California building code window requirements come from Title 24, the state’s building standards code, which sets rules for egress, fall protection, safety glazing, energy performance, and installation. As of January 1, 2026, the 2025 Energy Code applies to all new permit applications, tightening thermal standards across many of the state’s 16 climate zones.1California Energy Commission. 2025 Building Energy Efficiency Standards Compliance is mandatory for new construction and most replacements, and inspectors check these rules at final sign-off.
Egress Windows in Every Sleeping Room
Every bedroom and any basement with habitable space must have at least one window large enough for an occupant to escape or a firefighter to enter. The California Residential Code sets four minimums that all apply at the same time:2City of East Palo Alto. Residential Emergency Egress Windows Worksheet
- Net clear opening area of at least 5.7 square feet, reduced to 5.0 square feet for grade-level windows that open directly outside
- Minimum clear height of 24 inches
- Minimum clear width of 20 inches
- Maximum sill height of 44 inches above the finished floor
The dimensions trip people up. A window that is exactly 24 inches tall and 20 inches wide produces only about 3.3 square feet of opening, which fails the 5.7-square-foot test. At least one dimension has to exceed its minimum by a comfortable margin. All measurements are taken with the window fully open and any screens removed.
If you install bars, grilles, or security grates over an egress window, they must open from the inside without keys, tools, or special knowledge. Any hardware that could slow a panicked exit at night is a code violation.
Fall Protection on Upper Floors
Separate from egress, the code works to prevent children from falling out. When an operable window sits more than 72 inches above the exterior grade below, the lowest point of the clear opening must be at least 24 inches above the interior finished floor. For any window opening within 24 inches of the floor, the operable section cannot allow a four-inch sphere to pass through.3Tuolumne County. Residential Egress Windows
If a window does not meet the geometry on its own, you have two paths. You can install a window opening control device that limits the initial opening to four inches but releases to allow full escape in an emergency. Or you can add a window guard or fall prevention screen. Either device must meet ASTM F2090, which covers fall prevention for children five and younger while preserving egress.4ASTM International. Standard Specification for Window Fall Prevention Devices With Emergency Escape (Egress) Release Mechanisms F2090-21 The emergency release must work without keys, tools, or excessive force. A device that stops a child from falling but also traps an adult inside a burning room defeats the purpose of having an egress window at all.
Where Safety Glazing Is Required
Certain window locations carry a higher risk of someone walking or falling into the glass, and the code requires tempered or laminated safety glazing in those spots. The common hazardous locations include:
- Glazing within a 24-inch arc of either vertical edge of a door, where the bottom edge sits less than 60 inches above the walking surface5Humboldt County. Guards and Window Fall Protection CRC R3
- Glazing within 60 inches horizontally and vertically of a bathtub or shower drain inlet
- Individual panels where the exposed bottom edge is less than 18 inches above the floor and the top edge is more than 36 inches above the floor
- Glass panels along stairways, landings, and ramps where the bottom edge is less than 60 inches above the walking surface
Safety glazing carries a small permanent etching in one corner identifying the manufacturer, the glass type, and the applicable standard. If you replace glass in any hazardous location, the new pane must be safety glazed regardless of what the original was. California Health and Safety Code Section 25997 reinforces this for all glazing replaced in these locations.
Energy Performance Under the 2025 Code
Title 24, Part 6 governs the thermal performance of every window installed in the state. Two numbers matter most. The U-Factor measures how fast heat escapes through the glass and frame, and the Solar Heat Gain Coefficient (SHGC) measures how much solar radiation the window lets inside. Lower is better on both.
New Construction
For permit applications filed on or after January 1, 2026, the 2025 Energy Code tightened the prescriptive U-Factor for new residential construction.1California Energy Commission. 2025 Building Energy Efficiency Standards The 2022 cycle capped U-Factor at 0.30 everywhere. The 2025 code drops the cap to 0.27 in many cooler and inland climate zones while keeping 0.30 in the rest. SHGC continues to apply in warmer zones, generally capping at 0.23. California has 16 climate zones, and the requirements shift with each one.6California Energy Commission. Climate Zone Tool, Maps, and Information Cooler zones like 1, 3, 5, and 16 have no prescriptive SHGC requirement because blocking solar heat is not a priority where you want the warmth. Warmer zones treat SHGC as a hard limit.
Replacement Windows
Replacement projects get slightly easier treatment up to a point. Replacing up to 75 square feet of window area in an existing home triggers a relaxed prescriptive standard: maximum U-Factor of 0.40 and maximum SHGC of 0.35 in applicable climate zones. Once the replacement area exceeds 75 square feet, or when you are adding entirely new windows, the tighter new-construction numbers apply.7Napa County. Windows, Skylights, and Other Fenestration – Guide to Energy Code Requirements
NFRC Labels
Every new or replacement window must carry a label from the National Fenestration Rating Council certifying its U-Factor, SHGC, visible transmittance, and air leakage.8California Energy Commission. Building Energy Efficiency Standards Inspectors look for these labels at final inspection, and a missing label can fail the inspection even when the window itself performs well. Leave the labels on until the inspector signs off.
Flashing and Installation
A window that meets every thermal and safety spec can still fail in practice if the installation does not manage water. The California Residential Code requires approved, corrosion-resistant flashing applied in a shingle pattern around the entire perimeter. The flashing must tie into either the exterior wall finish or the water-resistive barrier behind it so that water hitting the window drains outward rather than into the wall cavity.
Pan flashing at the sill is mandatory. It catches any water that slips past the window’s weather seal and sends it back outside before it can reach the framing. Skipping the pan is one of the most common installation mistakes, and the damage often hides inside the wall for years before showing up as mold or rot. Air sealing around the gap between the frame and the rough opening is also required to limit moisture migration and energy loss. When the window manufacturer provides installation instructions specifying fastener types and spacing, those instructions govern.
Lead-Safe Work in Pre-1978 Homes
Replacing windows in any home built before 1978 triggers federal lead-safety requirements on top of the California building code. The EPA’s Renovation, Repair, and Painting rule requires the contractor to be a certified renovation firm, with at least one certified renovator on the job who has completed EPA-accredited training.9US EPA. Renovation, Repair and Painting Program – Firm Certification California does not run its own version of this program, so the federal rules apply directly.
The practical impact is real. Before any old window comes out, the work area must be sealed off with plastic sheeting extending at least six feet in every direction for interior work, or 10 feet for exterior work. Warning signs go up, and HVAC ducts in the work area must be sealed shut so lead dust does not circulate. After the work, the certified renovator cleans with a HEPA vacuum and wet-wiping methods, then performs a cleaning verification on every window sill using disposable cloths checked against a standardized verification card. Contractors who skip these steps face fines of up to $37,500 per day per violation, and homeowners who hire uncertified contractors have no regulatory protection if contamination occurs.
When You Need a Permit
Whether your project needs a building permit depends on the scope. Replacing glass within an existing frame, or inserting a vinyl insert without disturbing the existing weather seal, generally counts as maintenance and does not require a permit in most California jurisdictions. Once you remove the entire window including the frame, replace the flashing, change the size of the opening, or cut a new opening in an exterior wall, a permit is required.
Permit fees vary by jurisdiction and commonly run from $75 to several hundred dollars per project. The fee is not the main cost of skipping it. Unpermitted window work can surface during a home sale, trigger a requirement to bring the entire project up to current code, or void homeowner’s insurance coverage for water damage traced to a faulty installation. For any permitted project, the local building department will schedule at least one inspection, typically after installation but before interior trim goes on, so the inspector can verify flashing, fastening, air sealing, and NFRC labels. Build that inspection into the schedule so you are not tearing off trim later.
The Federal Tax Credit No Longer Applies
Homeowners researching window projects will find widespread references to the Section 25C energy efficient home improvement credit, which covered 30% of product cost up to $600 per year for qualifying windows.10Internal Revenue Service. Energy Efficient Home Improvement Credit That credit is gone. Federal legislation terminated Section 25C for any property placed in service after December 31, 2025.11Internal Revenue Service. FAQs for Modification of Sections 25C, 25D, 25E, 30C, 30D, 45L, 45W, and 179D If you installed windows in 2025 or earlier and have not yet claimed the credit, you can still do so on the applicable return. For windows installed in 2026 or later, the federal credit does not apply.