Heating & Cooling

Do You Need an Air Exchanger with a Heat Pump?

Air Exchanger

Over the past few decades, there have been rapid improvements in heat pump technology. Seemingly every year the technology improves. 

However, in recent years additional components have been released into the marketplace that aid heating and cooling systems to improve overall indoor air quality. Air exchangers are used in conjunction with heat pumps and other types of HVAC systems to improve indoor air quality.

You may be wondering if you need an air exchanger with your heat pump system? An air exchanger is not mandatory to have with your heat pump system, however, it may be a worthwhile investment. If your home has been built since the year 2000, you would benefit from having an air exchanger installed. Air exchangers help to improve your indoor air quality by removing stagnant air from the inside and exchanging it with fresh air from the outside. 

First and foremost you need to understand that an air exchanger and a heat pump system are not the same things. Each is independent of one another. 

Your heat pump system is the primary means of heating and cooling your house. The heat pump system draws in air from the return inside your house and heats or cools the air and redistributes it through the supply ducts. 

An air exchanger is used to improve ventilation in your home. It does not provide heating and cooling. Its main function is to exchange indoor air with exterior air to improve indoor air quality

To determine if you would benefit from an air exchanger we need to dig into this a little deeper. Let’s examine what a fresh air exchanger is, why they are important, and who would benefit from installing one.

What is an air exchanger?

Air Exchanger

Simply put an air exchanger takes indoor air and exchanges it with fresh air from the exterior. Over time, the indoor air becomes stagnant and stale. Stagnant air contains bacteria and other contaminants that can affect your family’s health. An air exchanger exchanges this stale and stagnant air with fresh air from outside. 

This helps to improve indoor air quality by keeping a constant exchange of air. Years ago this wasn’t a problem because homes were naturally ventilated and opening doors and windows were a common occurrence.

Today’s homes are built to be airtight to conserve energy. Most families do not open doors and windows like in the past. It was common for people to open windows and doors to air out their houses and allow heat to escape. Those days are gone.  

The turnover of fresh air helps to remove bacteria, mold spores, and other air contaminants that become trapped inside your home. 

If you are prone to chronic sicknesses or suffer from sick building syndrome (SBS) an air exchanger may be exactly what you need. Sick building syndrome occurs when you bring sicknesses into your home and constantly spread it from person to person over and over again. It becomes harder and harder to get over illnesses.

An air exchanger helps to remove contaminants trapped in stale indoor air by drawing this stale air out of the home and drawing in fresh air into the filtration system.

There are two main types of air exchangers on the market; energy recovery ventilator (ERV) and heat recovery ventilator (HRV). 

ERV’s are commonly used in warmer climates and HRVs or more commonly used in colder climates. Your climate will determine which system is right for you. You should consult with a licensed heating and cooling contractor for more information about which is right for you.

Energy recovery ventilators work by exchanging the energy contained in normally exhausted indoor air and using it to pre-condition incoming fresh air before it enters your heat pump system. During warmer months the system will pre-cool and dehumidify incoming air. During colder months the system will pre-heat and humidify incoming air. The system will help to maintain an indoor relative humidity level of 40% to 50%. 

Heat recovery ventilators are also referred to as mechanical ventilation heat recovery (MVHR) and are a version of the energy recovery ventilation system. Heat recovery ventilators help to recover the heat from interior air and transfer it to incoming fresh air. Interior warm air is used to either warm-up or cool down fresh income in the air depending on climate conditions in the time of year.

Why is an air exchanger important?

Older homes were constructed to be naturally well ventilated. These homes would exchange air through exterior walls, floors, and ceilings naturally due to relatively low levels of insulation and single-pane windows. The drawback to this is these homes would have extremely high energy costs in the winter and summer months. 

In an effort to reduce energy costs, new homes are now constructed to be well insulated and airtight. This helps to reduce energy costs by holding in cooler air in the summer and warm air in the winter. The downside is that these homes are not well ventilated unless they are mechanically done so. That’s where the air exchanger comes in.

These newer homes trap air inside which prevents the natural exchange of fresh air in the home. Unless you are a person who routinely opens up your windows and doors, you will experience stagnant air inside your home and would benefit from an air exchanger. 

What is indoor air quality?

Indoor air quality affects the health, comfort, and well-being of those living in the home. Poor indoor air quality has been linked to sick building syndrome.

Indoor air quality can be affected by a variety of pollutants like carbon monoxide, mold spores, bacteria, and a multitude of other contaminants found in the air.

A list of common indoor pollutants includes:

  1. Secondhand tobacco smoke – This occurs from smoking indoors
  2. Radon gas – Radon gas is an invisible radioactive, atomic gas that results from the radioactive decay of radium which is naturally found in rock formations beneath building structures. 
  3. Mold spores – mold spores are naturally found in the environment. There are two classes. There are thousands of types of mold spores in the environment. Homes with moisture problems can experience mold growth which can produce toxins into the air. 
  4. Carbon monoxide – carbon monoxide is a colorless, odorless gas that is the byproduct of combustion. Carbon monoxide gasses in a confined space can buildup and become deadly.
  5. Carbon dioxide – Carbon dioxide is a natural contaminant that is emitted into the atmosphere by humans and animals through the natural breathing process. 
  6. Volatile organic compounds – VOCs include a variety of chemicals, such as paint, lacquers, paint strippers, cleaning supplies, and pesticides just to name a few. Many of these items are stored in garages that are attached to homes.
  7. Indoor fires – Wood burning stoves, chimneys, and burning candles can produce harmful contaminants into the air such as black carbon, nitrogen oxides, sulfur oxide, and other harmful emissions. 

In airtight newer homes, indoor air quality will diminish over time as airborne contaminants can not escape the building. 

Heat pumps have air filters that collect airborne contaminants at the air return. However, this can only help maintain air quality but will never improve it. This also assumes the air filters are changed on a routine basis. Improvements in indoor air quality require a turnover of fresh air inside the home.

Ideally you want indoor air to have a humidity level of 40% to 50%. The air in homes that are airtight can be much drier than this particularly in winter months.

Who would benefit from it a fresh air exchanger

If you live in an older home, i.e. a home built prior to 1980, you likely would not benefit from the installation of a fresh air exchanger. The reason being is these homes do not meet the same energy efficiency standards as newer homes. However, there are some exceptions.

For example, if your home has undergone a major renovation that has improved the insulation to current standards and has replacement energy-efficient windows then you would likely benefit from an air exchanger in your home. 

To determine if you would benefit from a fresh air exchanger you need to look at your environment. Questions to help determine if you need a fresh air exchanger in your home: 

  • Do you have pets in your home?
  • Do you commonly find moisture or mold growth  on the interior side of your windows?
  • Do you commonly find mold or mildew growth on furniture and other wood surfaces in your home?
  • Do you routinely burn candles in your home?
  • Do you suffer from chronic respiratory illnesses?
  • Do you live in an extremely hot or cold climate?

Final thoughts

There is no clear-cut answer as to whether or not you would benefit from an air exchanger. The fact of the matter is, every home and situation is different. What affects your health and well being will affect the health and well being of others differently. As we’ve also discussed, your daily habits and activities also affect your overall indoor air quality. 

Looking at the construction of the home alone, if your home has been built after 2000 it should be airtight and built to high energy efficiency standards. 

Most home builders do not install fresh air exchangers with heat pump systems as part of new home construction. These are considered aftermarket improvements that would need to be made by the homeowner.


Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.