Home Ventilation: A Guide to Understanding & Improving Airflow in Your Home

When people think about handling the air inside their homes, they may focus on the structure's ability to maintain the right temperature. However, there are other aspects related to indoor air management apart from heating or cooling. To ensure their interior space is comfortable, homeowners should also pay attention to their ventilation, a combination of structure and systems that provide a continual source of fresh air for the home.

Ventilation removes contaminants and controls the humidity of the indoor air. It also increases the home's energy efficiency. Some forms of ventilation are as old and simple as a door or window. Others, like whole-house ventilation, are as current as the system that heats or cools the room. With this guide, people will know the most common forms of ventilation and how they can best use them in the places that need ventilation most.

Types of Home Ventilation

There are several types of home ventilation that homeowners may use. Older homes often have one or two. In most cases, people may need a combination of techniques to maintain an ideal temperature and ensure a higher level of indoor air quality.

Natural Ventilation

Natural ventilation is one of the oldest forms of ventilation and can be present in virtually any home. This type of ventilation relies on wind or changes in pressure to cycle air throughout the structure. Homeowners may be familiar with wind ventilation. When there are two windows open on parallel sides of the house, the wind can blow fresh air through one window and carry stale air out through the other. This method relies on the strategic positioning of windows and readily available wind.

Stack ventilation is another type of natural venting commonly used in houses. With this approach, builders take advantage of the fact that warm air has a lower density. As air increases in temperature, it rises toward the ceiling. Older homes commonly have a vent, or even an open hole in the attic, to allow hot air to escape. In this design, the structure needs windows located on the lower levels to draw in the cooler, fresh air. The benefit of stack ventilation is that it is not dependent on wind, which can be an essential distinction in regions with hot summers.

Spot Ventilation

While natural ventilation can be helpful for most rooms of the home, spot ventilation may be necessary for rooms like the kitchen or bathrooms. These spaces tend to produce more heat and moisture due to the activities conducted there. Natural ventilation usually is not sufficient to remove the heat from the room and dry up the moisture. Spot ventilation typically comes in the form of an exhaust fan installed in various places, commonly located at or near the ceiling.

Spot ventilation often comes as a function that homeowners can turn on and off at will. Exhaust fans for the kitchen must cycle 100 cubic feet per minute, compared to 25 cubic feet per minute for bathrooms. Some people choose to connect the exhaust system with other room elements like lighting. Otherwise, homeowners must remember to use spot ventilation while engaging in activities that produce heat and moisture. People should keep in mind that the ventilation provided in an above-the-range microwave may not be sufficient, particularly for high-end ranges.

Whole-House Ventilation

Most modern homes rely on some form of whole-house ventilation. There are essentially four different types, including:

• Exhaust
• Supply
• Balanced
• Energy recovery or heat recovery

The best system for any given home depends on the structure itself as well as the climate. For example, an exhaust system only draws air out of the house. During that process, air can be forced in from air leaks around doors and windows. This type of system may be appropriate for cold climates but not for areas with humid summers.

The other types of whole-house ventilation rely on a supply of fresh air. A supply ventilation system is the simplest. It has a fresh air supply and exhaust ventilation to deliver filtered and conditioned air into the home. By comparison, a balanced ventilation system ensures the same amount of air comes in and goes out, keeping the home pressurized. These systems will work in almost any climate. An energy recovery ventilation system re-captures the energy used to heat or extract heat from the indoor air. Given the additional equipment and energy used for that process, the system is most appropriate for homes in regions with extreme temperatures.

Home Ventilation & Health

Home ventilation has a direct correlation to the health of the people living in it. When the home does not have a good way to cycle out air, toxins can collect. Over time, those pollutants may accumulate in people's bodies, turning into various chronic health problems.

The Effects of Poor Ventilation

Decades ago, building experts began to realize the effects of creating structures that were tightly sealed. Air sealing a building is often ideal because it increases energy efficiency and makes it easier to control the conditioning of the space. After all, an older building with lots of air leaks makes heat transfer happen more quickly and allows harmful particles in at the same time.

In modern buildings, air leaks are minimal. Homeowners leave windows and doors closed in favor of air conditioning or heating. In this environment, ventilation is more important than ever.

When ventilation is not running in a tightly sealed building, there is less opportunity to cycle out pollutants and maintain an ideal condition for the indoor air. This can decrease oxygen levels, which increases the likelihood that people who live in the home will get sick. The inability to remove environmental contaminants can aggravate allergies or asthma. Worse, it can promote mold growth, which damages the house and threatens residents' health. Without regular, adequate ventilation, people may end up with chronic lung problems or even cancer.

Signs of Poor Home Ventilation

Although most homes have some ventilation, it may not be sufficient. In some cases, homeowners do not know how to use it properly. The following signs indicate that certain rooms could benefit from improved ventilation, if not the entire home.

Mold

Mold and mildew are types of fungi that grow in dark, damp places. Controlling them is vital for human health as well as the durability of the structure. One of the most important functions of ventilation is humidity control. Without it, certain areas of the home may not have sufficient moisture removal, including:

• Kitchens
• Bathrooms
• Basements

Although mold can grow in visible places, like the floor or corners of a room, it can also thrive behind walls and above the ceiling. If it is left to grow over time, it can spread to furniture and clothing as well.

Dust

A significant dust accumulation signifies that the ventilation system may not be appropriate for the property or the climate. Dust enters the home through a variety of paths, including:

• Doors and windows
• Air leaks in the home
• Excessively dirty ductwork

The best way to prevent dust from accumulating is to seal air leaks around doors and windows and in the attic or basement. Otherwise, people may want to consider sweeping regularly and use a whole-house ventilation system instead of leaving doors or windows open.

Moisture on Surfaces

Moisture on surfaces that takes longer to dry is an indicator of high humidity in the home. Ideal humidity inside of a structure ranges from 30 to 50 percent. Beyond that, condensation can accumulate on walls and windows, as well as anything touching them.

Condensation on Windows

In the summer, opening windows for ventilation can draw hot, humid air inside. That moisture may collect on the windows in the form of condensation. In certain regions, homeowners may want to consider using a dehumidifier in addition to an air conditioner. Dehumidifiers extract water from the indoor air, turn it into condensation, and collect it in a container that homeowners can empty. Homeowners who do not have an effective air conditioner may find this helpful to address the problem, even if it is not a complete solution. Condensation on the inside of a window can also be a sign of other problems, such as cracks that allow humid air to seep inside the home, which can cause higher power bills and water damage.

Musty Smell

Musty or stale odors in a room indicate that the room does not receive sufficient sunlight or ventilation. It is a common factor of attics and basements, particularly in older homes with fewer windows. A musty smell can also be an early sign of moisture accumulation, as the odor may result from mildew. Homeowners can clean the affected surfaces with a diluted bleach solution and ensure the area receives adequate ventilation from that point onward.

Little Airflow Through Home

Many homes, especially older homes relying on natural forms of ventilation, may not have sufficient airflow throughout the structure. It is common for people to enter a room in these houses and notice the air feels stuffy or stale. A lack of fresh air may make a room seem warmer. Additionally, homes with inadequate ventilation may have odors that are difficult to get rid of, particularly in the kitchen or bathrooms. For example, someone who notices that they can still smell the dinner cooked two nights ago may need to increase the ventilation in the home entirely.

Hard to Cool or Heat Rooms

Ideally, homes should have adequate heating and cooling for every room. In practice, this is often not the case. Rooms that are closed off from the whole-house ventilation system are usually harder to heat and cool, especially if they are left closed most of the time. A room that always feels cold in winter may be an indicator of excess moisture, as that can make even a heated room feel cooler. By comparison, a room on the upper floor of the home that always feels hot in summer may need additional ventilation to cycle the low-density, warmer air out of the room.

Frequent Sickness in Household

Ultimately, ventilation is a significant factor in a home's indoor air quality. Buildings with insufficient or ineffective ventilation leave not just odors but possible pollutants in the indoor space. People who find they have seasonal allergies year-round may be dealing with allergen accumulation inside the house. Without a practical solution, indoor air quality may continue to worsen. As such, people with allergies or asthma should consider changing or improving ventilation as a possible solution.

How to Ventilate a Home

The right way to ventilate a home depends on the room. Homeowners usually have several options to consider. They typically need more than one type of ventilation, especially if they produce a lot of heat, moisture, or pollutants in the space.

Garage

Properly ventilating a garage is crucial to the safety and security of the home. Homeowners often store toxic substances like paint or cleaning solutions in the garage to keep them out of the house. Additionally, the use of fuel-burning equipment in the garage, such as a vehicle or tool, can contribute to carbon monoxide buildup in the space. People may choose to ventilate the garage by leaving the vehicle access door open, but this is unwise during periods of extreme weather.

Although garages may not be sealed as tightly as the building envelope for the rest of the home, they still need sufficient ventilation. This is particularly important if the garage opens directly into the house. While the garage doors or windows may serve as one form of ventilation, people who work in the garage often need more ventilation to remove pollutants and control the temperature.

During summer, garages can absorb significant heat, mainly if they contain concrete walls or flooring. Concrete becomes hot from the sun during the day; after sunset, the surface releases heat into the room. Without an exhaust fan, the heat will remain trapped in the garage longer. Homeowners who have attached garages may notice the heat or fumes from garage activities flood the house whenever they open the door. Installing and operating a fan while working in the garage or during hot days will help minimize the problem.

Attic

Although the attic might seem like an afterthought in terms of ventilation, it is one of the most important places to vent for the stability of the structure. As air becomes warmer, it loses density and rises. Eventually, much of it ends up in the attic.

During the summer, a hot attic increases energy costs for cooling. In winter, it can create an ice dam. Ice dams occur when a part of the roofing structure continually melts snow and refreezes it into an ice sheet. Over time, ice dams can ruin a roof. Homeowners may need a variety of ventilation options for the attic, including:

• Ridge vents: allow warm air to escape out of the top of the roof
• Box or dome vents: static vents that extend from the roof and may contain a fan
• Gable vents: control intake and exhaust
• Soffit vents: provide a cool air intake

The right vent depends on the home, although homes may have most or all of these options. In many cases, the missing component is the fan that cycles the air through. Homeowners still having problems with the ventilation in their attic should consider installing an attic fan. These devices can turn on and off automatically when the attic reaches a specific temperature. People might consider this a reasonable alternative to conditioning the attic.

Bathroom

Bathrooms are one of the most common sources of excess moisture and low indoor air quality. Without sufficient ventilation, the steam from a hot bath or shower turns into condensation that can accumulate in the walls and ceiling. Additionally, cleaning products with toxic fumes could create health problems if homeowners are unable or unwilling to cycle the air out regularly. Fortunately, the installation of a bathroom fan and proper use may solve these problems.

Homeowners can usually tell they have a problem with ventilation if they are running the fan, but they still see condensation buildup on the mirror. Over time, condensation can turn into mildew or mold growth in the walls. The best way to address the issue is to install a fan that can cycle the air and vent it outside the home. Fans with vent ductwork that goes directly outside the house are more likely to be effective, mainly if they do not contain joints.

People who cannot install a bathroom fan may choose to use a portable one instead. They should aim for a model that cycles air relating to the size of the bathroom. For example, a 35-square-foot bathroom might need a fan that can cycle at least 50 to 75 cubic feet per minute. They may also choose to use a dehumidifier to remove excess moisture without sending it throughout the house.

Crawl Space

Like the attic, a home's crawl space is one where people do not generally go. However, the area still requires careful consideration for ventilation. Crawl spaces are common in regions where people may not want to build basements or might need to elevate the home slightly above the property. An unconditioned crawl space could be a harbor for pests, animals, and mold. Homeowners may choose to ventilate it in a variety of ways.

As a general rule, crawl spaces must have at least one square foot of vents for 150 square feet of floor surface. These vents usually come in the form of metal plates with small holes, grills, or mesh. Even if adequate ventilation meets these requirements, people may have problems with their crawl spaces. In humid areas, particularly during a wet summer, vents allow moisture to enter and accumulate.

To solve moisture problems, homeowners may prefer to install an exhaust fan and additional insulation with a vapor barrier, which keeps the moisture from penetrating the flooring or walls of the home. Crawl spaces with an exhaust fan draw air out of the area. To replace the air and keep the space pressurized, an intake vent from the inside of the home provides fresh, conditioned air. This approach helps ensure the humidity in the crawl space is no higher than the home's interior while continuously cycling the air.

Kitchen

The kitchen is likely the most important place for ventilation within the home. People spend a lot of time cooking and washing in the kitchen, which produces a large amount of heat and moisture that can spread to the rest of the house. Additionally, the kitchen can create exhaust related to cooking that can become toxic. For example, a gas-burning range produces a byproduct that can turn into deadly carbon monoxide. Without sufficient ventilation, it can accumulate in the kitchen.

Unfortunately, many kitchens only have a small fan above the stove that recycles the air but does not vent it outside the home. Older homes may only offer a window nearby.

When homeowners design a kitchen for new or existing construction, they may want to place the range on an exterior wall to install a range hood. A proper range hood should draw at least two cubic feet of air per minute proportional to the kitchen's footprint. A window near the range can also provide an immediate source of fresh air. Homes without kitchen ventilation may need a few additions, such as a:

• Portable fan, placed toward a window or exterior door
• Portable air cleaner with HEPA filter
• Dehumidifier
• Downdraft ventilation for island ranges

These options may work for tenants as well as homeowners. Installing a carbon monoxide detector may be a practical choice for those with a gas range.

Home Ventilation Mistakes to Avoid

In many cases, homeowners think they are adequately ventilating their homes but have failed to do so. Problems happen when people make assumptions about what they will need without doing the proper research. For example, recommendations on the right amount of air movement from an exhaust fan presume an average ceiling height. Someone who has a kitchen with vaulted ceilings may need more.

Additionally, people can add too many ventilation options and create more problems than they solve. An oversized exhaust fan that runs too loudly may turn into a device that residents will not use. It may be more practical to buy a moderately sized, quiet fan and plan to run it longer or more frequently to compensate. In some cases, oversized fans can even increase moisture in the space if they are pulling unconditioned air from outside.

Ultimately, whole-house ventilation is the best long-term ventilation option, although homeowners should also use spot ventilation as needed. Keeping vents and exhaust fans clean and in good condition will ensure better output and efficacy over time. Teaching everyone in the home how to use the ventilation system is an ideal approach.

As a system, ventilation may be something that homeowners do not think about very often. They might not consider it or even use ventilation regularly until they develop health problems like asthma directly affected by it. Without proper ventilation, people usually end up with an uncomfortable space at best and, at worse, a highly toxic one. Adding ventilation to the home and ensuring fans are functional may be a quick solution.

Understanding how ventilation works depends on the system. In most cases, homes need ventilation that cycles fresh air into the space while exhausting heat, fuel byproducts, and moisture directly out of the home. Homeowners may use more than one type of ventilation to achieve these goals, particularly in areas like the attic or crawl space. By taking care of the ventilation, people create a more comfortable, healthy home.

Additional Reading

• https://greenhome.osu.edu/natural-ventilation
• https://www.moffittcorp.com/natural-ventilation-definition/
• http://buildipedia.com/knowledgebase/division-23-heating-ventilating-and-air-conditioning/23-05-00-common-work-results-for-hvac/spot-ventilation
• http://coolvent.mit.edu/intro-to-natural-ventilation/basics-of-natural-ventilation/
• https://www.energy.gov/energysaver/weatherize/ventilation/whole-house-ventilation
• https://smarterhouse.org/ventilation-and-air-distribution/whole-house-ventilation-strategies
• https://www.hrv.co.nz/latest/10-signs-your-home-might-not-be-well-ventilated
• https://enviroklenz.com/how-to-prevent-mold-growth-in-poorly-ventilated-home
• https://homeefficiencyguide.com/seal-air-vents/
• https://www.hvac.com/blog/home-ventilation-tips-5-signs-need-dehumidifier/
• https://www.bobvila.com/articles/how-to-get-rid-of-mildew-smell/
• https://www.ehinz.ac.nz/indicators/indoor-environment/about-the-indoor-environment-and-health/#poor-indoor-environment
• https://minnicks.com/learning-center/indoor-air-quality/how-to-ventilate-your-bathroom/
• https://hayesplumbing.ca/vent-keep-older-bathroom-dry/
• https://www.thisoldhouse.com/bathrooms/21247447/improve-bathroom-ventilation
• https://www.danleysgarageworld.com/how-to-ventilate-garage/
• https://www.askthebuilder.com/hot-garage-ventilation/
• https://garagetransformed.com/does-a-garage-need-ventilation/
• https://www.bobvila.com/articles/attic-ventilation/
• https://www.energystar.gov/campaign/seal_insulate/do_it_yourself_guide/about_attic_ventilation
• https://www.aireserv.com/about/blog/2019/may/how-to-vent-an-attic/
• https://homeguides.sfgate.com/design-wellventilated-kitchen-33779.html
• https://www.thekitchn.com/10-survival-tips-for-when-you-dont-have-a-range-hood-rental-kitchen-problems-215897
• https://www.bobvila.com/articles/kitchen-ventilation/
• https://www.greenbuildermedia.com/iaq/ventilating-crawl-spaces-the-wrong-way-and-the-right-way
• https://yespest.com/2018/03/15/properly-ventilate-crawl-space/
• https://www.thespruce.com/crawlspace-ventilation-requirements-1821946
• https://www.bobvila.com/articles/bathroom-ventilation/
• https://www.eltatrade.in/dos-and-donts/
• https://coastalhvac.biz/articles/6-key-dos-and-donts-for-proper-home-ventilation
• http://www.chayaseattle.org/2019/01/22/poor-ventilation-and-the-health-consequences-that-comes-with-it/