Built from 18 Years of Field Experience
R-Value Calculator exists because most online insulation tools don’t model real wall assemblies. They give you R-value per inch. This tool builds the actual assembly — layer by layer — and checks it against code.
Why this tool is different
This calculator was built by someone with 18 years of hands-on experience in roofing, siding, and spray foam insulation in residential construction. The assembly logic, layer ordering, and code references reflect how buildings are actually built — not how they look in a textbook.
What the Calculator Does
You choose your wall type and build the assembly layer by layer using the same materials you’re actually using on the job. The tool calculates the total R-value of the completed assembly and checks it against the applicable minimum from IECC 2021 (for US climate zones) and OBC / SB-12 (for Ontario).
The result is a clear pass or fail, a visual cross-section of your assembly drawn to physical scale, and the exact code citation that applies. No textbook required.
Accuracy & Disclaimer
The R-values, code minimums, and assembly logic in this tool are based on published IECC 2021 tables, OBC SB-12, and manufacturer data for common insulation products. Values are updated when code editions change.
These calculations are for reference only. Local amendments, specific product specifications, and AHJ interpretation can all affect compliance. Always verify with your local building department or a qualified professional before finalizing an assembly for a permit application.
Sister Sites
Contact
Found an error in a code value or R-value? Have a suggestion for a material or assembly type that should be in the tool? Get in touch.
Send a message