How Much R-Value Do I Need? Try Our R-Value Calculator

Find out exactly how much insulation your home needs—without the guesswork.
Let’s get one thing straight: when it comes to keeping your home warm in the winter and cool in the summer, R-value matters. A lot. But most homeowners (and even a few contractors) don’t really know what R-value they need, where, or why.
That’s why we built a free, easy-to-use R-Value Calculator—to give you clear, code-backed recommendations based on where you live and what part of your home you’re insulating.
But before you jump in and start punching in numbers, let’s cover the basics so you actually know what you’re looking at. Here's what we'll cover in this article:
What Is R-Value, Anyway?
R-value is how we measure insulation’s resistance to heat flow. Think of it like SPF for your house—higher R-value = more protection. The better the R-value, the slower your heated (or cooled) air escapes through your walls, ceilings, and floors.
So when someone says “You’ve got R-13 in your walls,” they’re talking about how well that insulation holds the line between inside and outside temperatures.
Different insulation types have different R-values per inch:
- Fiberglass batts: ~R-3.2 per inch
- Cellulose: ~R-3.5–3.8 per inch
- Spray foam (closed-cell): ~R-6.5 per inch
Why Does R-Value Matter?
Simple: it’s the difference between a home that stays comfy for cheap... and one that bleeds money every time the heat kicks on. Insufficient R-value leads to:
- Drafty rooms
- Sky-high utility bills
- HVAC systems working overtime
- Unhappy homeowners (maybe you?)
The Department of Energy and local building codes require specific R-values depending on where you live. But unless you’ve memorized the DOE’s climate zone map (we have, but we’re weird like that), figuring it out on your own is a pain.
A Quick Note on Climate Zones
The U.S. is divided into climate zones (Connecticut is mostly Zone 5), and those zones determine how much insulation your home needs.

For example:
- Zone 3 (warmer southern states) might only need R-30 in the attic.
- Zone 5 (Connecticut) usually calls for R-49 to R-60 in the attic.
- Zone 7 (northern tier)? You’re looking at R-60+ and tight air sealing.
You also need different R-values depending on whether you're insulating an attic, basement or wall. Garage's don't have unique R-Values. That's where things get tricky.
Enter: the R-value calculator.
R-Value Calculator
We built this tool to take the confusion out of calculating R-value. Just plug in:
- Your state and county
- The part of your home you want to insulate
...and boom—you’ll get the recommended minimum and maximum R-values based on your local code and climate.
✅ No digging through PDFs
✅ No guessing
✅ No wrong answers
Whether you’re upgrading attic insulation, finishing a basement, or insulating a new addition, this calculator gives you a clear starting point. From there, we can help you figure out the right material and get the job done.
Try Our R-Value Calculator
Use this R-value calculator to find out what your home really needs—and let’s make sure you’re not under-insulated, overpaying, or leaving comfort on the table.
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