Bypass Humidifiers

Bypass Humidifiers in Northern Virginia

There are multiple types of humidifiers on the market which are designed for different applications. Depending on the cubic footage of space that needs to be humidified, it is important to select the correct humidifier. Bypass humidifiers are one type of humidifier that can be installed to humidify your entire home.

If there is not enough space to mount a fan powered humidifier onto the supply duct or if the cubic footage of your home does not require the capacity of a steam humidifier, then a bypass humidifier would be a great solution. One of the advantages of installing a bypass humidifier is that the space required for mounting it is smaller. Bypass humidifiers are generally connected to the duct that returns the air back to the furnace or air handling equipment.

What type of bypass humidifiers do we recommend?

The bypass humidifiers we recommend are the flow-through style. What this means is that fresh water will flow through a special water panel inside the humidifier each time it comes on. The water that is not absorbed into the air stream as humidity will drain out so the water used to produce humidity will be fresh water. There are reservoir type humidifiers on the market also, however, that is not a style we neither install nor recommend because they are susceptible to bacteria growth since there is free standing water in the reservoir.

Determine how much humidity is needed

It is important to calculate the amount of humidity needed before choosing a bypass humidifier. These humidifiers are lesser capacity than fan powered humidifiers and significantly less capacity than steam humidifiers. If you install a humidifier that is too small, then it will not be able to keep up with humidity demands and would not be worth the investment.

Where is a bypass humidifier installed?

Bypass humidifier are most commonly installed on the return duct of your heating and air conditioning system but can also be installed on the supply duct. The humidifier relies on the force produced by the fan of the indoor unit to introduce humidity into the air stream. As this moist air is absorbed into the air stream, it is distributed through-out the living space.

A humidifier is only as good as it is installed

There are multiple manufacturers who manufacture bypass humidifiers and honestly, there a lot of good products to choose from. However, installing the best humidifier on the market incorrectly will result in poor performance. Although bypass humidifiers are less capacity, when sized and installed correctly, they are a great solution for areas of tight access or when there is not enough room on the supply duct to mount a humidifier.

What do we see done incorrectly

We have been doing this for a long time and too common we see bypass humidifiers installed incorrectly. Bypass humidifiers were designed by manufacturers to accommodate space restraints. We have seen bypass humidifiers wired incorrectly, bypass ducting connected incorrectly and the humidistats installed incorrectly to mention a few deficiencies that significantly affect the overall operation and performance of the humidifier.

Controlling the humidifier

Humidifiers come with a controller called a humidistat. Most of the controllers on the market are digital, however is it still common to see analog style humidistats. The humidistat is most commonly installed into the return duct which takes humidity level samples as the air passes back to the furnace or air handler. Many of the newer heating and air conditioning systems have thermostats with built in capabilities to control the humidifier automatically. This is a great feature that allows for optimal humidity control since the humidity readings are taken from the living space. Also, these thermostats are connected to an outdoor sensor that can regulate indoor humidity based off outside temperature. This also helps to keep the windows in the home from collecting moisture on the real cold days.


Bypass humidifiers need regular maintenance. There is a water panel inside the humidifier where the water will trickle down all season long. Although these water panels have a special coating on them, the minerals in tap water will eventually break down this coating so manufacturers recommend the water panel replaced on an annual basis. In some areas of harder water, these water panels may need to be replaced twice a year. Some humidifiers also have a plastic orifice which regulates the amount of water that flows through the humidifier. It is important to change this orifice annually because the minerals from tap water will gradually cause the opening of the orifice to enlarge, which would then cause a lot of water waste.

We service bypass humidifiers in Alexandria, Arlington, McLean, Fairfax, and all surrounding cities.

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Frequently Asked Questions

One company is offering me an air conditioner that they say is 15.5 seer and another company is offering the same air conditioner (same model #) and telling me it is 19 SEER....Who do I believe?

This is a common question we hear. If you look at the brochure for the proposed air conditioner, it probably states that the air conditioner can operate up to 19 SEER. Each split system cooling unit has a nominal SEER rating. The SEER rating of a system is derived based on the combination of equipment installed. The outdoor equipment (heat pump or air conditioner), as well as the indoor equipment (evaporator coil and furnace, or air handler), play a vital role in the rating. Ask your contractor to show you the data that shows what SEER you will actually achieve for your application.

Why should I install a humidifier?

There are many reasons to install a humidifier. One is to keep you from getting sick. Have you ever noticed that we tend to get sicker in the winter than in the summer? This is not because it is cold outside (actually there are fewer viruses in the winter than in the summer). This is a result of your body’s membranes drying and cracking which allows a direct channel for viruses to enter the bloodstream. Other reasons are to reduce dry itchy skin, static electricity and to protect wood, furnishings and musical instruments in your home. Also, by adding a humidifier, it allows you to remain comfortable at lower temperatures, which lowers your utility costs.