Energy efficiency in smart buildings

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Energy efficiency in smart buildings has become a top priority for businesses, government agencies, and many property owners. It's not just about saving on electricity or gas bills: it's about improving comfort, reducing emissions, and maximizing the benefits of technologies like artificial intelligence, the Internet of Things (IoT) , and advanced building automation.

In recent years, buildings have evolved from mere containers of activity to strategic assets within the energy transition . Thanks to sensors, digital platforms, and centralized building management systems (BMS), a building can react in real time to what is happening inside and in its surroundings: adjusting climate control, optimizing the use of renewable energy, anticipating breakdowns, and adapting lighting according to occupancy and natural light, among many other functions.

Energy efficiency as a priority in the infrastructure transition

Recent international studies on infrastructure highlight that energy efficiency in facilities and buildings has risen to become the number one priority for organizations seeking to decarbonize and improve their competitiveness. Just a few years ago, it held a secondary position, but today it is seen as a critical factor for keeping costs under control and meeting climate goals.

According to Siemens' Infrastructure Transition Monitor 2025 report, more than half of the executives surveyed say they plan to increase their investment in energy efficiency, smart building technologies, and facility electrification in the near term. Specifically, 57% intend to invest more in efficiency, 55% in smart building technologies, and 54% in heating and cooling electrification.

This same study shows that many organizations consider on-site renewable energy generation and the electrification of heating and cooling to be in mature or advanced stages. In other words, they are no longer "pilot" projects, but solutions that are being routinely integrated into new developments and major renovations.

The priority is not only environmental: greater energy efficiency allows for a significant reduction in operating costs throughout the building's lifespan. In a context of volatile energy prices, having facilities that make better use of every kWh consumed and that maximize the use of renewable sources becomes a key element of competitiveness.

Even so, the same report points out that, despite many modernizations offering a solid return on investment (ROI) , companies and entities continue to encounter a significant "funding gap" that hinders energy rehabilitation, automation and digitalization projects in buildings.

Economic challenges and new financing models: from CapEx to OpEx

One of the biggest obstacles to boosting energy efficiency in smart buildings is the initial cost of investment . Modernizing equipment, installing sensors, deploying a complete BMS, or integrating advanced AI solutions represents a significant outlay that many organizations are not in a position to make all at once.

The main barriers identified include a lack of available capital, rising energy prices, and the high cost of new technologies . In many cases, this is compounded by the difficulty in reliably quantifying future savings, which complicates the internal approval of large-scale efficiency projects.

To overcome this problem, some leading providers have begun offering Energy-as-a-Service (EaaS) models. With this approach, large capital expenditures (CapEx) are transformed into operating costs (OpEx) linked to measurable results, such as energy savings or _CO2 emission reductions.

These schemes involve contracts based on guaranteed energy savings and emissions reduction targets . In this way, financing relies on the cash flows generated by the project itself: the company or owner pays for the service using the savings achieved, with greater financial security and without having to tie up as much capital upfront.

These types of solutions accelerate the renovation of heating, ventilation, air conditioning, lighting, monitoring, and photovoltaic systems, as they reduce financial risk and facilitate project completion even in budget-constrained environments. In the medium term, the combination of Energy as a Service (EaaS) with smart technologies is poised to become one of the most powerful drivers for modernizing existing buildings.

Digitalization and data: the silent engine of the smart building

Digital technologies have become the backbone of the new generation of buildings. More than half of the organizations surveyed in recent studies believe that digitalization has a strong or transformative impact on energy efficiency , and a significant number also expect reductions in operating costs thanks to these tools.

However, only around 50% of organizations report having sufficient, high-quality data to make informed decisions about decarbonization and energy management. This lack of detailed information on consumption, performance, and emissions makes it difficult to prioritize investments, plan renovations, or implement optimal maintenance strategies.

The answer lies in deploying building-specific technologies: sensors, advanced measurement systems, energy management platforms, comprehensive BMS, and real-time monitoring solutions. All of this is connected to an analytics layer (often based on Big Data and machine learning ) capable of transforming data into actionable insights.

For building managers and facility managers, digitalization offers a key advantage: complete transparency into the building's energy performance . Knowing how much each area, piece of equipment, or installation consumes, during which times of day, and under what conditions, allows them to identify inefficiencies, compare themselves to benchmarks, and make decisions based on sound technical and economic principles.

Furthermore, well-recorded historical data is the basis for developing predictive maintenance strategies , automatically adjusting air conditioning setpoints, or even anticipating the impact that changes in occupancy or renewable production will have on the overall consumption of the building.

How is the energy efficiency of a building measured?

A building's energy efficiency is not an abstract concept: it is measured with quantifiable indicators that allow for comparisons between buildings and an assessment of the impact of improvements. The basic metric is usually the energy consumed in a year, expressed in kWh per square meter of usable floor area (kWh/m²·year), considering standard usage and occupancy conditions.

In the Spanish and European regulatory framework, the annual CO2 emissions per square meter, measured in kgCO2/m²·year, are also used as the main indicator _. Based on this _value , and other complementary indicators, the building's energy rating is obtained, represented by the familiar A to G label.

A building with an A rating is considered highly efficient, consuming up to 90% less energy than a building with the lowest rating. This difference not only impacts energy bills and the climate, but also the property's value, its attractiveness to tenants, and its image with investors and other users.

Additional indicators include data such as annual non-renewable primary energy use , heating and cooling demand, and the efficiency of heating and cooling systems. All of this feeds into standardized calculation models that allow for the simulation of a building's energy performance under comparable conditions.

In practice, one of the major differences between a traditional building and a smart building is that, in the latter, these indicators can be monitored continuously and in real time , not just estimated from monthly or annual invoices. This opens the door to much more dynamic and proactive management.

Architectural design as the basis of efficiency

Before discussing sensors, AI, or automation, it's worth remembering that the primary opportunity to save energy lies in the building's design itself . Orientation, thermal envelope, exposure to sunlight and wind, and the choice of materials all have a significant impact on heating, cooling, and lighting demands.

A thorough analysis of the architecture allows for the optimization of elements such as the insulation of facades, roofs and floors , the quality of windows (ideally with double or triple glazing), the airtightness of joinery and doors, and the treatment of thermal bridges that can cause unwanted losses of heat or cold.

It is also essential to check all those points where there may be a waste of energy resources : hot water leaks, lighting left on in empty areas, equipment on permanent standby, oversized ventilation systems or air conditioning operating outside of actual usage times.

This “passive” approach to efficiency—focused on reducing energy demand through good architecture and a carefully designed building envelope—is the foundation of any powerful sustainability strategy. Upon this foundation, layers of automation and digitalization are then built, enabling the leap to the smart building.

In other words, a truly efficient Smart Building combines passive efficiency (design and construction) with active efficiency (technology and management) , so that both reinforce each other and are not limited to isolated patches.

Key actions to improve energy efficiency in a building

To transform a conventional building into a much more efficient one, a coherent set of measures is necessary. Some of the most important involve the preventive maintenance of heating and cooling systems . A poorly adjusted boiler or dirty air conditioning units can significantly increase energy consumption without anyone noticing on a daily basis.

Knowing the lifespan of energy equipment helps in planning its replacement in an orderly fashion. For example, a boiler can last around 10-15 years with proper maintenance, but after a certain point, it may be more cost-effective to replace it with a more efficient model than to continue repairing it.

Another important lever is the integration of renewable energies, such as photovoltaics , through solar panels on roofs or facades. These systems allow for the on-site generation of some of the electricity the building needs, lowering the bill and reducing the carbon footprint associated with consumption.

At the same time, it is advisable to replace old light fixtures with high-efficiency LED technology , which consumes less energy and generates almost no heat. Combined with occupancy sensors and dimming systems based on natural light, the lights turn on only when and where needed.

All of this is enhanced by the digitization of the building for optimized energy management . A good monitoring system makes it possible to detect anomalous consumption patterns and implement continuous improvement strategies, instead of simply reacting when an unexpectedly high bill arrives.

From traditional building to smart building: real-time control

In most traditional buildings, owners only know their actual energy consumption when they receive the bill—that is, after the fact and with no room for maneuver . At that point, nothing can be done to reduce expenses for that period; they can only pay and hope the following month is better.

In a smart building, on the other hand, it's possible to monitor the consumption of electricity, gas, and other resources in real time for each zone or system. This instant visibility allows for immediate action: modifying climate control settings, adjusting lighting, reorganizing operating schedules, or checking equipment that is consuming more than expected.

Implementing a building management system (BMS) provides a central platform for integrated control of all energy assets . Thanks to connected sensor devices, the BMS receives data on temperature, humidity, occupancy, flow rates, electricity consumption, and more, and executes automatic actions or actions guided by the building manager.

Typical functions of a Smart Building include intelligent climate control , regulating the indoor temperature based on occupancy, outdoor weather and time schedule, or automatic adjustment of ventilation according to indoor air quality measured by sensors.

Similarly, optimized irrigation systems can be managed in sports facilities or landscaped areas, based on scheduling, soil moisture, and weather forecasts. Photovoltaic energy can also be controlled to prioritize the use of electricity generated on-site over that from the grid, maximizing savings.

Smart buildings also allow for central coordination of advertising panels and information boards in spaces such as town halls or hospitals, activating them only when needed, as well as monitoring electric vehicle charging stations, analyzing historical data to decide whether it is necessary to expand the number of charging points or redistribute them according to actual demand.

Integrated trading platforms: the Nexus Integra case

To manage this entire ecosystem of systems and devices, many organizations opt for integrated operations platforms that allow them to visualize, analyze, and control building energy and services from a single environment . These solutions act as the "brain" of the infrastructure.

A prime example is Nexus Integra, a platform designed to centralize the management of utilities, lighting, climate control, irrigation, video surveillance, access control, parking, Wi-Fi, information panels, and waste management , among many other services. All these elements connect to a single digital platform, simplifying control and analysis.

The philosophy behind these solutions is that the building manager can have a 360º view in real time , access historical data, create automation rules, and generate detailed reports without having to jump from one software to another or manually cross-reference spreadsheets.

With this approach it is possible to combine the “passive” energy efficiency of the building (good insulation, optimized design, suitable materials) with active energy efficiency driven by technology , achieving performance levels that are difficult to achieve with disconnected systems.

Furthermore, these platforms facilitate collaboration between technical teams, sustainability managers and management, as they allow complex data to be translated into clear indicators and actionable decisions , supporting decarbonization strategies and medium- and long-term investment plans.

What exactly is a smart building and how does it work?

A smart building can be defined as one that integrates innovative technologies to optimally manage its facilities and energy consumption , dynamically adapting to user needs and environmental conditions. Although it is often associated with large commercial complexes, the concept also applies to smaller buildings and even homes.

The European Union's Energy Performance of Buildings Directive explicitly incorporates the concept of smart buildings . It links this concept to the efficient use of energy, the integration of renewable energy sources, and the secure exchange of building data with stakeholders (owners, managers, users, public authorities, etc.).

Within this framework, the creation of a Smart Readiness Indicator is proposed , which will measure a building's ability to use information technologies, automation, and electronic systems to adapt to its occupants and the electrical grid, improving its energy efficiency and overall performance.

The purpose of this indicator is twofold: firstly, to raise awareness among owners and users about the value of automation and electronic monitoring , and secondly, to build confidence in the real savings these technologies provide. The aim is for digitalization to cease being perceived as an "extra" and instead be seen as a structural component of building quality.

In terms of their operation, Smart Buildings rely on the installation of sensors in equipment and systems (HVAC, lighting, elevators, security, irrigation, etc.), which record real-time data on variables such as temperature, humidity, occupancy, CO2 levels _, electricity consumption or air quality.

This data is transmitted through the network to a central system or BMS, which analyzes it and makes decisions automatically or semi-automatically . In this way, the building adjusts its operation at any given time to internal and external conditions: regulating ventilation according to air quality, adapting heating and cooling capacity to occupancy, coordinating lighting with natural light, and managing available energy storage.

Connectivity, eco-efficiency and automation: pillars of Smart Building

The first major characteristic of a smart building is the connectivity between its spaces, systems, and facilities . Thanks to a robust communications network, devices can exchange information and act in a coordinated manner, multiplying the possibilities for optimization.

This connectivity relies on technologies such as the Internet of Things (IoT) , Big Data, cloud computing, machine learning, and artificial intelligence . These advances allow for the transport and processing of enormous volumes of data in a very short time, something unthinkable just a few decades ago in the building sector.

The second pillar is eco-efficiency as a central objective . The technology behind a Smart Building seeks to maximize energy savings, manage resources (water, energy, materials) effectively, minimize waste, and reduce the environmental footprint, while simultaneously ensuring safety, comfort, and accessibility for occupants.

Real-time information allows heating, cooling, ventilation, and lighting to be adjusted to actual needs, preventing oversizing and waste. For example, the flow of fresh air can be modulated according to the number of people in a room, or the level of artificial light can be adjusted according to the solar radiation at any given time.

The third pillar is advanced automation . Digital sensors constantly capture data that is sent to the central system, where it is interpreted to automatically execute actions. The result is continuous operation that adapts to the building's actual demand without the need for constant human intervention.

Furthermore, in large commercial buildings—such as corporate offices, hospitals, shopping centers, stadiums, or government buildings—automation also encompasses powerful security, access control, and fire detection systems , which benefit from the same logic of monitoring and rapid response to events or anomalies.

Key technologies: AI, IoT, sensors, home and building automation

Within the ecosystem of a smart building, artificial intelligence plays an increasingly important role . Through machine learning algorithms, systems can identify consumption patterns, predict demand, anticipate breakdowns, or recommend operational adjustments without the need to manually program every possible scenario.

The Internet of Things (IoT) enables interoperability between devices from different manufacturers , connecting them to a single platform that facilitates remote control and data integration. Thanks to standardized communication protocols, it's possible to add new devices relatively easily and create complex routines that involve lighting, climate control, blinds, or security systems simultaneously.

Sensors constitute the building's "digital skin." These include sensors for presence, temperature, humidity, lighting, air quality, water quality, energy consumption, and motion detection , among others. These wired or wireless devices send continuous information to the central system, which uses it to optimize overall performance.

The distinction between home automation and building automation helps to clarify the issue: home automation refers to automation in homes , while building automation applies to non-residential buildings . In houses and apartments, home automation allows, for example, raising and lowering blinds automatically, turning the heating on or off from a mobile phone, regulating lighting with voice assistants, or simulating occupancy to increase security.

In office buildings, hotels, educational centers, or healthcare facilities, building automation focuses on optimizing energy, security, and comfort on a large scale . Since energy consumption is much higher than in a single-family home, the potential for savings is also considerable, and smart systems can recoup the investment in relatively short periods.

Advantages and challenges of automation in homes and large buildings

Home automation, although on a smaller scale than in the commercial sector, can bring significant savings. Many studies show that home automation increases user awareness of their energy consumption , which in itself leads to more rational energy use and reductions of between 25% and 30% in certain cases, depending on the integrated functions.

However, context matters. In southern European countries, where residential heating consumption is typically lower than in colder regions, the return on investment for purely energy-efficient home automation may be more limited. In some scenarios, the cost of a complex home automation system could exceed the economic savings achieved over the installation's lifespan, so it's advisable to carefully analyze each case.

In the case of high-energy buildings (offices, hotels, hospitals, etc.), automation has a much more significant impact in terms of absolute savings , due to the scale of use. Here, the potential for reducing consumption and emissions is very high, and investments are more easily justified, both in terms of ROI and corporate sustainability goals.

One of the practical challenges in residential settings is the user experience of control interfaces . It's not always more efficient to have to use a smartphone, open an app, and search for a button to turn on a light, when a traditional physical switch can be faster and more intuitive. Finding the balance between automation and ease of use is key to ensuring that technology doesn't become a hindrance.

Another common challenge is integrating devices from different manufacturers . Many users purchase smart plugs, connected light bulbs, voice-activated speakers, IP cameras, and so on independently, without ensuring that all these components can be coordinated through a single system. This creates isolated automation systems that are difficult to manage in a unified way.

From a cybersecurity perspective, smart buildings and connected homes face risks stemming from the increasing number of IoT devices connected to the network . Protecting against potential attacks and unauthorized access is essential, especially when automation affects doors, alarm systems, cameras, or critical HVAC and energy equipment.

Therefore, integrated automation solutions with robust security architectures and regular updates are generally recommended over a heterogeneous collection of connected devices without a common strategy. As the number of IoT devices grows globally, integration and security will remain key issues in the coming years.

Additional benefits: health, comfort and predictive maintenance

Beyond direct energy savings, smart buildings have a very positive impact on the health and well-being of their occupants . Thanks to sensors that monitor air quality, temperature, humidity, and lighting, it's possible to maintain indoor conditions that promote comfort and productivity.

For example, a smart system can increase ventilation when it detects high levels of CO2 _, adjust lighting to minimize glare and eye strain, or prevent sudden temperature changes that are bothersome to those who work or live in the building.

In work environments, these factors translate into improved perceived well-being, fewer complaints about environmental discomfort, and often, increased productivity . In hospitals and senior care facilities, suitable indoor conditions are especially critical for the health of patients and residents.

Predictive maintenance is another major advantage of digitalization. By continuously collecting equipment operating data, it's possible to detect anomalies before they become serious breakdowns , allowing for interventions to be planned when they are less costly and less disruptive to building use.

This ability to anticipate problems reduces downtime, prevents inefficient energy use by aging equipment, and extends the lifespan of assets. Essentially, a smart building is one that "listens to itself" and corrects itself before problems escalate.

Everything suggests that the combination of efficient design, digital technologies, innovative financing models, and increasing regulatory pressure will mean that, within a few years, most new buildings and a significant portion of the existing building stock will incorporate smart energy management solutions . As these technologies mature and become more affordable, the boundary between conventional and smart buildings will blur until what is truly exceptional is, precisely, not being efficient.