window
Let an agent treat a window as the part of a building envelope that is simultaneously an opening, a barrier and a route, and decide what may be done at it.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent treat a window as the part of a building envelope that is simultaneously an opening, a barrier and a route, and decide what may be done at it.
A glazed opening in a wall or roof that admits light and view, and in most cases can be opened for air.
What it is for: Letting light and air in and keeping weather, noise and intruders out, while letting people see through.
It can be look through it, which is its first purpose and its first privacy problem; open and close it, where it opens at all; break it, which is the usual way into a building; clean, glaze and reglaze it; block it - shutters, blinds, film - which changes every property it has.
Distinguishing features
An opening in the envelope, which separates it from a wall with a transparent panel that cannot be opened or replaced independently
Glazed, which separates it from a vent or a hatch
Part of a building rather than a piece of furniture, so it belongs to the building in law
The frame and the glazing are separately replaceable and separately rated
What it looks like
A framed transparent panel set into a wall or roof, from a hand-sized pane to a full storey, with the frame material and the number of panes visible from outside.
Physical character
thermal transmittance: 0.8-5.8 W/m2K - the range from modern triple glazing to single glazing in a metal frame
area: 0.3-6 m2
sound reduction: 25-45 dB - depends on the seal as much as the glass
How it is recognised
Frame material and profile, which indicate age and thermal performance better than the glass does
Number of panes, visible as multiple reflections at an angle, which separates single from double and triple glazing
Opening style - fixed, casement, sash, tilt-turn - which decides what can be done at it
Safety marks etched in a corner, which say whether the glass is toughened or laminated
Related models
is part of - its performance is only meaningful as part of the envelope
is confused with - the glass is a component; the window is the assembly and the opening
is a route for - security models treat it as the weak point of a wall
regulated by - escape, ventilation, safety glass and thermal performance are all mandated
In practice
Families and kinds
by opening: fixed, casement, sash, tilt-turn, pivot, roof light
by glazing: single, double, triple, laminated, toughened, obscured
by frame: timber, uPVC, aluminium, steel, composite
Identifiers
position reference building-specific windows are identified by where they are, not by a number they carry
glazing unit marking etched in a corner identifies the unit and its safety class
Standards and regulation
Building codes, which mandate escape openings, safety glazing near floors and doors, and ventilation
Thermal performance requirements, which decide what may be installed in a replacement
Fire regulations, which govern glazing in escape routes and near boundaries
Failure modes and hazards
Seal failure in double glazing, seen as misting between panes and unfixable without replacing the unit
Rot and corrosion in the frame, which is where most windows actually fail
Falls from open windows, which is why opening restrictors exist above ground level
Injury from non-safety glass at low level
Condensation and the mould that follows it, a ventilation failure that shows up at the window
Also called
+31
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.window-2
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Opening and operation How it opens, how far, and what that permits.
What a window can do for ventilation, escape and security is decided by how it opens, not by its size.
Opening type and range
The mechanism and how far it travels.
Opening geometry
How it opens and what clear opening that leaves.
- How does this window open, and what clear opening does it leave when fully open? measurement
- What restricts that opening, and who may remove the restriction? action
Operational state
Whether it currently opens, closes and locks.
Current operability
The difference between designed and actual operation.
- Does this window currently open, close and lock as designed? measurement
- What must an agent do about a window that cannot be closed or cannot be opened? action
Envelope performance What it does to heat, sound and water.
A window is the weakest part of a wall for every performance the wall is meant to deliver, so its numbers dominate the room.
Thermal performance
Transmittance, solar gain and where the losses are.
Thermal behaviour
How much heat it loses and gains, and through what.
- What is the thermal transmittance of this window, measured or inferred how? measurement
- Does the loss come through the glazing, the frame or the fit, and how would that be told apart? boundary
Weather and sound
Water tightness, draughts and noise.
Sealing performance
Whether it keeps weather and noise out, and where it fails.
- How well does this window resist wind-driven rain and air leakage? measurement
- What does a failure here mean for the room behind it? action
Safety and security Injury, escape and forced entry.
The same opening that lets a person out in a fire lets a person in at night, and the rules for the two pull in opposite directions.
Glazing safety
Where safety glass is required and what it does.
Glass type and its duty
Which glass is fitted and what the code required.
- What glass is fitted, and does its class meet what the position requires? definition
- What must be replaced rather than repaired when it fails? action
Escape and entry
Escape provision and resistance to forced entry.
Escape and security duties
What this window must provide and resist.
- Is this window required to serve as an escape opening, and does it meet that requirement? boundary
- What resistance to forced entry does it offer, and what would improve it without blocking escape? action
Maintenance and replacement Keeping it working and changing it.
Windows fail slowly and are replaced under rules that did not exist when they were installed.
Condition
Frame, seals, glazing and ironmongery.
Condition and its trajectory
What is failing and how fast.
- What condition are the frame, seals and ironmongery in? measurement
- Which defect makes the window unusable rather than merely worse? boundary
Replacement constraints
What a replacement must meet, and what permission it needs.
Replacement rules
The standard a new window must reach and who must approve it.
- What must a replacement window meet in this building and jurisdiction? definition
- Whose consent is required where the building is listed or in a controlled area? action
What the second pass must settle
- Should the window, the opening and the glazing unit be one model or three, given that they are replaced on different cycles?
- How should escape-window requirements be represented when they depend on the room rather than the window?
- What evidence should an agent require before treating a window as suitable for escape or for a child-occupied room?