COVID-19 Resources for Contractors (PDF)

Humidity control – become an indoor air improvement expert, in 30 minutes or less


The filter on the right protects the customer’s furnace; the filter on the left protects their lungs. (Photo by Alison Logan)

By Glenn Mellors

If you recall from the last edition, I had an article called “The other 77 Things You Should Consider When Building A New Home-HVAC.” I shared my distress about how much attention was given to closet space over HVAC design. In that article, I said that we need ample space for a mechanical room capable of housing the necessary equipment to provide the best HVAC system the customer can afford.

So, here’s the deal!

Let us break it down to simple terms; HVAC equals indoor air quality (IAQ). How so?

If we break down what makes for great indoor air quality, we have four major contributors. They are:

  • Temperature
  • Humidity
  • Airborne particles
  • Volatile organic compounds

Let’s skip the temperature part and get to the other three forgotten components of an ‘indoor air improvement system.’ I personally like that term better than ‘indoor air quality’!

Humidity control key

On the list of items that contribute to a great HVAC system for your dream home client would have to be humidity control. Humidity levels contribute to our personal health as well as the health of our homes and furnishings.

Let’s skip over the fact that proper humidity levels in the home protect our hardwood floors, furnishings, artwork and pianos and get to OUR health. Improper levels of humidity will affect our breathing, sinus soreness, cold and flu, and the harbouring of dust mites and other critters that can bring on bouts of asthma.

There is no such thing as the perfect temperature as we all feel heat and cold differently, but there is such a thing as the perfect humidity level. In the winter, the healthy home should be between 40 and 50 percent relative humidity. In the summer, we should target 30-50 percent humidity levels to keep the health of our home at peak performance.

Keeping the humidity level correct dramatically reduces the impact of bacteria and contaminants.

HRVs,  ERVs and humidifiers

An HRV is a controlled ventilation system that reduces high humidity, pollutants and odours by replacing stale air with fresh warm air… The two air streams are always 100 percent separated. The fresh air introduced into your home is warm and dry and provides a permanently fresh, healthy, indoor environment.

Energy recovery ventilation (ERV) is the energy recovery process of exchanging the energy contained in normally exhausted building or space air and using it to treat (pre-condition) the incoming outdoor ventilation air in residential and commercial HVAC systems.

Whole-home humidifiers come in a variety of configurations. There is the drum type, where a rotating foam pad dips itself in a stand tray of water and air passes through the drum, transferring water into the air to create vapour.

Next is the pad style humidifier where the pad is standing upright as water is trickled down over the pad while air passes over it, picking up the moisture and transferring it to the home.

A step-up form of this model is the “power humidifier” that works on the same principle, but this unit has its own fan to deliver a higher amount of air across the pad. This process is a more efficient use of water.

The least common is the steam humidifier. This unit creates steam by either heating the water or pressurizing the water through jets that inject water vapour into the air stream of the system. All the above can assist in maintaining humidity levels to healthy levels in varying degrees of competency.

Too much humidity

Condensation on the window may indicate too much humidity.

But what about TOO much humidity?

The most under-utilized product we have available to us is the whole-home dehumidification system. The whole home dehumidifier extracts moisture out of the air by having the warm moist air passing over a coil like that of an air conditioner coil. The coil temperature is maintained at a temperature equal to the dew point of the incoming air, digitally controlled by sensors and circuitry.

When the warm moist air hits the coil, the water vapour condenses into a liquid and is extracted from the air. Not only is it controlling the ability for dust mites and other critters to survive, but it reduces the load on our whole-home air conditioner, making the whole system more effective and efficient.

Airborne Contaminants

There is a litany of air filtration products on the market today so to explore any of them would be confusing. In order to become an expert on indoor airborne particle entrapment you need to understand two things:

First, the Minimum Efficiency Reporting Value, commonly known as MERV rating, is a measurement scale designed in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to rate the effectiveness of air filters.

Particulate arrestors are measured in MERV; the higher the number the better the particle entrapment.

Secondly, a human being’s nose cilia and lungs filter MERV rating are eight, so it only makes sense that if we want to protect ourselves than we require a filtration system capable of one to 1-½ times our own body filter, so 12 MERV or above is recommended.

Do not confuse the thickness of the pleats of a filter cartridge with its efficiency. Thickness only means a longer use life before face loading occurs.

Volatile organic compounds

This manufacturer graphic illustrates a typical forced air system dehumidifier installation.

Volatile organic compounds – wow! VOCs include a variety of chemicals that can cause eye, nose and throat irritation, shortness of breath, headaches, fatigue, nausea, dizziness and skin problems. Higher concentrations may cause irritation of the lungs, as well as damage to the liver, kidney, or central nervous system. Even more scary!

One way a customer can reduce their exposure to VOC’s is to print off a list of off-gassing products and reduce or eliminate them from their home. To further protect yourself or client from exposure, utilize one of the many UV light systems available today.

It is important to understand that the U.S. Environmental Protection Agency (EPA) states UV light itself cannot destroy VOCs, but UV is used as a part of a process called photocatalytic oxidation, which can reduce or virtually eliminate VOCs from the indoor air. In this process, VOCs are trapped by a photocatalyst – most often titanium dioxide (TiO2) – which is activated by high intensity UV light.

The harmful VOC are oxidized and turned into water and carbon dioxide. At this point, our selection of a MERV-12 or higher filter can collect these particulates. There are some manufacturers that produce multi-step systems that can do it all within one cabinet.

Educate yourself, customer

It is not important what make or type of products that you use. What is important is that we take the time to educate ourselves on the products and services that our customers can truly benefit from! It is our duty and responsibility to pass along this knowledge so that when designing their new “dream home” you have provided them a safe haven to live in and rest their head at night knowing you did a good thing by passing on your wealth of knowledge!


Comments are closed.