Courtyards, Jalis, Thermal Mass: The Specs That Were Already RightPREVIEW

Jalis filter solar radiation. Courtyards
move air. Thick walls store heat.
Vernacular architecture solved the 9-month
heat problem 400 years ago. Modern
buildings chose to forget.

Vernacular Indian architecture evolved
over centuries in response to 9 months of
continuous heat. Three mechanisms work
together: thermal mass (heavy stone or mud
walls absorb daytime heat and release it
at night), natural ventilation (courtyards
and jalis create convection as heated air
rises and cooler air enters), and solar
shading (deep overhangs and lattice
screens reduce direct radiation reaching
walls and windows).

Thermal mass in thick masonry walls
operates on the same latent heat principle
as the soil in a Terrapod. Stone has a
specific heat capacity of approximately
800 to 1,000 joules per kilogram per
degree Celsius. A 45-centimetre thick
sandstone wall spanning 10 metres of floor
area, when heated from 20°C to 35°C during
the day, stores approximately 13.5
megajoules of energy. This energy releases
slowly at night as exterior temperature
drops, moderating the rate at which indoor
air temperature rises the following
morning.

Jalis, or lattice screens, reduce incident
solar radiation on walls and windows by 60
to 80 percent depending on geometry. This
is not decoration. This is thermal
engineering. Courtyards create stack
ventilation: as air in the courtyard is
heated by afternoon sun, it becomes less
dense and rises. Cooler air from covered
colonnades flows in to replace it,
creating continuous ventilation without
pumps.

Modern buildings abandoned these
mechanisms in favour of mechanical HVAC:
all cooling through electricity, no
passive mechanisms. The cost is 9 months
of thermal dependence on the grid.
Biothermal Microconditioning returns
cooling to biology, using areca palms as
living jalis (shade + filtration +
evapotranspiration) and Terrapods as
portable thermal mass. Easy Retrofit. One
day to place clusters. No structural
changes. Results measurable immediately.