5 Best Boiler Humidifiers

Honeywell HE360A


If you live in a dry climate, you’re probably aware of the irritating effects of regularly breathing dry air – it can cause permanent itching of the nose and throat and even contribute to respiratory infections. While you can add moisture to the air by installing small humidifiers in your home, a better solution is to opt for a whole-house humidifier. The best furnace humidifier is installed directly into your home’s HVAC heating system to add moisture to the air that is heated and circulated through your home.

To help you find the best boiler humidifier, we have analysed some of the key features of these units. Firstly, we’ve looked at the type of unit – bypass or fan-assisted – which has a significant impact on the effectiveness and price of the humidifier. We also looked at the size of the home each humidifier is designed for and the maximum moisture output per day, which you should consider based on the size of your home. Finally, we looked at the size of each unit, as it must fit in the often cramped space of the boiler room.

We spent dozens of hours reading the technical specifications and customer reviews of the most popular oven humidifiers. The result is our list of the top five furnace humidifiers for every household and budget, shown in the table below. Read on for detailed reviews of each furnace humidifier, with pros and cons. Our buying guide covers everything you need to know about choosing the right furnace humidifier for your home. Finally, we summarise our three favourite humidifiers on the market today.

GeneralAire 1000A Humidifier

Users love this fan humidifier from GeneralAire, which offers excellent performance for mid-sized homes up to 3,000 square feet. The unit humidifies up to 18 gallons per day when your heater is running at full capacity, which is in line with humidifiers designed for homes with an additional 1,000 square feet to humidify – so you’ll notice the difference in your air immediately.

Users have found the humidifier to be extremely easy to install as it comes with everything you need to get it working. The instructions also provide details on wiring the humidifier as it only requires 24V instead of 120V – GeneralAire offers an additional 24V sensing relay kit which many users chose to purchase during installation.

The humidifier does make some fan noise when running at full power – usually when the heater is turned up – but most users have not found this to be a problem. The humidifier also has an automatic mode with a temperature compensation control that allows the humidifier to be set and forgotten.

Another significant benefit of this unit is that it comes with a 10-year warranty, the longest of any humidifier we reviewed. However, note that GeneralAire strongly recommends installation by a contractor to avoid voiding the warranty. Users have reported no problems with the humidifier breaking down in the first few years of use, and many have commented positively on the GeneralAire customer service team.

Best Boiler Humidifiers

fan powered

3000 square feet

18 gallons/day

14.75 x 16 x 10 inches

4 pounds

Limited to 10 years

automatic mode with outdoor sensor for temperature compensation; built-in bypass damper for humidity control

Aprilaire 700

Users in large homes have loved this fan oven humidifier from Aprilaire, which can cover up to 4,200 square feet and produce up to 18 gallons of water per day. The humidifier has both manual and fully automatic controls, making it suitable for people who want to save energy and water in manual mode and for those who want to set the unit and forget about it. Users have found that the automatic digital controller works exceptionally well, while the manual mode provides service, temperature and relative humidity indicators so you can adjust the humidifier output accordingly. Many users have reported that they could feel the difference in the air in their home within days of turning on the humidifier.

The unit is quite large, which can make it difficult to install in narrow ducts around the boiler itself, so be sure to check if you will have room to install it. In addition, users have found that this humidifier is much less designed to be installed as a DIY project, and Aprilaire strongly recommends using an HVAC contractor for the installation, which adds several hundred dollars to the price. The humidifier also doesn’t come with a 24V wall plug transformer, so you’ll need to purchase one to ensure proper operation.

Best Boiler Humidifiers

Aprilaire offers a five-year limited warranty on this controller, although users report no durability issues over that time.

fan powered

4,200 sq. ft.

18 gallons/day

16 x 11 x 18 inches

8 pounds

Limited to 5 years

offers manual mode service, temperature and relative humidity indicators as well as

Honeywell HE300A1005

This humidifier is a great choice for homeowners who want to maintain consistent humidity in their home with Honeywell’s HumidiPRO digital humidity control. The controller requires no manual intervention, so you don’t have to think about the humidifier throughout the day, but it modulates the water intake of the unit to maintain constant humidity when your furnace turns on and off. The humidifier also works well for larger homes and is designed for 4,000 square feet of coverage, using up to 18 gallons per day when the heater is running at full capacity.

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Users have found this humidifier to be easy to install themselves and it comes with detailed instructions. However, customers note that while the humidifier can be connected to either a hot or cold water line, it is much more efficient when using hot water – which means it can significantly increase your energy bill. In addition, this humidifier is a little larger than other options, which can make it difficult to install in narrow ducts directly above the boiler. If this is a problem for you, it can also be installed on return air ducts, but the effectiveness of the humidifier will be reduced as the air will be colder.

Honeywell offers a five-year warranty on this humidifier and, unlike the other Honeywell unit we reviewed, this model does not appear to have any problems with circuit failure over time.

Coverage area

4000 square feet

18 gallons/day

15.5 x 16.8 x 10.3 inches

16.2 lbs

Limited to 5 years

includes HumidiPRO digital humidity controller

Aprilaire 600

This Aprilaire bypass boiler humidifier is a great option for those on a budget who do not need the high performance offered by a fan humidifier. Even without a fan, this humidifier is capable of adding 16.8 gallons of water per day to your air when your furnace is running at full capacity. It is designed to provide enough humidity to cover a 4,000 square foot home.

Users have appreciated the controls on this humidifier, which allow you to set either a constant program or a seven-day schedule to change the humidity settings for each day of the week – perfect if you’re away from home for work most of the week and want to save water and energy. If the humidifier hasn’t been running for a while, it uses an internal blower to sample the air and can then trigger humidification if the air is below a set humidity level. Best of all, your settings won’t be lost in the event of a power failure, as an internal battery allows the humidifier to retain a permanent memory. Although buyers have found that the humidifier uses a surprisingly large amount of water, most don’t mind given the improved air quality in the home.

Best Boiler Humidifiers

Installation is not intended for non-professionals, although many users have found that they can do it themselves by going to the hardware store. However, be careful not to void Aprilaire’s five-year warranty on the humidifier by installing it yourself without the help of an HVAC technician.


4,000 square feet

16.8 gallons/day

15 x 10 x 16 inches

11 lbs.

Limited to 5 years

permanent memory – programming, time and date are not lost during a power failure

Honeywell HE360A

Users have enjoyed the performance of this Honeywell fan furnace humidifier, which boasts a massive 4,200 square feet of coverage. The unit is very simple, with few of the digital controls and programming that other humidifiers offer, which is ideal for those who want to set the humidifier and forget about it until it’s time to change the filter a year later. Users have found that the humidifier works well throughout the house, never letting the humidity drop below 10-15%, even on the coldest, driest winter days.

Installation of the humidifier is relatively simple, but note that you will need to purchase an additional installation kit from Honeywell. Users have also appreciated the low-flow design of this humidifier, which allows it to protrude only about half an inch into the ductwork – making it a good option if you have a small duct area in the boiler room. In addition, the unit can be installed right above the furnace or almost anywhere in your duct system if you have a forced air supply.

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Some users have noted that the life of this humidifier is relatively limited, which may explain why Honeywell only offers a one-year warranty. Users have found that both the water supply solenoid and the circuit board are prone to burn out, likely due to poor interior construction that allows them to get wet over time. You should therefore plan to replace the solenoid and potentially the whole unit after about five years of regular use. Be aware that buyers have also reported problems with Honeywell customer service when trying to activate the one-year warranty.

Honeywell HE360A
  • fan-powered
  • 4200 ft.
  • not specified
  • 14 x 15.25 x 10.25 inches
  • 18.5 lbs
  • Limited to 1 year
  • mounted on the supply or return duct of any forced-air furnace

How do oven humidifiers work?

You may want to install a humidifier for a number of reasons. Some people buy humidifiers to relieve asthma and coughs, others desperately surf the net looking for the best humidifier for sinus problems. Whatever your reason, an oven humidifier is an effective solution for the whole house.

There are several types of furnace humidifiers, all of which work in different ways to produce steam and circulate it through your HVAC ducts. The main types of furnace humidifiers are evaporative (fan-driven) and bypass humidifiers.

Evaporative, or fan-powered, humidifiers simply expose the warm air produced by your furnace to a slow but steady stream of water. The warm air naturally evaporates some of the water as it passes through, gradually increasing the humidity of the air circulating through your ducts. Evaporative humidifiers are by far the most common type of boiler humidifier, as they are inexpensive to install and require very little maintenance other than changing the filter once a year or so.

Bypass humidifiers are cheaper; they are entirely dependent on your heating system as they do not have their own fan or steam generator. The airflow simply passes through the humidifier’s evaporation pad, allowing the humidity to be distributed throughout the house.

Features to consider when choosing a furnace humidifier

Not all furnace humidifiers are designed the same way or for the same types of homes. In this section, we’ll discuss the key features you need to know to help you choose the right furnace humidifier for your home.


One of the most important decisions you need to make when choosing a furnace humidifier is whether to choose a fan or bypass model. Fan humidifiers, as the name implies, have a fan that pushes air through the humidifier, while bypass humidifiers, like Aprilaire’s model, do not have a fan.

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This may not sound like much, but constant air movement allows more water to evaporate, which means the humidifier can operate more efficiently and produce much more moisture per day than a bypass system without a fan. Fan assisted humidifiers can also be used when the boiler is not on, as they do not rely on hot air convection.

However, fan humidifiers tend to be more expensive than bypass systems, and for this reason the latter are more common. In addition, because there is no fan, bypass humidifiers do not make noise and there are fewer moving parts that can break and require maintenance.

Coverage area

The coverage area is usually measured in square feet and describes the size of the house for which a furnace humidifier is designed. If a humidifier is installed in a home that is too large – for example, if the GeneralAire humidifier is installed in a home that is larger than 4,000 square feet – the air will not be sufficiently humidified to ensure comfort. On the other hand, having a humidifier with a massive coverage area for a small house is overkill and a waste of water and electricity. If your home is very small or if you don’t need it fully humidified, consider getting a powerful humidifier for larger rooms.

Best Boiler Humidifiers

Maximum daily output

The maximum daily output describes the amount of water that can be evaporated from your heated air over a 24-hour period when the humidifier is operating at full capacity. This flow rate is directly related to the rated coverage area of each humidifier, although there are variations between manufacturers. In general, a flow rate of 16 gallons of water per day or more is sufficient to cover most homes of 3,000 to 4,000 square feet.

Weight and Size

The weight and size of your humidifier can be an important factor if you need to place it in a cramped boiler room or if you need to transport it to a basement or attic. For example, if your boiler room is very small, you may want to consider a smaller boiler humidifier, such as this Honeywell unit.


An oven humidifier is one of those home investments that you only want to buy once and then forget about because it works so smoothly – so having a good manufacturer’s warranty can be necessary for your peace of mind. Many manufacturers offer five-year warranties, while <https://www.amazon.com/dp/B000WCL6R2/?tag=wisepick-20″> GeneralAire offers an impressive 10-year warranty on its oven humidifier.

Additional features

There are a number of other minor considerations when choosing a furnace humidifier. For example, some humidifiers, such as Honeywell’s, have automatic controls that turn on and off based on temperature and humidity, as well as programming features that allow you to set the levels at which they turn on and off.

For fan-driven boiler humidifiers, fan noise may also be a consideration – although this may not be as important to you as other features if your humidifier is installed in a basement boiler room.

Our verdict

Our three favourite boiler humidifiers on the market today are the GeneralAire 1000A, the Aprilaire 700 and the Honeywell HE300A1005.

Both the Aprilaire and Honeywell humidifiers are designed for homes of 4,000 square feet or more, making them perfect for families with multiple rooms to humidify, although both can be bulky to install in narrow vents. The Aprilaire unit comes with both manual and automatic controls, while we think the Honeywell unit’s HumidiPRO digital controller is one of the best automatic humidifier controls you can get to set the humidifier and forget it.

We consider the GeneralAire humidifier to be the best boiler humidifier you can get, especially if your home is no larger than 3,000 square feet, thanks to its impressive 18 gallons per day output over that area, the ease with which anyone can install the unit on their own, and the manufacturer’s 10-year warranty.

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