Cold plunge pools that hold temperature in Rwandan heat

Why altitude is a running-cost argument

A chiller fights the difference between your target water temperature and the surrounding air. In Kigali that gap is small for most of the day and almost closes at night, so the compressor cycles less, the unit lasts longer and the monthly bill is lower than the same installation at the coast.

It still only works with insulation. An uninsulated tub in the sun will beat any chiller you put on it. We build the tub as an insulated shell — closed-cell insulation in the wall cavity, an insulated lid that actually gets used — and then size the chiller. In that order.

Sizing the chiller

We work off volume and target temperature. As a rule of thumb: 1 HP for tubs up to about 260 litres, 2 HP to about 570 litres, 4 HP to about 1,200 litres, with a step up if the tub sits in full sun, is used back to back by a team, or is being held at 4 °C rather than 8-10 °C.

Filtration and sanitation matter more than people expect. Cold water does not hide anything, and a tub used by a gym needs a cartridge filter, circulation and an ozone or UV stage — otherwise it is a shared bath.

Tub, basin or pool

A timber-clad tub is the cheapest way to a good one and it moves if you move. A basalt or terrazzo basin built into a terrace is permanent, beautiful and needs the structure checked. A sunken pool for six to eight, with a bench and a ladder, is the commercial answer for a hotel or a club — and it needs a plant room, not a chiller sitting in the corner.

In short

• Insulated shell first, chiller second — insulation is what holds the temperature
• 1 HP ≤260 l, 2 HP ≤570 l, 4 HP ≤1,200 l, stepped up for sun, teams or 4 °C targets
• Cartridge filtration plus ozone or UV on anything shared
• Kigali's 16–17 °C nights mean lower running cost than any coastal city in the region