Title 24 §110.6 Mandatory Measures for Windows: What Every California Project Must Meet in 2026

If you are an architect, general contractor, property manager, or energy consultant working on a California building in 2026, there is one part of the energy code you cannot design your way around: the mandatory measures in Title 24, Part 6, Section 110.6. Everything else in Title 24 has flexibility built into it. The prescriptive path lets you trade one component against another. The performance path lets a whole-building energy model absorb a weak spot in the envelope. Section 110.6 does not bend. It is the floor that every window, skylight, glass door, and field-applied window film in the building must clear before any other compliance conversation begins.

At Rapid Window Tinting, 5300 Sunset Boulevard in Los Angeles, we spend a large share of our commercial calendar helping owners and their design teams hit these numbers on retrofit and tenant-improvement projects across LA County. This guide walks through what Section 110.6 actually requires for fenestration, what the air infiltration and NFRC rating limits mean in plain language, where the default value tables come into play, and how a properly certified window film satisfies the mandatory measures on an existing building. Where a specific numeric cell is code-year sensitive, we flag it for verification against the current 2025 California Energy Code rather than repeating a number that may have changed cycle to cycle.

What Title 24 §110.6 actually is, and why it is the floor

California's Building Energy Efficiency Standards live in Title 24, Part 6 of the California Code of Regulations. Within that document, the sections in the §110 range are the "mandatory measures": requirements that apply to essentially all buildings, in every climate zone, regardless of which compliance path the project uses. Section 110.6 is the mandatory measure that governs fenestration, which is the code's word for any glazed opening in the building envelope: vertical windows, glass doors, skylights, and the site-built or manufactured assemblies that hold them.

The reason §110.6 is described as a floor is structural to how the code works. A project can demonstrate compliance through the prescriptive path, which is a checklist of component-by-component requirements, or through the performance path, which uses approved energy modeling software to show the whole building performs at least as well as a prescriptive baseline. The performance path is powerful because it lets a design trade a heavily glazed south face against, say, a high-efficiency HVAC system. But no amount of modeling lets a project skip the mandatory measures. Even a building that sails through a performance analysis still has to prove every window meets §110.6. That is why we tell design teams to confirm the mandatory numbers first and treat the prescriptive or performance decision as a second, separate question.

For anyone comparing this to the federal framework, §110.6 is roughly analogous to the mandatory glazing provisions layered on top of the IECC, but California sets and certifies its own values through the California Energy Commission (CEC) and leans heavily on the National Fenestration Rating Council (NFRC) for the underlying test procedures. If you want the wider context on how these rules change by region, our complete Title 24 window film guide breaks down all three compliance paths in one place.

The air infiltration limit and what it means for window film

The first mandatory requirement in §110.6 that surprises people is air leakage. Manufactured fenestration products and exterior doors must be certified to an air infiltration rate no greater than 0.3 cfm per square foot of fenestration area. That value is established using the NFRC 400 procedure, which in turn is built on the ASTM E283 test method, measured at a pressure differential of 75 pascals (about 1.57 pounds per square foot). In practice, this is a product-certification requirement met by the window or door manufacturer, and it shows up on the product's rating documentation.

Where this matters for a window film project is in what film does and does not change. Applying a solar control or security film to existing glass does not alter the air infiltration rating of the window assembly, because film is applied to the surface of the glazing and does not touch the seals, the frame, or the operable hardware that actually govern air leakage. So on a retrofit, the air infiltration clause is generally satisfied by the existing certified assembly, and the film conversation moves to the thermal and solar numbers. It is still worth confirming the base window is a rated assembly, because a small number of older LA commercial buildings have site-built glazing with no infiltration certification on file, and that becomes the plan-checker's question, not the film's.

The NFRC ratings §110.6 relies on: U-factor, SHGC, and VT

The heart of §110.6 is three performance metrics, each with its own NFRC rating procedure. The U-factor measures how readily heat conducts through the whole assembly; lower is better for keeping conditioned air inside, and it is rated under NFRC 100. The Solar Heat Gain Coefficient (SHGC) measures the fraction of solar energy that passes through and becomes heat in the space; lower means less unwanted summer heat, and it is rated under NFRC 200. Visible Transmittance (VT), also addressed through the NFRC 200/300 procedures, measures how much daylight comes through, which matters for glare and for daylighting credits elsewhere in the code.

Section 110.6 requires that fenestration have an NFRC-rated U-factor and SHGC, determined and labeled according to those procedures, or that the project use the CEC default values described below when a rating is not available. For a new manufactured window, the numbers come straight off the NFRC label. For field-applied window film on existing glass, the relevant path is the film manufacturer's NFRC-certified performance data for the specific film-plus-glass combination, which is exactly the documentation a reputable commercial film carries. When a design team is weighing solar control against daylight, this is the trade to watch: pushing SHGC down aggressively with a darker film also pulls VT down, and the code and the tenants both care about the balance. Our team walks LA property managers through that trade during any commercial window film assessment.

Default values: Tables 110.6-A and 110.6-B

The code recognizes that not every product on every job will carry a full NFRC label, so §110.6 points to default value tables. Table 110.6-A provides default U-factors, and Table 110.6-B provides default SHGC and VT values, organized by frame type, glazing layers, and product category. If a fenestration product does not have an NFRC-certified rating, the project must use the applicable default from these tables, and the defaults are deliberately conservative, meaning they assume worse performance than a typical rated product would actually deliver.

The practical takeaway is that defaults are a fallback, not a strategy. Because they are conservative, leaning on default values usually makes prescriptive compliance harder and can push an otherwise fine design into needing the performance path. On film retrofits this is the single biggest reason we push for NFRC-certified film data: certified numbers let the project claim the film's real, tested SHGC and U-factor improvement instead of a punitive default. One caution for design teams reading this in 2026: the exact numeric cells inside Tables 110.6-A and 110.6-B are code-cycle sensitive and were adjusted between the 2022 and 2025 editions. Do not lift a figure from an older reference. Pull the current cell from the 2025 California Energy Code document published by the CEC and, if there is any doubt on a specific product line, flag it for the energy consultant to verify before it goes on a form.

Certification: the NFRC label, CEC defaults, and field-applied film

Section 110.6 also carries a certification and labeling requirement. Manufactured fenestration must be certified and labeled with its NFRC ratings so that a plan-checker or field inspector can verify the values that were entered on the compliance documents. For site-built fenestration and for some assemblies, the code provides alternative certification routes, but the through-line is the same: the number on the compliance form has to be traceable to either an NFRC certification or an approved default.

Field-applied window film sits in a specific and well-established place in this framework. Retrofit film products used for Title 24 compliance carry NFRC-certified ratings for defined film-and-glass combinations, and the film installer provides certificate documentation showing the post-film U-factor and SHGC. That certificate is what lets the film's improvement count on the envelope forms. When we quote a compliance-driven job, that paperwork is part of the deliverable, not an afterthought, and it is one of the reasons owners choose an established Los Angeles window film shop rather than a general handyman for code work.

How NFRC-certified window film satisfies §110.6

On an existing commercial building, the mandatory measures are met the same way they are for new glazing: by showing the assembly's U-factor and SHGC, as modified by the film, meet or beat the value entered for compliance, backed by NFRC-certified data. The film does not change air infiltration, so that clause rides on the base assembly. What the film changes, and documents, is solar heat gain and, to a smaller degree, the effective U-factor of the glazing, particularly with low-emissivity films that add a heat-reflective layer.

Among the products we specify for §110.6 retrofits, XPEL Vision's commercial line is our first recommendation on premium owner-occupied and mixed-use projects. XPEL Vision Clear View Plus is a high-clarity, non-metallic solar film that is frequently cited with visible light transmission around 42, 59, and 72 percent across its three shades, total solar energy rejected in roughly the mid-50s to about 60 percent, and SHGC values in the neighborhood of 0.40 to 0.45. We flag those numbers for verification against the current XPEL Vision spec sheet before any of them lands on a compliance form, because published values are revised and the certified figure for your exact glass is what the code cares about. XPEL's non-metallic construction is a genuine advantage in signal-sensitive buildings, since it will not interfere with cellular, Wi-Fi, or GPS the way some sputtered metallic films can. Where a project needs a different balance, we are equally comfortable specifying 3M Prestige, Solar Gard, or SunTek, and we say so plainly rather than forcing one brand onto every job.

The five most common §110.6 plan-check failures we see in Los Angeles

First, entering default values by habit when a certified rating exists. This throws away real performance and can tip a borderline design onto the performance path unnecessarily. Second, mixing code cycles, where a U-factor or SHGC figure from an older reference is dropped into a 2025-code project. Third, treating a window film's marketing numbers as if they were NFRC-certified compliance data; the two are not interchangeable, and a plan-checker will ask for the certificate. Fourth, forgetting that the mandatory measures still apply on a performance-path project, so teams model the building beautifully and then get flagged because a single window does not carry a rating. Fifth, assuming that because film does not affect air infiltration, the base window's infiltration certification does not need to exist at all; on older site-built glazing, that certification sometimes has to be established.

None of these are exotic. They are paperwork and sequencing failures, and every one of them is avoidable with the right documentation gathered before submittal. That is precisely the gap a specialized film partner fills on a compliance job, and it is why we bundle the certificates, the product data, and the form-ready values into a single package for the design team. You can see the full scope of what we handle on our services overview.

Where XPEL Vision fits for a §110.6-compliant retrofit

For most Los Angeles commercial retrofits driven by §110.6, the winning move is a certified, high-transmission solar film that lowers SHGC meaningfully while preserving daylight and, in signal-sensitive tenancies, staying fully non-metallic. XPEL Vision Clear View Plus fits that description on premium and owner-occupied buildings, and it pairs naturally with XPEL's integrated commercial and paint-protection accounts when a property owner also runs a fleet. On budget-sensitive or heavily west-facing elevations where maximum rejection matters more than clarity, we will often model a Dual Reflective option or a competitor's high-rejection film and let the numbers, not the logo, make the call.

The honest framing we give every owner is this: §110.6 is a pass/fail floor, and once you clear it, the interesting decisions are about occupant comfort, glare, fading, energy cost, and how the glass looks from the street. That is where film choice earns its keep, and where an experienced installer is worth far more than the few dollars per square foot that separate one product from another. If you are comparing what different films actually cost installed in LA, our window film pricing page is a useful starting point before you request a formal assessment.

What does Title 24 Section 110.6 require for windows?

Section 110.6 is California's mandatory measure for fenestration. It requires that windows, glass doors, and skylights have a certified air infiltration rate no greater than 0.3 cfm per square foot, an NFRC-rated U-factor and Solar Heat Gain Coefficient (or an approved default value), and proper certification and labeling so the ratings can be verified. It applies to every project regardless of climate zone or compliance path.

Does window film help a building meet Title 24 §110.6?

Yes. NFRC-certified retrofit window film lowers the Solar Heat Gain Coefficient of existing glass and, with low-emissivity films, can improve the effective U-factor, both of which are documented on the film manufacturer's certificate. That certified improvement is what counts toward the mandatory measures on an existing building. Film does not change air infiltration, so that clause rides on the base window assembly. Rapid Window Tinting in Los Angeles supplies the certificates and form-ready values with the install.

What is the air infiltration limit in Title 24 for windows?

Manufactured fenestration and exterior doors must be certified to an air infiltration rate of no more than 0.3 cfm per square foot, tested under NFRC 400, which is based on ASTM E283 at a pressure difference of 75 pascals. This is met by the window manufacturer's certification, and applying window film does not affect it.

What are Tables 110.6-A and 110.6-B?

They are the default value tables in Title 24. Table 110.6-A gives default U-factors and Table 110.6-B gives default Solar Heat Gain Coefficient and Visible Transmittance values for fenestration that does not carry an NFRC-certified rating. The defaults are intentionally conservative, so using them usually makes compliance harder than claiming a product's real certified numbers. Verify the current cells against the 2025 California Energy Code.

Do the Title 24 mandatory measures apply if I use the performance path?

Yes. The mandatory measures in §110.6 apply to every project no matter which compliance path you choose. Even a building that passes a whole-building performance energy model still has to show that each window meets the mandatory fenestration requirements. Modeling can trade off many things, but it cannot waive the mandatory measures.

Get a free Title 24 compliance assessment

If you are scoping a retrofit or tenant improvement in Los Angeles and need the glazing to clear §110.6 without derailing the schedule, we can help you get the certified numbers and paperwork right the first time. Rapid Window Tinting, 5300 Sunset Blvd, Los Angeles, CA 90027, (323) 358-2520, offers a free Title 24 compliance assessment for commercial owners and their design teams. Schedule your Free Title 24 Compliance Assessment and we will review your glazing, recommend a certified film, and hand your energy consultant form-ready values.

This article is educational and reflects our reading of the 2025 California Energy Code as an XPEL-authorized commercial film installer; it is not a substitute for a licensed energy consultant's compliance analysis. Verify all specific numeric values against the current CEC documentation for your project.