Construction Insulation Value Calculator
Build a wall, roof, or floor one layer at a time and watch its R-value, U-factor, and whole-wall thermal performance update as you go — then export the assembly straight to EnergyPlus. A schematic-design tool for studying envelope choices before detailed simulation.
The calculator stacks material layers in series — R = thickness / conductivity, summed across the assembly, with the overall heat-loss coefficient as its reciprocal (U = 1 / R). It runs entirely in the browser with no plug-ins, and is built to make the early envelope conversation visual and fast: pick materials, see where the resistance actually lives, and understand the gap between a wall's center-of-cavity number and what it really delivers once framing is accounted for.
Material library
Choose from roughly three dozen common building materials with built-in conductivities (ASHRAE Handbook—Fundamentals and Brown & DeKay), or enter your own k-value or R-value.
Surface air films
Interior and exterior film resistances follow the assembly's orientation and exposure — wall, roof, or floor; winter or summer wind. Toggle them off to reproduce legacy numbers.
See the resistance
A to-scale wall section and a per-layer contribution chart show exactly where the insulation works — and where a thermal bridge gives it all back.
Whole-wall R-value
The framing-factor mode adds the solid stud, joist, or rafter path and reports the area-weighted whole-wall R alongside the center-of-cavity figure — the difference codes care about.
EnergyPlus export
Generate a ready-to-paste IDF: full Material, Material:NoMass, Material:AirGap, and Construction objects with density and specific heat for a dynamic run.
Compare & convert
Switch between IP and SI units, check the total against a code or design target, and save assemblies side by side to compare designs.
Method & scope
This is a one-dimensional, steady-state calculation intended for schematic design — the stage before tools like EnergyPlus are warranted. It revives the graphic envelope-analysis methods of Sun, Wind & Light as a fast, interactive web tool.
The center-of-cavity result does not weight parallel framing paths unless framing mode is on, and it does not model moisture, air leakage, or dynamic mass effects. Built-in conductivities are typical reference values and should be confirmed against manufacturer data for design.