SettingsSettings for this calculationUS
The depth of each blade measured in the direction the sun passes through the canopy — for blades on edge in an overhead array, that is the blade's height.
Measure the projection of a single louver blade, not the overall assembly depth.
The sun angle above which the louvers should fully block direct sun.
Determine your target cutoff angle from your latitude and the season/time of day you want to block direct sun, e.g. using a solar path chart for your location.
Required louver spacing
0.5 ft
This gives full shading only for sun angles above the cutoff angle you enter — determine your target cutoff angle from your latitude and the season/time you want to block direct sun (e.g. using a solar path chart for your location).
They open the calculator with your figures already in it
Exterior Timber Louver Solar Shading Angle Calculator: 0.5 ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- For blades stood on edge in a horizontal overhead canopy — a brise-soleil over glazing or a deck — the spacing that blocks sun above a target altitude is: spacing = blade depth ÷ tan(cutoff angle). The division is what identifies the device: raising the cutoff angle CLOSES this array up, because high sun comes down through the gaps between blades. A vertical screen of horizontal blades on a façade is the other geometry and multiplies instead — spacing = depth × tan(cutoff) — and at a 60° cutoff the two answers differ threefold
Inputs used
- Louver Blade Depth
- 6 in
- Target Solar Cutoff Angle (° above horizontal)
- 45
Confidence note: This gives full shading only for sun angles above the cutoff angle you enter — determine your target cutoff angle from your latitude and the season/time you want to block direct sun (e.g. using a solar path chart for your location).
What this calculation does not cover
- Works from the sun's ALTITUDE, and blades respond to the profile angle — that altitude projected onto a plane cut square across the blade run. The two match only when the sun is square to the blades; swing round toward the ends of the run and the profile angle drops below the altitude, so sun the cutoff says is blocked comes straight down the channel between blades. Noon is the easy case; mid-afternoon is the one that leaks.
- Treats the blades as lines with no thickness. What this returns is the clear opening between blade faces, so a 45 mm (1.8 in) blade on a 115 mm (4.5 in) result sits at 160 mm (6.5 in) pitch — read it the other way and the array is either a third more open than designed or a third more timber than it was costed at, with the daylight and the view through it changing to match.
- Sizes the array optically and stops there. Blades that shade well are deep, on edge and close together, which is a lot of timber spanning between the bearers, and each blade still has to carry its own weight, wind uplift, and in the wrong climate wet snow packed into the gaps. The spacing fixes the shading; the blade's span, its section and the fixing at each end are what stop the array sagging into a wave visible from the ground.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- For blades stood on edge in a horizontal overhead canopy — a brise-soleil over glazing or a deck — the spacing that blocks sun above a target altitude is: spacing = blade depth ÷ tan(cutoff angle). The division is what identifies the device: raising the cutoff angle CLOSES this array up, because high sun comes down through the gaps between blades. A vertical screen of horizontal blades on a façade is the other geometry and multiplies instead — spacing = depth × tan(cutoff) — and at a 60° cutoff the two answers differ threefold
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