Louvre width is the size of each blade, top to bottom, in millimetres. The trade standardised on roughly 63, 89 and 114 mm (you'll see 76 in some ranges, it behaves like a slightly bigger 63). The choice changes five things, and only five, so let's do them honestly.
1. Light, when open
Fewer, wider blades means fewer horizontal bars across the opening, so at the same tilt a 114 mm shutter lets noticeably more light through than a 63. On a small or south-facing window this is the strongest argument for going wide.
2. View, when open
Same geometry, different pleasure: wide blades give you bigger uninterrupted slices of whatever the window looks at. If the window has a view worth keeping, harbour, ridge line, a good gum tree, wide blades keep more of it. If it looks at a fence, this argument doesn't vote.
3. Privacy, in fine increments
Narrow blades win the close-quarters game: each degree of tilt changes the sightline less, so on a street-facing terrace window a 63 mm louvre lets you hold that precise angle where light comes in and eyes don't. Wide blades are more all-or-nothing near a footpath.
4. Proportion
This is the one people feel but don't name. Tall, narrow period sashes carry narrow blades the way they carry narrow floorboards: in scale. A 114 mm blade on a Cooks Hill sash looks like venetian blinds drawn by a giant. Flip it for the new estates: on a Fletcher slider two metres tall, 63 mm blades read busy, like too many lines on a page, and 114 reads calm. Match the blade to the window's own proportions and the room simply looks right.
5. Cleaning day
A 63 mm shutter on a big window can have double the blades of a 114. Each one collects the same dust. Nobody regrets wide blades on the first cleaning day, and nobody ever will.
So: the honest defaults
| Window | Default | Because |
|---|---|---|
| Period sash, terrace front room | 63 mm | Proportion + fine privacy control near the street |
| Standard bedroom or living window | 89 mm | The safe middle: good light, easy clean, suits most frames |
| Big modern opening, slider, view window | 114 mm | Maximum light and view, calmest proportions at scale |
Mixing widths between rooms is normal and right; mixing them side by side on one wall of windows is the thing to avoid. And if two widths still feel plausible at your measure, ask to hold a sample of each against the glass, it settles the proportion question in about four seconds.
Still torn between 89 and 114? Take the wider one, in ten years of living with them, light and cleaning day win
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