Windows and Building Envelope

The building envelope is where size, climate zone and project type change the numbers most. These pages cover each component: windows, insulation, roofs, walls, floors and skylights.

Windows and Doors

Replacing one window or all of them, doors, labels, glass, film and shading.

• Do New Windows Need Title 24?
• Title 24 Exterior Door Requirements
• Title 24 Outdoor Lighting Rules for Homes
• Title 24 Aluminum Windows: Do They Comply?
• Glass Block Windows Under Title 24: Defaults, Labels and Averaging
• Windows in a Wildfire Zone: Vinyl, Aluminum and Title 24

View all Windows and Doors answers (25) →

U-Factor and SHGC

What the two window numbers mean, the limits by climate zone and which one matters for your project.

• Title 24 U-Factor vs SHGC: Which Number Matters?
• Dynamic Glass and Electrochromic Windows Under Title 24
• Mixing Window Types: How the Area-Weighted Average Works and What to Do When One Misses
• Are Double-Pane and Low-E Windows Required in California?
• Where Window U-Factor and SHGC Appear: CF1R, Plan Set, Label and Installer Certificate

View all U-Factor and SHGC answers (5) →

Insulation

Attic and ceiling insulation, spray foam, radiant barriers and quality installation.

• Which Wall Assembly Meets Title 24?
• Does an Attic Conversion Need Title 24?
• Vaulted Ceiling Insulation Under the 2025 Energy Code
• Cathedral Ceiling Insulation Under the 2025 Energy Code
• What Is Quality Insulation Installation (QII)?
• Title 24 for an Older Home With Unknown Insulation

View all Insulation answers (23) →

Roofs

Reroofing, cool roofs and what replacing a roof triggers.

• Title 24 Re-Roofing and Cool Roof Requirements
• Do I Need Title 24 for a Roof Replacement?
• Are Your Shingles Title 24 Compliant?
• Coating a Flat Roof: Title 24 Rules for Liquid-Applied Roof Coatings
• Cool Roof Requirements When Reroofing a House
• Solar Roof Tiles and Shingles: Do They Need a Cool Roof Rating?

View all Roofs answers (9) →

Walls

Wall insulation, siding and stucco work and what altering a wall triggers.

• Kneewall Insulation Under Title 24: R-Value, Air Barrier and What QII Checks
• Advanced Framing and 24-Inch Stud Spacing: How Title 24 Counts Wall Insulation
• Window and Door Header Insulation: R-3, R-5 and the Four QII Header Designs
• Insulating the Wall Between the House and an Attached Garage
• Commercial Air Barrier Under Title 24: The 25 Percent Wall Alteration Rule
• QII Hard-to-Insulate Spots: Corners, Tub Walls, Bump-Outs and Steel Framing

View all Walls answers (7) →

Floors and Slabs

Raised floors, crawl spaces and slab edges in additions and conversions.

• Cantilevered Floors and Overhangs: Floor Insulation Under Title 24
• Rim and Band Joist Insulation: Where Title 24 Wants It
• Do I Need a Vapor Barrier in California? Crawl Space, Walls and Attics
• Slab Floor Title 24 Requirements for Additions and Conversions

View all Floors and Slabs answers (4) →

Skylights

Skylight replacement and the limits that apply to them.

• Title 24 Skylight Requirements for Homes
• Skylight Shaft Insulation: What Title 24 Expects Around the Light Well
• How Many Square Feet of Skylight Can I Add Under Title 24?
• Skylight Replacement: Title 24 Requirements
• Solar Tubes (Tubular Daylighting Devices): Title 24 Rules

View all Skylights answers (5) →

Back to the Title 24 guide or all Title 24 questions.