Concepts and Types of Ventilation to Consider Today

Imagine a world with no clean air – it would be uninhabitable and lifeless.

We don’t even pay attention to breathing, but we are doing it every moment of every day. Did you know that an average human consumes over 12,000 liters of air daily!

The ventilation system serves as the lungs of any building or enclosed structure.

Without it, the health of the inhabitants of a building will deteriorate considerably. Sick building syndrome is a real and imminent problem, which is only being aggravated by the rising air pollution inside and out.

In a world where we spend nearly 90% of our time inside buildings, ventilation is more important than ever before!

But how do you assess the quality of ventilation in a building? And if it is not up to the mark, how do you improve it?

You’ll find the answers to all such questions in this guide. So take a deep breath and read on!

Everything You Need To Know About Ventilation

For the sake of brevity, we have explained the most common types of ventilation, followed by various concepts.

Without further ado, let’s get straight to the details.

Types of Ventilation

Ventilation can be broadly classified into five types – Mechanical, Natural, Hybrid, Spot, and Task-Ambient Conditioning (TAC).

Irrespective of where your building is and what it is used for, you will have to incorporate one of these five types of ventilation systems.

1. Mechanical Ventilation

Mechanical ventilation systems use fans to get the job done! A mechanical system may require fans to be installed in air ducts or directly in walls and windows. These fans supply air into or exhaust air from a room.

There are different types of mechanical ventilation systems that are used for different ventilation requirements. The type of mechanical ventilation system you should use should be based on the climate and the indoor air pollutants. Remember, you want to reduce interstitial condensation with the help of a ventilation system.

If you want to install a mechanical ventilation system in a building located in an area that has a hot and humid climate, it should be able to minimize or prevent infiltration. As such, a positive pressure system would be ideal.

Conversely, a negative pressure system would be the ideal choice for a building located in an area that has a cold climate. That’s because it can minimize or prevent exfiltration.

You can choose to maintain a slightly positive or negative pressure in the room by keeping a somewhat unequal supply and exhaustion rate of airflow. If you exhaust 10% more air than the supply, you get a slightly negative room pressure, which is ideal in a cold climate.

Types of Mechanical Ventilation Systems

Exhaust-Only, Positive Pressure 

Exhaust-only ventilation systems do not have a dedicated component to draw outdoor air into the building. The leaks in a building’s enclosure are required to do that part. It usually consists of a bath fan, which exhausts indoor air.

These ventilation systems are the most affordable when it comes to mechanical ventilation. And that’s in terms of installation as well as operating costs. Being relatively straightforward to install makes these ventilation systems very popular among homeowners.

Supply-Only, Negative Pressure 

Supply-only ventilation systems operate on the opposite end of the spectrum. It consists of a fan that draws outdoor air into the house. Indoor air escapes the building through exhaust fan ducts or leaks in the enclosure. It can be a dedicated system or a Central-Fan Integrated (CFI) system.

The CFI system may increase installation as well as operating costs.

Balanced

Balanced ventilation systems are combinations of exhaust-only and supply-only systems. There is a roughly equal airflow rate of indoor exhaust and outdoor supply in a balanced system. Moreover, it is capable of incorporating an Energy Recovery Ventilator (ERV) or a Heat Recovery Ventilator (HRV).

Energy-Recovery

Energy-recovery ventilation systems focus on minimizing energy loss through controlled ventilation. In the winter, it heats the ventilated air by transferring heat from the warm, evacuated air. Likewise, in the summer, the evacuated air cools the ventilated air.

An energy-recovery ventilation system can significantly reduce energy costs.

Advantages of Mechanical Ventilation

• Irrespective of the ambient temperature and wind, it can consistently deliver the desired flow rate.
• You can easily integrate it into the air-conditioning system.
• It can also be used to control indoor humidity and air temperature.
• You can install a filtration system in it to facilitate the removal of particulates, odor, and harmful microorganisms from the air.
• All you need is electricity for it to work.
• It allows unparalleled control of the airflow direction.

Drawbacks of Mechanical Ventilation

• Improper installation of a mechanical ventilation system can lead to unreasonably high maintenance costs.
• Backing up mechanical ventilation for a critical facility can be very expensive.
• The regular operation of a mechanical ventilation system is often interrupted by equipment failure or utility service interruption.

2. Natural Ventilation

Natural or traditional ventilation systems rely on natural forces like wind and thermal buoyancy to transmit fresh, ambient air into buildings. Three factors come into play for natural ventilation to work effectively – building design, human behavior, and climate.

As far as building design is concerned, you need purpose-built openings like doors, windows, wind towers, trickle ventilators, and solar chimneys. If it works efficiently, a natural ventilation system can enhance cooling and thereby lead to a 20 to 25% energy savings.

In many traditional buildings, you will find high ceilings and air spaces below the eaves or at the ceiling level. This age-old component of old architectural design was used to enhance the outward venting of heat during the daytime and cross ventilation during the nighttime.

But it isn’t as simple as opening the windows and doors of a room. Natural ventilation can do more harm than good in places where outdoor air pollutants exceed indoor air pollutants. Extreme weather conditions render a natural ventilation system completely redundant. And who can forget the inherent risk of letting in pests along with natural ventilation!

Due to the considerable limitations and lack of control in a natural ventilation system, it is being substituted by mechanical systems. Today, you will find central heating or cooling systems being used throughout the year in the majority of houses.

Types of Natural Ventilation Systems

Buoyancy-Driven

Buoyancy-driven natural ventilation is more commonly known as stack or temperature-induced ventilation. It arises because of a difference in the temperature of indoor and outdoor air, which results in different densities.

Warmer air has a lower density or more buoyancy and rises above cooler air, something we know as an upward air stream. The primary prerequisite for it to work is that the air temperature inside and outside the building must be different.

Say there are openings in a building close to the floor as well as the ceiling. If the air inside has a higher temperature than the air outside, the warmer indoor air will rise and escape through the higher opening. The colder outdoor air will enter the building through the lower opening. This creates up-flow displacement ventilation.

Now, if there were only a high opening close to the ceiling, both the inward and outward airflow would take place through it. This would result in mixed ventilation. We have explained different ventilation principles like displacement and mixed later in this guide.

Wind-Driven

Wind-driven ventilation is much simpler. It is also referred to as single-sided ventilation and cross ventilation. This type of ventilation depends on the wind behavior and interaction with the openings (such as chimneys or inlets) in a building envelope.

One of the common misconceptions people have is that opening the windows solves the ventilation problem. Even if you are lucky enough to get just the right wind velocity outside, wind-driven ventilation can significantly increase energy costs.

Advantages of Natural Ventilation

• In an ideal scenario, it can provide a high ventilation rate at a low cost.
• If there is no need for heating, it can be very energy efficient.
• It can be used to get higher levels of daylight.
• The maintenance cost is very low.

Drawbacks of Natural Ventilation

• It is variable and depends on the climatic conditions outside.
• You have negligible control over it, especially the airflow direction.
• Improper natural ventilation significantly increases the risk of airborne pathogens being transmitted.

3. Hybrid Ventilation

A hybrid ventilation system incorporates aspects of both natural and mechanical ventilation. By default, it relies on natural ventilation to provide the desired airflow rate. When required, the system uses mechanical ventilation to bridge any gap between the required and natural ventilation flow rates.

There are two common ways of using hybrid ventilation. The first involves the installation of whirlybirds. These are wind turbines that do not require electricity to function. You can use these to increase the airflow in a building through a roof-exhaust system.

The second and perhaps most common use of hybrid ventilation involves exhaust fans. When natural ventilation is not adequate, you can install exhaust fans to increase the ventilation rate. But there are a few things concerning exhaust fans that you should keep in mind:

• Exhaust fans need to be installed where room air can be exhausted outside directly through a wall or roof.
• The size and number of exhaust fans you install should be in line with the target ventilation rate you want to achieve.
• Large exhaust fans can be challenging to install, and high-power exhausts tend to be quite noisy.

4. Spot Ventilation

Spot ventilation is used to improve the effectiveness of natural or mechanical ventilation systems. So, it is safe to say that it is more of an ancillary system. It involves the use of localized exhaust fans, like those used in bathrooms and kitchens.

You can use spot ventilation to effectively remove moisture and indoor air pollutants at the very source.

5. Task-Ambient Conditioning (TAC)

Traditional ventilation systems are not capable of meeting the preferences and requirements of an individual. For instance, someone may not want a lot of airflow or low temperature in an office. That’s where personalized ventilation or TAC comes to the rescue!

It is a relatively new technology that has the potential of more customized and better ventilation to an individual occupant. These systems may supply air from the desks, workstation partitions, or floor near the occupant. Moreover, a TAC enables you to adjust the direction, temperature, and airflow as per your preferences.

Ventilation in Different Places

Before we get to the various concepts related to ventilation, it is essential to understand how these systems vary across several non-residential buildings. We have covered some of the most common non-residential buildings that an average human is most likely to visit.

The importance, requirements, and type of ventilation changes drastically, as you are about to see.

1. Healthcare Facilities

Hospitals and clinics need to ensure that they provide patients with optimal conditions for a speedy recovery. And proper ventilation makes one of the indispensable components of those optimal conditions.

Here’s how ventilation is different in healthcare facilities:

• Continuous humidity and temperature control is required
• It must meet the high hygiene standards
• A high-quality filtration system is needed to remove harmful microparticles and indoor air pollutants

2. Kitchens

Ventilation is one of the most critical aspects of the planning phase of a kitchen. After all, a significant amount of heat is generated daily inside a kitchen.

Here’s what you need to know about kitchen ventilation:

• Heat discharge and the cooling mechanism needs to be well planned in a kitchen
• The excess heat from a kitchen can be used to heat other parts of the building in winters
• It needs to be designed per the kitchen hood and ceiling
• The filters need to be changed more frequently because of the more greasy kitchen air

3. Restaurants

Restaurant ventilation is closely linked to kitchen ventilation. Imagine you are sitting in a fine-dine restaurant, and you can smell all kinds of odor coming from the kitchen. Wouldn’t be a fine-dine experience!

The most significant issue to be addressed is how to prevent the smell of food from spreading in the entire restaurant. 

4. Educational Institutions

Ventilation in kindergarten and schools is more important than we think! Children are more susceptible to catching allergies or colds from pollutants. So, there must be a constant, high rate of air exchange.

Schools accommodate a lot of people – students, teachers, janitors, cafeteria staff, and more. The air must be well-filtered to prevent claustrophobia and discomfort. Moreover, the proper distribution of air is equally important.

5. Fitness Centers

Fitness centers and gymnasiums need to have a constant exchange of air. The indoor air in a gym is almost always full of sweat and odor. Without regular transfer and proper cooling of the indoor air in a fitness center, it would turn into a stinking, unhealthy environment.

It gets worse in changing rooms and sanitary facilities. Because of their small space and frequent visitors, the air quality there is horrible.

6. Shopping Complexes

Shopping centers and malls experience large footfall consistently, especially during holidays and festivals. Shops have several internal heat sources, such as electronics, people, computers, and so on.

During summers, the internal heat and large crowds can quickly become unbearable for customers and shopkeepers alike. So, the ventilation system needs to be efficient enough to drive out the internally generated heat fast.

7. Hotels

A hotel has many components, each with different ventilation requirements. We have already discussed the specifics of ventilation in restaurants, kitchens, and fitness centers, which can all be found in a hotel.

To run successfully, hotels need to ensure that their guests experience top-notch comfort from the moment they step in until the time of checking out. There should be a constant supply of fresh air in every room and the common areas like the reception.

8. Industrial Establishments

Industrial enterprises, factories, and production floors often require a particular temperature to be maintained. Ventilation costs are quite high for such buildings. Some of the common industries that have specific ventilation requirements include the food industry, plastic industry, pharmaceutical industry, and data centers.

• Buildings may require exact temperatures for material processing
• Productions halls may need a massive cooling output to ensure favorable working conditions
• Some processes may need short-interval moisture retention
• Specific industries may require clean rooms

9. Commercial Offices

People generally spend more than half of their “awake” time in offices. So commercial buildings must have top-notch ventilation to ensure an optimal working environment. The indoor air should move slowly and consistently.

If an office fails to have a sufficient amount of fresh air, an unpleasant odor may linger always. Inadequate ventilation can adversely affect the productivity of people.

Concepts of Ventilation

Now that you know all the types of ventilation, it is time to address different concepts related to it.

Ventilation Principles

Other than the types of ventilation we have already discussed, it makes sense for you to understand the different principles on which they are based. As such, there are four principles you should know:

1. Displacement

The displacement principle involves supplying air with a very low velocity very close to the floor. The average air in the residence zone is warmer than the ventilated air but colder than the evacuated air near the ceiling.

It cannot be used for heating a room.

2. Piston

You can think of the piston principle as an extreme variant of the displacement principle. The ventilated air moves through the room like a piston with minimum airflow turbulence.

A ventilation system based on the piston principle will be quite complicated and expensive. That’s why it is used mostly for special purposes, like in an operating theatre or cleanroom.

3. Mixed

The mixed principle requires ventilated air to be delivered into the room at high speed or the use of local fans to get a homogenous air mass in the room.

It can be used for both heating and cooling the room.

4. Shortcut

You don’t get much of a ventilation system if it is based on the shortcut principle. The ventilated air is evacuated even before it reaches the residential zone in the room. You won’t find ventilation systems based on this principle being used anywhere.

Ventilation Performance

Building ventilation involves three essential elements:

1. Ventilation Rate

The ventilation rate deals with the quality and amount of outdoor air that is being ventilated into a particular space. Buildings need to adhere to ventilation rate standards, which usually vary for residential and commercial buildings. And the typical unit used for ventilation rate is liters per second (L/s) or cubic feet per minute (CFM).

2. Airflow Direction

The airflow direction, as the name suggests, tells you the direction in which the ventilated air is moving within the room. It should ideally be moving from a clean zone to a dirty zone.

3. Air Distribution

The air distribution (aka airflow pattern) deals with how efficiently the ventilated air is delivered to, and airborne pollutants are removed from each part of the room.

Based on these elements, you can evaluate the ventilation performance of a building on the following four grounds:

• Does it have a sufficient ventilation rate to meet the standard requirement?
• Does the airflow direction go from clean to dirty zones?
• Does the system deliver outdoor air all over the room?
• Does the system efficiently remove airborne pollutants from every part of the room?

If you want to get an in-depth analysis of ventilation performance, we recommend using either of these two indices.

1. Air Exchange Efficiency

It can be used to determine how efficiently fresh air is distributed in a room. You can calculate it using the room mean age of air and the air change per hour. The different ventilation principles have different air exchange efficiencies:

• 100% for piston-type ventilation
• 50% to 100% for displacement-type ventilation
• 50% for mixed-type ventilation
• Less than 50% for shortcut-type ventilation

2. Ventilation Effectiveness

It can be used to determine how efficiently airborne pollutants are removed from the room. Measuring the ventilation effectiveness is a bit more complicated and involves simulation or measurement.

Importance of Efficient Ventilation

To understand the importance of a fully functioning, efficient ventilation system in a building, we will be discussing its benefits, its need, and the downsides of not having it.

Benefits of a Ventilation System

1. Controls impurities and pollutants

People often fall prey to the misconception that the air outside is more polluted and impure than that inside. But you’d be surprised to know that the air within a building carries a lot of pollutants too.

Installing a sound ventilation system ensures that the building continuously expels bacteria, moisture, pollutants, and odor.

2. Stops condensation

One of the biggest hassles in an enclosed space tends to be condensation. Nobody wants to deal with damp conditions. And if you don’t have an efficient ventilation system in place, nothing is stopping condensation from rotting and molding the surfaces.

Damp conditions can also lead to health problems for you, such as respiratory problems and allergic reactions.

3. Regulates air quality and temperature

There is no way for you to gain control over the airflow in a building without a ventilation system. And you need to control the airflow to make sure that the quality and temperature are favorable.

Too much of anything is bad! And the same is valid for fresh air, as too much of it can increase the energy bills of your building. Moreover, ventilation systems help keep a crowded room comfortable and cool.

4. Provides health benefits

The lack of an efficient ventilation system gives unlimited leeway to indoor air pollutants. You will find several health problems persisting in a poorly ventilated space. Sinusitis, headaches, asthma, rashes, and allergies are some of the common health problems that can be avoided with the help of a ventilation system.

Why Do You Need Ventilation in Buildings

Perhaps the most crucial reason that necessitates ventilation is the presence of indoor air pollutants. Some examples of the most significant indoor air pollutants include:

• Bacteria, dust, animal dander, microorganisms, and human dandruff in private homes.
• Carbon dioxide, carbon monoxide, nitrogen dioxide, and tobacco smoke from combustion
• Volatile organic compounds like pesticides, chemicals, paint, and varnish gases in dry cleaning shops

Without efficient ventilation, these indoor air pollutants would grow unchecked and gradually render a building uninhabitable. Ventilation assists in maintaining optimal air quality by removing these pollutants.

The downsides of poor or no ventilation in a building can mostly be seen in the way of health problems of occupants. Some of the common health problems that arise because of improper ventilation include:

• Headaches
• Dry eyes
• Fatigue
• Itching
• Asthma
• Allergies
• Deteriorated concentration
• Respiratory infection
• Irritation in the eyes, nose, lungs, and throat

We recommend that you do not to reduce ventilation costs. Consider is as a one-time investment that will pay dividends in the long run. 

Summing It Up

We have covered a lot of information in this guide to ensure that all your questions about ventilation are appropriately answered. Whether you are renovating your house, moving into a new one, opening a restaurant, or investing in a healthcare facility, this information will come in handy.

Having an optimal ventilation system is a necessity. The general life expectancy of people has reduced over the years due to many reasons. The last thing you need is a health problem caused by poor ventilation at home or in the workplace.

Did we miss out on any crucial details about ventilation? Let us know in the comments section below.

Till next time!