This Modular Wall System Has Built-In Solar Panels, Heat Pumps, and Ventilation

We like to repeat architect Carl Elefante's adage that "the greenest building is the one already standing," but there are untold millions of square feet of office buildings around the world with leaky curtain walls and inefficient heating systems that will have to be upgraded in the next few years. The German research organization Fraunhofer has come up with a really interesting solution for the typical column and slab buildings from the '50s through the '70s: a prefabricated wall system that integrates a heat pump, ventilation with heat recovery, high-efficiency glazing, with the solid portions of the wall covered in photovoltaic panels.

According to Fraunhofer's press release:

 “We are not renovating the entire building, just the facade. In the future, the old facade will be replaced using new, industrially prefabricated modules with integrated systems technology, providing a multifunctional solution that meets the latest energy standards,” explains Jan Kaiser, project manager and scientist at Fraunhofer IEE. “All the heating, cooling and ventilation equipment required for the adjoining offices is integrated within the facade.”

The technical part of the unit, containing the heat pumps and ventilation, is a standard four feet wide and a foot deep, and is insulated with vacuum panels, and can service an area of about 260 square feet. The press release notes the installation just takes a few hours: "Since the heating and ventilation technology is already integrated, there is no need to lay any new pipes within the building. The facade simply needs a power connection to continue air-conditioning and ventilating the rooms during periods without PV electricity."

There is no word on how much electricity is produced by the solar panel, or what percentage of the electricity needed to run the heat pumps and ventilation system it is estimated to cover. We have asked and will update if and when Fraunhofer responds, but I suspect it's not much. However, it's still a very good idea, and the whole system is projected to cut electricity consumption by 75%.

“The new RE modular facade provides perfectly coordinated protection against heat and sunlight combined with low power consumption and a high level of user convenience,” emphasizes Michael Eberl, scientist at Fraunhofer IBP who worked with Jan Kaiser on the project. Between 1950 and around 1990, approximately 25 to 30 percent of all office buildings in Germany were constructed using frame construction methods. Together, they consume 3200 gigawatt hours (GWh) of electricity each year. “Using our RE modular facade would reduce this to 600 GWh. The high level of prefabrication would also increase the low renovation rate of just one percent per year,” explains Kaiser."

The ventilation system appears to be independent of the heat pumps and is based on an LTG single-duct pulse ventilation "breathing" system. According to the Fraunhofer website: "Unlike conventional facade-mounted ventilation units, FVPpulse does without separate air ducts for outside and exhaust air: instead, it has a single fan and just one opening in the facade and uses a system of dampers to switch cyclically between the intake and outlet functions. This non-stationary ventilation results in the thorough mixing of the air in the room at low air velocities and high air volumes."

We have seen pulsed ventilation systems before in the teensy Lunos HRVs that have a heat exchanger core that is warmed when the air goes one way and gives the heat back when it reverses. It looks like this unit works the same way, and claims heat recovery efficiency of up to 90%.

In some ways, this might be a missed opportunity: Alex De Gagné's Minotair "magic box" integrates the heat recovery ventilator with the heat pump and gets even better performance. He should develop a vertical version that would likely make a better wall unit for the Fraunhofer concept.

Fraunhofer is really on to something here. It is a quick and easy, plug-and-play response to a serious issue. American writer Stewart Brand wrote in "How Buildings Learn" that "because of the different rates of change of its components, a building is always tearing itself apart." The columns and slabs of a concrete office building can last a long time, but the skin has a shorter life and, according to designer and architect Rachel Wagner, "often has the biggest impact on long-term durability, occupant comfort and building energy performance."

Here, in one slick move, Fraunhofer is fixing problems of insulation, glazing, heating, cooling, and ventilation, much of the stuff with the short lifespan that has the biggest impact in this climate crisis. This is clever stuff.