How to Insulate a Crawl Space Basement
Insulating a crawl space basement is one of the smartest upgrades we can make for comfort, energy savings, and long-term home health. Done right, it keeps cold floors away, manages…
R11 and R13 insulation differ mainly in thickness, thermal resistance, and where they’re approved to be used. In short, R13 insulates better, costs a bit more, and is required in more situations.
Quick answers that matter most:
Before comparing materials or costs, it helps to understand what R11 and R13 actually mean.
R-value measures how well insulation slows heat transfer. The higher the number, the better the insulation performs. According to guidance from the U.S. Department of Energy, proper R-values can significantly reduce heating and cooling costs when matched to climate and wall design.
R11 insulation provides moderate thermal resistance. It’s usually about 3.5 inches thick and was common in homes built decades ago.
Homeowners still see R11 in:
R13 insulation is thicker, usually around 3.5 to 4 inches, and fits standard 2×4 exterior wall cavities. It slows heat loss more effectively and improves comfort.
R13 is now standard in many regions because it:
This comparison highlights the practical differences homeowners care about most.
| Feature | R11 Insulation | R13 Insulation |
|---|---|---|
| Thermal resistance | Lower | Higher |
| Typical thickness | Thinner | Thicker |
| Common wall use | Interior or older walls | Exterior 2×4 walls |
| Energy efficiency | Basic | Improved |
| Code compliance | Limited | More widely accepted |
Data from the Energy Star insulation guidelines shows that higher R-values in exterior walls directly reduce heating and cooling demand, especially in cooler regions like the Pacific Northwest.
Different insulation materials reach R11 or R13 in different ways. Thickness, density, and installation quality all matter.
Fiberglass batts are the most common option for R11 and R13.
Industry data from the North American Insulation Manufacturers Association shows gaps or compression can reduce fiberglass performance by up to 30 percent.
Mineral wool offers higher density and better sound control.
Rigid foam boards don’t fit the traditional R11 or R13 batt category, but they can supplement wall systems.
Cellulose can reach R11 or R13 depending on depth and density.
This section answers the question homeowners usually ask next: does R13 really make a difference?
In simple terms, R13 reduces heat transfer about 18 percent more than R11. That difference adds up over time, especially during long heating seasons.
You may notice:
R13 also dampens sound slightly better due to its added density. That matters in bedrooms, home offices, and shared walls.
R11 is cheaper upfront, but the savings are small when spread across a whole home.
Typical considerations:
In many cases, choosing R11 to save money can lead to higher heating bills year after year.
Building codes increasingly favor R13 for exterior walls in residential construction. While older homes may be grandfathered in, renovations often trigger updated requirements.
A professional insulation contractor can:
This is where homeowners often shift from research to action.
While R11 and R13 are common reference points, spray foam insulation delivers higher performance in less space.
Spray foam:
For homes in the Seattle area, this approach often outperforms traditional batts, especially in older structures.
R11 works in limited situations, but R13 is the better choice for exterior walls, comfort, and energy savings. The right insulation depends on wall depth, local code, and long-term goals.
If you want clear guidance for your home, talk with a local professional who understands regional building needs.
Cascadia Spray Foam of Seattle Email: [email protected] Phone: (425) 386-3500
Yes, but mostly in interior walls or older homes. Exterior walls usually require higher R-values.
Yes. Homes with properly installed R13 typically lose less heat, which reduces heating and cooling costs.
Sometimes. Blown-in or spray foam insulation can improve performance without full wall removal.
Spray foam and rigid foam boards deliver higher R-values per inch than batts.
Mineral wool performs more consistently, but fiberglass is more affordable and widely available.
Energy-efficient upgrades often improve buyer appeal, especially in colder climates.
