Buildings at Altitude
Climate-responsive passive solar in the Trans-Himalaya
Winters in Dho Tarap, at 4,000 m in Dolpo, are long and hard. Concrete built the lowland way loses heat fast there. Crystal Mountain School has gone back to stone, mud mortar and south-facing glass, and this work measures what that buys. We know of no long-term thermal record of a real building at this altitude in Nepal; the school's new hall is meant to give one.
Twenty-five sensors, set into the walls
The instrumented building is the new multipurpose hall at Crystal Mountain School: about 170 m², for 100 people, with a Trombe wall on the south side — 450 mm of stone in mud mortar behind glazing. The north, east and west walls are 450 mm stone on the outside, a rat-trap-bond insulation block layer inside it, and timber planking up to the sill.
25 temperature sensors go into the hall. Eighteen form six through-wall stacks: three sensors in a line from the outer face to the inner, all about 1.22 m above the plinth, with every cable led out on the inside face so a stack can be reconnected later. The other seven measure interior air and outdoor ambient temperature. The sensors go in as the masons build, because a sensor cannot be retrofitted into the middle of a stone wall.
The stacks, as a list
- S: three sensors through the wall, with the glazed Trombe cavity outside.
- E: three sensors through the wall, with the entrance vestibule outside.
- N: three sensors through the wall, with open air outside.
- W: three sensors through the wall, with open air outside.
- SE: three sensors through the wall, with open air outside.
- NW: three sensors through the wall, with open air outside.
South — the Trombe wall ▸
One stack sits in a solid stone pier between the windows. Its outer side is the glazed cavity, not open air, so it records the charge–discharge cycle that is the core of passive solar performance: the wall absorbing solar gain by day and releasing it into the room at night.
North, west and the two corners ▸
Four stacks — north, west, north-west corner and south-east corner — through walls with open air outside. Same build, same height, different orientation: comparing them measures what orientation alone does.
East — the buffered wall ▸
The east stack sits between the two doors from the entrance vestibule, so its outer side is an unheated buffer space, not the outdoors. It measures what the vestibule is worth.
From each stack the dataset gives the temperature gradient through the wall, which becomes a heat flux once the wall's conductivity is measured; the thermal lag, how many hours the inner daily peak trails the outer one; and the decrement factor, how much of the daily swing survives the trip through the wall. The goal is to model and validate the building's thermal behaviour against simulation, and to quantify what passive solar design actually delivers at 4,000 m.
Outdoor air temperature at Dho Tarap from a weather model, hour by hour. The daily swing is what the walls have to smooth out; the hall's own sensor readings will go beside it.
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Source: Open-Meteo weather forecast models · CC BY 4.0.
Heat flow through a Himalayan wall
Heat moves from warm to cold by conduction, described by Fourier's law:
For steady flow through a wall of thickness d and area A, the heat lost is set by the temperature difference and the wall's thermal resistance R = d/k:
Heating demand over a season is summarised by heating degree-days — the accumulated gap between a comfort base temperature and the daily mean, which the monitoring dataset lets us compute from real interior and exterior readings:
Crystal Mountain School, in the Dho Tarap valley, Dolpo, at 4,000 m in north-west Nepal.
Thermal Sovereignty and Vernacular Resilience: Tracing Climate Adaptation and Technology Transfer in Dolpo, Nepal — a case study of the school's buildings, their design and how they were built, written from years of work with the Dolpopa community. Submitted; awaiting the referees' reports. The thermal analysis follows once the sensors have logged a winter.
Under way. The hall's stone walls are going up, and the 25 sensors are being set into them as they rise. Readings will be published here from the first one logged.
