📐Additions & Remodels

Are Small Additions Exempt from the Washington Energy Code?

The R502.1.1 Exemption — What It Actually Says

Per WAC 51-11R-50200 R502.1.1: “Additions not greater than 150 square feet in floor area shall not be required to comply with the provisions of Section R406.”

Section R406 is the energy credit section — the part of the code requiring you to earn a certain number of “credits” by choosing efficiency upgrades. For projects exempt from R406, you don’t need to pick credits, fill out the Schedule R worksheet, or calculate energy performance trade-offs.

This is the section wsec.ai’s wizard exists to help with. If your addition qualifies for the R502.1.1 exemption, you don’t need our tool.

What Still Applies (Even for Exempt Additions)

The R502.1.1 exemption is narrow — it only waives R406. The rest of WSEC-R still applies to your addition:

R402 — Envelope requirements: New walls, floors, and ceilings in your addition must meet minimum R-values for your climate zone.
R403 — Mechanical systems: Any new mechanical equipment installed must meet current efficiency requirements. Duct insulation requirements still apply.
R404 — Lighting: New lighting installed in the addition must meet high-efficacy requirements.

Don’t read “R406 exempt” as “WSEC exempt.” You still need code-minimum construction; you just don’t need the credit-selection math.

Examples

8’ × 12’ bedroom addition (96 sq ft) — R406 exempt. R402/R403/R404 apply.
10’ × 14’ sunroom (140 sq ft) — R406 exempt.
12’ × 14’ kitchen bump-out (168 sq ft) — exceeds 150 sq ft, NOT exempt. Falls in the 150–500 tier (2.0 credits required).
20’ × 25’ family room addition (500 sq ft) — addition-small tier boundary (2.0 credits required at exactly 500 sq ft).

What Documentation You Still Need for Permitting

Even with the exemption, your local AHJ will likely require:

Construction drawings showing the addition
Insulation specifications meeting R402 minimums
Mechanical equipment specifications (if installing new equipment)
A statement that the addition qualifies for R502.1.1 exemption — this is usually a simple line on the building permit application or a one-page certification

Important: Different jurisdictions handle exempt-addition documentation differently. Some require nothing beyond the regular permit set. Others want a written exemption claim. Always check with your local AHJ before submitting to know what they specifically require.

When the Exemption Doesn’t Apply

The R502.1.1 exemption is ONLY for additions. It does NOT apply to:

Alterations or renovations of existing space (those have their own Chapter 5 rules)
New construction of any size
Repeat applications — you can’t claim two 100 sq ft additions to skirt the threshold; AHJs treat connected work as one project

Addition over 150 sq ft? Check your compliance.