Natural Light and Ventilation in House Design: A Practical Guide

What good light and air look like in a plan

Natural light and ventilation in house design is a planning problem, not a decoration problem. If every main room touches two outside walls, or one outside wall plus a courtyard or shaft, the house will be bright and airy no matter what the elevation looks like. If the rooms are stacked three deep from front to back with walls between them, no amount of glass on the front will fix the middle.

In our Indore studio we check three things on every plan before anything else. Does each bedroom and the living room have openings on two sides? Is the total window area in each room at least 15 percent of the floor area? Is there a high opening somewhere for hot air to leave? Plans that pass these three almost never get complaints about dark or stuffy rooms after possession.

The rest of this post explains how to pass them on real plots, including the 20 and 25 foot wide ones where side windows are not an option.

Orientation and which walls get the openings

The orientation of a house for sunlight in most of India is simple. North gives soft, even light all day with little heat. East gives pleasant morning sun. South gives strong light and heat in winter, less in summer when the sun is high. West gives the harsh afternoon sun that heats rooms for the evening.

• Put the largest windows on the north and east. These can be floor to ceiling without much heat gain.
• Keep south windows medium sized with a 2 foot chajja, which blocks summer sun and lets winter sun in.
• Keep west openings small, high, or screened with louvers. Put the stair, toilets and store on the west.
• Bedrooms do best on the east or north east. Kitchens tolerate the east or south east morning sun.
• The terrace and roof get the most sun, so insulate or use light coloured tiles.

You rarely get to choose the plot orientation, but you can choose which rooms go where. On a west facing plot we move the living room to the back and give the front to the porch, stair and a screened verandah. Our pillar on modern house elevation design ideas shows how louvers and deep balconies handle the west face without giving up the view.

Window sizes that actually work

The window size for a bedroom that we use is 15 to 20 percent of the floor area in glass, which is a 5 x 4 foot window plus a 3 x 2 foot ventilator for a 12 x 12 foot room. Most Indian homes have a single 4 x 4 window in a room that size, about 11 percent, and the room needs a light on in the afternoon.

Two smaller windows on different walls beat one large window on one wall every time, because the second one creates cross ventilation. A ventilator at 8 to 9 feet, where hot air collects, is worth more than adding a foot to the main window. Our urban planner also checks that the window sizes keep within the setback and projection rules of the colony, because a bay window can count as built up area.

Cross ventilation in house plans

Cross ventilation in a house means air enters from one opening and leaves from another on a different wall, ideally the opposite wall, so the room is flushed rather than stirred. Two windows on the same wall do not do this. A window and a door to a passage do very little unless the passage itself has an opening.

Rules of thumb we draw by

1. Inlet low, outlet high. Wind enters at sill level and leaves at ventilator level, which also pulls out hot air.
2. Outlet bigger than inlet. A slightly larger outlet speeds the air through the room.
3. Line of air no longer than 40 feet and not through more than two rooms.
4. Internal doors with a 1 inch gap at the bottom or a louvered panel let air move when doors are shut.
5. The stair shaft, if open to the top, acts as a chimney that pulls air from every floor. Put a ventilator or skylight at the top of it.

Where the staircase sits decides whether this chimney effect works. Our post on staircase position in a house plan explains why we place it against an outside wall with a tall window when possible.

Ventilation for narrow plot houses

Ventilation for a narrow plot house is the hardest case. A 20x50 plot has two long side walls shared with neighbours and only the front and back open. Rooms in the middle have no outside wall at all.

The answer is a light well in the house, a shaft open to the sky of at least 6 x 6 feet, placed roughly in the middle of the depth. Every middle room gets a window into it, and the shaft becomes a second front for light and air. Smaller shafts of 3 x 3 feet work for toilets and the kitchen exhaust but do little for a bedroom.

On 25 and 30 foot plots we often widen the shaft into a small courtyard of 8 x 10 feet with a tree or a water body. It costs 80 sq ft of floor on each level and gives back a house that never needs a tube light in the daytime. Our post on courtyard house design in India has layouts for each plot width, and our small plot house design tips cover the setback tricks that free up a side window.

Skylights, clerestories and jaalis

Skylight design for a house in India must deal with heat. A horizontal glass skylight on a flat roof lets in five times more heat than a vertical north window of the same area. We use skylights only on the north slope of a raised roof or with a double glazed, tinted unit and an internal blind.

A clerestory, which is a strip of window high on a wall where the roof steps up, gives the same deep daylight with far less heat, and it opens for ventilation. On a G+1 house we often raise the living room roof by 2 feet above the dining and fit a clerestory strip in the step.

Jaalis, perforated screens in brick, concrete or metal, are the traditional Indian answer to light with privacy and shade. A jaali on the west face of a stair or a balcony cuts direct sun, keeps the breeze and throws a pattern inside. In 2026 a laser cut metal jaali costs Rs 450 to Rs 900 per sq ft, a precast concrete jaali block much less.

Mistakes that make bright houses dark

• Deep balconies on the north cutting the only soft light the room gets. Keep north balconies shallow.
• Wardrobes built across the window wall because the plan did not leave another wall for them.
• A toilet with a window into a 2 x 2 foot shaft that is covered at the top, so the smell never leaves.
• Dark floor and wall colours in a north room, which absorb the little light there is.
• Grills so dense that the window is a wall. Choose grills with 4 to 5 inch spacing.
• Fixed glass where an openable shutter was needed. Light without air is only half the job.

Most of these are fixed on paper in a day. On site they cost a wall.

Next step

If your plan has a room that worries you, send it to us with the plot orientation. Our floor plan design service marks window area and air path on every room, and our 3D visualization shows the light inside at different hours before you build. The first consultation is free, call +91 73165 33888.