What is Ventilation?

Home air ventilation can simply be defined as a ‘system that provides and circulates fresh air into and within a space.’ We know that buildings are inherently filled with air pollutants such as volatile organic compounds, dust, and allergens that are found even in the cleanest of indoor spaces. One way ensure the health of people who live and work within a building is to properly ventilate the space. Home air ventilation takes place in two ways – first, fresh air from outside is added into an indoor area to lessen the effects of, or dilute, the polluted indoor air. This clean air is then circulated throughout the room or building.

The second way that home air ventilation systems work is to remove the contaminated air from an indoor space by allowing it to escape to the outside environment. By utilizing fresh air from the outdoors, a home ventilation system accomplishes essentially the same task as an air purifier: providing clean air to an indoor space.

Home air ventilation can range from the simple process of opening a window to intricate systems that account for the removal of certain pollutants and odors while providing an indoor space with clean air at one’s desired temperature and humidity.

In this post we will walk you through the benefits of a good ventilation system, what could happen if your home has poor ventilation, and a little bit about how these different home air ventilation systems work.


HVAC technician installing ventilation system

What are the Benefits of a High-Quality Ventilation System?

A high-quality ventilation system is good for both the home and the health of its inhabitants. Good ventilation can turn a contaminated, uncomfortable space into one that is pleasant and livable. It can be the difference between a smelly, stuffy house and a fresh escape from the outdoor elements.

We intentionally create ‘air-tight’, insulated, buildings to minimize heat lost through walls, windows, and doors. This helps to keep our heating and cooling costs low.

The trade-off to minimizing heat-loss, though, is that we have ensured that pollutants and moisture (also) cannot escape from our living spaces. This makes things a bit tricky - how do we make sure that the polluted indoor air is being replaced by fresh air from the outside?

A good ventilation system.


woman enjoying fresh indoor air

Why do You Need an Effective Ventilation System?

Good Ventilation is Best for our Health

While it may not always be on our minds, our day-to-day activities produce a lot of airborne pollutants that are harmful to a building and the people inside of it. We take showers to clean our bodies, but at the expense of producing excess moisture which can lead to mold. We have fireplaces to keep us warm in the winter and use stoves to heat up our food, but in turn, are simultaneously introducing carbon monoxide into our living rooms and kitchens.

Even while not using any appliances, other harmful gases such as radon may be entering into our homes through the ground. Other dangerous gases and fumes are in our homes from off-gasing from cleaning supplies, paint cans, etc.

The dangers of these pollutants to people living in these spaces can range from what is known as sick building syndrome (or SBS) which may produce symptoms such as headaches, fatigue, dizziness, or nausea to cancer caused by radon and cigarette smoke. Since it’s not very practical to stop showering or cooking in our homes, we need a way for the pollutants to escape from our living spaces and for fresh air to properly circulate through our homes – we need effective ventilation in our homes to stay healthy.

This is critical as most heating and cooling systems in a home do not bring in fresh outdoor air. Rather, they recirculate the air within a home.


Good Ventilation Allows Us to be Comfortable

What comes to mind when you think of indoor spaces that you are most comfortable in?

Perhaps you’re thinking of your favorite space to relax in. Maybe it’s a spot where you are able to let go of everything else to allow yourself to work most efficiently.

How does this place smell?

It is a good temperature?

What about the moisture level in this space?

Whether your desired indoor place has ocean views or is a window-less room in a basement, we don’t need to cite scientific studies to safely guess that the indoor space you thought of smells nice, is at a moderate temperature, and is kept dry and free of excessive moisture build-up.

While indoor air pollutants may not always cause illness like described above, people need to spend time in comfortable indoor spaces. Fresh air, balanced temperatures, and desirable moisture levels can all be provided with a good ventilation system.

Air ventilation systems that introduce and circulate clean air are especially important in areas with higher concentrations of pollutants (like bathrooms and kitchens) and areas where we spend most of our time (like living rooms and bedrooms). Nobody wants to spend time in a stuffy room with stale air – luckily good house ventilation systems are an effective and easy solution to add comfort to any indoor space.

mother and daughter enjoying healthy home

Good Ventilation is Best for the Quality of our Homes

In addition to the negative side effects that poor indoor air quality and ventilation can have on your health and comfort, efficient ventilation is vital for maintaining the quality of a building.

Have you ever seen condensation build up on windows in a stuffy room?

Or had a hard time opening a door due to an imbalance in air pressure?

These are both symptoms of what could happen if your home has poor ventilation. Excess moisture can lead to the buildup of mold and other fungi that damage wood, dry wall, and tile within a living space. It doesn’t need to be said that this can lead to unnecessary and undesirable work for a homeowner, which, again can be avoided with proper fresh air circulation.


Good Ventilation is Best for the Environment

Homeowners are also concerned with the energy efficiency of their homes and for good reason. Excessive cooling and heating of a home can be expensive while requiring the use of fossil fuels and creation of carbon dioxide that damages our environment.

One way to cut down on these costs and lower your carbon footprint?

An efficient ventilation system that puts less stress on other aspects of your HVAC (heating, ventilation, and air conditioning) system.


How do Different Home Air Ventilation Systems Work?

Now that we know why a homeowner needs a proper ventilation system, how do these systems work and which is best for the homeowner?

The type and complexity of a home air ventilation system is ultimately up to the needs of the homeowner. Someone who lives in a very mild climate may find natural ventilation that utilizes building design to allow wind to pass through windows and doors to be a sufficient mode of home air ventilation.

However, most homeowners will want a ventilation system that is a bit more complex to improve indoor air quality with the removal of heat, odors, smoke, dust, bacteria, carbon monoxide, and other harmful gases. These mechanical ventilation and hybrid ventilation systems utilize home design, HVAC systems, whole house fans and exhaust fans, and air ducts to direct airflow and distribute fresh air into a room while removing dirty air from the space. Regardless of the complexity of the ventilator, every type revolves around the same basic concept: air naturally flows from areas with higher pressure to areas with lower pressure. This means that three situations can exist within a building: positive pressure, negative pressure, and balanced pressure.

With positive pressure, the polluted indoor air is leaked out of an indoor space because the air pressure inside a house is higher than the pressure outside of the building.

In negative pressure situations, the clean outdoor air is sucked into an indoor space because the pressure inside a house is lower than the pressure outside of the building. An example of this is a whole house fan that pulls in outdoor to help cool a home by pushing hot, stale air into the attic space.

When ventilation is balanced, an equal amount of fresh outdoor air replaces the stale indoor air that is exhausted from the home.

To tie this all together we can apply these concepts of air ventilation to meet the specific homeowner needs depending on their region and building type. Positive pressure systems that reduce condensation are best for those living in warm and humid areas; while negative pressure systems are best for preventing unwanted moisture that can build up inside of buildings that are warmer than the outside air.

Negative pressure ventilation is also used in bathrooms, kitchens, and other rooms where indoor air pollutants are at the highest concentrations. Hospitals even use negative pressure rooms to keep harmful airborne pathogens away from immune-compromised patients.

What are the different types of ventilation?

Natural ventilation moves clean air into and around a space (or ‘building envelope’) while removing polluted air without using any machinery. These systems utilize structures such as windows and pressure differences between the indoor and outdoor environments to create air movement.

Major benefits of natural ventilation systems are reduced costs and increased energy efficiency. However, these benefits come at the cost of a heavy reliance on local weather and climatic conditions (temperature + moisture levels) rather than putting the user in control to ensure proper ventilation.

The other major category of ventilation is called mechanical ventilation – mechanical systems rely on fans to either drive air into or out of a building to create the desired conditions.

There are three types of mechanical ventilation: (1) exhaust ventilation, (2) supply ventilation, and (3) balanced ventilation.

Exhaust ventilation pushes polluted air out of the home with fans. This air is then replaced by outdoor air that enters through leaks and other openings in the building’s structure. These fans are typically placed in the areas most prone to contamination, such as bathrooms and kitchens.

Exhaust ventilation is most common in older homes – ones built before building codes and increased energy efficiency awareness started the air-tight home craze a few decades ago.

Like natural ventilation, a large benefit of exhaust ventilation systems is the cost. Installation and operating costs are the lowest among the mechanical ventilation systems.

The main problem that many have with exhaust ventilation, though, is the fact that contaminants may be sucked into the living space through the walls and ceiling. This brings us to the next type of mechanical ventilation: supply ventilation.

Supply ventilation uses fans to draw air into a house from the outdoors. The indoor air leaves through openings in the building enclosure.

This type of ventilation allows the designer to decide exactly where the outdoor air is entering from. Supply ventilation solves the main problem of exhaust ventilation – the concern that contaminants will be pulled into a home through unwanted spaces like the attic, garage, or other structural gaps.

While supply ventilation does provide the user with more control, there can be some downsides.

For example, either the heating or cooling systems need to be operating in order to receive fresh air with ‘central fan integrated supply’ systems. The other major shortcoming of a supply ventilation system is the lack of an exhaust system – you’re not able to pull contaminated air out of the most vulnerable spaces. Which brings us to our next type of mechanical ventilation: balanced ventilation.

Balanced ventilation systems are a combination of both exhaust and supply ventilation. The goal is for the exhaust and supply systems to provide roughly equal amounts of work to create a balanced air flow into and out of the house.

With homes becoming increasingly air-tight and larger, the more basic forms of mechanical ventilation just won’t cut it.

Most balanced ventilation systems allow us to provide fresh air to spaces that people spend the most time in (such as living rooms and bedrooms) while exhausting dirty air from areas that are the most prone to contamination (like bathrooms and kitchens).

The major downside of balanced ventilation, probably unsurprisingly, is the price of installation and operation.

Energy Recovery Ventilation (ERV): We can’t talk about balanced ventilation without talking about Energy Recovery Ventilation (or ERV). ERV is a process that ‘preconditions’ the fresh air that enters from outside.

In short, ERV systems use energy from air leaving a building to either heat or cool the fresh air entering a building – depending on the season.

During winter, moisture is transferred from air as it leaves the building to air entering the building. This warms and humidifies the fresh air before it gets to the living spaces.

As warm and humid summertime air enters the building it is cooled by passing dry air as it exits the building.

By ‘preconditioning,’ ERV systems really cut down on costs and the heavy reliance on other heating and cooling systems in the long run. While they may cost more up front and require the installation of new ductwork, ERVs are gaining popularity due to their environmental efficiency.

Climate regions in the USA

It’s nothing new that the US is a very large and diverse place - that’s something that makes this country so special! Just as the accents, foods, and attractions vary from region to region – so do the houses.

There aren’t a lot of adobe houses in Vermont or homes with basements in Florida and that’s not a mistake. We build homes that are practical – homes that maximize efficiency and make sense based on the available resources, climatic extremes, and the soil in that area. It’s not all aesthetics.

Apart from the obvious differences in home design, ventilation systems can also vary quite a bit from region to region.

We have divided the United States into four regions defined by the US Census Bureau. Places within these regions share similar climates and will allow us to better generalize our ventilation recommendations.

The northeastern US is generally wet all year and experiences cold winters and warm summers.

The Midwest has similar conditions as the Northeast overall, but sees a little more variation between locations within the region and from season to season.

The southern US is best characterized by hot and humid summers with mild winters.

The West also has a lot of variation (think differences between hot summers in Arizona, frigid winters in Montana, and the constant drizzle in the Pacific Northwest), but is generally drier than the eastern US overall.

Good ventilation systems use home design to work with the temperature and moisture levels of the area to achieve comfortable conditions.

Ventilation systems that don’t match that the conditions of that region are doing unnecessary work. This unnecessary work means higher costs for the homeowner and more impact on the environment.

Matching region to ventilation type



So which type of ventilation system is best for each region?

Since ventilation relies on the replacement of polluted indoor air with fresh outdoor air, we need to match ventilation type to climate.

Northeast

An exhaust-only system should be utilized to ventilate homes during the cold northeastern winters. These ventilation systems can help reduce condensation buildup inside of walls, meaning less chance of poor air quality and structural damage due to mold.

A balanced ventilation system may be desirable in the areas with more extreme temperatures, especially in newer air-tight homes.

A natural ventilation system is sufficient if the summers are mild; otherwise, a supply-only system is best for hot and humid summers to prevent problems from unwanted moisture-filled air from being sucked in through the walls of a house.

Midwest

A balanced system is necessary in areas that experience extremely cold winters, and again, with newer air-tight homes.

If the winter is more mild, then an exhaust-only system would be sufficient.

It is important not to use a supply-only system during cold winters because the ventilation system could condense the moist air and pull unwanted moisture into the wall cavity.

Like with the northeast, a mild summer means the potential for natural ventilation.

Alternatively, a supply-only system should be used during this area’s humid summers.

South

Mild winters give homeowners the opportunity to use natural ventilation.

During the hot and humid summers, however, homeowners should consider a balanced ventilation system with an air conditioner, especially if conditions are closer to the extreme end.

A supply-only system should also be sufficient; while an exhaust-only system must be avoided to reduce the potential for moist air forming in the wall cavity.

West

The western US is more varied than it’s often given credit for. In the ‘dry-heat’ parts of the southwest, a natural ventilation system is likely sufficient during the mild winters.

Like with the southern US, a balanced system with an air conditioner is often necessary to reduce excess heat during the intense summers.

An exhaust-only or balanced ventilation system is best for harsh winters in the colder areas of the interior west; though these areas can often get by with natural ventilation during the relatively mild summers.

Homes in the Pacific Northwest should use natural or supply-only ventilation systems all year to avoid sucking the wet outside air into buildings.

As stated above, homes are continuing to increase in square footage and air-tightness in every region of the US. To deal with this, a balanced ventilation system is always best to provide fresh air, remove polluted air, regulate temperature and control condensation levels while maximizing energy efficiency.

Summary

A home ventilation system works by introducing fresh air from the outdoors while removing polluted and contaminated indoor air from a building. Ventilators are able to remove unpleasant smells, excessive moisture, heat, dust, and dangerous gases from a space to make it more livable.

Additionally, an effective ventilation system can even cut down on costs for a homeowner by prolonging the life of a building and creating a more energy efficient house. Regardless if one uses natural ventilation, mechanical ventilation, or a combination of the two – with good ventilation we can ensure healthy people in a healthy home.