Window & Ventilation Checker
Research natural light, ventilation, emergency escape, and fall-protection questions across named jurisdictions.
Enter the jurisdiction, room and opening geometry, sill condition, and design path to organize the potentially applicable light, ventilation, emergency-escape, fall-protection, and overheating checks. Verify each result against the current adopted source.
The Problem
Window questions often combine different authorities and scopes: light, natural or mechanical ventilation, emergency escape, fall protection, safety glazing, energy performance, and overheating. A threshold from one jurisdiction or room type cannot be reused as a universal window rule.
How It Works
Select the jurisdiction and enter the room area, opening geometry, sill height, and proposed use. The assistant organizes relevant questions and source paths, highlights where checks interact, and provides preliminary comparisons for verification rather than a combined compliance determination.
"120 SF bedroom, minimum window size for IRC?""window sill 18" from floor, 3rd story. need restrictor?"Key Features
Who It's For
Architects sizing windows during design. Building inspectors checking compliance. Window manufacturers verifying product specs. Energy consultants balancing ventilation with thermal performance.
This public GPT is a preliminary research aid, not a multi-jurisdiction compliance engine. It does not establish the adopted authority, evaluate every exception, design mechanical ventilation, or verify glazing, structure, weatherproofing, or dynamic-overheating models. Confirm the selected source and project facts with the responsible professionals.
Frequently Asked Questions
What percentage of floor area must be glazed for natural light?
Under the 2024 IBC §1204.2 natural-light path, net glazed area is at least 8% of the floor area of the room served, subject to scope and opening-location conditions; artificial light is a separate permitted path. IRC and other jurisdictions use their own scope and section sequence, so select the source before calculating.
What is the minimum openable window area for ventilation?
IRC §R303.1 requires openable area of at least 4% of floor area. UK Part F requires 1/20 of floor area (window opening >30°) or 1/10 (opening 15-30°) for purge ventilation. A 100 sq ft room needs 4 sq ft openable (IRC) or the metric equivalent under UK rules.
When is a window fall protection restrictor required?
IRC §R312.2: when an operable window is more than 72 inches above grade AND the sill is less than 24 inches from the floor. IBC §1015.8: sill less than 36 inches. UK AD K §4: sill below 800mm in buildings where children under 5 may be present. Restrictors must limit opening to 4 inches (100mm UK) with emergency override.
What is the minimum egress window size for a bedroom?
IRC §R310 requires bedroom emergency escape and rescue openings (egress windows) to have: minimum net clear opening area of 5.7 square feet (5.0 sq ft for ground floor), minimum net clear opening height of 24 inches, minimum net clear opening width of 20 inches, and maximum sill height of 44 inches from the floor. The 5.7 sq ft is the net clear area after deducting the frame, mullions, and sash — not the rough opening size. A common 3'0" x 4'0" window yields approximately 8 sq ft gross but only 5-6 sq ft net clear depending on the manufacturer.
What are the UK Part F 2021 trickle vent requirements?
UK Approved Document F 2021 increased minimum equivalent area (EA) for trickle vents: habitable rooms now require 8,000 mm² EA (up from 5,000 mm²), kitchens 4,000 mm², and bathrooms/WCs 4,000 mm². These are in addition to openable windows for purge ventilation. For dwellings with air permeability below 5 m³/(h·m²) at 50 Pa (highly airtight), continuous mechanical extract ventilation (MEV) or mechanical ventilation with heat recovery (MVHR) may be required regardless of window provision. Trickle vents must be positioned in the window frame or head to distribute fresh air across the room.
How do I balance natural ventilation with UK Part O overheating requirements?
UK Approved Document O (Overheating, 2022) limits glazing on high-risk orientations (south, west, east facades in moderate and high risk areas). The simplified method limits glazing area as a percentage of floor area by orientation and building type. This can conflict with Part F ventilation requirements and daylight targets. When Part O limits glazing below what Part F requires for ventilation, you may need trickle vents or mechanical top-up ventilation. In complex cases, CIBSE TM59 dynamic thermal modelling demonstrates compliance as an alternative to the simplified method.