Module 02 · Ideas

Small moves, cooler rooms

Practical thinking for Tamil Nadu homes — most of these cost paint, plants, and placement, not a renovation.

Diagram comparing a hot space, where heat is trapped, with a cool space, where heat is blocked, reduced and removed

Converting hot spaces into cool spaces

Swap dark walls for lime-washed light tones, add a jute or bamboo layer underfoot, and pull furniture off west-facing walls. The room reads — and measures — cooler by evening.

Diagram of shading devices, light-coloured surfaces, a reflective roof and planting reducing indoor heat gain

Reducing sunlight & heat gain indoors

Layer bamboo chick blinds outside the glass and sheer linen inside. The outer layer blocks heat before it enters; the inner one keeps the light soft instead of gone.

Diagram of clerestory windows, skylights, light shelves and reflective surfaces bringing daylight deeper into a room

Borrowing natural light

A mirror placed perpendicular to a window — not opposite it — doubles usable daylight deep into the room. Pale ceilings and satin-finish walls carry it further.

Diagram of cross ventilation, high-level ventilators, operable windows and ceiling fans moving air through a home

Letting air move

Cross-ventilation needs a clear path: align openable windows on opposite walls and keep tall storage out of the line between them. Ventilated jaali panels do the rest.

Where the idea comes from

The ancient “air conditioner” of Yazd

Long before electricity, Persian architects cooled homes in a 45°C desert using nothing but wind, water, earth and thick walls.

It is called a Badgir — Persian for “wind catcher.” For over 2,500 years these towers have cooled buildings in Yazd, where summers regularly pass 40–45°C. Instead of fighting the climate, the architects worked with it — the same instinct behind every idea on this page.

  1. 01

    Catch the wind

    The tower rises above the rooflines. Openings at the top catch moving air and turn it down into the house.

  2. 02

    Cool it on the way down

    Air passes thick mud-brick walls, a shaded basement (sardab), and often a pool or an underground qanat — losing heat to the earth and to evaporation before it ever reaches a room.

  3. 03

    Let the hot air leave

    Warm indoor air rises and escapes through a second shaft. Cool air is drawn in behind it — continuous ventilation with no fan and no power.

Cross-section: wind enters the tower, is cooled by the basement and qanat water, and hot air exhausts back up the tower QANAT — COOL GROUNDWATER LIVING ROOM SARDAB (BASEMENT) BADGIR WIND EVAPORATION HOT AIR RISES OUT
  • 2,500+Years in use
  • 45°CYazd summer highs
  • 33.35 mTallest badgir, Dowlat Abad
  • 0 WElectricity required

What it teaches us in Tamil Nadu

  • Design with the climate, not against it.
  • Exhaust natural ventilation before reaching for machines.
  • Use courtyards to build a cooler microclimate.
  • Place water where air passes over it.
  • Choose high thermal-mass materials in hot, dry heat.
  • Let passive strategy carry the load; let HVAC finish it.

Wind-catcher types range from one-sided (a prevailing wind) to four- and eight-sided — Yazd favours four, effective whichever way the wind turns.

Learning from termites

The building that copied an insect

A shopping centre and office block in Harare stays comfortable through African summers with no conventional air conditioning at all — because it is built like a termite mound.

The Eastgate Centre was studied from the mounds of Macrotermes termites, which hold their nests at a nearly constant temperature while the savanna outside swings from freezing night to fierce afternoon. The termites are not cooling for comfort — they farm a fungus that dies outside a narrow temperature band, so the mound has to work.

  • 1996Completed
  • HarareZimbabwe
  • Mick PearceArchitect
  • ArupEngineering
  1. 01

    Draw cool air in low

    Fans pull night-cooled air in at the base, exactly as a mound takes air through openings around its foot.

  2. 02

    Store the cool in the structure

    Heavy masonry absorbs the night chill and releases it slowly through the day — thermal mass doing the work a chiller would otherwise do.

  3. 03

    Let the warm air climb out

    Air warmed by people, lights and sun rises through the central atrium and leaves by chimneys at the roof, pulling fresh air in behind it.

  4. 04

    Shade before you cool

    Deep overhangs and a textured facade keep direct sun off the walls, so there is less heat to remove in the first place.

Diagram of passive cooling in a termite mound: cool air entering low, warm air rising through the central chimney and escaping at the top
The Eastgate Centre in Harare, its facade broken up by deep shading and rooftop chimneys
Inside the Eastgate Centre: a tall glazed atrium that carries warm air up and out of the building
Cutaway of a termite mound showing the chimney, fungus gardens, royal chamber and foraging tunnels

What it teaches us in Tamil Nadu

  • Shade the wall before you try to cool the room.
  • Use heavy materials to carry night coolness into the afternoon.
  • Give warm air a way out at high level, not just a fan at low level.
  • Open the house at night; close it against the midday sun.
  • A stairwell or double-height space can work as your chimney.
  • Design the envelope first — machines should finish the job, not do it.

Eastgate Centre, Harare — architect Mick Pearce with Arup, completed 1996. Modelled on the mounds of Macrotermes termites.