People gathered in spacious modern atrium.

Transforming Yesterday's Buildings into Tomorrow’s Resilient Sanctuaries

by Damon Bosetti & Margaret Naughton

As discussed previously, most buildings that exist today will still be standing in 20501. That’s a good thing: the greenest building is the one that’s already there2,. Learn more in one of our previous blogs. Cities are home to more than half of the world’s population3, and the people living in them are dealing with extreme heat waves and air pollution. The topic of today’s blog is HVAC systems – Heating, Ventilation, and Air-Conditioning - and how existing buildings can use Variable Refrigerant Flow (VRF) to upgrade comfort and cut energy costs. These modern heat pumps have grown more capable and sophisticated since their introduction in the 1980s, and offer building owners win-win solutions to:

  • Improve fire and life safety by eliminating combustion risks from a major building system.
  • Make building-wide “heating” and “cooling” seasons a thing of the past by giving occupants fine-grained control.
  • Offer an easier upgrade option for buildings with far less interior disruption.

What is Variable Refrigerant Flow (VRF)?

VRF takes old design ideas about moving energy around a building and turns them upside down. The legacy approach brings air from different rooms to a central point where it's heated or cooled and then returned to those same rooms. This painstaking balance of ductwork and fans uses energy and is often delicate - if you want to get a building manager going on a rant, ask them about their airflow balancing.

Instead, VRF moves refrigerant around the building. In each room, there is a small head and circulating fan that can then warm or cool the space. The system uses less energy to circulate this material, and the small copper lines use less space in walls and ceilings. Installers can get creative with their routing, bringing comfort to rooms that would have previously been cold spots or warm spots compared to neighboring rooms. Industry has worked hard to expand the operating envelope of these systems in cold climates, and solutions are now available that can produce their fully rated heat capacity down to -15° C [5° F].

Something worth focusing on is VRF’s ability to re-route power. This phrase may have you thinking back to Star Trek episodes when engineers would “re-route power” at the tap of a few buttons in the engine room. While that was fantasy, this is reality, and VRF systems with heat recovery can do it! These systems usually feature a third copper line. This lets them recycle energy by removing heat from areas needing cooling and then moving it to areas needing warmth. This simultaneous operation turns waste into an asset, slashing energy use while solving the age-old facility manager's headache of resolving warring temperature complaints.

What's Coming Next?

We all owe a tip of the cap to the engineers and technicians who keep us comfortable since HVAC systems are fantastically complex. Not only do they combine microprocessors, electrical switching, and mechanical controls, but all in service of managing a complex and always-changing flow of material that's sometimes a gas, sometimes a liquid, and sometimes an indistinguishable supercritical fluid. To keep getting more out of these challenging physical systems, we need to advance what we're sensing and how we're controlling it based on these measurements. Then, we need to make sure the distributed system components can communicate to coordinate their actions.

Analog Devices is here to help. Our stepper motor and solenoid drivers are the perfect companions to Electronic Expansion Valves (EEVs) and solenoid valves, acting as sensors that enable closed-loop control and give system microcontrollers visibility into wear-out of these critical electro-mechanical components. These same drivers also allow systems to fine-tune their operation in real-time. Designers no longer need to use cautious headroom or rules of thumb that sacrifice efficiency, since every aspect of device actuation is monitored and controllable.

ADI is a world leader in rugged wired communications transceivers. Our AC inductor-free Homebus parts save installers time with simple, long-reaching 200 kbps multi-drop arrangements. These same parts provide up to 70 mA of current to edge devices - all with a solution size 10x smaller than the competition.

Keeping a building's HVAC/R systems steady can sometimes feel as chaotic as the Enterprise's engine room but with Analog Devices technology on your side, your VRF systems will be cruising at Warp 9 for light-years to come! To learn more, visit

Find the past blog here.