West-Facing Window Design (India): Taming the Harsh Afternoon Sun — Why the west wall is the hardest orientation to glaze, and how to minimise, shade and layer the defences against the low afternoon sun.

West-facing room with a tall picture window screened by vertical aluminium fins and a deciduous tree, late afternoon

The west wall is where good window design earns its keep. In the Indian afternoon the sun drops low in the western sky exactly when the day is hottest, firing heat and glare almost horizontally through the glass. A horizontal chajja that tames the high south sun does almost nothing here, because the sun is not overhead, it is in your eyes. Get the west wrong and you build a room that is unbearable from 3 pm to sunset for half the year; get it right and you protect comfort, energy bills and your air-conditioner.

This guide is about designing the window on a WEST wall. For where every wall faces and how it ties together, start with our planning pillar, the window placement guide. For the house as a whole rather than the window, the south-facing house design guide covers plot orientation; here we stay zoomed in on the opening itself.

The west window is the only orientation where the default advice is: make it smaller. Everywhere else you optimise; here you also subtract.

Why west is the problem wall

Compare the four walls. The numbers are indicative and depend on latitude, but the pattern holds across India.

Wall	Sun character	Heat and glare	Shading difficulty
North	Soft, even, almost no direct sun	Lowest	Trivial (little to shade)
East	Gentle low morning sun	Moderate, but in the cool morning	Hard (low angle), but heat is low
South	High midday sun	Controllable	Easiest (a horizontal chajja works)
West	Harsh low AFTERNOON sun	Highest, at the hottest hour	Hardest (low angle plus peak heat)

West combines the two worst factors: the low sun angle that defeats horizontal overhangs (the same geometry problem as east, covered in the east-facing window design guide) AND the peak air temperature of the day. East shares the awkward angle but gets it at dawn when the air is cool; west gets it at 3 pm to 6 pm over a wall that has already baked all day. That is why west glass is the single biggest avoidable load on a hot-climate home.

Section comparing high south midday sun cut by a chajja versus low west afternoon sun sliding under it

The heat math, simply

Solar gain through a window is roughly the glass area, multiplied by how much sun hits it, multiplied by the glass SHGC (Solar Heat Gain Coefficient, where lower lets in less heat). On the west wall every term works against you: the area is the choice you control, the incident sun is at its peak intensity and duration, and ordinary clear glass has a high SHGC of around 0.8.

The practical takeaways:

Shrink the area. A 5 ft by 4 ft west picture window admits far more afternoon heat than a 4 ft by 3 ft one. On the west, smaller is a feature, not a compromise.
Cut the SHGC. Swapping clear glass (SHGC near 0.8) for a spectrally selective low-E unit (SHGC around 0.25 to 0.30) removes most of the gain through whatever glass you keep. See the best glass for a hot climate guide for which glass to specify.
Stop the sun before the glass. External shading is several times more effective than internal blinds, because once the sun is through the pane the heat is already inside.

Under the Eco-Niwas Samhita 2018 (ENS), more glass forces lower-SHGC glazing to keep the wall envelope within RETV of 15 W/m2 or less, and a minimum VLT applies as the window-to-wall ratio rises. The code itself is nudging you to keep the west modest and the glass smart.

Layer the defences

If a view, a balcony or a fixed plan forces glass onto the west, do not rely on one trick. Stack them, outermost first.

Plan-and-section diagram of layered west defences: deciduous tree, vertical fins, low-SHGC glass, internal blind

1. Landscape (outermost). A deciduous tree or tall shrub on the west casts shade in summer and drops its leaves to let winter sun through. Even a pergola with creeper or a screen wall helps.

2. External shading sized for a LOW sun. Horizontal chajjas fail here. Use vertical fins or louvres, set at an angle to block the afternoon sun while keeping a sliver of view. Deep verandahs, jali screens and operable external louvres or shutters all work because they intercept the low rays.

3. Solar-control glass. Low-SHGC, spectrally selective or reflective glazing, ideally in a double-glazed (DGU) unit. This is your last line at the plane of the wall.

4. Internal blinds (innermost). Light-coloured blinds or curtains for glare control and late-evening privacy. Useful, but weakest, because the heat is already inside.

Think of the west window as a fortress with rings of defence. The cheapest, most effective rings are the outer ones, the tree and the fin, not the curtain.

The fin geometry matters: a vertical fin to the south side of the opening blocks the late-afternoon western sun while a north-side return catches little. A jali screen (a perforated stone, terracotta or concrete-block screen) is the traditional Indian answer, diffusing the harsh light and accelerating breeze through its holes.

What to put behind a west window

Not every room suffers equally from afternoon heat. Use the west for spaces you do not occupy in the late afternoon.

Room	West wall verdict	Why
Master bedroom	Avoid large glass	You want it cool for evening sleep; the wall radiates heat at bedtime
Living / TV room	Accept with full defences	Often occupied in the evening; layer fins plus low-SHGC glass plus blinds
Study / home office	Avoid	Afternoon glare on screens is brutal; prefer north or east
Kitchen	Small high window only	Heat plus cooking heat is a bad combination; a small awning above the counter at 1050 to 1200 mm sill
Bathroom	Fine (small)	Small high obscured window at about 1500 mm sill; little glass, privacy preserved
Staircase / utility / store	Good place for west glass	Buffer zones you pass through, not dwell in; they shield the rooms behind
Garage / parking	Ideal	Put the unconditioned buffer on the hot west and let it absorb the heat

A powerful planning move is to bank the west wall with the rooms you do not air-condition, the stair, the store, the utility and the garage, so they soak up the afternoon heat before it reaches your bedrooms.

Sizing and sills on the west

Standard sizes and sill heights still apply, just bias toward the smaller end and toward higher sills that admit less low sun.

Room	Indicative size	Sill height
Bedroom (west)	4 ft by 4 ft or smaller	600 to 750 mm
Living (west)	Keep to 5 ft by 4 ft, fully defended	600 to 750 mm
Kitchen (west)	4 ft by 3 ft or less	1050 to 1200 mm (above counter)
Bathroom (west)	2 ft by 1.5 ft	about 1500 mm (privacy)

Remember the NBC 2016 rule of thumb: openable area of at least 10 per cent of the room carpet area for light and ventilation (verify local bye-laws). You can meet this on the west with a modest, well-shaded openable casement rather than a heat-trapping picture window, because casement and louvre windows ventilate their whole opening, unlike sliding windows that open only about half.

Decision matrix: by room on the west, accept or avoid, with the defence stack required

Vastu and the west window

Vastu guidance aligns neatly with the building science here: it recommends big windows to the north, east and northeast; small windows on the west and south; and avoiding the southwest almost entirely. That is exactly what the heat reality demands, keep the west modest. So vastu and passive design agree, which makes the west an easy call. For how to reconcile vastu room-by-room, see vastu for modern homes; this guide stays focused on the window's climate logic. Differentiate the two clearly: vastu gives the directional preference, building science gives the reason and the defence stack.

Vastu-and-climate compass showing favoured north/east glass and restrained west/south/southwest glass

Frame and glass quick picks

The frame matters less than the glass on the west, but heat-conducting bare aluminium will radiate the absorbed warmth inward. Prefer uPVC, or aluminium with a thermal break, and put the energy into the glazing. Full detail in the best window material for a hot climate guide. For the glass itself, the rule is simple: lowest SHGC you can afford, double-glazed where budget allows, with enough VLT to stay bright, as set out in the hot-climate glass guide.

The west window checklist

Make it the smallest window the room can live with.
Specify low-SHGC, spectrally selective or reflective glass, ideally DGU.
Use vertical fins, louvres, deep verandahs or jali, never a lone horizontal chajja.
Plant a deciduous tree or grow a creeper screen on the west.
Add light-coloured internal blinds for evening glare and privacy.
Park buffer rooms (stair, store, utility, garage) on the west to shield the bedrooms.
Keep an openable section to meet the NBC 10 per cent rule and allow night purge once the sun is down.

Design the west well and you turn the home's hardest wall into a controlled one. Compare it with the friendlier orientations in the north-facing window guide and the east-facing window guide, and plan the whole set together from the window placement pillar.

References

BIS Guide for Using NBC 2016: https://www.bis.gov.in/wp-content/uploads/2022/08/Booklet-Guide-for-Using-NBC-2016.pdf
Eco-Niwas Samhita 2018 (BEE/ECBC): https://ecbc.in/econiwas.html
IS 3362 natural ventilation of residential buildings: https://law.resource.org/pub/in/bis/S03/is.3362.1977.pdf
Vastu for doors and windows (Livspace): https://www.livspace.com/in/magazine/vastu-for-house-doors-windows
Standard window size by room (CiviConcepts): https://civiconcepts.com/blog/standard-window-size