How does an enthalpy heat exchanger work?
Enthalpy Heat Exchangers for Ventilation Units – Comparison
At Rekupex, we offer enthalpy heat exchangers for a wide range of ventilation units from various manufacturers. We continuously expand our range to cover as many commonly used ventilation systems on the market as possible.
Our customers also play an important role in expanding the product range by helping us identify new types of ventilation units and their compatible enthalpy heat exchangers. Thanks to this cooperation, we can continuously develop our offer and adapt it to the real needs of users. Thank you for your feedback and suggestions.
To make it easier for you to understand the differences between enthalpy exchangers from RECUTECH, ZERN Engineering, CORE, and AIRWOODS, we have prepared a clear technical comparison of exchangers of the same size 366 × 366 × 400 mm, which can be directly compared thanks to their identical dimensions.
The overview also includes three key diagrams, which make it possible to compare exchanger behavior depending on the air volume flow rate:
- pressure drop at different air flow rates
- heat transfer efficiency
- moisture transfer efficiency
Technical Comparison Diagrams
Click on the diagram to open the high-resolution detail.
Pressure drop vs. air volume flow rate
Heat transfer efficiency
Moisture transfer efficiency
Input conditions according to EN 308:2022
- Outdoor air temperature: 5 °C
- Outdoor air relative humidity: 72 %
- Extract air temperature: 25 °C
- Extract air relative humidity: 50 %
The results were obtained using the selection and design software of the individual manufacturers.
Comparison of Enthalpy Heat Exchangers (366 × 366 × 400 mm)
The input parameters are unified according to EN 308:2022, unless stated otherwise. For AIRWOODS, different input values according to the manufacturer’s documentation were used, therefore the inputs differ.
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| Parameter | CORE F-ERV 366 | ZERN EC-EX6 366 | RECUTECH METALPIC RKF+16 | AIRWOODS WXL-LB 366* |
|---|---|---|---|---|
| Exchanger photo |  |
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| Input conditions | ||||
| Outdoor air temperature [°C] | 5 | 5 | 5 | -5 |
| Outdoor air relative humidity [%] | 72 | 72 | 72 | 25 |
| Extract air temperature [°C] | 25 | 25 | 25 | 25 |
| Extract air relative humidity [%] | 50 | 50 | 50 | 80 |
| Performance at air volume flow rate of 150 m³/h | ||||
| Pressure drop [Pa]¹ | 28 | 37,65 | 25,18 ⭐ best | 29,9 |
| Temperature efficiency [%]¹ | 84,1 | 82,36 | 87,1 ⭐ best | 85,75 |
| Moisture efficiency [%]¹ | 70,9 | 58,96 | 66,5 | 75,73 ⭐ best |
| Performance at air volume flow rate of 400 m³/h | ||||
| Pressure drop [Pa]¹ | 134 | 141 | 114 ⭐ best | – |
| Temperature efficiency [%]¹ | 77,5 | 71,4 | 78,3 ⭐ best | – |
| Moisture efficiency [%]¹ | 51,7 | 47,84 | 58 ⭐ best | – |
| Construction and materials | ||||
| Exchanger casing material | Unspecified plastic | HPS (High Pressure Structure) | Corrosion-resistant aluminum | Unspecified plastic |
| Exchanger construction type | Polymer plate exchanger | Polymer plate exchanger | Metal enthalpy heat exchanger ⭐ | Polymer plate exchanger |
| Enthalpy membrane carrier | The membrane is part of the supporting material | HPS (High Pressure Structure) | Aluminum carrier (expanded metal) | Plastic separators |
| Type of enthalpy membrane | Formable polymer membrane (integrated in the plates) | Polymer microporous membrane | Ion-exchange membrane (METALPIC) | Polymer microporous membrane |
| Transport packaging | Polystyrene protection + cardboard box | Polystyrene protection + cardboard box | Wooden transport crate (also suitable for storing the original exchanger) | Polystyrene protection + cardboard box |
| REKUPEX evaluation | ||||
| Overall evaluation | High efficiency at lower flow rates. Thanks to its low weight and smooth casing, it places minimal demands on installation. | Robust and mechanically durable construction. Good availability of dimensions for a wide range of ventilation units. | All-aluminum exchanger with METALPIC membrane. Excellent efficiency / pressure drop ratio. Highest heat transfer efficiency and, at higher air volume flow rates, also very good moisture transfer. | Proven exchangers used by a number of European unit manufacturers thanks to a good price / performance ratio. |
| Strengths | Very good moisture efficiency at lower air flow rates. Low weight. | Very solid workmanship and high mechanical durability. | Very good results at medium and higher flow rates. Low pressure drop across the entire range. | Favorable price while maintaining solid parameters. |
| Possibility of adapting exchanger dimensions | Limited | Limited | Very wide possibilities for adapting dimensions ⭐ | Limited |
| Availability of newly identified and less commonly used exchangers | Limited availability | Good availability | Excellent availability ⭐ | Limited availability |
| Note about the manufacturer | – | – | RECUTECH provides excellent customer and technical support, making it possible to effectively design, adapt, and integrate exchangers into a wide range of ventilation units. Thanks to the robust construction with an aluminum casing, the exchangers are also very suitable for retrofit applications and modernization of older ventilation units. | – |
| Certification and compliance | ||||
| Eurovent | – | – | YES | – |
| DIN ISO 9001:2015 | YES | YES | YES | – |
| Hygiene certificate | VDI 6022 | VDI 6022 | VDI 6022 | ANTI BACTERIAL + Antimicrobial test report |
| RoHS | YES | YES | YES | YES |
| REACH | YES | YES | YES | YES |
| Data source and calculation | ||||
| Exchanger manufacturer | CORE GmbH | ZERN Engineering | RECUTECH | AIRWOODS |
| Availability (sales) | www.rekupex.cz | www.rekupex.cz www.rekupex.de |
www.rekupex.cz www.rekupex.de |
On request by e-mail: info@rekupex.cz |
| Calculated size | 366 × 366 × 400 mm | 366 × 366 × 400 mm | 366 × 366 × 400 mm | 366 × 366 × 400 mm |
| Calculation software | Online (manufacturer’s website) | Online (manufacturer’s website) | Offline design selector | Offline design selector |
| Calculation date | 3 March 2026 | 3 March 2026 | 3 March 2026 | 3 March 2026 |
⭐ best value in the given category
¹ The values were determined based on calculations in the manufacturers’ selection programs under the input conditions defined by EN 308:2022.
* Different input values according to the manufacturer’s documentation were used for AIRWOODS.
REKUPEX Recommendation
Based on our long-term experience with the design and integration of enthalpy heat exchangers into various types of ventilation units, we particularly recommend RECUTECH exchangers, which stand out thanks to their very good efficiency / pressure drop ratio, robust construction, and above all excellent technical support from the manufacturer.
Thanks to this cooperation, the exchangers can be easily adapted to a wide range of ventilation units, including retrofit installations in older equipment.
Which Enthalpy Heat Exchanger Should You Choose?
The comparison shows that individual manufacturers optimize their exchangers for different operating conditions. Some exchangers achieve very good results especially at lower air volume flow rates, while others are optimized for medium and higher air flow rates.
When choosing an enthalpy heat exchanger, it is therefore important to consider not only the efficiency itself, but also pressure drop, exchanger construction, compatibility with the ventilation unit, the possibility of adapting dimensions, and the availability of replacement exchangers.
Frequently Asked Questions About Enthalpy Heat Exchangers
What is the difference between an enthalpy heat exchanger and a standard heat recovery exchanger?
An enthalpy heat exchanger transfers not only heat, but also part of the moisture from the extract air to the supply air. This helps maintain a more comfortable indoor humidity level, especially during the winter season.
What is the typical efficiency of an enthalpy heat exchanger?
The temperature efficiency of modern enthalpy heat exchangers usually ranges approximately between 75–90 %.
The moisture transfer efficiency is usually lower and generally ranges approximately between 40–75 %.
Both values are significantly influenced by the exchanger design, membrane quality, and especially the air volume flow rate at which the exchanger is operated.
Can an enthalpy heat exchanger be installed in an older ventilation unit?
Yes, at RekupeX we not only sell exchangers, but also technically adapt them for specific ventilation units. We manufacture our own sealing and mounting profiles, and if necessary we also produce reduction casings. Thanks to this, we can offer an enthalpy replacement even for older ventilation units, where compatibility may at first glance appear problematic. A typical example is exchangers for Atrea units.
Note: The technical data and graphs presented in this overview were prepared based on the technical documentation of the individual manufacturers and the results of their selection or design tools. Although we have made every effort to ensure maximum accuracy, individual values may vary depending on the specific operating conditions, unit configuration, or updates to the data provided by the manufacturers.
The stated REKUPEX evaluation is based on our long-term practical experience with the design, sale, and integration of enthalpy heat exchangers into various types of ventilation units.
If any manufacturer identifies an inaccuracy or has a comment regarding the stated data, we will be grateful for the notice and will be happy to adjust the data.
If you are unsure which enthalpy heat exchanger is suitable for your ventilation unit, do not hesitate to contact us. We will be happy to help you choose the right solution.
Enthalpy Exchanger in Summer: Less Humidity, More Comfort
An enthalpy exchanger is not designed only for the winter period. It also plays a very important role in summer, when it helps reduce the amount of humidity brought into the house from the outdoor air.
In winter, the enthalpy exchanger helps return part of the moisture back to the interior, reducing excessively dry air in the house. In summer, however, it can work the opposite way. If the outdoor air is warm and humid and the house is cooled inside, the enthalpy exchanger helps transfer part of the moisture from the incoming outdoor air to the exhaust air from the house.
As a result, cooled air with lower humidity enters the house. This is crucial especially for modern houses with cooling, fan coils, ceiling cooling, or air conditioning, where high humidity significantly reduces thermal comfort.
Why is Humid Air a Problem in Summer?
In summer, we often deal with the opposite problem compared to winter. In winter, the air in the house tends to be too dry. In summer, however, the outdoor air is often warm and very humid at the same time.
| Higher perceived temperature | humid air feels heavy, stuffy, and worsens thermal comfort |
| Higher cooling load | air conditioning, fan coils, or ceiling cooling must handle not only temperature but also humidity |
| Risk of condensation | higher humidity increases the risk of condensation on cold surfaces |
Therefore, it is not enough to only address the temperature of the supplied air. The amount of water vapor brought into the house through ventilation is also important.
Standard Exchanger vs. Enthalpy Exchanger in Summer
| Standard Exchanger | Enthalpy Exchanger |
| transfers coolness from the exhaust air | transfers coolness from the exhaust air |
| barely reduces the humidity of the supplied air | also transfers part of the water vapor |
| Cooled but still humid air enters the house. | Cooled air with lower humidity enters the house. |
A standard exchanger mainly helps with temperature. An enthalpy exchanger helps with both temperature and limiting the humidity brought in from the outside.
Graphical Representation of the Exchanger Principle in Summer
Below is a direct comparison between a standard non-enthalpy exchanger and an enthalpy exchanger in summer operation.
A standard exchanger brings cooled but humid air into the house. An enthalpy exchanger brings cooled air with lower humidity.
Model Input Conditions
For a clear comparison, we use a summer scenario where it is hot and humid outside and the house is cooled inside.
| Condition | Outdoor Fresh Air | Exhaust Air from the House |
| Temperature | 35 °C | 25 °C |
| Relative Humidity | 50 % RH | 60 % RH |
| Absolute Humidity | 17.8 g/kg | 11.9 g/kg |
| Airflow | 50 m³/h | |
Result at the Supply to the House
The comparison is based on calculations for two exchangers of the same size:
- RECUTECH RSK+16-500-25 – standard non-enthalpy exchanger
- RECUTECH RFK+16-500-28 – enthalpy exchanger
| Supply Air Parameter | RSK+16-500-25 standard exchanger |
RFK+16-500-28 enthalpy exchanger |
| Supply air temperature | 25.5 °C | 25.5 °C |
| Supply air relative humidity | 86.0 % RH | 71,2 % RH |
| Supply air absolute humidity | 17.75 g/kg | 14.60 g/kg |
| Difference compared to standard exchanger | 0 g/kg | -3.15 g/kg |
Both exchangers bring air into the house at a similar temperature. The difference lies in the humidity. In this calculation, the enthalpy exchanger reduces the absolute humidity of the supplied air from 17.75 g/kg to 14.60 g/kg.
What Does a Difference of 3.15 g/kg Mean in Practice?
At first glance, a value of 3.15 g/kg may seem small. However, a ventilation unit operates many hours a day and brings in tens to hundreds of cubic meters of air every hour. In total, this represents a significant amount of water that would otherwise enter the house.
| Operating Situation | Approximate Amount of Water Kept Out of the House |
| At a flow rate of 50 m³/h | approx. 0.18 l/h |
| At a flow rate of 200 m³/h | approx. 17 l/day |
Practical Significance:
On a model summer day, the enthalpy exchanger can significantly limit the amount of water that would enter the house solely through ventilation at a standard flow rate.
How Does an Enthalpy Exchanger Transfer Moisture?
An enthalpy exchanger features a special membrane that allows the transfer of part of the water vapor between two air streams. The direction of moisture transfer is not fixed. It always depends on the current conditions outside and inside the house.
| In winter | the air outside is cold and dry, while the air inside is warmer and more humid – the enthalpy exchanger helps return part of the moisture back into the house |
| In summer | the air outside is often warm and humid, while the house is cooled inside – the enthalpy exchanger helps transfer part of the moisture into the exhaust air |
That is why an enthalpy exchanger is a year-round solution. In winter, it helps against excessively dry air; in summer, it helps against excessive moisture intake from the outside.
Main Advantages of an Enthalpy Exchanger in Summer
| Less moisture from the outside | reduces the amount of water vapor brought into the house by ventilation |
| Lower cooling load | the cooling system does not have to deal with such a high humidity load afterward |
| Higher comfort | the air feels more pleasant and less stuffy |
| Year-round use | helps retain moisture in winter, limits its intake in summer |
| Suitable for modern houses | ideal for houses with mechanical cooling, fan coils, or ceiling cooling |
Important Notice
An enthalpy exchanger is not a condensation dehumidifier or an air conditioner with active dehumidification.
If there is a long-term very high humidity in the house, for example, due to a new build, wet structures, construction moisture, laundry drying, or another strong source of moisture, the enthalpy exchanger alone will not solve the problem immediately.
Its main benefit lies in limiting the intake of new moisture from the outside during ventilation. By doing so, it helps stabilize the indoor climate and reduces the house's humidity load.
Myth vs. Reality
| Myth | Reality |
| An enthalpy exchanger increases humidity in the house during summer. | In a typical summer operation with a cooled interior, it conversely limits the intake of moisture from the outside. |
| A standard exchanger is always better in summer. | A standard exchanger transfers coolness, but it still brings moisture from the outdoor air into the house. |
| An enthalpy exchanger only works in winter. | It works year-round. In winter, it helps against dry air; in summer, against the humidity load. |
| If I have cooling, I do not need an enthalpy exchanger. | It makes great sense precisely when cooling, as it reduces the amount of moisture brought in through ventilation. |
Frequently Asked Questions
Does an enthalpy exchanger make sense in summer too?
Yes. If the outdoor air is warm and humid and the house is cooled inside, the enthalpy exchanger helps reduce the humidity of the supplied air.
Does this mean there will automatically be ideal humidity at home?
Not automatically. The resulting humidity depends on outdoor conditions, ventilation, cooling, and sources of moisture in the house. However, the enthalpy exchanger limits the intake of moisture from the outside.
Should I swap the enthalpy exchanger for a standard one in summer?
In most cases, no. If you are dealing with high humidity in the house, an enthalpy exchanger is advantageous for summer operation.
Will an enthalpy exchanger help with fan coils or ceiling cooling?
Yes. It reduces the humidity load caused by the supplied air, which is very important for cooled houses.
Summary
A standard exchanger in summer transfers coolness but does not transfer moisture. Thus, cooled but still humid outdoor air enters the house.
An enthalpy exchanger transfers both coolness and part of the water vapor. Thanks to this, cooled air with lower humidity enters the house.
In the model calculation, the absolute humidity of the supplied air decreased from 17.75 g/kg to 14.60 g/kg. At a standard flow rate, this difference can mean up to approximately 17 liters of water per day that do not enter the house at all.
Therefore, an enthalpy exchanger is a year-round solution: in winter, it helps against dry air; in summer, it helps against an excessive supply of moisture from the outside.
Do You Need Advice on Choosing an Enthalpy Exchanger?
Send us the type of your heat recovery unit or the dimensions of the original exchanger. We will verify compatibility and recommend a suitable solution for year-round operation – both in winter and summer.
We will be happy to help you choose the right enthalpy exchanger for your unit.
An enthalpic heat exchanger should be used all year round. In winter, it prevents excessive drying of the indoor air, and in summer, it helps maintain comfortable humidity and temperature by reducing heat transfer and returning part of the moisture to the fresh supply air. This increases comfort and saves energy in every season.
An enthalpic heat exchanger works on the principle of counterflow air streams. During ventilation, two separate airflows meet inside – the warm, humid exhaust air from indoors and the cold fresh air from outside. A special membrane transfers both heat and water vapor from the exhaust air to the incoming fresh air without mixing the two streams. This way, fresh air enters the home with a more comfortable temperature and humidity, improving comfort while saving energy.