Founder | BPI® Energy Auditor Certified Professional
HRVs, also known as heat recovery ventilators, are essentially balanced ventilation systems with a unique heat-exchanger core.
The system introduces fresh, outdoor air into your living space like any ordinary ventilation system while removing the stale indoor air. If you want to improve your indoor air quality and ensure that your living space feels fresh and clean, an effective ventilation system is necessary.
But what makes the HRV genuinely unique is its heat-exchanger core, which can transfer heat from the incoming air to the outgoing and vice versa, depending on your needs. However, while heat is shifted from one airstream to another, the outgoing and incoming airstreams never actually mix.
When Is It Time to Consider Installing an HRV?
Consider installing an HRV system if the air smells stale and polluted, or if your home gets too hot in the summer and uncomfortably cold during winter. Additionally, if your energy bills are high because your HVAC system is working too hard to maintain a consistent temperature, an HRV might be right for you.
The Importance of Ventilation in Modern Homes
HRV systems are essential in modern, energy-efficient, airtight homes that do not allow much natural ventilation. Natural ventilation or leaks in older homes can exchange conditioned indoor air with unconditioned outdoor air.
This exchange can negatively impact the thermal comfort of your home and cause your energy bills to go up, as your furnace or air conditioner would have to work extra hard to heat or cool the new outdoor air. Not only does this lead to unnecessary wastage of energy, but it also makes your home less comfortable.
So airtight homes do serve an essential purpose. However, they also prevent fresh, clean air from entering your living space.
The conditioned air inside your home becomes stale, polluted, and extremely humid over time due to daily activities like cooking, showering, and even just breathing. In addition, if many people live in your home, the indoor air will become stale and humid much more quickly.
In airtight homes, any dust, debris, pet dander, or other pollutants inside cannot escape if the old indoor air is not regularly expelled.
Airtightness can lead to several problems, such as:
- Bad odors inside the house
- The oversaturation of dust and pollutants in the indoor air
- Lowering of the indoor air quality
- Health issues such as cough, asthma, and allergies
- Too much humidity in the indoor air
So, if you have recently been noticing any of these problems in your home, it might be time to install a high-quality HRV system.
How Does an HRV System Work?
A typical HRV system is comprised of two blower fans installed within two adjacent ventilation ducts. These ducts extract stale and stuffy air from the room and replace it with fresh outdoor air.
The HRV also contains a heat exchanger core equipped with thin metal plates. These plates are stacked together with a tiny amount of space in-between. The two different airstreams – incoming and outgoing air – pass through the spaces in-between the metal plates.
Heat is transferred from one airstream to the other through the metal plates. This system of heat transfer offers an efficiency rate of about 90 percent. The heat transfer coefficient of the metals used to make the plates will affect efficiency.
Furthermore, the metal plates ensure that the outgoing and incoming air streams are entirely separated at all times. Thus, you can be confident that the outdoor air introduced to your home by the HRV system is 100 percent fresh and healthy.
Indoor Humidity and Condensation Control
This ventilation and heat transfer process also impacts the level of humidity in indoor air. For example, when cold air is warmed, it decreases relative humidity because hot air can hold more water molecules. Hence, the relative humidity in the air goes down as the temperature of the air rises.
When the incoming, outdoor air is warmed inside the HRV core, its relative humidity drops. Thus, an HRV system will also help control condensation in your home. In addition, reducing relative humidity levels will minimize the risk of mold growth, dust mite infestation, and other common moisture-related issues.
Seasonal Variation
How an HRV system works will change slightly depending on the season.
In winter, the indoor air is warmed by the furnace. It also absorbs heat from cooking stoves, hot water heaters, night store heaters, etc.
Outdoor air, on the other hand, is naturally cold during the winter months. Hence, the heat exchanger core extracts heat from the furnace-warmed indoor air and transfers it to the cold outdoor air drawn into the house. As a result, the incoming air is already warm before being introduced into the living space.
During the summer, indoor air is cooled by the air-conditioner, while the outdoor air is quite hot. Thus, the heat-exchanger core captures some of the heat from the incoming outdoor air and passes it to the indoor air being expelled. As a result, the temperature of the incoming air drops, and the outgoing air rises.
This heat exchange also helps reduce energy consumption, since your air-conditioner will not have to cool each batch of fresh air drawn into the home. It has already been cooled down inside the ventilator core, with the chill from the outgoing, conditioned air.
When Should You Install an HRV System?
Now that you know what an HRV system is and how it works, it is time to consider installing one in your home. (Click here to learn about some of the best HRV systems currently available.)
A high-quality HRV system can solve several problems. If you have been experiencing any of these in your home, it might be time to install this unique mechanical ventilation system. Read on to learn more about the problems (and how an HRV could solve them).
If Poor Indoor Air Quality Is Causing Health Problems
The average home is full of common allergens, including dust, pollen, pet dander, and mold. Since most modern homes are designed to be as airtight as possible, these common airborne allergens keep circulating within the house, without a chance to escape outside.
According to a US Environmental Protection Agency report, indoor air contains between 2 to 5 times more pollutants than outdoor air. And a significant reason for this is the lack of proper, natural ventilation in modern, airtight homes.
So, if you (or a family member) have recently been suffering from allergies, dry coughs, or respiratory issues like asthma, the quality of your indoor air might be part of the problem. And installing a reliable HRV system can quickly solve this problem.
The HRV will constantly refresh the indoor air, drawing out stale air and introducing fresh outdoor air. This process will help residents struggling with allergies or asthma, as it won’t allow any of the common airborne allergens to linger in the living space.
If Your Energy Bills Are Untenably High
The HRV system helps keep your home cool during the summer and warm during the winter. However, it does not generate any heat (or chill) on its own. Instead, it simply transfers heat from one airstream to another, depending on the season.
This exchange is a much more energy-efficient process than active heating or cooling, so HRV systems can help reduce your energy consumption. Which, in turn, will both reduce your carbon footprint and lower your electricity bills.
So, if your energy bills are unsustainably high, installing an HRV system might be a good idea. (Click here for more ways to save money on your HVAC system.)
The furnace and air-conditioner use up a lot of energy to heat and cool the indoor air, respectively. When fresh, outdoor air is introduced into the home, they have to work extra hard to heat or cool the unconditioned outdoor air until it has reached room temperature.
The HRV system reduces the load on your furnace and air conditioner by transferring heat from the outgoing air to the incoming air during the winter.
During summer, on the other hand, it transfers heat from the incoming outdoor air to the outgoing indoor air so that the fresh air has cooled down somewhat before it is introduced into the living space. This cooling saves a lot of energy by recycling the existing heat.
If You’re Dealing with the Growth of Mold and Mildew
Are you dealing with condensation building on your windows? Or with the growth of mold and mildew on bathroom walls, on the trim around your windows, and on other damp surfaces in your house?
Mold growth might signify it’s time to install an HRV system for better moisture control. By raising the temperature of cold, outdoor air before it is introduced inside your living space, an HRV system helps reduce the relative humidity in your home.
Too much humidity can cause many problems, including mold and mildew infestations, the warping of wooden furniture, and an increase in respiratory issues. And an HRV system is an effective way of dealing with all of these problems simultaneously.
However, it would help to adjust the humidity control of your HRV system with the changing seasons. For example, the humidity control should be higher during the summer and lowered in winter for optimal functioning.
If Your Home Has Become Draughty and Uncomfortable
If your home is too cold during winter and too hot in summer, you can solve this problem by installing a high-quality HRV system.
Draughts of cold outdoor air can make your home uncomfortably chilly during the winter. On the other hand, the steaming outdoor air during the summer can undo a lot of the work done by your air conditioner.
Not only will these issues minimize the comfort of your home, they can also cause health problems. Being exposed to too much cold air during the winter, for instance, could lead to pneumonia.
Therefore, it would be best to shut your doors and windows, seal any leaks in your building envelope, and rely solely on an HRV system for fresh, outdoor air, especially during extreme weather conditions.
The HRV system will keep your home cozy, clean, and well-ventilated throughout the year, regardless of outside weather. So, you will no longer have to worry about cold draughts or heat waves while indoors.
Concluding Note
Before deciding whether or not your home is ready for an HRV system, you should consider some of the abovementioned points. For example, such a system might be advantageous if you deal with poor indoor air quality or excess moisture in your home.
If you decide that an HRV system would be beneficial, be sure to discuss your options (and the potential costs) with one or more experienced HVAC technicians.