Choosing a Passive School Massing in Hot-Arid Kerman
A 1,500 m² primary school is planned on a 60 m by 50 m site in Kerman. The site slopes 1.5 m from north to south, and the street is on the south. The climate is hot-arid: July mean maximum 38°C, January mean minimum -6°C, diurnal swing 16 K, annual precipitation 150 mm, and prevailing summer wind from the northeast. The brief requires 12 classrooms, a library, an administration block, and a multipurpose hall. The client's preferred scheme is a two-storey linear block along the south boundary, 18 m deep, with 40% glazing and a single-loaded corridor on the north. A second scheme is a one-storey courtyard plan with classrooms around a shaded central court and a basement for the hall and service spaces. The budget is fixed, and the client wants low operating energy. The architect must choose a massing and envelope strategy, and justify it with passive cooling and heating performance rather than style.
1. Compare the two schemes for summer overheating, winter heat loss, daylight, and construction cost. Recommend one.
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The linear block has a fatal flaw for Kerman: 18 m deep, single-loaded, with 40% glazing. The south-facing classrooms will overheat from spring to autumn, and the west end will get low-angle sun; 40% glazing is roughly double what a hot-arid school should have. The single-loaded corridor wastes heat and creates a long, exposed north wall. The courtyard scheme is lower and more compact, with a shaded court and earth-tempered basement; it costs more in roof and excavation but reduces cooling load and creates a protected yard. The linear scheme is cheaper to build and easier to phase, but its operating energy will be higher. I would choose the courtyard scheme, but not as a one-storey ring: keep two storeys on the north side to reduce roof area, put the hall and service in the basement, and use the south side as a one-storey classroom wing with deep shade. This gives 1,500 m² with a compact envelope and a genuine microclimate.
2. Specify orientation, window-to-wall ratio, shading, thermal mass, and ventilation for the chosen scheme. Quantify where possible.
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Orient the long axis east-west, with classrooms on north and south. North classrooms get steady diffuse light; south classrooms get winter sun but need a 1.5 m overhang and 0.6 m vertical fins to cut summer sun. Limit glazing to 20% of wall area, use double glazing with a low-e coating, and insulate the roof with 100 mm and walls with 50 mm mineral wool or XPS. Use 250 mm brick or 200 mm concrete as internal thermal mass, exposed to the room, and night ventilation at 6–8 air changes per hour through high and low openings. The courtyard should have a water channel and planted shade; a north-facing wind catcher can capture the prevailing northeast summer wind and drive stack ventilation, with a solar chimney on the south. Shade the court in summer but keep it open to winter sun. These measures target a cooling demand well below the linear scheme's, and they are passive first, mechanical second.
3. How would you use the site slope and the courtyard to improve comfort and drainage?
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Use the 1.5 m slope to drain the site from north to south and to place the basement on the north, where the ground is higher; the basement can be daylit on the north side and entered by a ramp that follows the slope. The courtyard should step down with the site, with the lowest point at the south outlet, so stormwater runs away from the building. A 1.5 m drop is enough for a shallow amphitheatre and a planted swale; do not flatten the site, because earthworks cost money and destroy drainage. The basement slab should be above the water table and tanked; perimeter drainage and a French drain protect against rising damp. The court's shaded south edge can be a two-storey arcade, which also braces the building. In winter, the slope lets low sun reach the north classrooms over the one-storey south wing; in summer, the same wing shades the court. This turns a constraint into a passive strategy.