In the past, buildings were ventilated naturally by opening a window or door and letting in fresh air. However, with more advanced air-sealing techniques emerging, this approach is inadequate. Here’s where mechanical ventilation comes in. It offers a number of ways to move stale indoor air outside and fresh outside air inside. This short white paper will examine each mechanical ventilation alternative and go through how it functions, its advantages, and any potential drawbacks.

1. What is the ventilation system?

A ventilation system is a mechanical framework of interconnected components that regulates airflow in small, frequently residential and commercial environments. Its primary purpose is to continuously introduce fresh air, typically from the outside, while exhausting stale air. These systems frequently include fans, pumps, vent grates, and air flow tunnels, but most of the time, the main functioning components are all installed inside the structure’s walls and ducts.

Fresh Air Ventilation Systems

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2. Importance of ventilation systems

Ventilation is simply the interchange of indoor and outdoor air at its most basic. It seems simple to swap out stale old air with fresh new air. But there are a variety of methods for doing so as well as a few different mechanical house ventilation systems to pick from that can help.

Without a new-old air exchange, dangerous indoor air pollutants are forced to continue flowing within, necessitating ventilation. You and your family are stuck breathing because something within is stuck circulating. The many variables that influence indoor air quality are numerous. The air quality is harmed by a variety of issues, including too much moisture, improper humidity control, dogs in the house, cooking gas emissions, and others. Additionally, they raise the importance of ventilation.

3. Types of ventilation

3.1. Natural ventilation

Natural ventilation was once the most frequent way of allowing fresh outdoor air to replace indoor air in a dwelling. Today, most homes are properly air sealed for energy efficiency, making it less often the optimum ventilation approach. Additionally, natural ventilation frequently fails to adequately regulate moisture.

3.2. Spot ventilation

The efficiency of natural ventilation can be increased by using spot ventilation. However, you should think about a whole-house ventilation strategy if spot and natural ventilation taken together are insufficient to meet the ventilation needs of your home.

By eliminating indoor air contaminants and/or moisture at their source, spot ventilation enhances the efficacy of other ventilation systems, including natural and whole-house ventilation. Spot ventilation comprises the use of focused exhaust fans, as those used in bathrooms and over cooking ranges.

Spot ventilation increases the efficacy of other ventilation techniques, such as natural and whole-house ventilation, by eliminating indoor air contaminants and/or moisture at their source. Localized exhaust fans, like those found over kitchen ranges and in restrooms, can be employed as a form of spot ventilation.

3.3. Whole-home ventilation

One or more fans and ductwork are used in a whole-home or whole-building system to efficiently bring fresh outdoor air indoors and remove stale indoor air.

The purpose of a house ventilation system is to properly ventilate a big room while also enhancing indoor air quality. A whole-home system has many advantages. Fresh air is continuously drawn in while stale air is expelled. It continuously works to raise the standard of the air supply. Whole-home ventilation systems are able to provide regulated ventilation for a complete house since the procedure may utilize the ductwork already present in a space and installed directly into the HVAC system. Additionally, the air is filtered while being circulated through the current HVAC system, creating cleaner, healthier indoor air.

types of ventilation system

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4. Types of whole-home mechanical ventilation systems

To exchange indoor and outdoor air without wasting energy, a home’s fans, vents, and ventilation apparatus all function as a single “ventilation system”. There are four different types of ventilation systems: exhaust, supply, balanced, and heat-recovery. The environment and the requirements of the construction will determine the best ventilation system for each particular home.

Exhaust ventilation systems are favored in cold areas because they are less prone to attract damp air into the structure. In contrast, supply ventilation systems are more effective at managing moisture in warm regions. Both cold and warm areas can benefit from balanced ventilation systems, although they are more expensive to install. Systems for recovering heat interchange indoor and outdoor air.

4.1. Exhaust ventilation

Exhaust ventilation systems operate by depressurizing a structure. The system exhausts air from the home, generating a shift in pressure that draws in outside makeup through building shell leaks and purposeful, passive vents. Since depressurization in warmer climates can pull moist air into wall cavities where it may condense and cause moisture damage, exhaust ventilation is best suitable for cooler climates.

Installation of exhaust ventilation systems is comparatively easy and inexpensive. An exhaust ventilation system typically consists of a single fan coupled to a single exhaust point that is positioned in the middle of the house. It is preferable to connect the fan to ducts from multiple rooms, ideally those that produce pollutants, such as the kitchen and bathroom..

Instead of relying on leaks in the building envelope, it is possible to create passive, movable vents through windows or walls in other rooms. However, in order for passive vents to function efficiently, higher pressure differences than those created by the ventilation fan may be necessary.

4.2. Supply ventilation

A fan is used in supply ventilation systems to pressurize a building, bringing in outside air while allowing air to escape through shell holes, bathroom and range fan ducts, and purposeful vents (if any exist)

Supply ventilation systems are as easy and affordable to install as exhaust ventilation systems. A typical supply ventilation system has a fan and duct system that brings fresh air into one or more of the rooms that inhabitants use the most, including the living room and bedroom, though ideally more than one. Other rooms’ walls or windows may have movable vents as part of this system.

Compared to exhaust ventilation systems, supply ventilation systems enable better control of the air entering the house. Supply ventilation systems pressurize the home to reduce exterior pollutants inside and stop combustion gasses from appliances and fireplaces from being drawn back into the living area. Additionally, supply ventilation enables the filtration of incoming outdoor air to remove pollen and dust or the dehumidification of indoor air to regulate humidity.

Systems for supply ventilation perform best in warm or mixed climates. These systems have the potential to result in moisture issues in cold areas since they pressurize the home. Warm internal air from the supply ventilation system leaks out through sporadic holes in the outside wall and ceiling throughout the winter. Mold, mildew, and decay may develop in the attic or the cold outside portions of an exterior wall if the internal air is sufficiently damp.

Ventilation System

4.3. Balanced ventilation

If properly planned and built, balanced ventilation systems don’t pressurize or depressurize a building. Instead, they bring in and let out roughly equal amounts of clean outside air and contaminated indoor air.

A balanced ventilation system typically contains two duct systems and two fans. Every room can have fresh air supply and exhaust vents installed, but a typical balanced ventilation system is built to provide fresh air to bedrooms and living rooms because those are the areas where residents spend the majority of their time. Additionally, it removes air from areas like the kitchen, bathrooms, and laundry room that are frequently where moisture and contaminants are produced.

Some designs employ a single-point exhaust, and because they provide outside air directly, balanced systems permit the use of filters to filter the air before bringing it inside. All climates benefit from balanced ventilation systems.

Balanced ventilation systems, like supply and exhaust systems, do not modify or eliminate moisture from make-up air before it reaches the house. Consequently, in contrast to energy recovery ventilation systems, they can result in increased heating and cooling expenses. Similar to supply ventilation systems, it may be necessary to combine indoor and outdoor air before delivering air in order to prevent chilly drafts during the winter.

Balanced ventilation systems are typically more expensive to install and maintain than supply or exhaust systems since they require two duct and fan systems.

4.4. Energy recovery & heat recovery ventilators

Energy recovery ventilation systems allow you to ventilate your home while minimizing energy loss. By transferring heat from the heated exhaust air from within to the fresh (but chilly) supply air from outside, they lower the cost of heating ventilation air in the winter. In order to lower cooling expenses in the summer, the inside air cools the warmer supply air.

Energy Recovery Ventilators (ERVs) and Heat Recovery Ventilators (HRVs) are the two different types of energy recovery systems. Both kinds of machines come equipped with a heat exchanger, a fan or fans to move air through the device, and controls. There are a few tiny wall- or window-mounted types, but the bulk of ventilation systems are central, whole-house ventilation systems with their own duct systems or shared ductwork.

In addition to costing more to build, complex systems frequently require more frequent maintenance checks and use more electricity. In most homes, it generally won’t be cost-effective to try to recover all of the energy from exhaust air. 

Additionally, these ventilation systems are still not particularly widespread. Only a few HVAC contractors have the necessary technical know-how and work history to install them.