Difference Between HRV and ERV

With the increasing pollution, the importance of ventilation has increased tremendously. So, the introduction of various types of ventilation has manifested to be useful in these times, but also with so many categories one can easily get confused between them.

One such topic of discussion is the HRV and ERV. Both are types of ventilations that appear to be strikingly similar but are fundamentally different.   

HRV vs ERV 

The main difference between HRV and ERV is that HRV stands for Heat Recovery Ventilation and is an air exchange system that primarily transfers heat, while ERV is an air exchange system that transfers both heat and moisture and enhances the indoor air quality by reducing the heating cost.   

HRV vs ERV

HRV or Heat Recovery Ventilation is a type of ventilation that operates between two sources of temperature. It usually reduces the heating and cooling demands of the house thereby enhancing the air quality index.

It operates with less energy loss but is slightly expensive than other ventilation systems.  

On the other hand, ERV or Energy Recovery Ventilation is a system that uses both heat and moisture in the stale exhaust air to purify. Thus, an ERV system makes sure that during winters the indoor air does not become too dry by retaining the moisture and humidity.  

Comparison Table Between HRV and ERV 

Parameters of Comparison    HRV ERV 
Stands For    Heat Recovery Ventilation/Ventilator  Energy Recovery Ventilation/ Ventilator  
Retains  Heated/ Cooled Air  Heat, Moisture, Relative Humidity   
  
Suitable For    Humid Houses in Winters    Dry Houses in Winters  
Efficiency    About 55-75%  Approx. 70%  
Perks    Saves Heating Bills  Reduces load on Dehumidifier  

What is HRV?

Aforementioned, the HRV or Heat Recovery Ventilation System (also referred to as MVHR-Mechanical Ventilation Heat Recovery) is one of the systems used to enhance indoor air quality by retaining and purifying the heat from the stale exhaust air.

It primarily uses this heat to preheat the air entering the house. It is often compared heavily to the human breathing system.   

The HRV Ventilator Core is considered to be the lungs of the system. It is the only place where the exchange of air primarily takes place.

Although it is a single area where this process takes place, both the incoming and outgoing air never mixes as they pass through separate tunnels and exchange takes place through the principle of conduction.   

An HRV usually requires a fan to operate 24/7 and still saves and recovers most of the energy cost. This recovered energy determines the ‘Efficiency Rate’. It is different for different brands of HRV but typically varies between 55 to 75%.

Some HRVs can go up to 93% efficiency depending on the quality of the fan. Although these high-efficiency HRVs are slightly over-priced than other HRVs but provide amazing service and quality.   

The only disadvantage of an HRV is the quality of the fan that needs to operate continuously. Most of the low-priced HRVs carry low-quality fans that can be damaged easily.

But with increasing demand, almost all the companies are now ready to give full-time warranty and replacement guarantee.   

Usually, high-efficiency HRVs are found and extensively used in Canada, The United States, Europe, but with each passing year, the use of HRVs is increasing tremendously.   

What is ERV? 

As mentioned above, ERV or Energy Recovery Ventilation System focuses on enhancing the indoor air quality index by retaining both heat and humidity from the stale exhaust air thus minimizing the energy loss and reducing the load on air conditioners and dehumidifiers.

ERV generally captures the moisture to lightly increase the humidity of the dried-out room in winters. It usually maintains the humidity of the room in winters from 40-60%.

In summers, an ERV typically precools and humidifies the air in the room whereas in winters it preheats and humidifies the room.  

There is a slight energy requirement of ERVs than other ventilation systems as they use a blower which requires certain power. ERV is often referred to as ‘Total Enthalpic Devices’ as they transfer latent heat as well as sensible heat.    

ERVs work reversely in the summers by removing the humidity in the air outside the room before injecting it into the house thus saving the energy load on air conditioners.

ERVs have great efficiency of at least 70% but studies and researches are going on to at least increase the efficiency up to 90%. ERV is perfect for houses that get too hot and dry in winters.  

Apart from slight energy requirement, there is practically no huge disadvantage of ERVs, they have manifested to be useful in improving air quality and reducing global warming drastically. 

Main Differences Between HRV and ERV   

  1. HRV or Heat Recovery Ventilation System uses the transfer of heat only, on the other hand, ERV or Energy Recovery Ventilation System uses the transfer of both heat and humidity/ moisture.   
  2. HRVs can only transfer sensible heat, in contrast, ERVs can transfer both sensible heat and latent heat.   
  3. HRVs are referred to as the Sensible Only Devices, whereas ERVs are referred to as the Total Enthalpic Devices.   
  4. HRVs are used for newly built airtight homes with good reasonable humidity, on the other hand, ERVs are perfect for homes that are older with less humidity and drier rooms.   
  5. HRVs typically have an efficiency of 55-75% with maximum efficiency up to 93%, in contrast, ERVs have efficiency up to 70%.  

Conclusion 

From the above-mentioned points, it is clear that even though both HRV and ERV are indoor air quality enhancing systems and appear to be strikingly similar there are subtle differences between them that are unavoidable.

Almost all ERVs can be considered as HRVs but not all HRVs can be considered as ERVs.  

The choice between HRV and ERV is highly specific considering the parameters like climate, house type, age of the house, area of the room, humidity, etc.

HRV is preferred when there is already existing humidity in the room whereas ERV is preferred when there is an enormous amount of dry air inside the house.

Nevertheless, both these ventilation systems are quite useful in the 20th century not only for the respiratory health of human beings but also to maintain the quality of the home.   

References 

  1. https://www.emerald.com/insight/content/doi/10.1108/MEQ-06-2012-0050/full/html 
  2. https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.504.7820&rep=rep1&type=pdf 

 

 

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