Bellingham sits in marine climate zone 4C, and under the current Washington energy code the prescriptive insulation targets are about R-49 in the attic, R-21 in the walls, and R-30 under the floor. Those are the numbers a new home has to hit, and they are the numbers the PSE rebate is built around. The trouble is that most older Bellingham homes were built long before those levels were required, so they fall well short, which is exactly why so many houses here are cold and expensive to heat.
What R-value actually means.
R-value measures how well a material resists heat flow. Higher R means slower heat loss. It is additive by thickness, so more inches of the same material means a higher R. But R-value only describes heat moving by conduction; it says nothing about air leaks. A perfectly R-49 attic that leaks air around the can lights and top plates will still feel drafty and lose heat, which is why we always pair the R-value with air sealing. The number on the bag is only half the story.
The three numbers for Bellingham.
| Assembly | Target (zone 4C) | What older homes often have |
|---|---|---|
| Attic / ceiling | About R-49 | R-11 to R-19, often settled lower |
| Exterior walls | About R-21 | R-0 to R-11, sometimes empty |
| Floor over crawlspace | About R-30 | R-0 to R-19, often fallen or wet |
These are the prescriptive targets contractors and the PSE rebate work from. The exact code path has some flexibility, an attic can meet the requirement with R-49 of loose fill over the full ceiling under one common exception, for instance, but R-49 attic, R-21 wall, and R-30 floor are the working numbers for our area.
Why our climate makes the vapor side matter.
Marine zone 4C has stricter vapor-control rules than a dry inland zone, and that is the whole reason insulation here is different. It is not freezing-cold, it is cold and wet for eight months, so the enemy is moisture as much as heat loss. Hitting the R-value without managing the vapor, the crawlspace ground moisture, the attic ventilation, the vapor retarder on the correct side, is how cheap jobs trap water in the wall and grow mold. We hit the R-value and get the moisture control right, because in Bellingham you cannot separate the two. Our guide on insulation and mold goes deeper on this.
In our climate, the R-value tells you how warm the house will be. The vapor control tells you whether the insulation will still be dry and working in five years.
What this means for your older home.
If your Bellingham home was built before the energy code caught up, you are probably under code in at least one of these assemblies, and often all three. The attic is usually the cheapest and highest-impact to bring up to R-49. Empty walls can be brought close to R-21 with dense-pack and no tear-out. Cold floors over the crawlspace come up to R-30 with floor insulation and a vapor barrier. Bringing an under-insulated home up to these levels is also what qualifies you for the PSE rebate, so the code targets and the rebate line up.
Frequently asked questions.
What R-value should attic insulation be in Bellingham?
About R-49 under the current Washington energy code for our climate zone. A lot of older Bellingham attics have R-11 to R-19, often a 1970s blown-in layer that has settled and lost value. Bringing the attic up to R-49 is the standard job here, and it is the level the PSE rebate is built around.
What R-value do walls and floors need in Bellingham?
About R-21 for exterior walls and about R-30 for the floor over a crawlspace, under current code for zone 4C. Many older homes have little or no wall insulation and fallen or missing floor insulation, so they are well short. Dense-pack can bring empty walls close to R-21 without tear-out, and floor insulation plus a vapor barrier brings floors up to R-30.
Do I have to meet code R-values to get the PSE rebate?
The PSE insulation rebate is generally tied to bringing an assembly up to the target R-value from a lower starting point, so the code numbers and the rebate line up closely. The exact amount depends on your home and how much insulation it needs. We size the work to hit the target and qualify, and we help you file. See our rebate guide.
Is a higher R-value always better?
Up to a point. Hitting the code targets, R-49 attic, R-21 walls, R-30 floor, captures most of the benefit for our climate. Going far beyond that has diminishing returns, and the money is usually better spent on air sealing and moisture control, which is often the bigger win in a leaky Bellingham home. We help you put the budget where it actually pays off.
For a free assessment of what your home has and what it needs, request a free assessment and we will get back within 15 minutes during business hours.