Lesson 0.1Lesson 0.1 · How to Read a Climate
One Country, Five Climates
A single rulebook that flatters one Indian climate will quietly punish the other four.
Two identical houses, opposite fates
Take one house — thick walls, small deep-set windows, a flat terrace. Build it in Jaisalmer and it is a comfort masterpiece. Build the same house in Kochi and it traps heat and breeds mould. The building did not change. Only the sky did. So the first question of this whole course is never "is this a good house?" It is: good for which climate?
Good for which climate? Write that question at the top of every site analysis you ever do.
India is five climates, not one
The National Building Code (and SP 41 before it) divides India into five climate zones, defined by mean monthly temperature and humidity. Each has an anchor city you can hold in your head:
Hot-dry — hot, low humidity, a huge day-night swing. Jaisalmer. Warm-humid — warm, high humidity, a small swing. Kochi. Composite — all three conditions across a single year. Delhi. Temperate — mild more or less year-round. Bengaluru. Cold — cold and dry with intense winter sun. Leh.
A sixth label, *moderate/temperate*, and local microclimates complicate the edges — but these five are the spine. Name your site's zone before you name anything else.
The same wall, two opposite outcomes
Why does the identical house flip from masterpiece to failure? The wall.
In hot-dry Jaisalmer, a heavy wall absorbs the day's heat and releases it slowly into a cool desert night. The huge day-night swing does the work — the mass is a battery that discharges every night.
In warm-humid Kochi, there is no cool night to discharge into. The mass soaks up heat all day and then radiates it back into the bedroom all night, while high humidity blocks the sweat-cooling the body relies on. Same wall, opposite outcome — because the boundary condition (the night) changed.
The wall didn't fail. The night did. Always ask what the night is doing before you trust the mass.
Drop one house into all five skies
A masterpiece. Mass soaks the day's heat and dumps it into the cool desert night; tiny windows keep the glare out. This is the house's home climate.
Three altitudes on the same idea
Read the band that fits you — or all three.
If you live on a humid coast, don't copy the thick-walled Rajasthan "haveli look" you saw on Pinterest — it will hold heat against you. On a coast, prioritise cross-ventilation and shade over mass. The picture that's right for a desert is wrong for you.
Make climate zone an explicit line item in your site analysis, written above the envelope strategy in the brief. Envelope decisions — wall mass, window size, roof type, shading — are all *downstream* of the zone. If the zone isn't named, every later decision is a guess.
The two numbers that govern mass are time lag φ (hours the wall delays the outdoor peak) and decrement factor f (the fraction of the outdoor swing that survives the trip inside). A 450 mm stone wall gives roughly φ ≈ 8 h and f ≈ 0.3 — a 10 °C outdoor swing arrives indoors as 3 °C, eight hours late. The full derivation is in Lesson 2.1.
“Vernacular architecture is always climate-responsive, so I can copy any traditional Indian house.”
Run the method yourself
Run the method once, on real Indian cities, before the next lesson.
- 1Classify Bikaner, Panaji and Shillong by NBC zone. (Hint: one desert, one coast, one cool hill station.)
- 2For each, name the one envelope instinct you'd protect first — mass, ventilation, or insulation.
- 3Identify a place where the rule "thick walls = good" backfires, and explain why in one sentence about the night.
↳ Use the worksheet below to record your answers.
Take it with you
No building is good for every sky
We keep saying "comfort" without defining it. The next lesson replaces that vague word with a measurable band — and shows the Indian body is far more adaptable than the AC industry admits.