Just sixty years ago, the idea of a “connected building” seemed like something out of a sci-fi movie. Having different aspects of your home or building communicate with each other to optimize experience and create a fully connected building would seem like little more than a dream.

But, much has changed. Smart, connected technology is a part of many of our everyday lives, and it certainly isn’t going anywhere.

As this technology evolves, so does the role of the engineer. Designing and managing buildings today means thinking beyond individual systems: it’s about creating integrated environments that are equally efficient, adaptable and sustainable. Connected buildings are reshaping system integration, but what does that mean for engineers, and how can smart design choices today future-proof buildings for tomorrow?

Connected vs. smart

There are lots of questions about smart and connected buildings. Some people think the two terms are interchangeable, but that’s not quite true. According to the University of the Built Environment, “While both utilize technology, smart buildings are focused on optimizing building performance, operational efficiency and the occupant experience. In contrast, connected buildings emphasize the connectivity between building systems.”

A smart building uses automation and analytics to enhance performance, while connected buildings require systems within the building – like HVAC, lighting, security and more – to be digitally linked to one another and able to communicate, typically through a centralized building management system (BMS) – which we’ll go into later.

The rise of smart technology began in the 1980s; a time when technology was booming, and people were looking to add it into every aspect of their lives. Answering machines, camcorders, personal computers and LAN operating systems were invented or popularized in the eighties – tech was truly king!

According to WiredScore, “The shift towards intelligent buildings coincided with a significant property boom, caused by an increase in service-sector employment. As a result, new buildings were built pre-equipped with centralized electronic systems and communication systems, which enabled text, voice and image transmission throughout the buildings.”

Early instances of smart, connected technology in homes was, like all new and exciting technology, mostly reserved for the wealthy. In fact, an early smart home device was called the “The Butler in a Box” (fun fact, this electronic home controller system wasn’t created by an engineer, but by Gus Searcy, a professional magician, and computer programmer Franz Kavan!) and cost $1,500; roughly $4,100 today. The product was an early example of a voice-control system with connectivity; it had the ability to control the lights, make phone calls, and act as a home assistant.

This early innovation was the beginning of what was to come: connected systems that are able to communicate with one another to make life easier. While products like this were often buggy – the Butler in a Box had to be extensively trained to recognize the voice of the homeowner, and would have to be completely recalibrated if the power went out for a few hours – it paved the way for smart, connected buildings.

Past vs. present

In the not-so-distant past, mechanical engineers were masters of air, water and structure; that is, they were focused on designing HVAC systems, selecting ductwork, sizing equipment and ensuring code compliance. Their world was largely isolated: HVAC was HVAC, lighting was lighting, and plumbing was plumbing. Easy, right? Automation meant a simple thermostat or timer — nothing integrated, nothing intelligent.

These systems were designed independently, with mechanical engineers responsible for:

• Load calculations for heating and cooling based on envelope performance (or the ability of a building's envelope to regulate the flow of heat, air and moisture, maintaining a comfortable and healthy indoor climate while minimizing energy consumption) and occupancy
• Duct and piping layouts, ensuring compliance with energy and building codes
• Coordination with architects and structural engineers during schematic and design development phases.

Each system functioned in relative isolation. Controls were basic; often limited to programmable thermostats, time clocks or local direct digital control (DDC) controllers. There was little to no communication between HVAC, lighting or security systems.

But, a lot has changed in the past few decades. The role is no longer limited to designing and specifying the aforementioned systems in isolation; today’s mechanical engineers must be data-aware systems thinkers capable of understanding and navigating complex intelligence systems.

The modern engineer is both creator and custodian:

• Designing smart HVAC, lighting and plumbing systems to be responsive, efficient and networked.
• Implementing BMS platforms that combine physical operations with cloud dashboards and predictive analytics.
• Working cross-discipline with software developers, IT and controls engineers to deliver resilient systems.
• Ensuring sustainability goals are met through energy tracking, demand-response integration and predictive maintenance.

As digital technologies and IoT (Internet of Things) platforms advanced in the late 2000s and 2010s, the focus shifted from isolated systems to interconnected ecosystems. With the adoption of open communication protocols like BACnet, Modbus and KNX, multiple building systems could now share real-time data through centralized Building Management Systems (BMS).

Emphasis on interoperability

BMS act as the centralized platform that unifies all the data and control logic from various building systems. It provides a graphical interface and control environment where facilities teams, engineers and even occupants can monitor building performance in real time; adjust setpoints, schedules and occupancy modes; generate alarms and fault detections reports; and analyze trends in energy, air quality or occupancy. Most modern BMS platforms are IP-based and cloud compatible, and many use AI for optimization.

The integration of BMS has been paramount to the success of connected buildings, especially for engineers. These systems can be used as both a design tool and operational platform; enabling smarter design decisions, better building performance and long-term sustainability.

Some commonly used BMS include:
BACnet (Building Automation and Control Networks):

• Developed by ASHRAE, BACnet is the most widely used protocol in commercial buildings. The company celebrated 30 years of BACnet in 2025.
• It supports communication between heating, ventilating and air-conditioning control, lighting control, access control and fire detection systems.
• It allows engineers and integrators to connect devices from different manufacturers without custom middleware.

Modbus:

• Originally developed by Modicon in 1979 for industrial control.
• The program is open protocol, meaning that it is free for manufacturers to build into their equipment without having to pay royalties.
• Offers a cost-effective way to bring non-networked equipment into integrated systems.

KNX:

• Created in 1990.
• Widely used in Europe, and increasingly in smart homes and commercial buildings.
• Manages lighting, blinds and shutters, HVAC, security systems, energy management, audio and video, domestic appliances, displays, remote control, etc.
• Enables device-level control, and is recognized by ISO/IEC as a global standard.

Interoperability is the heart of connected buildings. Programs like BACnet, Modbus and KNX are just a few examples of systems that engineers must use to adhere to today because of the increased demand for connected buildings.

Working with these programs is a requirement for modern engineers designing connected buildings. They are the central command point for the building: using sensors and meters to collect data and using actuators and controllers to execute on simple commands and control tasks and communicating with the separate systems via signal transmissions and real-time feedback.

The logistics of connectivity

To design for connectivity, engineers need to consider how systems will interact with each other from the very beginning of a project. Gone are the days of designing mechanical systems in isolation; engineers must plan for sensor placements, actuator specifications, control zones and data points during schematic designs.

“Interoperability is a major contributor to the difference between being a smarter building versus being a smart building.” According to Marc Petock, chief marketing & communications officer for Lynxspring. “Devices and equipment communicating via open protocol with each other and exchanging data and information efficiently (regardless of manufacturer), is fundamental to our industry.”

This requires early coordination with several groups: architects, electrical engineers and IT specialists to ensure that physical systems and data infrastructure align from the very beginning of the project.

Successful integration demands collaboration across disciplines: architects ensure wiring and sensor placements are concealed yet accessible; mechanical and electrical engineers define devices, data flows and zones; and controls and IT teams design platform integration and cybersecurity (a must when it comes to smart systems).

How does one achieve that early connectivity? It starts with enabling interoperability by choosing devices that support open communication protocol – like the ones discussed earlier. This does a lot of the work for you; it enables all systems to exchange data intermittently and reliably. Early integration allows designers to define functional diagrams detailing data flow, storage, analytics and user interface pipelines across systems.

Equally as important is designing the physical and digital architecture: designing the physical and digital architecture. Planning ethernet cabling and network zones alongside traditional MEP infrastructure ensures adaptability and ease of deployment. Strategic sensor placement – coordinated across disciplines – ensures data accuracy, visual integration and long-term maintainability. By foreseeing integration needs, from occupancy sensors controlling lighting to future digital twin models, engineers and architects set the groundwork for building performance and future scalability.

Connected for sustainability

The call for connected buildings has many reasons: at the forefront are sustainability and compliance. In today’s connected landscape, mechanical engineers are increasingly tasked not only with system design, but also with ensuring compliance and transparency in environmental and sustainability reporting.

In the shift toward smarter, more sustainable buildings, engineers wear yet another hat: sustainability enablers. Their responsibilities now extend into energy modeling, real-time data integration and ESG accountability. By designing for connectivity from the start, engineers can unlock powerful environmental benefits.

Connected buildings leverage sensors, digital platforms and automations to help with sustainability goals. They optimize resource use, reduce waste, and decrease carbon emissions. In fact, research shows that connected digital technologies could reduce energy usage in buildings by 30-50% by the year 2024, according to José L. Hernández of the energy division of CARTIF Technology Center.

Engineers are now pivotal in shaping how buildings demonstrate sustainability and operational excellence. By embedding submeters at the system or zone level, they enable highly detailed tracking of energy, water and carbon usage; critical for meeting standards like ASHRAE 90.1 and qualifying for LEED or BREEAM credits.

Web systems like BREEAM and LEED recognize submetering as absolutely fundamental to operational efficiency. LEED, for example, offers points for energy and water submeters that provide automated, frequent data and accurate measurement down to system or zone levels.

Submetering, or installing meters at system or zone levels, provides the granular data required for accurate tracking of energy, water, and carbon use. This data is critical for compliance with standards such as ASHRAE 90.1, and supports benchmarking, verification of efficiency upgrades, and continues to inform building performance post-commissioning.

Additionally, many BMS and Energy Management Software (EMS) now support automated sustainability reporting, which can help reach sustainability goals. For example, the Keppel Bay Tower in Singapore was a retrofit project that achieved 30% energy reduction by using smart lighting, efficient cooling control, solar film and solar PV. Continuous monitoring, using a digital twin, helped the project reach ongoing performance improvements – saving both money, and carbon.

Future proofing capabilities

Future-proofing buildings has become a critical consideration; not just for resilience, but for long-term adaptability. Engineers play one of the most indispensable roles: designing buildings that remain relevant and efficient well into the future.

Future-proofing calls for engineers to be strategic partners who embed adaptability, intelligence and resilience into the DNA of a building. Through thoughtful planning across digital infrastructure, renewables, AI readiness, and perhaps most importantly connectivity, engineers can significantly extend a building's relevance and sustainability over decades to come.

Digital twins are one fascinating way that connected buildings can become future-proof. These live, digital models of buildings offer incredibly powerful capabilities for simulating performances, optimizing resource use, and most importantly, monitoring the building’s lifecycle. Engineers can use these tools to analyze design iterations completely virtually, and predict maintenance and system issues before they ever happen. Paramount to sustainability goals, they can also track environmental impact throughout the building’s lifecycle.

Digital twins support future adaptation without costly disruptions.

Looking ahead, it’s possible that digital twins may even evolve beyond operational tools toward autonomous agents, managed by AI to operate within sustainability parameters – AI is developing at a fast rate, after all.

What’s at the center of the connected future?

Buildings have evolved. No longer are they static structures: they’re dynamic, responsive ecosystems. And engineers are no longer system designers: system integrators, strategists, stewards of sustainability – the list goes on.

Connected, future-ready buildings don’t happen by accident. They’re the result of hours of planning, designing, and strategizing. Engineers that understand interoperability and lifecycle thinking are just as important as duct sizing and load calculations.

Connected buildings are completely redefining how we think about and manage energy, comfort and performance, and especially how we design. The work that engineers are doing today isn’t just for right now; it’s the first step in creating a connected future.