Nothing switched on yet — pick a setting above to bring its controls and view into the workspace.
Site & Feasibility · Sun geometry
Sun path — where the sun is, all year
The site's solar geometry: altitude and azimuth hour by hour, the seasonal arcs from the winter to the summer solstice, and the shadow angles that follow. This is the geometry every shading, glare and orientation decision downstream is built on.
Site & Feasibility · How light works
How light works — four quick animations
The mental models behind every number in LUMEN. Why we treat the sky as a dome falling on a building, how light sheds energy as it bounces toward the back of a room, what "lux" actually measures and how a surface bends it, and how curved surfaces gather or spread daylight.
Building · Massing & envelope
Incident solar radiation — which façades take the heat
Cumulative solar energy landing on a vertical façade by orientation, across the year (kWh/m²). The beam follows the sun, so this is fully orientation- and climate-dependent — the fast read on where cooling load and glare concentrate, and which elevations need the deepest shading.
RAD
Orientation radiation rose
Isotropic-sky (Liu–Jordan) transposition of the site's hourly beam, diffuse and ground-reflected radiation onto a vertical surface facing each way. Longest petal = hottest elevation.
Hottest façade
—
Peak radiation
— kWh/m²
cooler moderate hottest
Site & Feasibility · Massing separation
Sky View Factor — how much sky a point can see
The share of the sky hemisphere visible from a point, cosine-weighted for a horizontal surface. Pure geometry — no sun, no climate — so it reads the same on any orientation, anywhere. Use it early to test how close massing and neighbours can sit before they starve the site of sky.
SVF
Obstruction & the open dome
Raise the surrounding obstruction or pull it closer and the open sky shrinks from the horizon up. The rim of the dome counts for little — cosine weighting means a degree of sky near the zenith is worth far more than one near the horizon.
Sky View Factor
—%
Obstruction angle
—°
Open sky Obstructed Obstruction
Site & Feasibility · Design sky
Sky type — what you're designing against
Pick the sky the building's metrics are judged against. The overcast worst case is sun-free and the same in every direction, so orientation and location drop out. Put the real sun back in — Boise's actual year — and orientation and climate start to drive everything.
Design basis
02
Sky type — what you're designing against
The sky dome painted by relative luminance — look up at it in 2-D, orbit it in 3-D, or read a meridian slice. The Daylight Factor assumes the overcast sky: sun-free, dimmest at the horizon, brightest at the zenith — the conservative worst case. Reality is rarely that tidy.
Zenith : horizon
—
Direct sun
—
Dim sky Bright sky Circumsolar / sun
Site & Feasibility · Your year
Boise's year — the skies you actually get
The real climate behind the annual metrics. Three sunny seasons mean the overcast Daylight Factor badly under-states daylight here — the design problem is taming sun and glare, not scraping for light. The exception is the Dec–Jan inversion, when the overcast worst case finally bites.
03
Boise's year — the skies you actually get
Percent of possible sunshine, month by month (NWS Boise 1991–2020 normals). High desert: brilliant spring-through-fall, with valley inversions dimming midwinter. Hover a bar for the day length behind it.
Annual sunshine
2,983hrs / yr
Sunniest — July
86% possible
Dimmest — Dec/Jan
38% possible
Why it matters here: clear skies dominate Boise for three seasons, so the overcast-sky Daylight Factor badly under-states real daylight — the design problem is taming sun and glare, not scraping for light. The exception is the Dec–Jan inversion window, when the overcast worst case finally bites.
04
Shading calendar — when to block, when to admit
Hour-by-hour through the year, when direct sun on the glazing is welcome heat versus an overheating or glare risk — the schedule that tells overhangs and fins what to do.
05
Daylight availability — hours the sky delivers
How many hours each part of the year the sky alone meets a useful work-plane target — the climate ceiling that sDA can reach toward.
06
Sky cover — clear, mixed and overcast across the year
The measured split of clear, partly-cloudy and overcast skies month by month — the fuller picture behind the percent-of-possible-sunshine summary above.
Room | Space · Plan-depth check
No-sky line & daylit depth — how deep is too deep
A fast, pure-geometry check before any simulation. The no-sky line marks where occupants lose a direct view of the sky; the rule of thumb says useful daylight reaches about 1.5–2× the window-head height into the room. If either leaves much of the plan dark, the room is too deep for its windows.
NSL
Section through the room
Raise the window head to push daylight deeper; add an external obstruction and watch the no-sky line march in from the back wall. Geometry only — orientation and climate never enter.
No-sky line at
—
Floor with sky view
—%
Daylit depth (2×head)
— m
Depth verdict
—
Daylit zone (≤2×head) Sky view, low light No sky view
The opening
Total width of glass along the window wall
Taller glass pushes light deeper into the room
Sill + height sets the window head — the deeper the daylight reaches
Clear double glazing ≈ 70%. Tints and coatings lower it
Elevation of facing buildings, seen from the window
The room
How far the back wall sits from the window
Pale walls bounce more light around the room
Dirt on glass cuts the light that gets through
By default the Room follows the Building tab's sky; switch to Set locally to pick your own. Idealised design sky — or activate a measured site weather file below.
Site weather file (EPW)
Using idealised sky — no weather file active
The room in section
side view · light fades with depth
The room in plan
looking down · useful floor —
The window wall in elevation
looking at the glazing · true scale
The room in 3D
isometric · daylight on the floor
az 315° · el 27° · ×1.0drag to orbit · scroll to zoom
Too dark · <100 lxSupplementary · 100–500Useful · 500–2,000Glare risk · >2,000
Daylit floor · by comfort band0 m² floor
Too dark0%0 m²
Supplementary0%0 m²
Useful0%0 m²
Glare risk0%0 m²
Avg Daylight Factor
0%
target ≈ 2–5%
Vertical Sky Component
0%
27% = good access to sky
Est. workplane light
0lx
room average, this sky
—
The math, live
hover a term
Average Daylight Factor — BRE / Lynes formula
Vertical Sky Component
Try a scenario — watch every panel move
Electric lighting
off
Solve a luminaire grid for a target work-plane level and lay it into the room above
Can
Descriptive luminaire family — labels the grid and its plan symbol (a Troffer draws at true 0.6 × 1.2 m footprint); the lumen math is set below
Picks an IES-style recommended work-plane level and the space-by-space LPD allowance (Code-check tab)
Mounting & throw set a representative coefficient of utilization — the share reaching the work plane
Dirt and lamp aging over life — 0.85 is the usual design value
Switch On above to solve a luminaire grid for the room.
Luminaire grid over the room
true-scale plan — daylit zone vs. back of room
daylit zone — can dimback of room — always on
Fixtures
—
Connected load
—
Delivered
—
Daylit share
—
Luminaires for a target level — lumen method
Energy & daylight savings
Office · M–F day
Sets occupied hours and the daytime share — daylight only harvests while the space is occupied and lit by the sun. Now: 2,500 h/yr, ~95% in daylight hours.
Annual operating hours — set by the schedule above; drag to fine-tune
Share of lit hours daylight meets target in the daylit zone (≈ daylight autonomy). Set it by hand.
Continuous dimming
Daylight-harvesting controls dim the daylit zone; whole-load controls trim the rest
Used for the annual cost saved
Added cost per daylight-controlled fixture (photosensor + dimming premium) — for the payback line
Turn on Electric lighting · Room to compute the room's lighting energy.
Annual lighting energy — this room
occupied hours × connected load
Baseline
—
Saved
—
Cost saved
—
Annual saving — daylight harvest + whole-load trim
Code check (LPD)
2024
ASHRAE 90.1 / IECC space-by-space allowances by edition
Space-by-space method — sets the allowed LPD below
From the selected space & edition — drag to match your adopted code
Turn on Electric lighting · Room to run the LPD check.
North–south plate depth is the daylighting bottleneck
Thinner wings daylight to the core; thick wings leave a dark middle
The open light well, sized independently of the ring. Its walls read as an inverse perimeter daylight zone.
0° = façades face N/S/E/W. Rotation blurs them between orientations
Floor area
m²
Off
Off: dimensions move freely. On: the gross per-floor area is held to the target — change one dimension and the perpendicular one reacts to keep the area. Total = per-floor × number of floors.
Height & floors
m
m
Height = floors × floor-to-floor — an impossible combination flags an error. (Metric for now; the unit toggle comes later.)
Sky & glazing
Top of glass — sets how deep the daylit perimeter band reaches
The aDF each façade's WWR is sized to deliver
Partitions
Off
Average DF stays the default. Switching on splits the plate into rooms with a 45° corner allocation and runs the proper per-room BRE Daylight Factor.
Depth of the perimeter rooms — explore where the daylit edge gives way to the core.
Glazed interior partitions feeding the core. 0% = solid walls, dark core.
Open
Subdivide the core into rooms. It still has no daylight of its own — the grid just shows the planned layout.
Turns each façade's DF into a real lux level. Site uses the EPW activated in the Room tab.
Window-to-wall, by façade
Auto derives each façade's obstruction angle from the buildings & trees placed in Sundial & shadows.
Guide: maximise S/N, restrain E/W — per the daylighting deck
The floor plate in plan
north up · daylit perimeter vs. dark core
The south elevation
The building in section
N–S cut · daylight reach vs. dark core
The massing in 3D
isometric · south façade highlighted
az 315° · el 27° · ×1.0drag to orbit · scroll to zoom
Daylit — façade meets targetLit but under-glazedOver-glazed — glare/heatNon-daylit core
Daylit floor
0%
of the plate within a daylit band
Overall WWR
0%
glazing ÷ gross wall, all façades
Glazing area
0m²
per floor, this WWR mix
—
Façade
Length
Sky θ
WWR
Req. WWR
aDF
Interior lux
State
The math, live
click a façade row · hover a term
Average daylight factor — South façade
Vertical sky component — South façade
WWR to hit the target average DF — South façade
Rule-of-thumb floor (code daylight credit)
Try a scenario — watch the core grow and shrink
Sun & site
How high the sun climbs. 43.6° ≈ Boise, ID
South
All floors
“All floors” edits the whole façade at once; pick a floor to single it out (e.g. F3). The chosen floor is highlighted in the elevation and shown in plan.
Summer
Façade & window
Shading device
Overhang
Overhang, balcony & louvers cut high sun from above; vertical fins cut low sun from the side; blinds & roller shades sit inside the glass.
How far the device reaches out from the wall
Blank wall between the glass top and the device
Share of sun that slips through the slats
Interior light shelf
Off
Splits the window into a view pane and a daylight pane above
A bright top throws more light onto the ceiling
Sun & shadow — section
drag time to move the sun
Where the sun lands — plan
looking down · sun patch on the floor
The window wall in elevation
shaded vs. sunlit glass · true scale
Sun & shade — isometric
the device against the sun in 3-D
az 315° · el 27° · ×1.0drag to orbit · scroll to zoom
Direct sunSunlit glass / floor patchShaded
Sun altitude
0°
above the horizon
Profile angle
0°
the sun's tilt onto the glass
Direct sun reach
0m
across the floor
—
Summer noon
—
Winter noon
—
The math, live
hover a term
Vertical profile angle — the sun projected onto the section
Shadow drop on the glass & floor penetration
Try a scenario — watch the sun and shadows move
Electric lighting · whole plate
off
Solve a luminaire grid for the whole footprint (all floors) at a target work-plane level
Can
Descriptive luminaire family — labels the grid; the lumen math is set below
Penetration depth — how far the head-of-glass beam travels
Try a scenario — watch the bands stretch and shrink
Daylighting Multipliers · Getting the details right
Getting the details right
How interior finishes carry daylight to the back of a deep room — the multiplier that decides whether a deep plan works.
01
Interior finishes — bouncing light to the back
At the window, light comes straight from the sky. At the back of a deep room the direct sky view is nearly gone, so almost all the light arriving is light that has bounced. The ceiling does most of that work. Push the reflectances and watch the dark zone retreat.
Bounced floor (IRC)
—% DF
DF at back
—%
Too dark (<100 lx) Supplementary (100–300) Useful (300–3000)
The multiplier: the ceiling and upper walls are weighted ~5× the floor in the bounced light. A bright ceiling is the cheapest way to daylight a deep plan.
Daylighting Multipliers · Getting the Details RightUniversity of Idaho · Integrated Design Lab