What You Should Know About Central Humidifier Ratings

January 19, 2024

Our team at Save Home Heat Company installs plenty of central humidifiers for our customers in the Denver-Boulder metro area each year. The Denver area’s high altitude desert designation doesn’t seem likely to change anytime soon, and adding some humidity to the air inside our homes can often make a world of difference during the heating season.

Depending on factors that include the size and layout of the home, the level of need of the owner, budget, and even aspects such as solar gain – in addition to potential health concerns – we consistently install both standard, flow-thru humidifiers, as well as steam-powered units.

wooden path flanked by humid forest

When we quote a new central humidifier for a potential customer, there’s often a discussion of the evaporative ratings of the units we recommend. Therefore, to help increase our readers’ understanding of what we propose, in this post we’ll dive a little deeper into who creates these ratings and the factors that play a role in creating them. We’ll also touch base on the central humidifiers that are currently trending with our customers. Spoiler alert: the status quo continues to prevail – and that’s just fine with us!

Why Choose a Whole-Home Humidifier?

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Central humidifiers offer a range of benefits for homeowners. Here’s a quick overview of how achieving proper indoor humidity levels can have a positive impact in our region:

  • Help reduce dry skin and common respiratory ailments, including dry, itchy and teary eyes, scratchy throat, sinus issues, and more
  • Help decrease airborne dust, pet dander, and more
  • Reduce the viability of airborne viruses and bacteria
  • Diminish static electric shocks
  • Help protect wood furniture, flooring, handrails, wood trim, and other household wood products
  • Achieve equivalent comfort levels with the thermostat set at a lower temperature – help in controlling utility bills!

Evaporative Ratings 101

aprilaire humidifier drawing

When you’re exploring options for home humidifiers you will come across evaporative ratings for each unit. Understanding these numbers can help you decide which product is the best fit for your home. Products are independently tested and the ratings published by the Air Conditioning, Heating and Refrigeration Institute (AHRI), providing a professional, objective measurement of how much moisture (i.e. humidity) a humidifier is able to add to the indoor environment within a given period of time.

In addition to central humidifiers, AHRI performs independent testing for a broad range of home comfort products, with the stated goal to promote consistency in manufacturer specifications and help give consumers confidence in their purchases. As well as helping homeowners, this information also helps direct the decisions of regulators and agencies such as ENERGY STAR and others.

AHRI gallons-per-hour humidifier ratings

Humidifier evaporative ratings are referred to in terms of either gallons-per-hour (gph) or gallons-per-day (gpd). Most manufacturers of residential humidifiers currently present these numbers in terms of gallons-per-day, and published comparisons of residential humidifiers typically refer to GPD ratings.

The majority of standard residential central humidifiers have evaporative ratings between 10 GPD and 20 GPD. These are typically flow-thru models with either a bypass or an internal fan-assisted design. Steam-powered units, on the other hand – note: 220 volt models perform best and are most popular – are rated between 20 and 30 gallons per day, a significant upgrade in humidifying capability, as compared with the more basic, standard models.

AHRI humidifier testing procedures take into account multiple ‘average home’ factors, including:

  • Furnace and humidifier run-time per day
  • Incoming water temperature to the humidifier
  • Temperature of the air entering the humidifier
  • Airflow from the furnace or air handler, measured in cubic feet per minute (CFMs)
  • Water pressure supplying the humidifier
  • Static pressure (resistance to airflow) in the ducting system
  • And even more!

Of course, you may not live in an “average home” as defined by the AHRI for its testing purposes. Therefore, these numbers’ greatest value may lie in simply comparing the humidifying capability of one unit versus another.

Our Takeaway on Humidifier Ratings for the Denver-Boulder Area

Keeping it nice and simple, in our region, with our sunshine and our at times rapidly changing weather, when looking at standard flow-thru humidifiers, it often makes sense to select the option with the greater GPD evaporative ratings. More on that below when we look closer at the Aprilaire Model 600.

Regarding the higher performing, steam-powered humidifier option, there are absolutely cases this could be just ‘what the doctor ordered.’ See the Model 800, below.

Top Trending Humidifiers with our Customers

Aprilaire Logo - Feel Good Inside

The two central humidifiers that we install most often are manufactured by Aprilaire, aka. Research Products Corporation.

The Aprilaire Model 600: Our top performing standard humidifier

The Model 600 flow-thru, bypass humidifier from Aprilaire is our most popular central humidifier with the Denver-Boulder metro area homeowners our team serves. It has an evaporative rating of 17 GPD, very high for a standard unit, and uses virtually zero electricity. Airflow thru the Model 600 is provided by the furnace fan and a 6” sheet metal pipe that connects the duct-mounted humidifier to the furnace’s main return air duct. All of this is installed cleanly, accessible for service, immediately adjacent to the furnace.

Aprilaire 600 humidifier and thermostat

The Model 600 depends on heat produced by the furnace in order to do its job. Full disclosure: If the heat isn’t running on a regular basis, this type of humidifier may not be able to consistently meet the home’s demand for humidity. Regardless, standard central humidifiers have proven to be a great solution for many homeowners and are effective at raising and maintaining a home’s humidity when the furnace is running regularly. Due to the rapidly changing conditions we often experience in the Boulder-Denver area, we often recommend the highest capacity standard unit available, for best response and recovery. In this case, that’s the Aprilaire Model 600.

If it’s critical to maintain a consistent humidity level in the home (health issues, valuable investments, etc.), 24/7, then we often end up discussing the Model 800.

Aprilaire Model 800: High performance, steam-powered humidification

The Model 800 steam humidifier is a high capacity, high performance central humidifier that has its own internal heat source for producing water vapor to be circulated to the home thru the ducting system. It doesn’t require that the heat be running in order to do its job, and is designed to turn on the furnace fan to circulate humidified air to the home, whenever needed, regardless of heating demand.

This versatile, central steam-powered unit is rated to deliver up to 34.6 gallons-per-day of humidity. It’s the highest performing central humidifier our team offers, with approximately 75% greater humidifying ability than standard, flow-thru models. In addition to concerns such as potential medical conditions, the Model 800 is a good option for large homes that have one furnace and high humidity needs.

A word for planning sake, and more full disclosure: In addition to being appreciably more expensive to install than the Model 600, the Model 800 uses electricity to produce steam inside the unit. It’s impact on your utility bill will depend on a variety of factors. The 220 volt model uses electricity more efficiently and as alluded to above, has a higher evaporative rating than the 110 volt model. This is the steam unit most preferred by our customers.

High Quality Central Humidifiers in the Denver-Boulder Metro Area

While there are certainly a number of similarities to be found between different types of homes and homeowners in the Boulder-Denver metro area, it’s important to take the time to learn about what makes the most sense for your specific circumstances before making an investment in a central humidification system. Our team loves it when a prospective customer asks questions!

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To learn more about central humidifier options that make sense to consider for you and your home, please reach out to our home comfort team at Save Home Heat Company today to schedule a free, highly informative, low-pressure install quote.

Please contact me to schedule a central humidifier install quote!