Annual net-zero electricity feasibility of Riyadh villas depends more on subdivision into separate dwellings than on the 2024 massing rules
This study demonstrates that for Riyadh villas, subdividing properties into multiple dwellings has a significantly greater impact on achieving annual net-zero electricity status than the 2024 massing rule changes, which primarily increase floor area but offer limited gains in solar panel capacity due to setback constraints.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the sun-drenched cities of Saudi Arabia, the single-family home, known locally as the villa, is the dominant form of housing. These structures are designed to keep the intense heat out while relying heavily on air conditioning to keep the inside cool, a process that consumes a massive portion of the nation's electricity. As the country seeks to balance its energy use with its environmental goals, a critical question has emerged: can these homes generate enough of their own electricity from rooftop solar panels to power themselves entirely over the course of a year? This concept, known as net-zero energy, depends on a delicate balance between how much energy a home uses and how much sunlight its roof can capture. However, the shape of a building and the rules that govern its construction play a huge role in this balance. A roof that is large but heavily shaded by the building itself or its neighbors will produce far less power than a smaller, sunnier roof.
In 2024, the Saudi government updated the rules for building these villas, allowing for larger homes and permitting a single plot of land to be divided into separate, independent apartments. The intention was to increase housing density and provide more living space. A researcher set out to test whether these new, larger, and more crowded homes could still achieve that goal of generating their own electricity. They built a detailed digital model of a typical Riyadh villa and simulated thousands of variations to see how the new rules affected the amount of solar power the roof could produce compared to the energy the home would need. They accounted for the specific requirements of the new regulations, such as mandatory gaps between the solar panels and the roof edges for maintenance, and the shadows cast by the building's own upper levels and neighboring structures.
The researcher found that the new construction rules, while successful at adding more floor space, did not add much more room for solar panels. Because the rules require buildings to stay a certain distance away from the property lines, the size of the main living area is often limited by these gaps rather than by the total size of the plot. When the new rules allowed for a larger upper-level extension, it actually covered up much of the main roof where solar panels could have been placed. Consequently, for a single-family home, the ability to generate enough electricity to meet its own needs changed very little under the new rules. The ratio of solar power generated to energy used shifted by only a small margin, meaning the new regulations did not significantly help or hinder the single-family villa's path to energy independence.
However, the story changed dramatically when the researcher looked at what happened when a single villa was split into multiple separate households. The study revealed that the number of families living on a plot mattered far more than the size of the building itself. When a home was divided into three separate dwellings, the total electricity demand skyrocketed because each family needed its own cooling, appliances, and hot water, yet the roof area available for solar panels remained the same. The simulations showed that a plot of land that was large enough to support a net-zero single-family home suddenly became too small to support three families, even with the most efficient equipment available. For a plot of 400 square meters, a single home could easily reach net-zero status, but adding two more families pushed the required land size up significantly, to a point where the available roof space could no longer generate enough power to meet the combined demand.
The researcher also discovered that the type of air conditioning system used made a substantial difference in the outcome. Their models suggested that if the homes used standard, single-speed cooling units rather than more advanced, variable-speed systems, the energy demand would be higher, making it even harder to reach net-zero status. In the most challenging scenarios, where the roof space was crowded with water tanks and air conditioning units, the researcher found that three families could not achieve net-zero energy on a 400-square-meter plot unless they gave up a significant portion of their living space. Specifically, to make it work, the upper-level extension would have to be reduced to a very small size, sacrificing the extra floor area that the new regulations were designed to provide.
Ultimately, the study concludes that the key to making these dense, subdivided homes energy-independent lies not in the building regulations themselves, but in how the roof is planned from the very beginning. The researcher found that the most influential factor was simply how much of the roof was actually usable for solar panels after accounting for maintenance pathways and equipment. If a roof is cluttered with services or shaded by the building's own structure, the potential for solar power drops sharply. The findings suggest that for subdivided villas to work as net-zero homes, architects and planners must prioritize the roof as a dedicated energy-generating surface, perhaps by grouping all the mechanical equipment in shaded areas to leave the rest of the roof clear for panels. Without this careful planning, the increased density of housing will likely outpace the ability of the roof to generate the electricity needed to power it.
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