Do Fans Improve Air Quality?

 

In today’s airtight homes, proper ventilation can be difficult to maintain.

Fans are a simple way to get air moving through your home, but can fans actually improve the air quality? In the United States, indoor air quality (IAQ) is mostly defined by the relative amount of pollutants in indoor air compared to the air outside. So naturally, a fan that has the ability to bring in fresh air and remove stale air will improve IAQ, as long as the outdoor air isn’t overly polluted.

But not all fans are created equal, and the answer requires more detail.

 

What “Improving Air Quality” Means

IAQ standards are a subset of standards that are set by the LEED (Leadership in Energy and Environmental Design) in the United States. In simple terms, IAQ standards are derived from green building standards.

These IAQ standards directly deal with indoor pollutants and dampness, and as a result, also indirectly have to do with temperature control.

So, a fan that improves IAQ technically has to have an ability to directly control pollutants and dampness, first and foremost.

Since indoor air tends to be 2 to 5 times more polluted than outdoor air (according to EPA), the goal of any IAQ-improving fan must be to bring in fresh air and to remove stale air from the indoors.

But just quickly should indoor air be exchanged with outdoor air in a home, assuming the outdoor air is normal?

ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) Standard 62 recommends 0.35 air changes per hour in a home. In other words, 35% of all the air within a living space must be changed once per hour and all the air in a home should be exchanged roughly every 3 hours.

 

Types of Fans (And Which Can Improve IAQ)

Ceiling Fans

Ceiling fans alone won’t be the best solution when it comes to removing pollutants or exchanging stale air for fresh air. Their primary purpose is redistribute hot air as it rises in the room, slightly controlling the temperature depending on how the fan blades are turning.

In other words, the same pollutants are being cycled in the room, although it helps somewhat that they’re being diluted throughout the space with the help of a ceiling fan.

 

Exhaust Fans

Your kitchen, bathroom and laundry exhaust fans do have the ability to remove pollutants and to improve IAQ.

Kitchen exhaust fans in the vent hood remove smoke primarily, while bathroom exhaust fans remove moisture and thus prevent the growth of mold and mildew. The key is that the air isn’t being reintroduced back into the indoors, but rather is discharged outdoors.

These types of fans are known as local exhaust systems and are specifically designed to work in one area of a home only.

Not all exhaust fans are equal – when shopping for exhaust fans, you must calculate the airflow capacity for the volume of the space. This is expressed as CFM, or the cubic feet of air that can be moved per minute against a resistance or static pressure. Generally speaking, the CFM fan capacity for kitchen exhaust fans is twice the CFM capacity for bathroom exhaust fans, or greater.

Don’t forget to check exhaust fans in areas of polluting appliances (like furnaces, laundry dryers, and hot water heaters), as well as your garage, crawl space, or basement.

Basements and crawl spaces are particularly prone to mold and radon damage, so a simple investment in an exhaust fan may help prevent a costly remediation bill in the future. Here’s an example from Amazon.

 

Fresh Air Intake Fans

Most older HVAC systems won’t bring fresh air into a home mechanically, but rather do so naturally.

There is a reason for this, though. Older homes were built less air tight anyway, so those homes have a natural way for fresh air to come into the home. Since newer homes are built to be more airtight and energy efficient, it is necessary to find less natural, more mechanical ways to introduce fresh air into the system and alleviate the negative air pressure.

Many newer homes nowadays typically have a fresh air intake system that allows fresh air to be supplied to the home to some extent.

This solution can be fairly inexpensive, especially it you can install the fan yourself.

 

Whole House Ventilation Systems

If you want to go beyond a single intake fan, you may wish to consider a whole house ventilation system.

A whole house ventilation system is a ducted system that’s equipped with multiple supply and exhaust fans. It not only dilutes existing pollutants by moving them away from an area of high concentration, but it also consistently supplies the home with fresh air.

While this system may cost anywhere from $500 to upwards of $1,500, it may be a good investment for many homes.

 

Don’t Forget Natural Ventilation

It’s easy to get carried away by the latest technologies and upgrades, but remember that the most efficient and cost-effective way to bring fresh air into your home is to just open the window every once in a while.

This is especially important if you’ve moved into a newly built home that’s built airtight and has new building materials that need to gas off.

You don’t need to keep your windows open the whole day.

Here are a few tips to follow:

  • Open windows and doors on opposite sides of the home, creating a draft.
  • Open nearby windows when cooking, or slightly crack them open when taking a shower.
  • Although opinions are mixed, most agree that outdoor air quality tends to be best slightly after the morning rush hour or slightly before the afternoon rush hour. Consensus is to keep the windows closed very early in the morning if you live in a crowded, polluted city.
  • Outdoor carbon dioxide levels tend to be high in the evening (after a day’s worth of plant respiration and busy traffic exhaust pipes), although many argue that it’s best to open windows late in the evening during the summer. But did you know what carbon dioxide levels also accumulate in bedrooms as well as we sleep? Some studies are now telling us to crack our windows open during sleep, or else we’ll suffer excess carbon dioxide levels (known as hypercapnia).
  • Always turn off your HVAC system when the windows are open.

 

Related Questions

Does air conditioning improve air quality?

It depends. At minimum, air conditioning is there to give a basic level of comfort, which mainly deals with maintaining the temperature and humidity levels. Basic air filters won’t remove most pollutants and have the purpose of protecting the AC system only.

However, by making some changes, an AC system can do more to improve air quality. For example, upgrading its supply and exhaust fans can remove more stale air (and thus, pollutants) and reintroduce more fresh air. Cleaning out the ducts and upgrading to a higher-rated filter can help remove smaller pollutants.

 

How do ceiling fans work?

The blades (or paddles) can either move in the forward or reverse direction. When moving in the forward (counterclockwise) direction, the warm air is pushed back down directly, creating the cooling effect of a strong breeze. When moving in the reverse (clockwise) direction, the warm air is pushed back down gently to the sides of the room.

 

What are common indoor pollutants?

Indoor pollutants range from the large and obvious to the small and invisible. They can also be divided into chemical and biological pollutants. For a detailed overview of what indoor pollutants are lurking in your home and how to prevent and eliminate them, check out this post.