Optimizing Smart Home Air Quality and HVAC Efficiency

The more we learn about the risks of poor indoor air quality (IAQ) on people’s health the more we find it is important to try and find ways of improving it. In fact, according to the Environmental Protection Agency (EPA) the air inside a home may be up to five times more polluted than the air outside a home and people may spend up to 90% of their time indoors.

In a February, 19th, 2019 article published on the Forbes by Jessica Baron titled “Brining Attention to Indoor Air Pollution”, Ms Baron quotes an ongoing scientific study by the University of Colorado, Boulder stating:

“…routine household activities generate significant levels of volatile and particulate chemicals inside the average home, leading to indoor air quality levels on par with a polluted major city”

It should also be noted that air quality is even more of an issue for older people. The EPA’s AirNow.gov web site states:

“As people age, their bodies are less able to compensate for the effects of environmental hazards. Air pollution can aggravate heart disease and stroke, lung diseases such as chronic obstructive pulmonary disease and asthma, and diabetes. This leads to increased medication use, more visits to health care providers, admissions to emergency rooms and hospitals, and even death.”

Many manufacturers sell a wide range of air cleaners that can be scattered around a home. On the other hand, a forced air heating, ventilation, and air conditioning (HVAC) system includes an air filter and a properly sized HVAC system is capable of cycling through all the air in a home in 2 hours. But, not all HVAC air filters are up to the task and not keeping your HVAC system operating efficiently can damage it.

The most damaging particles to our lungs that are floating in the air are those that are labeled PM2.5. These are particles that are under 2.5 microns in diameter. These particles are small enough to lodge deep inside lung tissue and even getting into our bloodstream. The most common type of PM2.5 particles are smoke from car exhaust, power plants, wood burning stoves, and even forest fires.

Unfortunately, just running the fan on a furnace for a few hours each day isn’t going to adequately clean the air in a home; unless the right filter is installed. Furnace filters are rated based on their effectiveness. This rating is called Minimum Efficiency Reporting Value (MERV). The rating for HVAC filters run from MERV 1 to MERV 16 where the higher the number the more effective the filter is at cleaning small particles. For example, filters rated at MERV 1 through MERV 8 are totally ineffective at cleaning PM2.5 particles from the air. The filter recommended by the US Department of Energy (DOE) is a MERV 13 filter that can clean 90% of particles 1-3 microns in diameter but less than 75% of particles .3-1 micron in diameter. Why doesn’t the DOE simply recommend that everyone install a MERV 16 filter for maximum air cleaning? Because, the higher the MERV rating the more restrictive to air flow the filter is and this can cause significant issues with an HVAC system.

If the airflow is restricted in an HVAC system it can lead to:

  • Increased energy usage by the blower motor trying to move air through the system
  • Reduced comfort as the HVAC system is unable to properly distribute warm air in the winter or cool air in the summer throughout the home

In extreme circumstances restricted airflow can lead to:

  • Icing of the cooling coils during the summer
  • A cracked heat exchanger during the winter

To complicate matters further, not all filters are created equally and some high MERV filters are less restrictive than another manufacturer’s lower MERV filter. An excellent article on this topic was published in Home Energy and is available here.

All things considered, to avoid problems a homeowner shouldn’t go overboard with an overly restrictive filter, such as one rated at MERV 16, and should change the filter when it is becomes dirty and restrictive. How often does a filter need to be changed? Good question because changing the filter before it needs to be replaced is just a waste of money.


FILTERSCAN: Wi-Fi Enabled Airflow Monitoring

FILTERSCAN is an award-winning Wi-Fi device that easily attaches to the HVAC system and monitors the airflow drop across the filter. The device then sends an email or text alert to the homeowner letting them know when to change the filter.

The FILTERSCAN can be installed upstream, downstream, or differentially across the air filter (using an available tubing kit). The FILTERSCAN is attached to the external wall of the HVAC system air duct a minimum of six inches from the filter. Five holes are drilled into the air duct; four of the holes are for mounting screws and the fifth hole is for the sensor. The FILTERSCAN must be located such that the front panel will be clearly visible by the homeowner. A small switch inside the FILTERSCAN is then turned on/off depending on whether the FILTERSCAN has been mounted downstream or upstream from the air filter. The FILTERSCAN is then powered using either four AA batteries (batteries last approximately 1 year) or with an optional six volt power supply. An alternate model can be powered using fifteen to twenty-four volts, AC or DC, from the HVAC unit through a conduit.

For text or email notifications the homeowner needs to the complete the Wi-Fi setup. This involves:

  1. Create an account on the manufacturer’s clean alert network web site
  2. Enter the homeowner’s contact information including their cell phone number and email address
  3. Enter the serial number and MAC address of the FILTERSCAN
  4. Connect to the homeowner’s Wi-Fi network by depressing the WPS buttons on both the FILTERSCAN and the homeowner’s wireless router.
  5. The FILTERSCAN will then connect to both the homeowner’s Wi-Fi network. It should be noted that the FILTERSCAN supports WPA-PSK and WPA2-PSK encryption.

If the homeowner’s Wi-Fi router doesn’t include a WPS button there is an alternate procedure for connecting the FILTERSCAN to the homeowner’s Wi-Fi network.

Finally, the homeowner then needs to install a new HVAC filter and go through a short calibration procedure.

The FILTERSCAN monitors the change in pressure over time as the air filter does its job and filters out the dust and debris from the air flowing through the HVAC system. When the differential pressure caused by the dirty, restrictive air filter reaches the threshold where the filter should be changed, a notification is sent to the homeowner. Depending on unique customer circumstances, this threshold can be adjusted through a dial on the front of the FILTERSCAN.

An optional bonus of the FILTERSCAN model that is powered through a conduit from the HVAC system is a contact closure output that is triggered when the filter needs to be changed. This output can be connected to a home automation processor / hub with a digital input to, for example, display messages that the filter needs to be changed on touch panels or to adjust programming associated with using the HVAC system for indoor air cleaning.

The FILTERSCAN is a simple to use, comprehensive product that helps assure the air filter is changed at the proper time to keep a homeowner’s HVAC system optimally running. It allows the homeowner to use a MERV 13 rated filter (as is recommended by the DOE) and not risk keeping the filter in their HVAC system too long; risking damaging the system. It also keeps the homeowner from committing to a basic schedule of changing their filter, for example, on a monthly basis; which may not be required and would be a waste of money.


HVAC air filter

ALVI: A Smart Electrostatic Furnace Filter

ALVI is an emerging product that has recently finished a successful funding round on Indiegogo that is targeted to be available in October, 2019. It is a smart, electrostatic furnace filter. ALVI consists of a smart filter frame with carbon rods that are charged to 7000 volts at a low current so this doesn’t pose a shock hazard. The rods creates a polarized field that charges particles as small as .1 micron so they will clump together and become large enough to be captured by the replaceable filter cartridge.

The ALVI smart furnace filter doesn’t fit into the standard MERV rating system. However, the testing done at a third party test facility has shown it to be effective in trapping particles as small as .007 microns and to be as effective at cleaning the air in a room as a unit with a HEPA rated air filter; all while using less energy. In addition, because of the technology of the filter, it can capture particles this small with lower resistance to flow than a conventional filter. According to Devin Ramphal, Co-Founder and CTO of CleanAir.ai, this results in improved circulation of air around the home and reduced energy costs.

ALVI includes the frame unit, a filter cartridge, and a power adapter. It comes in the size of a standard one inch thick furnace filter and simply replaces the homeowner’s original filter. The frame uses an optical sensor to monitor when the filter cartridge needs replacing and sends an alert to the ALVI mobile app. Through the mobile app the homeowner can order replacement filter cartridges. The plan is for the homeowner to also be able to order replacement filter cartridges through Alexa and Google Assistant. Other voice assistant functionality is still being determined.

Alternatively, filter cartridges can be sent automatically if the homeowner has signed up for them on a subscription basis.

In the future, ALVI will come in additional sizes for HVAC systems that use filters other than one inch thick.

ALVI requires:

  • HVAC system that uses a one inch thick filter
  • 110v AC outlet near the furnace. If this isn’t available the company is supplying Indiegogo backers with an adapter that adds an outlet to the light socket in the room where the HVAC system is located that the power adapter can be plugged into
  • 2.4 GHz Wi-Fi Network
  • Android or Apple Smart Phone

The installation process for the ALVI is:

  • Replace the existing HVAC filter with the ALVI
  • Plug the ALVI’s twenty-four volt power supply into a nearby wall socket or use the free adapter to add an outlet to the light socket in the room where the HVAC system is located
  • Download the ALVI app from the appropriate smart phone app store
  • Press the pair button on the ALVI filter frame. ALVI then creates its own Wi-Fi network
  • Connect to the Wi-Fi network using a smart phone
  • Follow the app’s prompts to connect the frame to the home’s Wi-Fi network

Once installed the homeowner can use the app to monitor the performance of the filter, get an estimate of how many days it will be until the filter cartridge needs to be replaced, and to view the reported air quality in the homeowner’s geographic area.

It is important to remember that ALVI is an emerging product. If it meets up to the promises it will be a system that can provide clean air throughout a home.

PuraClean: A Spray That Turning a MERV 6 Into a MERV 11

As discussed earlier, an overly restrictive HVAC filter can cause heating/cooling problems in a home and even damage the HVAC system. The best way to check if an HVAC system can handle a MERV 13 filter, as recommended by the DOE, is to have a professional check the system. The professional will validate that the filter isn’t too restrictive for the system by looking at the pressure drop across the filter and making sure that there is adequate air flow to all parts of the home using an anemometer.

A homeowner can take some steps on their own to make sure the filter isn’t too restrictive by validating that the airflow to registers throughout the home is not significantly changed when a MERV 13 filter is installed. This is best done by 2 people so one can swap filters, back and forth, and the other hold their hand above the register to check the air flow. While this isn’t nearly as accurate a test as can be done by a qualified professional it can give the homeowner some assurance whether a MERV 13 filter will work in the homeowner’s HVAC system.

If a MERV 13 filter is too restrictive then a system like ALVI becomes a good choice. There are add-on electrostatic filters that are installed by professional HVAC technicians but these typically cost in excess of $750 plus labor for installation.

Another alternative, that some professionals I spoke to have misgivings about, is PuraClean. PuraClean is a spray that can be applied to a MERV 6 filter that allows it to operate at a MERV 11 filtering level without reducing the flow of air through the filter. The product was developed by Mainstream Engineering for NASA to improve spacecraft ventilation systems. It includes:

  1. A component that attracts particles in the air electrostatically
  2. A “tackifier” that makes the filter element sticky to make it more effective at holding particles

Independent testing was done by Research Triangle Institute proved the effectiveness of the product. However, the effectiveness of the product drops as the size of the particles the filter is trying to capture get smaller. So, the product isn’t nearly as effective helping a filter capture the PM2.5 particles that are the most damaging to people’s health.

Can it help a lower MERV rated filter achieve the same performance as a MERV 13 filter? Unfortunately, the testing to determine this wasn’t done by the manufacturer so they weren’t willing to commit to it when I spoke to them for this article. So, if the HVAC system in a home can’t support a MERV 13 filter then the best approach is a smart electrostatic filter, like ALVI. That being said, a homeowner could also give PuraClean a try as it is inexpensively available online.

Managing Indoor Air Quality in a Smart Home

An automation system can, with an integrated smart thermostat and the proper HVAC filter, help to improve IAQ in a home. With a connected thermostat that includes the ability for the automation system to know when the HVAC system is operating the automation system can:

Track the amount of time the HVAC system has run during the day (The running time of the HVAC system is also the amount of time the air in the home has been run through the HVAC system’s filter)
If the system hasn’t filtered the air in the home for at least two hours the automation system can, through the integrated smart thermostat, run the HVAC system fan to complete the process of filtering all the air in the home.

It should also be noted that the above process can be enhanced with an integrated IAQ monitor. Some options are Foobot, Awair, and Dylos. The Foobot and Awair IAQ monitors are more general purpose products with a range of sensors in them that can be integrated with an automation processor / hub through IFTTT. Both also have direct integrations with select smart home thermostats that can trigger the thermostat to run the HVAC system fan whenever the monitor detects poor IAQ.

The Dylos is true laser particle counter that lacks the sensors for VOC’s, etc that are part of the more general purpose monitors. However, it is a much more sensitive monitor for particulate pollutants with the ability to measure particles as small as .5 micros. It should be noted that the Dylos monitor can only be interfaced with an automation processor / hub that includes an RS-232 port.

An IAQ monitor can inform the automation processor / hub when the air in the home requires cleaning so the automation system only runs the HVAC fan for additional time when needed; saving energy and money on the electrical bill.

The contact closure output on the FILTERSCAN can also be integrated with an automation processor / hub with a digital input to disable the HVAC system air cleaning process when the HVAC system’s filter needs to be changed. This may also be possible with the ALVI filter system but as the product is still in a state of development the integration options aren’t known at this time.

Hands On: Putting the FILTERSCAN and Foobot to the Test

For this article I purchased a FILTERSCAN (the ALVI system isn’t available yet) and Foobot for installation into my own home. The FILTERSCAN was easy to install in my HVAC system and the web site makes it easy to check the status of your filter and, again through the web site, I’ve configured the system to send me an email when the filter should be replaced. I will also be wiring the contact closure output directly to my automation processor so I can trigger logic in the automation system when the filter needs to be replaced.

FILTERSCAN has been around for a number of years and in some ways, it shows. Requiring everything to done through a web interface instead of an app is one way. In addition, there isn’t an API so the data can’t be directly queried by an automation processor. It would be nice if my processor could interrogate the FILTERSCAN to understand exactly how much life my filter has left. This would allow me to implement a warning when the filter is approaching its life instead of just receiving a notification when the filter needs to be replaced. I live in a small town and MERV 13 filters in the size I need are not readily available. This is especially true because I use a filter with activated carbon to also reduce VOC’s in the air. Knowing when the filter is approaching the end of its life would be a very useful reminder to allow me to order a filter so I can have it on hand when I need it.

The Foobot, on the other hand, has a wealth of integration options. It has a reasonably simple API and a full featured IFTTT interface. I chose to write the code for my automation processor to use the API. In addition, to provide the automation processor with outdoor air quality information I wrote a driver to interface with AirVisual (For those with a Crestron automation processor I’ve posted the code for both the Foobot and AirVisual on my github at .

The Foobot provides key air quality metrics including information on PM2.5 particulates and VOC’s. With the API integration the Foobot will now trigger my automation system to turn on the HVAC fan and use the HVAC filter to clean the air in the home.

This is a relatively simple indoor air quality system for any home; even if it isn’t equipped with a Crestron automation system. Any smart home hub that includes IFTTT integration and a smart thermostat can be used with a Foobot and a MERV 13 filter to create an intelligent whole house air cleaning system.

In Summary

Today, IAQ is an important issue for all homeowners. Purchasing HEPA rated air cleaners for rooms throughout a home can quickly become an expensive proposition. Leveraging the home’s HVAC system with either the ALVI filter system, or an EPA recommended MERV 13 filter and the FILTERSCAN (to assure it is changed as needed), can provide the homeowner with a whole home filtration system at a very reasonable cost. This is especially true since the EPA has stated that a MERV 13 filter is likely to be nearly as effective as a true HEPA filter at controlling most airborne indoor particles.

Additionally, the ability of both the FILTERSCAN and ALVI system to monitor the filter and prompt the homeowner when it needs to be replaced will keep an HVAC system running efficiently; saving the homeowner money on their heating and air conditioning expenses.


For more from Jay Basen, visit his blog, Topics in Home Automation.

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