have a cool roof would be inaccurate.

The current Energy Code contains project-specific prescriptive requirements, exceptions, alternative compliance methods, and performance approaches.

Whether a cool roof is required or used for compliance can depend on:

• Climate zone
• Building type
• Roof slope
• Roof construction
• Project scope
• Compliance approach

The project should be evaluated before a roofing specification is finalized.

Can Performance Compliance Allow a Different Roof?

Potentially.

For applicable projects using performance compliance, a proposed roof can sometimes have different characteristics from the prescriptive values when the complete building still satisfies the applicable energy-performance requirements.

That does not mean every roof choice will work.

The effect needs to be evaluated through the applicable Title 24 calculation.

Other building features may need to provide sufficient energy performance to offset a roof that does not follow the basic prescriptive configuration.

Can Additional Insulation Affect Cool-Roof Compliance?

In some applicable roof configurations, the Energy Code provides insulation-related tradeoffs or exceptions.

This is particularly important because roof energy performance involves more than exterior surface color.

The complete roof assembly can include:

• Roofing material
• Roof deck
• Continuous insulation
• Cavity insulation
• Attic space
• Ceiling insulation

The correct compliance strategy should be determined from the applicable code requirements rather than assumed from one component alone.

Can Solar Panels Affect the Cool-Roof Requirement?

Certain Energy Code provisions contain exceptions for roof areas occupied by qualifying building-integrated photovoltaic or solar-thermal systems.

The exact treatment depends on the building and code provision.

Standard rooftop solar panels and building-integrated products should not automatically be treated as identical.

The actual roof design needs to be reviewed.

Can Heavy Roof Construction Affect the Requirement?

Some California Energy Code provisions include exceptions for qualifying high-mass roof construction.

These provisions are project-specific.

Do not assume that tile, concrete, stone, or another heavy material automatically creates an exception without confirming the required construction and applicable code section.

How Does a Cool Roof Relate to Title 24?

California Requirements Vary by Building, Roof and Compliance Method

A cool roof can be one component of a California energy-compliance design.

It may appear in:

• Prescriptive requirements
• Performance calculations
• Roof-alteration requirements
• Compliance forms
• Architectural roof specifications

The Title 24 report and construction plans should agree on the roofing performance used for compliance.

What Happens if the Title 24 Report Specifies a Cool Roof?

If the energy documentation relies on a cool roof, the roofing installed during construction should meet the specifications represented in that analysis.

The project team should verify:

• Roofing product
• Rated solar reflectance
• Thermal emittance
• SRI when applicable
• Roof slope
• Applicable certification information

Installing a substantially different roofing product can create a mismatch between the approved calculations and construction.

Can I Change the Roof After the Calculations Are Finished?

Potentially, but the calculation should be reviewed when the change affects an energy characteristic represented in the approved design.

A roofing substitution can change:

• Solar reflectance
• Thermal emittance
• SRI
• Roof assembly
• Insulation strategy

A product that appears similar visually may not have the same rated characteristics.

Can I Remove a Cool-Roof Requirement From My Project?

Possibly, depending on the project and available compliance options.

However, do not remove the requirement from the plans without checking the energy analysis.

If the roof characteristics are part of the compliant design, another measure or revised calculation may be necessary.

For more information about how project features interact, review Title 24 energy calculations.

Can I Add a Cool Roof to Improve Energy Performance?

A higher-performing roofing product can potentially improve roof-related energy performance.

Whether that change materially affects a Title 24 calculation depends on:

• Building type
• Climate zone
• Roof area
• Roof slope
• Other envelope features
• Compliance method

The effect should be evaluated within the complete project.

What Code Is Currently Used?

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

The 2025 Energy Code includes current roof-envelope requirements for residential, multifamily, and nonresidential buildings.

For official information, review the California Energy Commission 2025 Building Energy Efficiency Standards.

The 2025 Code Includes Cool-Roof Compliance Documentation

The current California compliance materials include provisions and forms relating to roof-envelope performance.

For single-family projects, the California Energy Commission provides a Solar Reflectance Index calculation worksheet among the current envelope compliance documents.

The exact documents required depend on the project.

Why Should the Plans and Energy Report Match?

The architectural plans may identify:

• Roofing type
• Roof slope
• Roof color or finish
• Roof insulation
• Roof assembly

The energy analysis can use corresponding performance values.

If those documents describe different roofing systems, the building department may request clarification or revision.

What About Cool Roofs on Existing Buildings?

Roof Replacement, Roof Recover and Repair Are Not Always Treated the Same

Existing-building roofing work can be subject to different requirements depending on the scope.

California distinguishes among different types of roofing work.

These can include:

• Roof replacement
• Roof recover
• Roof recoating
• Roof repair

The scope matters because a limited repair is not necessarily treated the same as replacing a substantial portion of the roof.

What Is a Roof Replacement?

A roof replacement generally involves removal of the existing roof covering followed by repair of the substrate as needed and installation of a new roof covering.

When an applicable replacement triggers Energy Code requirements, roofing characteristics may need to comply with current provisions.

What Is a Roof Recover?

A roof recover places an additional roofing layer over an existing prepared roof covering rather than removing the existing covering entirely.

Applicable Energy Code treatment can differ according to:

• Building type
• Roof slope
• Area affected
• Climate zone
• Existing construction

What Is a Roof Recoat?

A roof recoat generally involves application of a fluid-adhered coating as part of roof maintenance or repair.

Roof coating products can also have solar-reflective properties.

However, the project scope and applicable code provisions should be reviewed before assuming that recoating creates the same requirements as complete roof replacement.

Does Every Roof Repair Need a Cool Roof?

No.

Limited roof repairs can be treated differently from qualifying roof replacements or alterations.

The amount of roof area being changed and the nature of the work can matter.

The project should be evaluated based on what is actually being replaced rather than simply using the word “roofing” for every scope.

Does Reroofing Trigger Title 24?

It can.

Applicable reroofing work can trigger Energy Code requirements for roofing products and, depending on the project, other roof-envelope measures.

However, requirements differ among:

• Single-family buildings
• Multifamily buildings
• Nonresidential buildings
• Low-sloped roofs
• Steep-sloped roofs
• Different climate zones

Do not assume that every reroof requires the same cool-roof product.

What if My Existing Roof Does Not Meet Current Cool-Roof Values?

An existing roof is not automatically required to be replaced merely because a newer Energy Code exists.

Current requirements generally become relevant according to the work being performed.

If the roof is being altered or replaced, the new work should be reviewed under the applicable current requirements.

Can Existing Insulation Affect a Roof Alteration?

Potentially.

Current Energy Code provisions can consider existing or proposed roof insulation in certain alteration situations.

This is why the complete roof assembly should be reviewed rather than looking only at the exterior roofing material.

What Information Should I Provide for a Reroofing Project?

Useful information can include:

• Building type
• Project address
• Roof plan
• Roof slope
• Existing roofing
• Proposed roofing product
• Roof area being replaced
• Existing insulation
• Proposed insulation
• Existing Title 24 documentation
• Building-department correction comments

AES can review the energy-compliance implications of the proposed scope.

Cool Roof vs. Radiant Barrier and Insulation

These Roof Measures Work in Different Ways

A cool roof, radiant barrier, and thermal insulation can all influence heat transfer through a roof system, but they do not perform the same function.

Cool Roof vs. Radiant Barrier

A cool roof works at or near the exterior roof surface.

Its performance is associated with how the roofing responds to solar energy.

A radiant barrier is generally located below the exterior roof surface within the roof-and-attic assembly.

Its purpose is to reduce radiant heat exchange within that assembly.

The two measures therefore address different stages of heat transfer.

Can a Building Have Both?

Yes.

A roof-and-attic system can potentially include:

• A cool-roof exterior surface
• A radiant barrier below the roof deck
• Ceiling or roof insulation

Whether all of those measures are necessary depends on the project.

For additional information, review the related page on What Is a Radiant Barrier.

Cool Roof vs. Insulation

Roof or ceiling insulation resists conductive heat flow through the building envelope.

A cool roof instead changes how the exterior roof surface responds to solar radiation.

One should not automatically be substituted for the other.

However, certain Energy Code provisions can allow specific tradeoffs involving roof insulation and solar reflectance.

Does a Cool Roof Eliminate the Need for Insulation?

No general rule allows a cool-roof product to replace all required roof or ceiling insulation.

Insulation requirements remain part of the applicable building-envelope design.

The exact assembly should follow the Title 24 analysis and construction plans.

Does a Cool Roof Eliminate the Need for a Radiant Barrier?

Not automatically.

The two measures address different heat-transfer mechanisms.

Whether a radiant barrier is required or modeled separately depends on the project and compliance strategy.

Does a Cool Roof Guarantee Lower Energy Bills?

No specific utility savings should be guaranteed.

Actual energy use depends on many factors, including:

• Climate
• Roof area
• Building orientation
• Insulation
• Windows
• HVAC efficiency
• Duct conditions
• Occupant behavior
• Thermostat settings

A cool roof is one building-envelope measure rather than a guarantee of a particular energy bill.

Can a Cool Roof Reduce Roof Temperature?

A roofing material with stronger solar reflectance and thermal emittance can operate at a lower surface temperature than a less reflective product under comparable solar conditions.

The actual temperature difference varies with:

• Sun exposure
• Weather
• Roof material
• Roof color
• Rated performance
• Building configuration

Can a Cool Roof Help Reduce Cooling Loads?

Reducing solar heat absorbed at the roof can reduce heat entering the roof assembly.

How much that affects cooling demand depends on the complete building.

The Title 24 performance method can evaluate the roof together with other building features when applicable.

Is a Cool Roof Always Better in Every Climate?

Not necessarily in exactly the same way.

California’s use of climate zones recognizes that buildings experience different heating and cooling conditions.

That is why cool-roof requirements vary instead of applying one identical roof specification throughout the state.

Need Help With a Cool Roof or Title 24 Roof Requirement?

Call (626) 365-1518 | Alternative Energy Systems

If your Title 24 report, construction plans, roofing contractor, architect, or building department references a cool roof, AES can review the energy-compliance side of the project.

Useful documents can include:

• Current construction plans
• Roof plans
• Building sections
• Roof slope
• Roofing-product specifications
• CRRC product information when available
• Insulation information
• Existing Title 24 calculations
• Building-department corrections

What if My Contractor Wants to Substitute a Different Roof?

Send the proposed roofing information for review before assuming it is equivalent.

Useful product information can include:

• Manufacturer
• Product name
• Color
• Rated solar reflectance
• Rated thermal emittance
• SRI when applicable

AES can compare the proposed change with the existing energy documentation.

What if My Plans Do Not Show the Cool-Roof Requirement?

If the Title 24 analysis depends on a particular roofing characteristic, the plans should be coordinated so the construction team can identify what needs to be installed.

A mismatch between the report and architectural plans can create:

• Plan-check questions
• Product-ordering mistakes
• Construction changes
• Energy-report revisions

What if the Building Department Requests a Correction?

Send AES:

• The complete correction notice
• The latest plans
• The existing energy report
• The proposed roofing specifications
• Any revised roof details

AES can determine whether the correction requires:

• A product clarification
• Updated roof values
• Revised Title 24 calculations
• Updated forms
• Coordination with the architectural plans

What Information Is Needed Before Title 24 Calculations Are Updated?

For broader project-document requirements, review what AES will need from you.

Energy calculations should be based on the actual proposed roof rather than an assumed product that will later be replaced.

Why Choose Alternative Energy Systems?

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

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

• New residential construction
• ADUs
• Garage conversions
• Additions
• Residential remodels
• Multifamily projects
• Mixed-use projects
• Commercial construction
• Tenant improvements
• Roof alterations
• Energy-related plan-check corrections

AES evaluates the actual project rather than assuming that every roof in California has the same cool-roof requirement.

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

Understanding What Is a Cool Roof comes down to measurable roof-surface performance.

A cool roof is designed to reflect more incoming solar energy and release absorbed heat effectively.

For Title 24 purposes, however, the important question is not simply whether a roofing product is marketed as “cool.”

The project must use the correct:

• Roof classification
• Climate zone
• Rated roofing values
• Compliance method
• Applicable Energy Code requirements

Alternative Energy Systems can review your project plans, roofing specifications, existing Title 24 calculations, and building-department comments to determine how the proposed roof should be represented in the energy documentation.

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 a Cool Roof?

What Is a Cool Roof?

A cool roof is a roofing system designed to reflect more incoming solar energy and effectively release absorbed heat compared with roofing products that have weaker solar-performance characteristics.

How does a cool roof work?

It reduces solar heat absorption through roofing characteristics such as solar reflectance and thermal emittance.

What is solar reflectance?

Solar reflectance describes the portion of incoming solar energy that a roofing surface reflects rather than absorbs.

What is aged solar reflectance?

Aged solar reflectance represents roofing reflectance after weathering rather than only the product’s initial performance.

What is thermal emittance?

Thermal emittance describes how effectively a surface releases absorbed heat.

What is SRI?

Solar Reflectance Index combines solar reflectance and thermal emittance into a roof-performance indicator that can be used in applicable compliance situations.

Does a cool roof have to be white?

No. Roofing products of different colors can have qualifying solar-performance characteristics.

Can a dark roof qualify?

Potentially. The rated product values matter more than visual color alone.

Who rates cool-roof products?

California Energy Code compliance uses applicable roofing-product ratings and labeling associated with the Cool Roof Rating Council.

Does every California roof need to be a cool roof?

No. Requirements vary according to building type, climate zone, roof slope, project scope, and compliance method.

Does Title 24 require a cool roof?

Title 24 contains cool-roof requirements for applicable projects, but those requirements are not identical for every building or roof.

Does climate zone matter?

Yes. California’s roof requirements can vary among its 16 building climate zones.

Does roof slope matter?

Yes. Low-sloped and steep-sloped roofs can have different applicable requirements.

What is a low-sloped roof?

It is a roof within the Energy Code’s lower-slope classification. The exact classification should be determined from the applicable code definition.

What is a steep-sloped roof?

California identifies steep-sloped roofs separately from low-sloped roofs, and different prescriptive requirements can apply.

Do residential and commercial buildings have the same cool-roof requirements?

No. Single-family, multifamily, and nonresidential buildings can have different applicable provisions.

Can performance compliance allow a different roofing product?

Potentially. In applicable performance projects, the complete building can be evaluated when the proposed roof differs from the prescriptive configuration.

Can additional insulation affect the roof requirement?

Certain Energy Code provisions provide applicable insulation tradeoffs or exceptions, depending on the project.

Can solar panels affect cool-roof requirements?

Certain code provisions include exceptions for qualifying building-integrated photovoltaic or solar-thermal roof areas.

Does reroofing trigger cool-roof requirements?

It can. The applicable requirements depend on building type, climate zone, roof slope, area affected, and the type of roofing alteration.

Does a small roof repair require a cool roof?

Not every limited repair is treated the same as an applicable roof replacement or alteration.

Can I use any reflective roof coating?

Do not assume so. The product should have the appropriate rated characteristics when it is being used for Energy Code compliance.

Can I change the roof product after my Title 24 report is completed?

Potentially, but the report should be reviewed when the new product has different solar reflectance, thermal emittance, SRI, or other relevant characteristics.

Can a cool roof replace insulation?

No universal rule allows a cool roof to replace all required insulation. The complete roof assembly must meet applicable Energy Code requirements.

Is a cool roof the same as a radiant barrier?

No. A cool roof works at the exterior roof surface, while a radiant barrier typically reduces radiant heat transfer within the roof-and-attic assembly.

Can a building have both a cool roof and radiant barrier?

Yes, depending on the building design and energy-compliance strategy.

Does a cool roof guarantee lower utility bills?

No. Actual energy use depends on the complete building, climate, HVAC systems, insulation, occupancy, and other factors.

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 a roof review?

Current plans, roof plans, roof slope, proposed roofing specifications, insulation information, existing Title 24 calculations, and any building-department corrections are useful starting documents.

How do I get help with a cool-roof requirement?

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