Lesson 4.1Lesson 4.1 · Composite and Temperate Strategies
Seasonal Switching
Delhi is a desert in May, a swamp in August and almost cold in January — so the house must change its mind with the calendar.
Three contradictory climates, one building — don't compromise, switch
Each climate so far had one answer: desert means heavy and closed, coast means light and open. So which should Delhi be? The honest reply is it depends on the month. In May it is fierce hot-dry — you want closed mass and night flushing. By July–August the monsoon turns it warm-humid — now you want cross-ventilation, and mass becomes a liability. Come December it is genuinely cold — you want to trap heat and chase the low sun. One building, three contradictory climates. The resolution is not a mediocre middle but a building that switches — a fixed shell with adjustable behaviour, run differently as the seasons turn.
Don't split the difference between three climates — build the switch between them.
A sequence of climates, not one
The composite zone — Delhi, Lucknow, Kanpur, Nagpur, Bhopal — does not have a climate; it has a sequence of them. So the design question shifts. It stops being what is the right strategy here? and becomes what is the right strategy this season, and how does one building manage to do all of them?
The answer is to build a shell that is good in the most demanding season, then hand the occupants and the automation the controls to reconfigure it: open or close, shade or expose, ventilate or seal, store heat or reject it.
Read the Delhi year as four borrowed toolkits. April to June is hot-dry — close up, lean on mass, night-flush, shade hard. July to September is the warm-humid monsoon — open up, cross-ventilate, defend against rain and mould. October and March are mild — open, enjoy, intervene as little as possible. December to February is genuinely cold — capture the winter sun, close at night, trap the heat. No single one of these is the building's answer; the sequence is.
The seasonal-switch dial — a reusable instrument
Picture a dial you turn through twelve months for Delhi. As the pointer crosses a season boundary the building changes mode and the active toolkit lights up: the desert kit glows through the dry summer, the coastal kit takes over in the monsoon, and the cold-climate kit comes on in winter.
Turn the dial slowly and the flips are unmistakable — the moment May tips into the monsoon, the whole strategy inverts, mass going from hero to hazard in a few weeks. Turn it on past September and the building quietens into its mild-season default before bracing for winter.
This is not a one-lesson toy. The same switch-by-season logic drives the rest of Module 4 — the year-round courtyard, the selective mass, the shaded-but-solar glazing are each a specific way of building one of these mode changes into a fixed element.
Don't ask which climate Delhi is — ask which month. The building has modes, not a setting.
Designing a building that can switch
Switching is adjustability deliberately built into a fixed shell. A handful of moves recur.
Operable everything — windows, vents, shutters and screens that genuinely open and close, sealed tight in May and thrown wide in August. Adjustable shading — deep enough to block the high summer sun, shaped so it still admits the low winter sun. Selective, controllable mass — mass that can be charged or bypassed, flushed or retained, rather than a fixed thermal load you are stuck with all year. And a plan that supports seasonal migration — a shaded cool core to retreat into in summer, sunny rooms and terraces to occupy in winter, cross-ventilated spaces for the monsoon.
The shell is permanent; the behaviour is seasonal. North-Indian havelis already knew this — a thick-walled shaded core and open terraces, adjustable jaalis, rooms used differently by season, the family migrating within the house across the year. Switching was social as much as mechanical.
Three altitudes on the same idea
Read the band that fits you — or all three.
In Delhi, Lucknow or Bhopal, the best home is not the one with a single clever trick — it is the one you can run differently through the year. Look for windows and shutters that really open and close, deep shades that still let the low winter sun in, and a layout that lets you shift into cooler shaded rooms in summer and sunnier rooms in winter. A sealed glass box can do none of this; operability beats it every time. When someone offers you a 'modern' fully-sealed, fully-glazed house in a composite city, remember it has given up the one thing your climate most needs — the ability to change its behaviour with the season.
Design the shell for the harshest demand, then engineer the adjustability in. Provide operable, secure, screened openings sized for monsoon cross-ventilation yet sealable for the dry summer and winter. Shade against the summer sun-path while admitting winter gain (the geometry of Lesson 1.1). Make the mass shaded and night-flushable in summer but able to receive winter solar gain — selective mass, taken up in Lesson 4.3. Zone the plan for seasonal use. Above all, avoid optimising for one season — a building tuned for May alone is wrong from June. And keep the controls simple enough that occupants actually operate them; a switch nobody throws is no switch at all.
Frame it as comfort hours H(S, m) delivered by strategy S in month m. A fixed strategy maximises the annual sum Sum_m H(S_fixed, m) — one S held all year. A switching building instead achieves Sum_m max_S H(S, m), picking the best strategy in each month.
Because max_S H(S, m) >= H(S_fixed, m) for every month, the switching total always meets or beats the best fixed total. The margin is small where the optimal S barely changes — and large in a composite climate, where the optimal strategy in May (mass + night-flush) genuinely differs from August (ventilation) and from December (solar gain). There is no single fixed optimum here. When the climate has modes, the building should too.
“For a mixed climate, design a balanced compromise that's moderately good all year.”
Run the method yourself
Turn the dial through a full year before the next lesson, and watch where the modes flip.
- 1Turn the dial through twelve months and note every point where the mode flips. How many distinct modes does the Delhi year actually demand?
- 2For each mode, name which module's toolkit it borrows — M2 hot-dry, M3 warm-humid, or M5 cold.
- 3Pick one fixed element, say a window, and describe how it should behave differently in May, August and January. That difference is the switch.
- 4Explain why a 'balanced compromise' mass would underperform a selective, switchable mass across the full Delhi year.
↳ Use the worksheet below to record your answers.
Take it with you
The switching building
A switching building needs seasonally versatile elements — and the most powerful is one you have already met twice, doing opposite jobs. In the hot-dry house the courtyard pooled cool night air; in the humid house an open court could trap stagnant damp. In the composite climate a well-tuned courtyard can be the **year-round mediator** — a shaded cool well in summer, a ventilation funnel in the monsoon, a sun-trap in winter. Next: the courtyard as the switching building's central organ.