CalcHab

Insulation Thickness & Thermal R-Value Calculator

The insulation thickness calculator determines the depth of continuous thermal insulation needed for exterior walls, roofs, and foundations based on building energy code R-values.

Recommended commercial thickness
50 mm

Minimum thickness: 24 mm

Wall heat loss reduction:-33%
Base wall R-value
2.66

m²·K/W

Total finished wall R-value
3.97

норма ДБН: 3.30 m²·K/W

З товщиною утеплювача 50 мм стіна повністю відповідає нормі ДБН (R = 3.97 > 3.30).

Thermal engineering guidelines

Exterior insulation protects the load-bearing wall from thermal expansion and shifts the dew point outward.
For aerated concrete blocks, use breathable mineral wool to allow moisture escape and avoid entrapment.
Extruded polystyrene (XPS) is best suited for foundations and plinths due to closed-cell moisture resistance.

How to use

  1. Select building assembly: exterior wall, pitched roof, attic floor, or slab.
  2. Specify existing structural substrate and thickness (brick, block, timber).
  3. Choose insulation type: rock wool, fiberglass, expanded polystyrene (EPS), or extruded XPS.
  4. Enter thermal conductivity (lambda value) or keep standard default values.
  5. Set target regional building code thermal resistance (R-value).
  6. Review minimum required insulation thickness and assembled envelope R-value.

What Does the Insulation Calculator Compute?

Target thickness: required depth of insulation to achieve building code compliance.

Thermal resistance: baseline versus retrofitted R-values of the complete assembly.

Material comparison: heat retention efficiency across mineral wool, EPS, and XPS.

Building Envelope Performance Standards

Modern standards mandate high thermal resistance (R = 2.8 to 3.3 m²·K/W for walls, and R = 4.5+ for roofs).

Applying external insulation moves the condensation dew point into the insulation layer, protecting structural masonry from moisture.

Frequently Asked Questions

How is required insulation thickness calculated?

Deduct the existing wall R-value from the building code target R-value, then multiply by the material thermal conductivity.

What insulation thickness is standard for brick walls?

Typically 100 mm to 150 mm (4 to 6 inches) of continuous external insulation is required.

Is mineral wool better than EPS foam?

Mineral wool is non-combustible and vapor-permeable, while EPS is moisture-resistant and cost-effective.

Why insulate externally rather than internally?

Exterior insulation eliminates thermal bridges and prevents condensation on cold internal wall faces.

How much energy does envelope insulation save?

Comprehensive wall and roof insulation reduces building space heating loads by 40% to 50%.

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