Lesson 1.4Lesson 1.4 · The Tools of Climate Analysis
The Bioclimatic Chart (Givoni)
Take the psychrometric chart, draw the passive strategies onto it as territories, and your city's point lands inside the answer.
A description is not a decision
We've learned to describe a climate — sun, moisture, degree-days. But a description isn't a decision. On a real site with a real budget you need one answer: which passive strategies are worth building, and which waste money? Givoni's bioclimatic chart divides the psychrometric chart into territories, one per strategy. Plot the point, read the territory, build the strategy.
Plot, read, build. The chart's whole job is to stop you building a desert wall on a humid coast.
From description to prescription
The psychrometric chart (Lesson 1.2) showed *where* a climate sits. The bioclimatic chart overlays strategy boundaries on top of it: inside a boundary, that strategy alone reaches comfort; outside it, the strategy fails and you reach for the next one.
Each territory answers the same question — *given a point that lands here, what do you build?*
Comfort — already comfortable → build nothing; don't over-design. Natural ventilation — warm, humid → cross-ventilation, fans, openness. Thermal mass — hot, dry, big swing → heavy walls, exposed mass. Mass + night flush — very hot, dry → mass charged by cool night air. Evaporative cooling — hot, very dry → water, courtyards, desert coolers. Passive solar / heating — cold → solar gain, insulation.
The boundaries are fuzzy frontiers, not walls. A point near an edge means two strategies half-work — so combine them.
Five cities, five territories, one chart
Plot a city's design-month afternoon and its point lands in a single Givoni territory, which names what to build. Walk five Indian cities across the same chart and the whole module appears at once.
Jodhpur, May → evaporative cooling (hot, very dry). Delhi, June → mass + night flush (hot, dry, big swing). Kolkata, July → natural ventilation (too humid for mass or evaporation). Leh, January → passive solar (the problem inverts — now you want heat in).
Five cities, five territories, one chart. The chart is where reading a climate (Module 0–1) becomes designing for one (Modules 2–5): plot, read, build.
The chart doesn't have an opinion about your city. It just tells you where your point landed — the wall, the water and the window are downstream of that.
Three altitudes on the same idea
Read the band that fits you — or all three.
Ask your architect to show your city on the chart. If your point lands in natural ventilation, thick walls are largely wasted money — you needed openness and a breeze. If it lands in thermal mass, big openable windows may simply let heat in. It's a one-page sanity check on where the design budget actually goes, before a single brick is bought.
Build the chart at concept stage and plot all twelve months, not just the hottest one — composite sites scatter across three or four territories. Put it in the design narrative as client justification for the envelope strategy. Climate Consultant generates it automatically from an EPW weather file (Lesson 1.3), so there is no excuse for guessing the lead strategy.
Each frontier is a physical limit met earlier in the module, now drawn as a line. Ventilation extends comfort right to ~28–32 °C (≈ 1 m/s air offsets 2–3 °C). Thermal mass extends right in the dry region, bounded by the diurnal swing (≈ ΔT/2 shaved off the peak). Evaporative cooling follows constant-wet-bulb lines and works only where T_wb is near comfort (~<24 °C). Jodhpur at 42 °C, T_wb ≈ 23 °C → evaporation can reach ~23 °C, so the point sits firmly in evaporative territory.
“The chart gives the one correct strategy for my city, full stop.”
Run the method yourself
Run the whole-year reading on your own site before the next lesson.
- 1Find the afternoon dry-bulb temperature and relative humidity for three contrasting months — peak summer, monsoon, and the coolest month.
- 2Plot each point and read off its Givoni territory.
- 3List the strategies your year demands. One territory = a simple climate; three or four = a composite climate that needs a switching building.
- 4Name one building feature that would let a single house move between your two most-demanded strategies.
↳ Use the worksheet below to record your answers.
Take it with you
Most climates are a scatter, not a point
The chart leans heavily on natural ventilation for humid India — but "let the air move through" depends on where the wind comes from, how hard, and when, plus the great monsoon reversal. The last lesson of Module 1 reads wind and monsoon as design forces, so when the chart says "ventilate," you know which way to point the building.