Building-within-a-building enables customized thermal comfort, delivered through the walls

With today’s “smart” homes, you can activate lights and air-conditioning with a simple verbal request. But are these systems really “smart” enough to know which room you’re in? Can they save energy by cooling just one specific corner of the room? That’s the idea behind the Human Building Interactions Laboratory (HBIL), a first-of-its-kind interactive facility at Purdue University that will enable HVAC systems to become truly reconfigurable, right down to the specific wall panels.



“This facility has been a long time coming,” said James E. Braun, Herrick Professor of Engineering, and Director of the Center for High Performance Buildings at Purdue University. “We are excited to explore new ways of delivering thermal comfort, and new ways of interacting with buildings.”

The HBIL consists of a fully enclosed building-within-a-building: 20 feet long, 12 feet wide, and 10 feet high. The interior walls, floor, and ceiling are a grid of 4-foot-by-5-foot thermally active panels, with hydronic heat exchangers inside. This allows each individual panel to be heated or cooled precisely, allowing uniquely localized thermal delivery. “Instead of a normal HVAC system, where hot or cold air comes in from static locations, now the walls themselves become localized thermal delivery devices,” said Panagiota Karava, the Jack and Kay Hockema Professor of Civil Engineering.

The building-within-a-building integrates removable wall panels with individual hydronic heat exchangers, enabling highly-localized thermal delivery for the occupants inside.

This enables a pinpoint-customizable environment as has never been done before. “Let’s say you have two occupants sitting on couches on opposite sides of the room, and one feels cold and the other feels warm,” said Davide Ziviani, Assistant Professor of Mechanical Engineering and Associate Director of the Center for High Performance Buildings.  “In real time, we’ll be able to adjust the temperatures of these panels so that both occupants feel comfortable. We’ll also be able to determine how this is best accomplished: automatically through sensors, or on demand by the occupants, like someone asking Alexa to make their space warmer or cooler.”

The interior panels, held in by magnets, are also removable and reconfigurable. Right now they emulate the drywall of a typical home, but they can also be swapped for other surfaces, to test thermal delivery and acoustic comfort. “We can set this space up as an office, as a living room, or partitioned as two smaller rooms,” said Travis Horton, Professor of Civil Engineering. “We’ll furnish it exactly as you would in your own home, so we can create high-fidelity experiments for human comfort and energy efficiency.”

The facility is located at Ray W. Herrick Laboratories, the largest academic HVAC lab in the world. It was built inside the Perception-Based Engineering Lab, a large chamber that enables precise control of lighting, temperature, and humidity conditions. It also contains windows for natural light, and a multitude of sensors that measure every aspect of the building’s operations.

“We can simulate a building in Minneapolis in the winter, where the outside walls are exposed to cold conditions,” said Braun. “We can also do the same thing in reverse, simulating Miami in the summer. What’s the most energy-efficient way to keep the occupants comfortable? We can explore every possibility, and test new technologies as they develop.”

Within the U.S., residential and commercial buildings account for about 41% of primary energy usage, 72% of electricity, 55% of natural gas, and 38% of CO2 emissions. The HBIL came about as an interdisciplinary project between the schools of mechanical engineering and civil engineering to explore advanced building concepts to address these sustainability issues, using modularity and embedded intelligence.

“This could only happen at Herrick Labs,” said Ziviani. “So many Purdue colleagues have lent their expertise to make this facility possible. There are labs elsewhere that simulate home environments, but nowhere else can you experiment with precise locally-distributed thermal comfort like this.”

The team is also looking to the future of “smart” buildings, integrating new technologies into the home as it is being built. “The next generation of residential buildings will be modular, constructed in a factory,” said Karava. “For example, when micro heat pumps are perfected, we can integrate them right into the wall, as the home is being built. Then the occupants can enjoy customized thermal comfort like we’ve demonstrated here, but more energy-efficient, and at lower cost.”

The Human Building Interactions Laboratory (HBIL) is a collaborative project between the School of Mechanical Engineering and the Lyles School of Civil Engineering at Purdue University. (Purdue University photo/Jared Pike)


Writer: Jared Pike,, 765-496-0374

Source: Davide Ziviani,

James E. Braun,

Panagiota Karava,

Travis Horton,