Window-to-wall ratio calculator
Multi-facade WWR analysis with performance insights and code compliance
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The Advanced Window-to-Wall Ratio (WWR) Calculator transforms glazing analysis from a simple percentage calculation into a comprehensive design decision support tool for early-stage architecture and energy performance optimization.
This calculator supports orientation-specific WWR analysis for all four facades (North, East, South, West) with an interactive building diagram. Click any facade to edit its properties and see real-time updates to performance metrics and compliance status.
Key capabilities include climate zone-aware calculations based on ASHRAE Standard 169-2021, glazing performance specification with U-factor, SHGC, and Visible Transmittance, simplified energy performance estimation for heating and cooling loads, daylight availability scoring, and detailed compliance checking against ASHRAE 90.1-2022 and IECC 2024 prescriptive requirements.
The optimization engine provides actionable recommendations based on your selected goal (energy optimization, daylight optimization, or balanced), with estimated cost savings and implementation guidance. Export your analysis to PDF or CSV for documentation and team collaboration.
Features
Everything you need
- Multi-facade WWR calculation (N/E/S/W) with interactive building diagram
- Climate zone selection from all 17 ASHRAE zones with representative cities
- Glazing library with preset specifications (U-factor, SHGC, VT)
- ASHRAE 90.1-2022 prescriptive compliance checking
- IECC 2024 prescriptive compliance checking
- Enhanced WWR limits for high-performance glazing trade-offs
- Heating and cooling load estimation by facade
- Daylight factor scoring with orientation weighting
- Annual energy cost estimation for glazing-related loads
- Goal-based optimization recommendations (energy, daylight, balanced)
- Trade-off strategies for non-compliant configurations
- PDF and CSV export with comprehensive reports
- Shareable links for collaboration
- Metric and imperial unit support
How it works
Simple workflow
- 1Configure building type, climate zone, floors, and floor height
- 2Click on the interactive building diagram to select a facade
- 3Enter wall area and glazing area for each facade orientation
- 4Choose glazing type from the preset library or customize properties
- 5Review calculated WWR percentages with color-coded compliance indicators
- 6Check ASHRAE 90.1 and IECC compliance with trade-off suggestions
- 7View performance metrics: heating/cooling impact, daylight factor, and costs
- 8Select optimization goal and review ranked recommendations
- 9Export results to PDF or CSV for documentation
Use cases
Built for real-world scenarios
Early design trade-offs
Explore how changes to glazing area, orientation, and specifications affect energy performance and daylighting during schematic design.
Energy code compliance strategy
Determine compliance paths for ASHRAE 90.1 and IECC, including trade-off options with high-performance glazing or area reductions.
Pre-modeling feasibility checks
Perform quick WWR optimization before detailed energy modeling to identify potential issues and set performance targets.
Facade optimization
Balance orientation-specific glazing ratios for optimal energy performance, considering solar exposure and climate.
LEED and green building documentation
Generate WWR analysis reports for LEED energy performance credits and daylighting documentation requirements.
Permit application support
Create compliance documentation showing WWR calculations and code conformance for building permit submissions.
FAQ
Frequently asked questions
WWR is the percentage of above-grade wall area that is glazed (windows). It's calculated as: WWR = Total Glazing Area ÷ Total Wall Area × 100%. Typical sustainable values range from 25-40% for most buildings, though optimal ratios vary by climate and orientation.
ASHRAE 90.1-2022 uses a 40% prescriptive WWR limit as the baseline. However, buildings with high-performance glazing (low U-factor) can qualify for enhanced limits up to 50% in hot climates (zones 1-3) and 45% in mixed climates (zones 4-5). Cold climates (zones 6-8) maintain the 40% limit due to heating concerns.
The calculator uses simplified steady-state calculations for early design guidance: heating impact is based on U-factor × area × temperature difference, while cooling impact includes both conductive gains and solar heat gains (area × SHGC × solar irradiance). These are directional estimates, not full energy simulations.
Glazing area includes all transparent and translucent fenestration: windows, curtain wall vision glass, and glazed portions of doors. The calculator allows you to include or exclude glazed doors, curtain walls, and spandrel glazing based on your project requirements.
Each facade orientation receives different amounts of solar radiation. South facades get the most consistent sun year-round (good for passive heating in cold climates). West facades receive intense afternoon sun that's difficult to shade. North facades have minimal solar gain. Optimal WWR varies by orientation and climate.
Solar Heat Gain Coefficient (SHGC) measures how much solar radiation passes through the glazing (0-1 scale). Lower SHGC reduces cooling loads in hot climates but may limit beneficial passive solar heating in cold climates. Energy codes specify maximum SHGC values that vary by climate zone.
The calculator provides trade-off strategies: upgrade to high-performance glazing to qualify for enhanced WWR limits, reduce glazing area on problematic facades (especially west), add external shading devices, or use the Energy Cost Budget (ECB) or Performance Rating Method to demonstrate overall energy equivalence through whole-building simulation.
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We're always looking to improve our calculators. If you have ideas for new features, improvements, or found something that could work better, we'd love to hear from you.
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