← Air, water and shade

ENERGY

Heat, light, energy

Showers and hammam consume heat, not electricity. That is why solar thermal is sized before photovoltaic, and not after.

Sectional model, on a medina hammam. It is an illustration and not a design.

1. 1. The service yard and the back door. The fuel comes in there and the ash goes out there: they never cross the house.
2. 2. The furnace, bayt an-nār, outside the bath and built against the wall of the innermost room, with the wood beside it.
3. 3. The copper vessel above the furnace: that is where the water is heated.
4. 4. The mouth, the arched opening flush with the floor, through which the flame passes under the paving.
5. 5. The chebka: the small brick piers. The channels are the voids between one and the next.
6. 6. The borma, the basin against the furnace wall from which water is drawn, and the copper bowls.
7. 7. Ad-dākhilī, the innermost room: the hottest because the nearest to the fire, and the most ornate.
8. 8. Al-wasṭī, the middle room.
9. 9. Al-barrānī, the first room: here the floor is no longer heated.
10. 10. The flue, at the end of the run.
11. 11. The cold-water tank.

The balance is built on the house at full strength, thirty residents, with workshops, collective kitchen, laundry and hammam: the services are sized for the maximum, not for the first intake, which numbers seventeen people. Domestic hot water is calculated at eighty-five litres per person per day, a high value chosen deliberately: in a house where people work with their hands, the repeated shower is not a luxury.

Heat

• — Solar thermal. About seventy-seven square metres of flat-plate collectors, sized to cover sixty per cent of the annual heat demand. Beyond that threshold the collectors would stand idle in summer, which ages them without producing.
• — Thermal storage. About five thousand eight hundred insulated litres, seventy-five litres for each square metre of collector.
• — Biomass boiler. One hundred and twenty kilowatts for top-up and for winter, fed by the prunings of the olive grove and the workshop offcuts. The solution, and with it heat recovery from the hammam furnace, is to be verified at detailed design stage with the services engineer: the sizing given here is indicative.
• — Radiant-mass distribution. One thousand four hundred square metres at low temperature, consistent with walls that work by inertia and without additional flues.

The hammam is the most demanding item and the most likely to overrun: radiant mass of the floor, steam, air changes, waterproofing and tadelakt. Three sessions a week are enough to make it the second heat consumer of the house after the showers.

The mass is heated, not the air

The criterion is the one adopted at Riad Al-Uns, and follows from the same observation: heating the air of a vaulted room is wasted work, because warm air rises, flattens against the vault and leaves by the first available opening, whereas a wall, a bench or a floor that have stored heat give it back by radiation over many hours, and the body receives it directly without passing through the air. In a building of heavy wall inertia, where the mass is already the main thermal device in summer, using it in winter too costs less than fighting it.

The house applies the criterion in two ways, and the line between them is that of sleep. Where people gather — the winter sitting room, the workshops, the refectory — a masonry storage stove, small firebox and great mass, threaded by flues in which the smoke winds a long way before leaving: it is charged in the evening, with everyone present, and radiates until morning with the fire out. In the winter sitting room the fireplace is added, which heats badly — most of the heat goes up the flue — but gathers people, and that is why it is there.

Where people sleep nothing is visible: low-temperature coils embedded in the plaster of the walls and the screed of the floors, fed by the thermal storage, that is by the solar, by the combustion chamber of the hammam — a fire that burns in any case on session days and whose heat would otherwise be lost — and by the biomass boiler for top-up. The warm wall does, incidentally, a job no other device would do: it stays dry, and in a limestone wall rising damp does more damage than cold.

From this follows the rule the niẓām ad-dār lays down without exception: no appliance burns in a room where someone sleeps, neither brazier, nor stove in operation, nor flame of any kind. The storage stove is the answer to that rule and not an exception to it, because it is charged while the house is awake and goes on heating with the fire out. Carbon monoxide poisoning kills every winter, and it kills exactly like this: combustion in a closed room and a sleeper who does not wake.

Electricity

The electrical loads are those of a house that works: dust extraction and workshop machines, collective kitchen, laundry and wardrobe for thirty people and the outfit, cold rooms, pumps for the well and the cisterns, recirculation of the water in the courtyard, indoor and outdoor lighting, mechanical extraction from the kitchen and the workshop, and from the hammam if at design stage it turns out that the draught of the flue is not enough.

The photovoltaic is sized at around forty-five kilowatts peak, with a margin covering the share not self-consumed and the growth of the loads, and an electrochemical storage of about sixty-four kilowatt-hours, a little less than half the daily consumption, which covers the evening and the night.

Where the panels go, and why not on the roofs

The photovoltaic array does not go on the roofs. It goes on the ground, on posts, raised so as to let the pasture pass beneath the modules, in a peripheral area adjacent to the masseria and not visible from the main fronts. There are three reasons, and none concerns aesthetics alone.

1. 1. The historic roofs are being remade with traditional covering and insulation: putting a foreign structure on top means piercing them and compromising their maintenance.
2. 2. On a listed building, a visible installation on the roofs is the kind of intervention that lengthens the authorisation process by months.
3. 3. A ground array can be inspected, washed and extended, and its yield is checked by walking beside it.

The exact location depends on the perimeter of the listing and on the buffer zone, which are among the checks of the current phase. The array is fenced, with a passage provided for the pasture, and connected by a buried cable duct laid in the same trench as the other services.

Mass and shade·The twenty-three hectares