With the growing emphasis on energy efficiency in building design, tightly sealed structures are becoming the norm—helping retain heat but also increasing the need for reliable ventilation. Proper ventilation is essential to maintain a healthy indoor environment by ensuring a continuous supply of fresh air.
Air handling units meet this demand by supplying fresh outdoor air, regulating indoor temperature, and improving air quality by reducing pollutants. Air-to-air heat exchangers are commonly used to recover sensible heat from exhaust air.
Enthalpy and humidity recovery systems further enhance indoor air quality, while significantly reducing energy consumption and operational costs ensuring both comfort and substantial savings.
Impact of low humidity
Health & comfort
Low humidity causes the respiratory tract to dry out more quickly, weakening its natural defenses against bacteria and viruses. Dry air can also lead to skin dehydration and itching, which can be particularly problematic for individuals with skin conditions like eczema. It also decreases moisture on the surface of the eyes, which can result in irritation or inflammation. Additionally, low humidity can cause damage to a wide range of household items.
Medical studies recommend 40% to 60% relative humidity (RH) indoors to minimize health risks [I, II]
(ASHRAE standard for acceptable RH).
Economic impact
Enthalpy heat exchangers outperform conventional heat exchangers by using a polymer membrane to transfer both heat and moisture between air streams, effectively maintaining humidity and significantly reducing energy costs.
In winter, they transfer heat and moisture to the incoming fresh air, increasing relative humidity in the fresh air, preventing freezing under typical conditions and therefore eliminating the need for a preheater. In summer, they extract heat and moisture from the fresh air, reducing the energy consumption of the cooling system, enhancing cooling performance. This dual function makes enthalpy heat exchangers essential for an efficient building energy system, leading to notable cost reductions in both cooling and heating.
To illustrate this, we will compare the difference in performance between an enthalpy and non-enthalpy exchanger in a short case study. The cost savings are calculated for an air handling unit with an airflow rate of 1,000 m³/h, based on an average occupancy of 30 people per day with a duration of stay of 10 hours, taking into account the local climate conditions in Amsterdam.
The graphics shows the daily cost savings in euros over the course of the year.
Results:
Exchanger 1: Enthalpy – Total energy savings cost savings per year: 3’446 Euro of which savings from moisture recovery: 1’008 Euro.
Exchanger 2: None-enthalpy – Total energy savings cost savings per year: 2’600 Euro of which savings from moisture recovery: 0 Euro.
Even with the sensible heat recovery being higher with exchanger 2, It is clear to see that Exchanger 1 shows higher total energy savings throughout the year due to its ability to recover moisture, resulting in significant cost saving.
Polybloc Enthalpy exchangers
Polybloc offers two types of Eurovent certified enthalpy heat exchangers. The VAPOBLOC CV and the crossflow VAPOBLOC VB.
The CV is a plastic counter-flow heat exchanger available in a wide range of sizes and damper configurations. Its robust and aerodynamic design allows for maximum heat recovery efficiency. Due to its construction, the product is fully recyclable, aligning with circular economy principles.
The VB is designed similarly to the classic POLYBLOC plate heat exchanger, using corrugated aluminum plates as spacers. This design grants the plate heat exchanger its unique mechanical stability. Various plate distances and edge lengths allow for optimal configuration regarding pressure drop and efficiency.
Summary
Through this short case study, we demonstrated that enthalpy exchangers outperform conventional non-enthalpy models in terms of overall energy savings and cost reduction, particularly due to their ability to manage humidity levels. The added efficiency in both heating and cooling cycles makes them a valuable investment for sustainable building operation.
Polybloc’s Eurovent-certified enthalpy heat exchangers, including the Counterflow CV and crossflow VB, provide high-performance solutions for energy-efficient ventilation. Their innovative designs ensure durability, recyclability, and optimal heat and moisture recovery, making them ideal choices for modern ventilation systems.
By integrating advanced enthalpy heat exchangers customers can achieve superior energy efficiency, enhance occupant comfort, and reduce operational costs, contributing to a more sustainable and cost-effective future.
[I] WHO guidelines for indoor air quality: dampness and mould, World Health Organization, 2009
[II] Criteria for Human Exposure to Humidity in Occupied Buildings, Sterling et al., 1985