Choosing Your Heating System (Table R406.2)

Your heating system selection is the single biggest credit decision in the entire R406 process. Table R406.2 — Fuel Normalization Credits — awards between 0 and 3.0 credits based on your primary heating fuel and equipment type. Choose wisely, because this one selection can make or break your compliance path.

R406.2: The First Decision

You select exactly one option from Table R406.2. This is the first question on the R406 worksheet, and it’s the biggest single factor in determining whether you’ll hit your credit target. The five options and their credit values are:

Why Heat Pumps Earn More

Option 4 — a heat pump as your primary system with no combustion backup — earns 3.0 credits. For a Medium-size home that needs 8.0 total credits, that’s over a third of the requirement from a single line item. A gas furnace (Option 1) earns 0, meaning you’ll need to find all 8.0 credits from R406.3 categories alone. That’s achievable, but significantly harder and often more expensive.

I-2066 Notice

Initiative I-2066 challenged portions of the energy code related to fuel-type credits. As of April 2026, the matter is pending before the Washington Supreme Court. The credit values shown above reflect the currently enforceable code, but they may change depending on the court’s ruling. Check with your local building department for the latest guidance.

Frequently Asked Questions

I already bought a gas furnace — am I stuck with 0 credits?

From R406.2 with a gas furnace alone, yes — combustion heating earns 0 fuel normalization credits. However, you have options. If you add a heat pump to work alongside the gas furnace (a dual-fuel system), you would qualify for Option 2 and earn 1.5 credits. Many builders add a heat pump to an existing gas system for exactly this reason.

Even without adding a heat pump, you can still reach 8.0 credits entirely through R406.3 options: upgraded insulation, better windows, a heat pump water heater, solar provisions, and other selections. It requires more effort in other categories, but it’s very doable. The wsec.ai wizard helps you find combinations that work for your project and budget.

What about dual-fuel systems?

A heat pump with a gas furnace as backup qualifies as Option 2, earning 1.5 credits. This is a common choice for builders in colder parts of the state who want heat pump efficiency but want gas backup for extreme cold days.