Thermal Bridging Calculator

Calculate the effective R-value reduction and heat loss penalty caused by thermal bridges in your building envelope.

Inputs

Gross Wall Area (sq ft)

Assembly R-Value

Linear Psi (Btu/hr·ft·°F)

Total Linear Bridge (ft)

Point Chi (Btu/hr·°F)

Number of Point Bridges

Heating Degree Days (HDD65)

Tab to move between fields

Results

Effective R-Value

16.48

Clear-field U-Value0.05

Effective U-Value0.06

R-Value Reduction3.52

Heat Loss Penalty (%)21.3%

Annual Bridge Loss (kBtu)1,920

Gas Wasted (therms)24

How to Use This Calculator

Enter Gross Wall Area in sq ft and the Assembly R-Value without bridging.
Enter Linear Psi value in Btu/hr·ft·°F and Total Linear Bridge length in feet.
Enter Point Chi value and Number of Point Bridges for bracket mounts and anchors.
Enter Heating Degree Days for your climate to calculate annual energy penalty.
Review Effective R-Value, R-Value Reduction, and Annual Bridge Heat Loss to justify continuous insulation.

How the result changes with Assembly R-Value

Assembly R-Value	Effective R-Value
8.9	8.13
29	22.15
52	33.45
72	40.72

What each input means

Gross Wall Area (sq ft): Total opaque wall area in square feet (excluding windows/doors).
Assembly R-Value: Clear-field R-value of the wall assembly without bridging (hr·ft²·°F/Btu).
Linear Psi (Btu/hr·ft·°F): Linear thermal transmittance per foot of bridge. Steel studs ~0.03-0.08, shelf angles ~0.05-0.15.
Total Linear Bridge (ft): Total length of all linear thermal bridges (studs, lintels, floor edges, shelf angles).
Point Chi (Btu/hr·°F): Point thermal transmittance per bridge. Masonry ties ~0.01, bracket mounts ~0.2-0.5.
Number of Point Bridges: Total count of point thermal bridges (cladding brackets, anchors, penetrations).
Heating Degree Days (HDD65): Annual heating degree days for your climate zone. Miami ~200, Denver ~6000, Minneapolis ~8000.

What each result means

Effective R-Value: True R-value of the assembly including all thermal bridges.
Clear-field U-Value: U-value of the wall without any bridging.
Effective U-Value: True U-value including linear and point thermal bridge contributions.
R-Value Reduction: How much R-value is lost due to thermal bridging.
Heat Loss Penalty (%): Percentage increase in heat loss due to thermal bridges.
Annual Bridge Loss (kBtu): Estimated annual heat loss through thermal bridges alone.
Gas Wasted (therms): Equivalent natural gas wasted annually through thermal bridges (assumes 80% furnace efficiency).

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Gross Wall Area (sq ft) = 1500, Assembly R-Value = 20, Linear Psi (Btu/hr·ft·°F) = 0.05, Total Linear Bridge (ft) = 200 = 7 input(s) provided
Calculate Effective R-Value
Effective R-Value = 1 / uEffective
16.48 = 16.48
Calculate Clear-field U-Value
Clear-field U-Value = 1 / assemblyRValue
0.05 = 0.05
Calculate Effective U-Value
Effective U-Value = uClear + uLinear + uPoint
0.0607 = 0.0607

Engine last updated July 26, 2026. Checked against 2 independently-derived tests — how we verify calculators.

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