Heat and Energy Recovery Ventilation

What is a Heat Recovery Ventilator (HRV) or an Energy Recovery Ventilator (ERV)?

At the forefront of innovation, heat recovery ventilators (HRVs) or energy recovery ventilation (ERV) systems transfer heat or coolness from stale exhaust air to fresh intake air. This balanced ventilation solution removes excess moisture, odors, and contaminants while conserving energy and enhancing comfort. In addition, ERV systems help keep indoor humidity levels at an optimum level.

How Does an HRV / ERV System Work?

As more and more homes are being built or retrofitted to be as energy-efficient as possible, the right ventilation becomes increasingly important. Whole home, balanced ventilation removes stale air from bathrooms, kitchens and utility rooms and replaces it with fresh, filtered air supplied directly to living spaces. Energy Recovery Ventilators (ERVs) and Heat Recovery Ventilators (HRVs) supply continuous fresh air exchange while helping to keep homes comfortable and energy bills lower. Ventilation is truly the lungs of a building. 

Zehnder ERVs and HRVs recover up to 92% of the home’s heat (depending on the model) from the extracted air and use it to heat the incoming fresh air stream—without mixing the contaminated extract air with the fresh air. Instead, as the airstreams pass through the core of the unit, only the heat  is preserved. In addition, an ERV unit helps to keep the home at optimum humidity levels year-round by extracting some excess moisture from the wetter air stream and returning it to the drier stream. This helps your home heating and air conditioning systems to keep the home from drying out in the winter and getting uncomfortably humid in summer. 

HRV or ERV? The best system for your project will depend on factors like location and climate as well as the size of your home and the number of bathrooms, kitchens and utility rooms. Our team of salespeople will recommend the best unit for your project, along with distribution components and controls to make keeping your home healthy and comfortable easy. 

The Importance of Indoor Air Quality

Did you know that the average person spends 90% of their time indoors? That’s why indoor air quality (IAQ) is so important—and it goes hand-in-hand with an excellent ventilation system! 

Many buildings, especially older ones, use mainly natural ventilation to move air. Natural ventilation includes opening windows and doors and also air moving through gaps and cracks in the building’s exterior—the drafts you might feel in a building that’s not airtight. 

Unfortunately, when we rely only on natural ventilation, much of the air we breathe indoors is stale or contaminated. Indoor air pollution can be especially concerning for people who have chronic illnesses, compromised immune systems, or sensitivity to mold or chemicals. 

Although the connection between indoor air quality and health issues such as asthma, allergies, and respiratory ailments is well-known, good IAQ is also important for cognitive function and mental health. Recent workplace studies have demonstrated that poor indoor air quality negatively affects our ability to concentrate, mood, and anxiety, and longer exposure can even lead to personality changes, impaired memory, and slower cognitive function. 

hrv system zehnder

Everyday activities like showering, cooking, washing dishes, and doing laundry all affect IAC in the home by producing moisture. Excess moisture can lead to mold growth. Other common causes of IAC concerns in the home are pollen, pet dander and volatile organic compounds (VOCs) that come from many common household items like cleaning supplies, new carpeting or furniture, cosmetic and hobby supplies. It’s inevitable that some contaminants will be introduced to air in the home simply as the result of our daily routine. 

There are steps you can take to reduce contaminants in your home air, but the best way to substantially improve IAQ is through a whole-home mechanical ventilation system. Zehnder systems use high-quality filters to remove many pollutants from the air before it enters homes and commercial spaces. High-MERV filters, like our F7 / MERV 13 intake filters, can stop even small particles, including pollen, bacteria, solid particles from smoke and smog, and mold spores, from entering your home or business. Our ERV and HRV systems are also designed to exhaust air specifically from bathrooms, kitchens, and utility rooms, where most home pollutants (fumes, particulates, and excessive moisture that can cause mold) originate. 

Zehnder systems are designed to operate 24/7, quietly providing a continuous flow of fresh, filtered air to your living space, replacing the stale, contaminated air extracted from bathrooms, kitchens and utility rooms. This keeps moisture and other contaminants from having the chance to build up in your home, meaning your family will have nothing but the best indoor air quality all day and all night. 

Energy Efficiency & Comfort

Inefficient ventilation systems drive up heating and cooling costs while decreasing indoor comfort. Much like venting a room by opening a window, inferior ventilation systems can degrade energy performance because they exhaust air without first capturing the heat. Some older systems even vent into attic spaces instead of outdoors, so stale, contaminated air is never really removed from the home! Because exhaust fans need makeup air to operate properly, they pull in unfiltered, unconditioned air through gaps and cracks in the building exterior, creating drafts. This has a huge impact on both comfort and energy costs. 

Zehnder ERV and HRV systems conserve energy, lowering utility bills. The heat from the exhaust air is transferred to the incoming air via a heat exchanger. Zehnder systems can preserve up to 92% of the home’s heat. In addition, an ERV will help transfer some humidity from the wetter air stream to the drier one. Heat and humidity transfer helps reduce use of HVAC equipment because it doesn’t have to work as hard to heat and cool when the intake air is already conditioned by the ERV/HRV. That means a comfortable home with lower energy bills! 

Ventilation Strategies for Passive House Certification

The Passive House Standard is a voluntary standard for ultra-energy-efficient homes and buildings. Projects built to this standard are 80% more efficient to heat and cool than a typical new building built to the minimum building code requirements. Most Passive House projects feature an extremely tight building envelope with continuous insulation and meticulous air sealing. Passive House construction in colder climates typically requires triple-pane windows, generous amounts of insulation, and heat recovery ventilation. Because very little air can leak in or out of the building, a mechanical ventilation system is essential to ensure that stale, contaminated air is removed and replaced with fresh air. 

Certified Passive House buildings (and buildings built to that standard but not officially certified) are growing in popularity. Several jurisdictions have policies that support Passive House and other high-performance construction methods, and more and more building professionals are getting trained in Passive House design and construction. 

passive home versus traditional home

Many Zehnder ERV and HRV systems are certified Passive House components and are widely used in Passive House projects, including mixed-use buildings, new homes, and retrofit projects. Because they are among the most efficient HRV units on the market, they are a favorite among Passive House builders, architects, developers, and engineers. 

Load requirements for the heating and cooling systems are greatly reduced or possibly eliminated when following the Passive House standard, cutting the cost of the HVAC system. Also, the operation and maintenance costs of a Passive House are typically much lower, because of the decreased utility costs and the durability of components. 

In addition to the Passive House Standard, Zehnder ERV and HRV systems are commonly found in other types of green buildings, including those with Leadership in Energy and Environmental Design (LEED) certification. As a prerequisite in the LEED for Homes program, a project must “design and install a whole building ventilation system that complies with ASHRAE Standard 62.2-2007,” a standard developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, which details ventilation rates and strategies for healthy homes. 

leed certified home

In addition, LEED for Homes awards two points to projects that go beyond basic ventilation measures and “install a system that provides heat transfer between the incoming outdoor air stream and the exhaust air stream.” An additional point can be earned by projects that undertake commissioning to verify that ASHRAE 62.2 ventilation requirements are being met by the ventilation system.

The Importance of Correct Installation 

Proper ERV or HRV system sizing, design, layout, and commissioning are essential for optimum system function and durability. Zehnder ventilation systems and HVAC systems are separate and should not share ductwork. This ensures proper airflow rates and energy efficiency. 

Our ventilation experts are available to help lay out the best system for a given project based on the location and size of the building as well as the number and purposes of rooms. Because our systems include the unit as well as distribution components, they are easier and quicker to install, even for professionals who aren’t experienced in ERV or HRV installation, saving time and money. 

Properly installed and commissioned ventilation systems are significantly more effective in improving air quality. Unbalanced systems can decrease the efficiency of a system, resulting in up to four times more energy loss. Commissioning a Zehnder system with a trained professional can also extend the life of the equipment and reduce operating costs for years to come! 

Zehnder manufactures its own distribution components, allowing systems to be seamlessly integrated into homes and commercial spaces. Zehnder components are designed for ease of installation and system longevity.  

Common Applications for Heat Recovery Ventilation

There are a variety of residential and commercial applications that are ideally suited for Zehnder ERV and HRV units. Some local building codes require heat recovery ventilation to promote indoor air quality and energy efficiency. Projects with tight building enclosures and energy-efficiency goals require heat recovery ventilation to ensure adequate indoor air quality and energy performance. 

Detached Houses:

This is one of the most popular applications for Zehnder systems for both new construction and retrofits. Stale air is extracted from bathrooms, kitchens, and utility closets, and fresh air is supplied to bedrooms and living spaces. 

Multi-family Buildings:

Urban areas, where apartment buildings and condominiums are common, can have highly polluted outdoor air. Zehnder systems filter the intake air, removing many common pollutants and making indoor air healthier. 


There is a strong connection between cognitive function and indoor air quality. Proper ventilation reduces carbon dioxide levels and filters out many contaminants, helping promote greater classroom learning

Office Buildings:

Studies have confirmed the impact of indoor air quality on worker productivity and mood. Zehnder systems extract contaminated air and bring in fresh air for a healthier and more productive workplace. 

Hospitals and Clinics:

A proper ventilation strategy is essential for preventing the spread of illnesses and promoting optimum health and healing. Zehnder systems are ideal for hospitals and medical clinics where fresh air is essential

Interested in a Zehnder system for your home or business? Fill out our Quote Request form today.