Shade, breeze and cool air

Riyadh summers are hard on anyone walking outdoors. A park the size of King Salman Park, which is about 17 square kilometres on most counts, cannot rely on one trick to make that bearable. Its designers use several at once, and some are quite old.

This story sticks to what has been published. Where the sources are silent, for example on measured temperatures, we say so.

Shade you can walk under

The park's pedestrian spine is the Loop, a circular route of about 7.2 km according to most sources. The Foundation's 2025 brochure describes 7.25 km of shaded, car-free pathways. Omrania, the lead design consultant, writes about a dense, breathable grid with a shaded public realm and finger parks that carry greenery out into the neighbouring districts, in its 15-minute city essay.

At the Art Park, Gerber Architekten lists shade canopies inspired by tree crowns around a circular path by the lake, in its project description. The Foundation says its retaining walls, 17 kilometres of them, built from 122,500 tonnes of local stone, shape the wadis and hills and also create shade.

Trees that cool the air

Trees along roads and near buildings are there for more than looks. The Foundation's chief executive, quoted in the Parsons announcement, said they are meant to absorb carbon dioxide, increase humidity and reduce the urban heat island effect. The Royal Commission gives a target of about a million trees.

The landscape is organised into climate zones, too. RIBAJ describes arid planting on the ridgelines, semi-arid planting below and lush planting at the bottom, in a valley form that makes the shaded places families gather. That zoning puts hardy plants where it is driest and saves the lush, cooling planting for places with more water. An aside from the same design team describes a deep, regenerative soil layer, about 2.5 metres in Arab News, which helps plants stay alive and keep their leaves, and leaves are what cool the air.

Cool air from a central plant

The most visible piece of engineering is district cooling. Instead of hundreds of separate air conditioners, a central plant makes chilled water and sends it through pipes to buildings. The Saudi Press Agency reported that the Foundation signed an agreement with Saudi Tabreed for the park's district cooling. Zawya reported a 25-year build-own-operate-transfer arrangement for 60,000 refrigeration tonnes, with 20,000 for the first phase. TradeArabia reported that SNC-Lavalin won the engineering, procurement and construction contract, a reported 27 months.

Saudi Tabreed describes the system as designed to replace many individual units, cutting energy use and emissions, as it says on its project page. We have not found a published figure for how much energy it saves in practice, and we would treat any such figure as unverified until a measured one appears.

Buildings that cool themselves

Buildings add their own contribution. Contractor Freyssinet describes the Grand Mosque, which has a basement with passive cooling and a photovoltaic roof, on its portfolio page. The park's design language, which the Foundation calls Salmani architecture, favours light-coloured materials, natural air circulation and shading from vegetation and structures, according to the research notes behind our building profiles (we link the primary sources on each building's page).

What we do not know

Three limits apply. First, the park's microclimate has not been measured publicly, because nothing is open and no data has been released, so we cannot say by how many degrees the shade and planting will cool a visitor's walk. Second, district cooling is contracted, but we have no commissioning date for the plant. Third, even the design team treats heat as a risk: the research behind this story lists extreme heat, plant losses and summer visitor comfort as residual risks that design reduces but does not remove.

There is also a link to the water story. Trees cool the air only if they stay alive, and in Riyadh that depends on a reliable supply of treated water. If the loop of recycled water holds, the shade follows.

The Foundation says it is preparing a phased soft opening, and some of the landscape could, in the acting CEO's words, open "tomorrow". The first visitors will be the real test of all of this. Until then, what we have is a design that treats cooling as a layered problem: shade overhead, planting underfoot, chilled water in the pipes and walls that do some of the work. That is a sensible way to approach a desert summer, and it is one we will be watching closely.