Climate Control for 64 Million Cubic Metres

The Mukaab’s HVAC system must solve a problem that has never been attempted: maintaining comfortable human habitation across 64 million cubic meters of enclosed space in a city where summer temperatures routinely exceed 45 degrees Celsius. The current largest building by volume, the Boeing Everett Factory at 13.4 million cubic meters, already experiences significant climate control challenges including interior fog formation due to temperature differentials. The Mukaab’s volume is nearly five times larger, and its mixed-use program demands far tighter comfort standards than an industrial facility.

Thermal Load Calculation

The cooling load for the Mukaab derives from multiple sources. Solar heat gain through the 640,000-square-meter facade represents the dominant external load, particularly on the south and west faces during summer afternoons when surface temperatures can exceed 80 degrees Celsius. Internal heat gains from lighting, equipment, and the metabolic heat of hundreds of thousands of daily occupants add significant load. The holographic dome technology and computing infrastructure required for the building’s digital systems generate additional heat that must be removed.

Preliminary estimates suggest cooling capacity requirements in the range of hundreds of thousands of tonnes of refrigeration — an order of magnitude beyond the largest existing district cooling plants. The Riyadh climate offers minimal opportunity for free cooling or economizer cycles, as nighttime temperatures in summer typically remain above 30 degrees Celsius.

AI-Enabled Climate Management

The AI climate control system planned for the Mukaab represents a step change in building environmental management. Rather than responding to thermostat setpoints, the AI system tracks air quality, temperature, humidity, occupancy, solar position, and weather forecasts to optimize conditions proactively. The system adjusts ventilation rates, cooling distribution, and air circulation patterns in real time based on predictive models of thermal behavior across the building’s diverse zones.

The vertical thermal stratification challenge is particularly demanding. Hot air naturally rises, creating temperature differentials of 10 degrees Celsius or more across the building’s 400-meter height. Managing this stratification requires air handling systems that can overcome natural convection patterns and maintain consistent conditions at observation decks 300 meters above ground level and at retail spaces at ground floor simultaneously.

Energy Implications

The energy demand for climate control in a structure of this scale has direct implications for the building’s net-zero energy aspirations. Even with the most efficient cooling systems available, the annual energy consumption for HVAC alone could rival a small city. The solar arrays planned for the building’s rooftop, while extensive, may provide only a fraction of the total cooling energy required.

Innovative approaches being explored include deep geothermal cooling using the desert substrate as a heat sink, ice storage systems that generate cooling during off-peak hours, and radiant cooling systems that reduce the need for energy-intensive air-based cooling. The smart grid infrastructure enables load shifting and demand response strategies that optimize energy use across the building’s daily and seasonal cycles.

District Cooling Integration

The Mukaab’s cooling requirements are so large that the building effectively requires its own district cooling plant — a centralized facility that produces chilled water and distributes it through an underground pipe network to air handling units throughout the structure. District cooling is well-established in the Gulf region, with Dubai’s Empower operating the world’s largest district cooling network at 1.74 million refrigeration tonnes. Riyadh’s district cooling infrastructure is expanding rapidly, with the Royal Commission for Riyadh City mandating district cooling for major new developments.

The cooling plant serving the Mukaab and the broader New Murabba development must produce chilled water at approximately 5-7°C and distribute it through insulated steel or HDPE piping to air handling units located throughout the building’s 70 floors. The pipe network alone — with primary headers potentially exceeding 1,200mm diameter — represents a significant infrastructure investment. The pump energy required to circulate chilled water to the building’s uppermost levels (400 meters above ground) against gravitational head pressure adds to the total energy demand.

Thermal energy storage (TES) systems using chilled water or ice storage tanks provide essential load management. By producing ice or chilled water during nighttime off-peak hours (when electricity is cheaper and ambient temperatures are 15-20°C lower), the system can store cooling capacity equivalent to several hours of peak daytime demand. The stored cooling supplements the chillers during afternoon peak periods when both cooling loads and electricity costs are highest. A TES system serving the Mukaab would require storage tanks with capacity measured in millions of litre-hours — among the largest thermal storage installations ever constructed for a single building.

Air Distribution Architecture

Distributing conditioned air throughout a 64-million-cubic-metre volume requires an air handling infrastructure without precedent in building engineering. The conventional approach — central air handling units serving floor-by-floor ductwork — breaks down at the Mukaab’s scale because the duct sizes required to serve 400-meter-tall vertical zones exceed practical fabrication and installation limits.

The solution involves a hierarchical distribution system. Primary air handling units located at mechanical floors (typically every 10-15 stories) receive chilled water from the district cooling network and produce conditioned air at each zone. Secondary distribution from these mechanical floors serves the occupied spaces above and below through local ductwork of manageable size. This approach mirrors the multi-zone strategies used in supertall towers like the Burj Khalifa and Shanghai Tower, but applied across a floor plate that is 25-50 times larger than any supertall tower’s floor area.

The holographic dome presents a unique air distribution challenge. The dome’s 300-meter vertical space cannot be conditioned floor-by-floor because it is a single continuous volume without intermediate floors. Instead, displacement ventilation — where conditioned air is introduced at low velocity at the base of the space and rises naturally as it absorbs heat — provides the most energy-efficient strategy. The spent warm air collects at the dome’s apex, where extraction systems remove it for reconditioning. This natural stratification-based approach works with rather than against the physics of warm air rising, reducing the fan energy required compared to fully mixed ventilation systems.

Humidity Management in Desert Conditions

Riyadh’s average relative humidity of 25-35 percent (dropping to 10-15 percent during summer) creates indoor air quality challenges distinct from those faced in humid climates. At these low humidity levels, occupants experience dry skin, irritated eyes, and respiratory discomfort. The World Health Organization recommends indoor relative humidity of 40-60 percent for occupant comfort and health.

Humidifying 64 million cubic meters of air to 40-60 percent relative humidity requires enormous water consumption. At an air change rate of 1.5 exchanges per hour (typical for commercial occupancy), approximately 96 million cubic meters of air must be processed hourly. Humidifying this volume from 15 percent to 45 percent relative humidity requires approximately 200-400 tonnes of water per hour — a consumption rate that rivals a medium-sized municipal water supply.

Water sourcing for humidification in Riyadh, where municipal water supply relies on desalination and deep aquifer extraction, adds cost and sustainability considerations. The Mukaab’s water strategy likely incorporates condensate recovery (capturing water condensed from cooling coils), greywater recycling, and potentially on-site atmospheric water generation systems. The sustainability features of the building must address this water-energy nexus — the intimate relationship between cooling, humidification, and water consumption that defines climate control in desert mega-structures.

Ventilation and Air Quality

Beyond temperature and humidity, the HVAC system must manage air quality for a building population that may reach hundreds of thousands of simultaneous occupants during peak events. Carbon dioxide concentration, volatile organic compounds from interior finishes, particulate matter from the desert environment, and biological aerosols all require monitoring and control.

The outdoor air intake system must filter Riyadh’s desert air — which carries fine sand particles, elevated PM2.5 concentrations during dust storms, and temperatures exceeding 50°C — before introducing it as ventilation air. High-efficiency particulate filtration (MERV 13 or higher), activated carbon for gaseous contaminant removal, and UV germicidal irradiation for biological control create a multi-stage air treatment process that adds pressure drop (and therefore fan energy) to the ventilation system.

During sand storms — which occur 20-30 times annually in Riyadh and can reduce visibility to near zero while elevating PM10 concentrations to 500+ μg/m³ — the building must switch to full recirculation mode, providing ventilation from interior air reserves rather than contaminated outdoor air. The building’s massive internal volume provides a significant air reservoir during these events, but CO2 accumulation limits the duration of full recirculation operation. The AI climate system monitors outdoor air quality sensors and weather forecasts to proactively switch ventilation modes before storm arrival.

Comparison with Existing Large-Volume Climate Control

The Boeing Everett Factory — the current volume record holder at 13.4 million cubic meters — famously generates its own weather patterns, including interior fog and cloud formation when warm moist air meets cold surfaces. The factory’s climate control system, while impressive, prioritizes manufacturing conditions (temperature stability for aircraft assembly) over human comfort.

The New Century Global Center in Chengdu (4.8 million cubic meters) contains an indoor water park with artificial beach, requiring climate control that maintains tropical conditions (28-30°C, 60-70 percent humidity) within a temperate climate zone. The energy density of this climate control — cooling and heating a water park in a continental climate — provides useful data points for the Mukaab’s mixed-use climate requirements.

Dubai’s Mall of the Emirates maintains skiing conditions (-1 to -2°C) in Ski Dubai while the rest of the mall operates at 22-24°C — demonstrating that dramatically different climate zones can coexist within a single structure when adequate thermal barriers and independent HVAC systems separate them. The Mukaab’s program envisions similarly diverse climate zones — from the temperature-stable retail environments at ground level to the potentially unconditioned observation platforms at the building’s crown — requiring zone-specific climate strategies united by a common energy and water infrastructure.

Commissioning and Operational Readiness

Commissioning the Mukaab’s HVAC system — the process of testing, balancing, and optimizing all climate control equipment before building occupancy — will be one of the most complex commissioning programs ever undertaken. The commissioning team must verify that thousands of air handling units, hundreds of thousands of meters of ductwork, tens of thousands of control valves and dampers, and millions of sensors operate correctly as an integrated system.

Seasonal commissioning adds timeline requirements. The HVAC system must be tested under both summer peak conditions (50°C+ exterior, maximum cooling demand) and winter conditions (near-freezing nights, potential heating requirements in upper levels). Since these conditions occur six months apart, the commissioning program spans at least 12 months of testing across both seasonal extremes. The AI control algorithms require training data from actual building operation — learning the building’s thermal response characteristics, occupancy patterns, and zone-specific requirements through machine learning that improves performance over the first 2-3 years of operation.

The operational team managing the Mukaab’s climate systems will rival the engineering departments of major utilities. Hundreds of HVAC technicians, controls engineers, energy managers, and water treatment specialists will maintain the systems that keep 64 million cubic meters of desert air comfortable for human habitation — a workforce requirement that contributes to the 334,000 jobs projected across the New Murabba development.

The Mukaab’s climate control engineering will establish new benchmarks for enclosed-volume environmental management. The solutions developed — AI-driven predictive control, hierarchical air distribution, natural stratification management, and desert-specific humidity and filtration systems — will become reference designs for future mega-structures worldwide, contributing to an engineering knowledge base that enables increasingly ambitious architectural visions in extreme climates.

Cooling Infrastructure and the $50 Billion Budget

The scale of the Mukaab’s cooling infrastructure reflects the engineering ambition embedded in the project’s $50 billion budget. The central cooling plant — housing centrifugal chillers, cooling towers, thermal storage tanks, and the primary pump station — occupies a footprint equivalent to a major industrial facility. AtkinsRealis has specified chiller units in the 5,000-10,000 refrigeration tonne class, with total installed capacity requiring 30-50 individual machines operating in coordinated arrays. The redundancy requirements for a building with hundreds of thousands of occupants in a climate where cooling failure constitutes a life-safety emergency demand N+2 chiller redundancy — two additional machines beyond the peak load requirement — adding capital cost but ensuring continuous operation through any combination of planned maintenance and unplanned equipment failure.

The cooling towers that reject heat from the chiller condensers to the atmosphere face Riyadh’s 50-degree-Celsius summer air temperatures as their heat sink — a condition that reduces cooling tower efficiency by 30-40 percent compared to temperate climate operation. Hybrid cooling towers combining evaporative and dry cooling modes, along with nighttime pre-cooling strategies that take advantage of the 20-degree diurnal temperature swing, maximize cooling tower performance across the daily cycle. The water consumption of evaporative cooling towers — estimated at 5,000-10,000 cubic meters per day during peak summer — intersects with Riyadh’s broader water sustainability challenges and the building’s net-zero aspirations.

Climate Control for 64 Million Cubic Metres