Insulation Calculator

Calculate R-values, U-values, and thermal resistance for building insulation systems.

Determine optimal insulation thickness, thermal performance, and energy efficiency for walls, roofs, floors, and other building components.

Examples

Click on any example to load it into the calculator.

Fiberglass Batt Insulation

Fiberglass Batt Insulation

Standard fiberglass batt insulation commonly used in residential construction for walls and attics.

Insulation Type: Fiberglass Batt

Thickness: 140 mm

Thermal Conductivity: 0.04 W/m·K

Wall Thickness: 200 mm

Area: 50

Temp Difference: 25 °C

Air Resistance: 0.8 m²·K/W

Additional Layers: 0.5 m²·K/W

Closed-Cell Spray Foam

Closed-Cell Spray Foam

High-performance spray foam insulation with excellent thermal resistance and air sealing properties.

Insulation Type: Closed-Cell Spray Foam

Thickness: 100 mm

Thermal Conductivity: 0.025 W/m·K

Wall Thickness: 180 mm

Area: 40

Temp Difference: 30 °C

Air Resistance: 0.8 m²·K/W

Additional Layers: 0.3 m²·K/W

Cellulose Insulation

Cellulose Insulation

Eco-friendly cellulose insulation made from recycled paper, commonly used for attic and wall insulation.

Insulation Type: Cellulose

Thickness: 120 mm

Thermal Conductivity: 0.038 W/m·K

Wall Thickness: 220 mm

Area: 60

Temp Difference: 20 °C

Air Resistance: 0.8 m²·K/W

Additional Layers: 0.4 m²·K/W

Mineral Wool Insulation

Mineral Wool Insulation

Fire-resistant mineral wool insulation with good thermal and acoustic properties for commercial applications.

Insulation Type: Mineral Wool

Thickness: 150 mm

Thermal Conductivity: 0.035 W/m·K

Wall Thickness: 250 mm

Area: 80

Temp Difference: 35 °C

Air Resistance: 0.8 m²·K/W

Additional Layers: 0.6 m²·K/W

Other Titles
Understanding Insulation Calculator: A Comprehensive Guide
Learn how to calculate thermal resistance, R-values, and U-values for building insulation systems

What is Insulation Calculator?

  • Thermal Performance Analysis
  • Energy Efficiency Optimization
  • Building Code Compliance
An Insulation Calculator is a specialized tool designed to evaluate the thermal performance of building insulation systems. It calculates key thermal properties including R-values (thermal resistance), U-values (thermal transmittance), and heat transfer rates to help architects, engineers, and construction professionals optimize building energy efficiency.
Core Thermal Properties
The calculator analyzes three fundamental thermal properties: R-value (resistance to heat flow), U-value (rate of heat transfer), and thermal conductivity (material's ability to conduct heat). These properties determine how effectively insulation prevents heat loss or gain through building envelopes.
R-value measures thermal resistance in m²·K/W, with higher values indicating better insulation. U-value measures thermal transmittance in W/m²·K, with lower values indicating better performance. Thermal conductivity (k-value) measures the material's inherent ability to conduct heat in W/m·K.

Common R-Value Examples

  • Fiberglass batt insulation typically has R-values of 3.0-4.0 per inch (25mm)
  • Spray foam insulation can achieve R-values of 6.0-7.0 per inch (25mm)
  • Cellulose insulation provides R-values of 3.5-4.0 per inch (25mm)

Step-by-Step Guide to Using the Insulation Calculator

  • Input Material Properties
  • Define Assembly Parameters
  • Analyze Results
Using the Insulation Calculator involves three main steps: inputting material properties, defining assembly parameters, and analyzing the results. Start by selecting the insulation type and entering its thermal conductivity (k-value) and thickness.
Material Selection and Properties
Choose the appropriate insulation material from the dropdown menu. Each material has specific thermal conductivity values that affect performance. Enter the insulation thickness in millimeters - thicker insulation generally provides higher R-values and better thermal performance.
Include additional thermal resistance from other building materials such as drywall, sheathing, and siding. These layers contribute to the overall thermal performance of the assembly and should be accounted for in the calculation.

Typical Additional Layer R-Values

  • For walls: Include drywall (R-0.45), sheathing (R-0.5-1.0), and siding (R-0.5-1.0)
  • For roofs: Include roof decking (R-0.5-1.0) and ceiling materials (R-0.45)
  • For floors: Include subfloor (R-0.5-1.0) and floor covering (R-0.5-2.0)

Real-World Applications of Insulation Calculator

  • Residential Construction
  • Commercial Buildings
  • Energy Retrofits
The Insulation Calculator finds extensive applications across various construction sectors. In residential construction, it helps determine optimal insulation levels for walls, attics, and basements to meet energy codes and achieve comfortable indoor environments.
Commercial and Industrial Applications
Commercial buildings use the calculator to optimize HVAC system sizing, reduce energy costs, and ensure compliance with building energy codes. Industrial facilities apply it to process equipment insulation, cold storage facilities, and thermal management systems.
Energy retrofit projects rely on the calculator to evaluate existing insulation performance and determine cost-effective upgrade strategies. It helps prioritize improvements based on thermal performance and return on investment.

Application Examples

  • New home construction: Optimize wall and roof insulation for energy efficiency
  • Commercial office buildings: Size HVAC systems based on building envelope performance
  • Industrial facilities: Insulate process equipment and storage areas

Common Misconceptions and Correct Methods

  • R-Value vs U-Value Confusion
  • Thickness vs Performance
  • Material Selection Myths
A common misconception is that R-value and U-value are interchangeable. R-value measures thermal resistance (higher is better), while U-value measures thermal transmittance (lower is better). They are inversely related: U = 1/R.
Thickness and Performance Relationship
Another misconception is that doubling insulation thickness always doubles R-value. While generally true for homogeneous materials, this relationship can be affected by thermal bridging, air gaps, and material compression. The calculator accounts for these factors through the thermal conductivity input.
Material selection myths include believing that all insulation types perform equally. Different materials have varying thermal conductivities, moisture resistance, fire ratings, and installation requirements that affect overall performance and suitability for specific applications.

Performance Relationships

  • R-value of 10 m²·K/W corresponds to U-value of 0.1 W/m²·K
  • Compressed insulation can lose 20-30% of its rated R-value
  • Thermal bridging can reduce effective R-value by 10-30%

Mathematical Derivation and Examples

  • R-Value Calculation
  • U-Value Derivation
  • Heat Transfer Analysis
The mathematical foundation of insulation calculations is based on Fourier's law of heat conduction and thermal resistance principles. R-value is calculated as R = d/k, where d is thickness in meters and k is thermal conductivity in W/m·K.
U-Value and Heat Transfer Calculations
U-value is the reciprocal of total thermal resistance: U = 1/R_total. Total thermal resistance includes insulation resistance, air film resistance, and resistance from other building materials. Heat transfer rate is calculated as Q = U × A × ΔT, where A is area and ΔT is temperature difference.
For multi-layer assemblies, total R-value is the sum of individual layer resistances: R_total = R1 + R2 + R3 + ... + Rn. This principle allows the calculator to account for complex building assemblies with multiple materials and air spaces.

Calculation Examples

  • 100mm fiberglass (k=0.040): R = 0.1/0.040 = 2.5 m²·K/W
  • 150mm spray foam (k=0.025): R = 0.15/0.025 = 6.0 m²·K/W
  • Total wall R-value: 2.5 + 0.8 (air films) + 0.5 (other layers) = 3.8 m²·K/W