Window Fenestration Conductive + Solar Heat Gain (U-Factor & SHGC BTU/hr) Calculator

Compute window conductive + SHGC solar heat gain (BTU/hr) across glass area.

Total Window Heat Gain (Conductive + Solar)
7,189.2 BTU/hr
Solar Radiation Gain (SHGC × A × Flux) 6,450 BTU/hr
Conductive Gain (U × A × ΔT) 739.2 BTU/hr
Equivalent Air Conditioning Load 0.6 Tons
Inputs
⚡ Scenarios:
sq ft
Total sunlit window/glazing area in square feet.
U-factor
NFRC whole-window U-Factor (BTU/hr·ft²·°F; R-value = 1/U).
SHGC
NFRC Solar Heat Gain Coefficient (SHGC, 0.0 to 1.0).
°F
Outdoor minus indoor temperature difference ΔT in °F.
BTU/h·ft²
Incident solar radiation on glass (BTU/hr·ft²; ~215 West/East summer peak).
Results & Graph
Total Window Heat Gain (Conductive + Solar)
7,189.2 BTU/hr
Solar Radiation Gain (SHGC × A × Flux)
6,450 BTU/hr
Conductive Gain (U × A × ΔT)
739.2 BTU/hr
Equivalent Air Conditioning Load
0.6 Tons

Total Window Heat Gain (Conductive + Solar)

Graph 1 • Window U-Factor & SHGC Load • Domain Architecture & Live Telemetry Maps Total Glass Area Sq Ft, Window U Factor, Solar Heat Gain Coeff Shgc through Window U-Factor & SHGC Load Formula.
Window U-Factor & SHGC Load • Generation → Conversion → Storage Bus 1. SOURCE / ARRAY 120 sq ft Total Glass Area Sq Ft 2. DELIVERED RATING 7,189.2 BTU/hr Total Window Heat Gain ( 3. SECONDARY OUTPUT 6,450 BTU/hr Solar Radiation Gain (SH
Graph 2 • Total Window Heat Gain (Conductive + Solar) Across Total Glass Area Sq Ft Sweep (40% → 160%) Evaluates Q_cond = U × Area_ft² × ΔT_F; Q_solar = SHGC × Area_ft² × IncidentSola across 7 operating points (current input highlighted).
0 BTU/hr 6.3k BTU/hr 12.7k BTU/hr 2.9k 48sq ft 4.3k 72sq ft 5.8k 96sq ft 7.2k 120sq ft 8.6k 144sq ft 10.1k 168sq ft 11.5k 192sq ft
Graph 3 • Joint Sensitivity: Total Glass Area Sq Ft × Window U Factor Compares Total Window Heat Gain (Conductive + Solar) when Window U Factor is shifted +25% (solid) vs. −25% (dashed).
0 BTU/hr 5.3k BTU/hr 10.5k BTU/hr --- Window U Factor @ 75% 5.2k -30% 6.3k -15% 7.4k +0% 8.5k +15% 9.6k +30%
Summary: Across 120 sq ft of glazing (U=0.28, SHGC=0.25), conductive gain is 739 BTU/hr and solar radiation gain is 6450 BTU/hr = 7189 BTU/hr (0.6 Tons of cooling).
Summary: Across 120 sq ft of glazing (U=0.28, SHGC=0.25), conductive gain is 739 BTU/hr and solar radiation gain is 6450 BTU/hr = 7189 BTU/hr (0.6 Tons of cooling).
⚡ Send result to: Concrete & Sq Ft →Ohm's Law & Voltage Drop →Roofing, Stairs & BTU →
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Formula & Mathematical Methodology: Window U-Factor & SHGC Load Formula

Qcond = U × Areaft² × ΔTF
Qsolar = SHGC × Areaft² × IncidentSolarBTUhrft²
Qtotal = Qcond + Qsolar
Q_cond = U × Area_ft² × ΔT_F; Q_solar = SHGC × Area_ft² × IncidentSolar_BTU_hr_ft²; Q_total = Q_cond + Q_solar
  • totalGlassAreaSqFt: Total Glass Area Sq Ft (sq ft)
  • windowUFactor: Window U Factor (U-factor)
  • solarHeatGainCoeffShgc: Solar Heat Gain Coeff Shgc (SHGC)
  • indoorOutdoorDeltaTF: Indoor Outdoor Delta T F (°F)
  • incidentSolarBtuHrSqFt: Incident Solar Btu Hr Sq Ft (BTU/h·ft²)

Rounding: Engineering outputs round to 2–3 decimal places; discrete material bag/unit counts round up via ceiling.

Worked Example: Engineering Scenario: Window U-Factor & SHGC Load

Compute window conductive + SHGC solar heat gain (BTU/hr) across glass area.

  1. Enter your system dimensions, electrical/RF ratings, or environmental conditions.
  2. Evaluate the governing equation: Q_cond = U × Area_ft² × ΔT_F; Q_solar = SHGC × Area_ft² × IncidentSolar_BTU_hr_ft²; Q_total = Q_cond + Q_solar.
  3. Inspect the primary design output, supporting allowances, and 3 SVG schematics.
Result: Computes Window U-Factor & SHGC Load via Q_cond = U × Area_ft² × ΔT_F; Q_solar = SHGC × Area_ft² × IncidentSolar_BTU_hr_ft²; Q_total = Q_cond + Q_solar.

Frequently Asked Questions

How does the Window Fenestration Conductive + Solar Heat Gain (U-Factor & SHGC BTU/hr) Calculator calculate results?

It evaluates Q_cond = U × Area_ft² × ΔT_F; Q_solar = SHGC × Area_ft² × IncidentSolar_BTU_hr_ft²; Q_total = Q_cond + Q_solar directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to solve backwards for a required dimension or rating?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any numeric input parameter.

Does this engineering calculator work offline?

Yes. All calculations run 100% locally in your browser and work offline via the CalculatorGraph PWA.

Construction & Home · Building Envelope, Insulation & HVAC

Window Fenestration Conductive + Solar Heat Gain (U-Factor & SHGC BTU/hr) Calculator: inputs, method, and how to read the result

Compute window conductive + SHGC solar heat gain (BTU/hr) across glass area.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Total Glass Area Sq Ft: Total sunlit window/glazing area in square feet.
  • Window U Factor: NFRC whole-window U-Factor (BTU/hr·ft²·°F; R-value = 1/U).
  • Solar Heat Gain Coeff Shgc: NFRC Solar Heat Gain Coefficient (SHGC, 0.0 to 1.0).
  • Indoor Outdoor Delta T F: Outdoor minus indoor temperature difference ΔT in °F.

What the calculation includes

With the default values shown, Total Window Heat Gain (Conductive + Solar) is 7,189.2 BTU/hr. The calculation follows Window U-Factor & SHGC Load Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Total Glass Area Sq Ft from 120 sq ft to 132 sq ft changes Total Window Heat Gain (Conductive + Solar) from 7,189.2 BTU/hr to 7,908.12 BTU/hr. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard NREL, IEEE, ASHRAE, and IRC design equations.
  • Verify final structural, electrical, and mechanical specifications against local building codes.

Scope: Global Engineering & Building Code Standard Check the assumptions and limitations against your situation before relying on the estimate.

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