Have you developed a plan to reduce the exposure of coronavirus COVID-19 in your home? There are many things to consider including indoor humidity, moisture control, ventilation systems, air filtration, air purification, and sanitation.
For many years, the topic of a healthy home has been an important consideration for energy auditors and energy efficiency professionals. During our training classes, we are all taught that the house works as a system and that we must be aware of the unintended consequences that can occur to a home after making certain upgrades. We perform a combustion safety test that identifies gas leaks and carbon monoxide hazards both before and after the upgrades are performed on the home. Leaving a contaminate like carbon monoxide unidentified in a home will only make it more dangerous as the building gets sealed up as there is simply less outdoor air to keep it diluted. The healthy home concept goes beyond combustion safety and is also applied to indoor humidity, ventilation, and air filtration. Each of these concepts can play a role in how easy or how difficult it may be to transmit viruses in a home.
The article will focus on actions homeowners can take to reduce exposures to the coronavirus while at home that complement (not replace) the recommendations of health officials such as handwashing, physical distancing (social distancing), enhanced cleaning, and isolation of infected individuals. The information here is not intended to replace the guidance from your health professionals or government agencies such as the Centers for Disease Control & Prevention , the U.S. Environmental Protection Agency, and the Peoria City/County Health Department. There are no suggestions here that offer a guarantee to halt the spread of the virus, but they can help you develop or enhance your risk mitigation plan for your home.
According to the latest understanding of how COVID-19 spreads from person to person, the focus is on sneezing, coughing, speaking, and exhaling. Each of these activities expels droplets into the surrounding air and surfaces. A cough or sneeze can send larger droplets into the surrounding air, while speaking and exhaling tend to disperse small air droplets. The droplets can be inhaled by another person or picked up by contact from a surface where the active virus is present. The larger droplets tend to be heavier and fall to the floor or surfaces and the smaller air droplets can stay in the air for some period of time. Previous studies on viruses have found a virus can remain airborne for hours.
To better understand the spread of droplets from a person, here are some great visuals from a fluid dynamicist and mechanical engineer at the National Institute of Standards and Technology. They show how droplets are expelled through talking and coughing without wearing a face mask and what happens when various types of face masks are worn. The high speed visualizations are quite effective in showing what we generally can’t see with the naked eye.
Everyone should have a way of measuring relative humidity in their home. What is humidity important? Health experts have found that viruses in our homes are more active when it’s humid or when it’s dry. Viruses are less active in the middle range. A study of the influenza virus by the CDC found it was most activate at levels below 23% and that “maintaining indoor relative humidity >40% will significantly reduce the infectivity of aerosolized virus.” According to the ASHRAE 2016 HVAC Systems and Equipment Handbook, the optimum levels of indoor humidity are between 30% and 60%. Below 30% is considered too dry for human comfort and provides an environment for viruses to thrive. Above 60% is considered too humid for comfort, increases the potential for mold growth in the home, and also provides an environment for viruses to thrive.
If you have a smart thermostat such as ecobee, nest, and certain Honeywell models, they have a humidity sensor built in that be read right on the screen. However, it’s better to be able to measure humidity on each level of the home and not just near the thermostat. Relative humidity can vary due the presence of moisture or varying degrees of temperature in different areas of the home. For example, a 2-story home with a basement would ideally have 3 gauges. Simple devices are called hygrometers or thermo-hygrometers and will display a reading directly on the screen such as the Mini Hygro-Thermometer from P3 International. You may also come across devices called weather stations that add more functionality such as remote sensors that take readings in another room or even outdoors. Check out the weather stations from Meade for examples. However, the best devices that measure humidity will also track the levels over time and are accessible via a smart phone, tablet, or computer. Check out the Indoor air quality monitors like Footbot, Awair, or uHoo that measure humidity and log it so you can graph out trends, hourly, daily, weekly, etc.
Humidity Control / Moisture Control
What if you start measuring humidity and find it outside the preferred range? There are numerous causes for a house to be too humid. Some are obvious like correcting the plumbing leak, stopping water from getting into the basement or crawlspace, or doing roof repairs. Other causes are less obvious like interior moisture control, use of ventilation fans, the operation of the central air conditioner or heat pump, or use of a dehumidifier. Homes that are too dry are typically an issue in the winter. Often the cause of a dry home is too many air leaks bringing cold winter air indoors that can dry out the interior. A humidifier may be needed if the home is below 30% relative humidity in winter, but this should be unnecessary in an airtight, energy efficient home. We can help diagnose these types of issues during our energy audits and provide solutions that make sense for your budget. Whether the house has moisture problems in the summer or it is too dry in the winter, we have the equipment and training that help you get to the root cause of the problems.
For more information on moisture control from the EPA, check out the Moisture Control Guidance for Building Design, Construction, and Maintenance.
Ventilation in bathrooms and kitchen, ventilation of the whole home
We encourage all of our clients to use the bath exhaust fans for 20 minutes after the shower and the kitchen exhaust fan whenever using the stove or oven. These are important steps to properly ventilate these areas of the home to remove indoor air contaminants and excess moisture, but they may also be used as part of a whole house ventilation system. Providing a system that can exchange air between indoors and outdoors is a common strategy implemented during energy efficiency upgrades and is a code requirement for new homes being built in Illinois and other areas of the country. These systems are designed to improve indoor air quality by preventing a build up of contaminants, and they have become even more pertinent during the current pandemic. If an infected person is in the house, they can be easily be spreading the airborne droplets throughout the house. If a ventilation system is installed, it can reduce the potential of the virus from overwhelming the indoor air of the home. In fact, it may be prudent to temporarily increase the ventilation rate of an installed system if there is an infected person in the home, workers have entered the home, or guests have been present.
What types of whole house ventilation systems exist? There are many variations and getting into the full details is beyond the scope of this article.
Briefly, here are the 3 basics concepts often considered for homes. A home can be set up with a special type of bath exhaust fan that runs on a program or is set to run 24 hours a day. The home could also have an air vent on the outside of the building that is connected to a duct that brings outdoor air into the main duct work of the house to allow the HVAC system’s fan to circulate the outdoor air inside the home. The third system may have a heat recovery ventilator or energy recovery ventilator installed that has it’s own filtration system and can capture a portion of the lost heat. We can help evaluate the ventilation needs of your home during our inspection, calculate the recommend ventilation rate for whole house ventilation, and help you decide which of these systems makes the most sense for your home.
To dive deeper into this subject, here is an article from the Home Ventilation Institute that goes into further detail about whole house ventilation systems.
Air Filtration – Upgrading Your Air Filter
It may be possible to filter out viruses that are in the indoor air using the main filter of your heating & cooling system. Not all air filters are created equal. Some air filters are specially designed to pull smaller particles out of the air and capture them in the air filter. These can be useful in capturing the smaller droplets that could hold the coronavirus. There are many variables here that would impact the effectiveness of capturing a droplet
including how long it remains airborne and whether it can get pulled into the air stream in the return duct work. In addition, the air filter system would need properly installed, appropriate for the system it is attached to, and well maintained.
How good is the air filter at filtering particles? There are 3 different rating systems for air filter effectiveness, so you may find different systems depending on where you are making your purchase. These include MERV (a commonly used industry rating established by ASHRAE), FPR (a proprietary rating used by Home Depot only), and MPR (a proprietary rating used by the manufacturer 3M). If you are looking at capturing a virus in the air stream, look for a minimum MERV-13, FPR 10, or MPR 1500. For more on filter ratings, check out this article from Energy Vanguard.
However, upgrading to a higher performing air filter can actually backfire if your heating and cooling systems is not designed for it. The more particulates the filter pulls out of the air generally means the less airflow that it allows through the filter. HVAC systems are designed for certain amounts of airflow. If airflow is too low, many things can occur including ruining the blower motor and freezing the air conditioner’s coils. During our inspection, we evaluate the airflow through the installed air filter by measuring the pressure drop across it. If the pressure drop is too high, the system is already outside the specified range and upgrading the air filter will only make it worse. We can assist the HVAC contractor in making sure the performance of the system is maintained with a new filter system.
DIY Air Filtration Option
An intermediate solution to getting some filtration can be done as a DIY project. If you have a box fan, an air filter, and some tape available you can make your own air filter system that can work for a small room. It’s not perfect, but it’s a step in the right direction. During the construction of our new work office, we used this setup to pull construction debris out of the air and were surprised at how much the filter captured including drywall dust and insulation fibers.
Air Filtration & Constant Air Circulation
Keep in mind that filtration only works if the blower of the furnace, air conditioner, or heat pump is running. If these systems are off, then air filtration is not occurring. Throughout the course of a year, a typical HVAC system runs only about 20% to 30% of the time (although some may run longer by design). To get continuous air filtration of the house, make use of the “fan on” mode on your thermostat by changing from “auto” to “fan on.” This will keep the blower running and air circulating throughout the home even when the heating or cooling systems are not operating. Indeed, this does account for some energy usage but not as much as you might think. Health and safety come energy efficiency, so use this mode in order to get continuous filtration. Here what the EPA says about using the HVAC system during the pandemic.
Taking precautions when changing the dirty air filter
When it’s time to change your air filter, be careful how you handle it. These filters are now full of particles and contaminants from the indoor air and studies have shown the filter can be biologically active. It’s best to wear your face mask and gloves when handling the air filter. Place the filter in a plastic bag and seal it before throwing it out. While washable air filters seem like a good way to save a few bucks, they aren’t appropriate if your goals are to provide a healthy home environment.
The National Air Filter Association (NAFA) has guidance about air filtration and the coronavirus on their web site.
Some homeowners have been asking about installing Ultraviolet (UV) lights in their duct systems. Typically, these are intended to be installed over the evaporator coil which is the indoor portion of your home’s cooling system. UV has been proven to deactivate the coronavirus. However, there is far less evidence at how well UV can handle bacteria, mold, and viruses in a stream of air. When you factor the velocity of air moving through the UV light, it may not be exposed to UV long enough to be effective. As always, the devil is in the details of how it’s installed. There is nothing wrong with adding one to your duct system, but know that it is better as a component of an overall strategy that includes these other measures mentioned above. When choosing a product, be sure the UV light is validated to not produce ozone which is a known respiratory irritant.
There are products that are designed to clean the air of the home or building. Portable air cleaners (AKA air purifiers or air sanitizers) are standalone units designed to clean the air of a designated room. HVAC technicians can add air cleaners to your central duct system that can provide the same effect for the whole home or building. Remember that there isn’t an air filter or air purifier that will eliminate all contaminants in a home, but these technologies may be components in your overall plan.
Speaking of ozone, this is one of many technologies on the market that can be used to clean contaminated spaces. However, ozone should only be used by professionals and in an unoccupied building only when necessary. It should never be used when people are in the home. Here is what the EPA says about ozone.
There are other air purifiers available on the market that may be useful to consider, but there are too many options to consider for this article. Again, this may be a component of your overall strategy. Here is a good resource from the EPA on Air Cleaners and Air Filters in the Home.
Cleaning vs disinfecting
It is important to understand the difference between cleaning and disinfecting. Depending on the types of cleaners you are using, this may be a 2-step process. Simply spraying a surface and wiping it down doesn’t mean the surface is disinfected. According to the CDC, that act of cleaning with soap and water reduces the number of germs and impurities on the surface while disinfecting means killing the germs.
As you are disinfecting surfaces, be sure to follow the instructions on the product. It may surprise you to learn that a disinfectant spray should sit wet
on the surface for up to 10 minutes to properly disinfect! As an example, here are the instructions from a bottle of Formula 409 multi-surface cleaner: “General cleaning – Spray product straight onto soils and wipe clean with a dry paper towel or lint-free cloth.” To disinfect: “Spray until thoroughly wet. Let stand 10 minutes. Then wipe.”
If you are using bleach to clean, it is vital that you open windows or doors in order to ventilate the space as the cleaner is a respiratory irritant.
Here is information from the CDC on cleaning and disinfecting.
Avoid bringing respiratory irritants into the home.
We talked about air filtration to pull contaminants out of the indoor air, but the best solution is to avoid exposing them in the home in the first place. There are a number of every day products that have been shown by health professionals to be respiratory irritants. This is a concern not just for healthy individuals but even more so for those who have respiratory problems like asthma, COPD, influenza, or a coronavirus like COVID-19. There should be no smoking or vaping in the home, limit the use of candles and air fresheners, use the exhaust fan if you have a gas stove or gas oven, and carefully select cleaners that have fewer chemicals. Make sure the household vacuum has a HEPA air filter so that it doesn’t just redistribute particles back into the air, and empty the vacuum bag or canister outdoors to avoid redistributing particles back into the home.
Putting an infected person in isolation
If someone in the household is infected with the virus and is going to put in isolation, here are some considerations for setting up the space to keep them comfortable and protect the other occupants of the house. Contact your health professional about the duration of time an infected person should be put in isolation.
- Keep the door closed to the room where the person is isolated.
- Exhaust the air from the contaminated room. If the room is attached to a bathroom that has an exhaust fan, turn it on and leave it on.
- If no exhaust fan is present, one can be created. Purchase a fan that can sit inside a window, open the window, and position the fan to blow air to the outside. A quick Internet search for “window fan” will show many varieties available such as this one from Lowes.
- If possible, the person should use their own bathroom and not share with others. If that’s not possible, but sure to clean & disinfect frequently using CDC guidelines.
- If possible, close off both supply and return duct work in the room so air from the room is less likely to exchange with the rest of the air from the house. However, it’s important to keep the person comfortable. Ideally, they would have a window air conditioner for cooling and an electric space heater (follow safety instructions) for heating.
- Open windows whenever possible to dilute the air in the room. That’s assuming that seasonal allergies from pollen aren’t an issue.
- Consider room filtration such as the box fan mentioned earlier or a portable air cleaner.
At the end of the day there may not be a single solution that works for every home, but there are a lot of common sense strategies here that can be incorporated into . As a reminder, we can help evaluate many of these strategies in order to help achieve a healthier home so give us a call at (309)253-2242. View our contact page. Curious about our energy audits? Check out our What Is an Energy Audit page.