Fenestration

Windows, glass doors and skylights are one of the biggest drivers of heat gain and loss in a home. Your CF1R lists the U-factor and SHGC every window was modeled with — the products installed need to match.

Orange sunset over the ocean with a palm tree in silhouette

The view is the reason for the glass — and glass is a big part of the energy model.

Not a HERS/ECC verified measure. Fenestration is documented by the installer on the CF2R-ENV-01 and checked by the building inspector. It’s here for information — because getting it wrong can still force a CF1R revision.

The two numbers that matter

Both are printed on the NFRC label on every window and glass door.

U-factor

Heat loss · lower is better

How much heat passes through the whole window — glass and frame. 2022 code: prescriptively, new windows need a U-factor of 0.30 or lower in every climate zone, and no window can exceed 0.45.
*NEW FOR 2025* 0.27 or lower in Climate Zones 1–5, 11–14 and 16 (0.30 in Zones 6–10 and 15), and no window can exceed 0.40.

SHGC

Solar heat gain · lower blocks more sun

Solar Heat Gain Coefficient — how much of the sun’s heat comes through. Prescriptively 0.23 or lower in most climate zones (Zones 1, 3, 5 and 16 have no limit).
*NEW FOR 2025* Climate Zone 15 drops to 0.20.

On a performance CF1R, the values that count are the ones in your CF1R’s fenestration table — they can be better or worse than the prescriptive numbers, and every window must meet what was modeled.

Prescriptive limits

From Table 150.1-A. Performance projects follow the CF1R.

Requirement	Limit	Code
Maximum U-factor — all fenestration (mandatory) — 2022	0.45	§150.0(q)
NEW FOR 2025 Maximum U-factor — all fenestration (mandatory)	0.40	§150.0(q)
Maximum U-factor — prescriptive, all climate zones — 2022	0.30	Table 150.1-A
NEW FOR 2025 Maximum U-factor — prescriptive, CZ 1–5, 11–14, 16 CZ 6–10 and 15 stay at 0.30. New homes of 500 sq ft or less in CZ 5 may use 0.30.	0.27	Table 150.1-A
Maximum SHGC — prescriptive, CZ 2, 4, 6–15 — 2022	0.23	Table 150.1-A
NEW FOR 2025 Maximum SHGC — prescriptive, CZ 15 CZ 2, 4 and 6–14 stay at 0.23.	0.20	Table 150.1-A
Maximum total window area	20%	Table 150.1-A
Maximum west-facing area — CZ 2, 4, 6–15	5%	Table 150.1-A
Exterior door maximum U-factor	0.20	Table 150.1-A

2022 requirements apply to permits applied for before Jan. 1, 2026; 2025 requirements apply on or after. Changes in the 2025 code are marked *NEW FOR 2025*. Your CF1R’s code cycle governs — projects permitted under earlier code cycles follow the CF1R for that cycle.

Before you order

Check the CF1R first

Send a copy of your CF1R with your window order so the supplier quotes the U-factor and SHGC your project was modeled with — it avoids confusion and costly mistakes. Then check the quote against the CF1R’s fenestration table before you order. Substituting a different window line, a different glass package, or adding a door that wasn’t modeled can push the project out of compliance — and a CF1R revision costs time and money. Leave the NFRC labels on until the inspector has seen them.

§110.6 · §150.1(c)3

Topa Topa Mountains at sunset — Topa Topa at sunset — the view worth the glass.

The code

Click a section to read the actual code language, or open it in the official CEC document.

§110.6Certified and labeled products (mandatory)

(a) Certification of fenestration products and exterior doors other than field-fabricated. Any fenestration product and exterior door, other than field-fabricated fenestration products and field-fabricated exterior doors, may be installed only if the manufacturer has certified to the Commission, or if an independent certifying organization approved by the Commission has certified, that the product complies with all of the applicable requirements of this subsection.
…
2. U-factor. The fenestration product and exterior door’s U-factor shall be rated in accordance with NFRC 100, or use the applicable default U-factor set forth in Table 110.6-A.

Read §110.6 in the official 2022 Standards (CEC PDF, p. 151) ↗

§150.0(q)Maximum U-factor (mandatory)

Fenestration separating conditioned space from unconditioned space or outdoors shall meet the requirements of either Item 1 or 2 below: 1. Fenestration, including skylight products, must have a maximum U-factor of 0.45.
Exception 1: Up to 10 square feet of fenestration area or 0.5 percent of the conditioned floor area, whichever is greater, is exempt from the maximum U-factor requirement.

Read §150.0(q) in the official 2022 Standards (CEC PDF, p. 339) ↗

§150.1(c)3Prescriptive U-factor and SHGC

A. Installed fenestration products, including glazed doors, shall have an area-weighted average U-factor and Solar Heat Gain Coefficient (SHGC) meeting the applicable fenestration value in Table 150.1-A and shall be determined in accordance with Sections 110.6(a)2 and 110.6(a)3.
Exception 1: For each dwelling unit, up to 3 square feet of new glazing area installed in doors and up to 3 square feet of new tubular skylights area with dual-pane diffusers shall not be required to meet the U-factor and SHGC requirements of Table 150.1-A.
Exception 2: For each dwelling unit up to 16 square feet of new skylight area with a maximum U-factor of 0.55 and a maximum SHGC of 0.30.

Not sure your windows match?

Send us the quote and your CF1R before you order.