Window-to-wall ratio calculator

Calculate WWR and verify energy code compliance

Try it now

Live calculator

Live preview

Loading calculator...

The Window-to-Wall Ratio (WWR) Calculator helps architects and designers determine the percentage of wall area occupied by windows and verify compliance with energy codes like ASHRAE 90.1 and IECC.

WWR is a critical metric for building energy performance, as windows typically have much higher heat transfer than opaque walls. Energy codes limit WWR to control heating and cooling loads, requiring better window performance or reduced glazing area for higher ratios.

Enter your wall and window dimensions to calculate WWR instantly. The calculator helps you understand how glazing area affects energy performance and ensures your design meets code requirements for different climate zones and building types.

Features

Everything you need

WWR calculation from wall and window areas
ASHRAE 90.1 compliance checking
IECC code verification
Multiple facade calculation
Glazing area optimization
Energy performance implications
Climate zone considerations

How it works

Simple workflow

1
Enter total wall area for each facade
2
Input window and glazing areas
3
Select building type and climate zone
4
Review calculated WWR percentages
5
Check compliance with energy code limits

Use cases

Built for real-world scenarios

Energy code compliance

Verify that window areas meet ASHRAE 90.1 and IECC requirements for your building type and climate zone.

Design optimization

Balance daylighting goals with energy performance by optimizing window sizes and locations.

LEED documentation

Calculate WWR for LEED energy performance credits and daylighting documentation.

Permit applications

Generate WWR calculations required for energy code compliance in 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 values range from 20-40% for most buildings.

ASHRAE 90.1 and IECC don't set absolute maximums but require better window performance (lower U-factor and SHGC) for higher WWR. Buildings with WWR over 40% typically need high-performance glazing to meet energy targets.

Higher WWR increases heating and cooling loads because windows have higher heat transfer than walls. However, windows also provide daylighting, which can reduce lighting energy. Optimal WWR balances these factors.

Glazing area includes all transparent and translucent fenestration: windows, curtain walls, skylights, and doors with glazing. Opaque spandrel panels and solid doors don't count toward WWR.

Have a suggestion?

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.

Related tools