If you’ve ever taken a deep breath outside somewhere far from the city, then you likely know the invigorating power of fresh air. It improves your heart rate, blood pressure, immune system, and even your ability to solve problems. It’s an essential element of good indoor air quality.
But if it’s so refreshing, why is it so rare? And how do we get more of it?
Modern buildings are designed to be airtight to prevent drafts and conserve energy. But airtight homes and commercial buildings often leave us breathing recycled air.
The lack of fresh air is a problem, and it brings with it more than just discomfort. Harmful pollutants such as pollen, dust, mold, chemicals, and diseases like COVID-19 can remain present in the air for hours at a time. In some cases, stale or unclean air can cause sick building syndrome, harmful effects and ailments caused by spending too much time in a building with poor air quality.
While some commercial buildings may be required to meet the EPA’s NAAQ standards or OSHA guidelines for indoor air quality, you may not realize the condition of the air in your own home.
As we continue to spend more time indoors and look to recover from a pandemic associated with an airborne disease, breathing fresh air is more important than ever before. Luckily, there are many ways to bring fresher air into your home without spending a fortune or compromising the comfort of your indoor spaces.
How to Create More Fresh Air
While there is a lot to learn about indoor air quality, the process of bringing in more fresh air is a combination of ventilation and filtration. To achieve these goals in your home, you need to do three things:
- Move fresh air in.
- Move stale air out.
- Clean the air that circulates in your house.
First, let’s look at how HVAC works in most modern buildings:
Typical HVAC Systems
Depending on where you live, air conditioning technology may take many different forms. However, the most common configurations are packaged and split systems. Here’s how they work:
- Packaged Systems – A packaged unit is completely self-contained and often sits outside the home. These units work by pushing conditioned air through ductwork connected to vents throughout the house.
- Split-Systems – A split system (also called a mini-split) does not require ductwork. Instead, it utilizes two connected units to heat or cool the space. One unit sits outside the home and works as a compressor. It is connected by refrigerant lines to the indoor unit (often called the indoor air handler) which blows conditioned air into the space.
While these systems are common in many homes, they aren’t always designed to bring in more fresh air. Instead, both packaged and split systems are designed to recycle the air that’s already inside the home.
In other buildings, you may see through-the-wall units like PTACs (Packaged Terminal Air Conditioners). These are made to bring fresh air into the space directly from the outside while also enabling individual temperature control for that space.
Understanding Proper Ventilation
To overcome the limitations of HVAC technology and increase fresh air indoors, we will need to focus on optimizing the space for better ventilation. The main things to focus on are air turnover rate and improved airflow.
Air Turnover Rate
Air turnover rate is the rate of exchange between fresh air and stale air. As you bring in new fresh air from outside, you want to remove the old air at the same time. A good air turnover rate is an equal ratio of fresh air intake to stale air exhaust.
In other words, you need to achieve a balance. Too much fresh air without enough exhaust allows more air to be recycled. On the other hand, too much exhaust can create negative pressure and humidity issues inside your home.
Both ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers) and the EPA recommend 0.35 air changes per hour per person for residential buildings.
As air moves into and out of your home, it’s important to remove obstacles that prevent adequate airflow. But this doesn’t mean airflow should go in any direction. You’ll want to create a laminar airflow instead.
Laminar airflow occurs when air moves in a single direction and speed without crossing over into other air streams or becoming turbulent. The advantage to creating laminar airflow is predictability and efficiency. Air that achieves a laminar flow doesn’t branch off in different directions or get trapped in corners. This helps create a consistent air turnover rate because the air is constantly flowing through the house at a steady pace.
You can often achieve laminar airflow through a combination of exhaust fans, hoods, dampers, and other indoor fans strategically placed to push air in one direction.
The Problem With Opening Windows
While opening a window may seem like a great way to bring in fresh air, it isn’t always an effective strategy. In most cases, the only way to bring in adequate fresh air through windows is to open all of them at once.
This can be effective when the temperature outside is comfortable, but opening windows is mostly inefficient in extremely hot or cold temperatures. While fresh air is coming in through open windows, pre-conditioned air is also moving out at an alarming rate. Even opening the windows for a very short period of time can drastically change the temperature indoors. This costs more energy, as your HVAC unit has to work to bring your indoor temperature back to the set point again.
Types of Ventilation
Depending on the design of your home, there are many different ways to achieve better ventilation. While mechanical ventilation systems are common to most homes, you can also combine these efforts with natural ventilation methods for a more efficient fresh air strategy.
Many homes attempt to bring in more fresh air via mechanical ventilation systems. These can take many different forms, but the most effective methods of whole-house ventilation are Centralized MEV and MVHR.
Centralized Mechanical Extract Ventilation (MEV)
This method uses a central air unit, ductwork, and multiple exhaust fans to pull stale air out of wet rooms and supply new air to dry rooms. The extraction happens with bathroom, kitchen, and attic exhaust fans, while fresh air is brought into other rooms using vents inside walls or around windows. This creates a steady air turnover rate with the aim of keeping the air constantly fresh.
Mechanical Ventilation with Heat Recovery (MVHR)
MVHR systems typically rely on central units that both extract stale air and supply fresh air via ductwork. Where MEV systems allow fresh air to come in through vents (without propulsion), MVHR systems rely on the central unit to propel air inside.
These systems are designed to create a balanced air turnover rate while also conserving heat. By allowing incoming and outgoing air to cross over in a heat exchanger, homeowners can prevent heat loss when stale air is exhausted through the unit.
With either of these strategies, you can improve airflow and ventilation using fans. Ceiling fans help spread the air around in your home while box fans and pedestal fans can focus the airflow in a single direction. In a room without exhaust fans, you may consider placing a box or pedestal fan near a window to blow stale air outside.
Natural ventilation methods have been used for many years before mechanical ventilation was available. But even today, you can utilize natural ventilation strategies to bring more fresh air into your home while enjoying a lower energy cost.
Cross ventilation works by allowing air to flow horizontally through a home. To achieve this, homeowners typically install vents or louvers on opposite ends of the house. The natural power of wind brings fresh air in while pressure on the other side draws air through the opposite vent. In many ways, this functions like an intentional draft.
Stack ventilation is a technique that takes advantage of vertical heat transfer and wind power. It works similar to a chimney. As new fresh air comes in through vents, air from wet rooms is exhausted naturally through vertical pipes or ducts (called stacks).
This method is often called “passive” stack ventilation because it doesn’t usually require fans. Instead, a balanced air turnover rate is achieved naturally because of wind suction above the stack and a warmer temperature inside the home.
That said, the efficiency and overall performance of stack ventilation may vary depending on wind and temperature change.
Part of getting more fresh air into your home is making sure incoming air is cleaned before you breathe it. That’s why it’s important to not only change your home’s air filters regularly (every 90 days) but also upgrade them when possible.
Most modern air filters contain some combination of fiberglass, pleated cloth, or charcoal. While these all work well to varying degrees, it is important to look at the micron rating and the MERV.
Microns (also called micrometers or μm) are the standard unit of measurement for a particle. The micron rating on a filter indicates the smallest particle size it can trap in its fibers. If a filter has a micron rating of 1, that means it can filter particles that are 1 micron wide and larger — but anything smaller than 1 micron will pass right through it.
Because of this, it’s best to choose a filter with a smaller micron rating. This means it can catch more particles.
While the average air filter is rated for 5 μm, it is often worth the extra money to buy a better filter to protect your home from harmful pollutants.
Minimum Efficiency Reporting Value (MERV) is a standard measurement in more common HVAC filters. MERV ratings range between 1-20. The lower end of the range (1-8) filters less particles. Usually these are rated for 3 μm and larger. MERV filters rated 8-20 can filter particles from 1.0 μm to 0.3 μm.
While most professionals agree that a MERV 8 is sufficient for most homes, a MERV 9 or higher will help you achieve more fresh air.
That said, here are a few types of filters to look for:
- HEPA – High Efficiency Particulate Air filters are the gold standard for indoor air filtration. Many are rated for 0.3 μm and some use charcoal for additional filtering power. Some studies even report that HEPA filters can stop the spread of particles carrying COVID-19. But while HEPA filters are believed to be the best, they can be expensive and may not work for your HVAC system.
- Pleated Filters – Pleated air filters use cotton or other fabrics to trap particles from entering your air stream. These filters are more commonly used because they are more affordable than HEPA filters and fit with almost any HVAC system. While pleated filters tend to restrict airflow more than HEPA filters, those that have a MERV rating of 17 or higher can often trap just as many particles.
- Washable Filters – Washable filters tend to have low MERV ratings and vary in their ability to catch particles. However, the main advantage is the ability to reuse them. Instead of buying a new disposable filter every three months, you can simply wash the same one, dry it out, and reuse it for many years. They may be expensive to purchase up front, but you will likely save money over time by not buying more of them.
Changing (or cleaning) your filter is important for many reasons. A clogged filter can end up blowing dust and pollutants back into the air. It can also prevent fresh air from coming in at all. Because filters build up layers of dust and other pollutants over time, a dirty filter will restrict airflow and put strain on the compressor. This can lead to costly repairs and may even shorten the life of your unit.
Other Tips for Fresh Air
Mechanical and natural ventilation methods offer many benefits, but getting more fresh air in your home can often be a juggling act between efficiency, energy conservation, comfort, and air quality. In some cases, it may be expensive to complete costly home renovations that would improve ventilation.
But don’t worry. Depending on your situation, there are plenty of ways to optimize your space for better ventilation and fresher air that won’t totally break the bank.
Seal Cracks and Drafts
Intentional ventilation is good, but unintentional ventilation from drafts can drain energy and create poor airflow. If not properly managed, these drafts can create humidity and condensation issues.
To achieve a controlled, laminar airflow and conserve more energy, be sure to repair cracks and drafts in problem areas around your home. Seal around the edges of vents and any through-the-wall units with caulk. You can also add weatherstripping or plastic to windows and doors.
Use an Air Purifier
Air purifiers filter, sanitize, and neutralize harmful particles in the air. While they aren’t always completely effective at cleaning the air, they can help remove some harmful pollutants. However, be mindful that air purifiers don’t introduce any new fresh air. Instead, they only clean the air that is already present.
Buy an ERV
While they’re not always common, some homes use an Energy Recovery Ventilator (ERV) to bring in fresh air and maintain temperature control. An ERV is a ventilation machine that brings in fresh air and expels stale air through a central chamber with the use of fans. Unlike the heat exchanger used in an MVHR system, an ERV doesn’t allow the two airstreams to cross. Instead, the conductive material inside the chamber allows moisture and heat to transfer from one stream to another.
These can be very effective at maintaining conditioned air and energy while increasing fresh air. They can also be installed in a variety of ducted HVAC systems. However, they often cost anywhere between $800 and $1500. Beyond that, installation may cost $1,000 to $2,000, depending on your system.
Install a PTAC
Packaged Terminal Air Conditioners are built to bring in fresh air without expensive technology or complex ductwork. Instead, they are installed through the wall and provide individual temperature control for individual rooms. For this reason, they are often used in hotels, hospitals, and office buildings. If sized properly, they can be quite energy efficient, and the upfront cost is lower than many other solutions on the market.
In a world where remote work is the new normal and concerns about climate change are causing many to value energy efficiency, bringing fresh air into your home is incredibly important. To avoid harmful effects of air pollutants and poor indoor air quality, creating a steady stream of fresh air is more than just a luxury. It’s a necessity.
But you don’t have to completely renovate your home to make sure you have an adequate amount of fresh air coming in. While traditional air conditioning and ventilation systems can help, there are plenty of simple and affordable ways you can optimize your space for better, breathable air.
Start bringing more fresh air into your building with a new or refurbished PTAC unit. Browse our store for the most efficient and affordable models today.