Optimal indoor climate in healthcare with maximum energy efficiency

The initial situation

In hospitals, indoor air quality plays a crucial role in the well-being of patients, visitors, and staff. At the same time, hospitals must meet high standards for hygiene, energy efficiency, and operational reliability.

For the ventilation system at Lausanne University Hospital (CHUV), an energy recovery solution was therefore required that combines high heat and humidity recovery with maximum hygienic safety.

As a relative indoor humidity of 40 to 60% is typically required in Swiss hospitals, humidity recovery plays a particularly important role during the winter months. It reduces the energy required for humidification and contributes to a comfortable and healthy indoor climate.

The challenge

For planners and operators, the solution had to meet several requirements simultaneously:

Conventional aluminum plate heat exchangers remain the most commonly used technology in commercial ventilation systems. While they provide high sensible heat recovery, they do not transfer humidity, resulting in increased humidification demand, particularly during winter. In addition, at low outdoor temperatures, additional frost protection measures such as preheating coils are often required, increasing energy consumption and reducing usable heat recovery.

While rotary heat exchangers provide high humidity recovery, plate heat exchangers are often preferred in hygiene-sensitive applications because their design allows for a particularly high level of hygienic safety.

The Polybloc solution

The VAPOBLOC enthalpy counterflow heat exchanger was integrated into a Monobloc air handling unit manufactured by Seven-Air Gebr. Meyer AG.

For this project, VAPOBLOC was designed to achieve a sensible heat recovery efficiency of more than 77% and a humidity recovery efficiency of 67%, providing exceptionally high heat and humidity recovery. At an airflow rate of 9,300 m³/h, the system achieves a total energy recovery capacity of more than 115 kW.

Thanks to the high humidity transfer efficiency of its selective polymer membrane, VAPOBLOC offers excellent frost resistance. Humidity is continuously transferred from the exhaust air to the supply air, significantly delaying ice formation compared with conventional plate heat exchangers. Frost protection measures are therefore only required at outdoor temperatures that are rarely reached in Central European climates. This increases usable heat recovery and reduces the energy consumption of the ventilation system.

At the same time, VAPOBLOC achieves a proven very low EATR (< 0.5% at a differential pressure of 250 Pa), making it particularly suitable for applications with high indoor air quality and hygiene requirements, such as hospitals.

Unlike rotary heat exchangers, the system operates without moving parts, providing reliable operation with minimal maintenance requirements.

Key benefits

The project provides measurable benefits for both system operation and indoor air quality:

The successful implementation demonstrates how modern enthalpy heat exchangers can improve the energy efficiency of hospital ventilation systems, reduce humidification demand, and simultaneously help meet strict indoor air quality and hygiene requirements.

Thanks to its design, VAPOBLOC is available in standard sizes for counterflow plate heat exchangers and can therefore be easily integrated into existing system concepts and product ranges. This enables equipment manufacturers and system designers to implement the technology without fundamental changes to the system architecture.

For system design and selection, detailed performance data and information on frost behavior are available through Polybloc’s WinPoly selection software. The software is available both as a desktop application and as a DLL for integration into third-party selection and design software.

This provides equipment manufacturers and system designers with a reliable basis for the precise design and selection of heat and humidity recovery systems across the entire operating range.

Heat recovery for critical applications

For more than 40 years, Polybloc has been developing and manufacturing high-performance heat recovery systems for applications with the highest requirements for energy efficiency, hygiene, and operational reliability.

With VAPOBLOC, system designers and operators have access to a solution that combines high heat and humidity recovery, maximum hygienic safety, and low operating costs in a single system.