What is the Best Humidity Level in Winter?

couple sitting on couch smiling

The healthy recommended indoor temperature is 18 – 21°C in winter. But what’s the best humidity level?

The Best Humidity Level in Winter Is…

We can’t give you one number, because it depends on the temperature, both inside and outside your home. But we can give you a range: between 30-40%.

It’s really important to adjust this number so you don’t get condensation on your windows…or you could damage your home and be in for some very expensive repairs.

To understand why, you first have to understand that humidity is the percentage of water vapour in the air. Then, you need to learn about condensation.

How Condensation Works…and How It Can Damage Your Home

When warm, moist air meets cold objects you get condensation. Think about enjoying a cold drink outside on a hot summer day. After a few minutes, the glass looks like it’s covered in sweat because the water from the warm air sticks to the glass.

The same thing can happen on the inside surface of your windows on a cold day, if your windows aren’t very energy efficient (think of single pane windows, or dual pane windows in which the seal between the two panes is broken). The windows get cold because they lose heat to the outside environment. The air inside your home is warm, so moisture wants to collect on the cold window.

It’s something you might not see if the temperature is close to zero, but if it drops to a colder temperature, the effect begins, and you can see condensation or (if the window is cold enough) frost.

A Balancing Act

Normally in winter, the air is so much drier inside our homes. That’s because the fire in the furnace dries the air out, literally burning the water vapour right out of it.

That’s why we use a furnace humidifier to prevent our homes from becoming too dry. Air that’s too dry can cause wood to shrink and crack, and can make your family’s eyes, throats, hair and skin dry too.

BUT… when condensation forms, it’s a sign you’re setting the humidity level too high.

How Condensation Leads to Damage

If the humidity builds up too much, condensation on the windows can eventually bead up and roll down until it soaks into the window frame. From there, it can leak into the wall below the window, leading to mold and wood rot. These are expensive problems to fix, especially if they become serious over time.

If you do see condensation on your windows, try adjusting your humidifier so your humidity level is lower. This should fix the problem, and you should see results in a short amount of time.

If it doesn’t, this could mean you have a ventilation problem, and you should contact us about your options.

Why? Most homes now are built to be airtight in the effort to save heat, but an unintended side effect is that humidity can’t escape. A ventilator system that retains heat but allows humidity out and fresh air in might be the right answer. These are called heat recovery ventilators, or HRVs.

These systems work so well that, as of January 2017, the Ontario Building Code requires new homes to have HRVs.

Other Problems with High Humidity Levels

Along with wood rot and mold, high humidity levels can lead to:

  • Respiratory issues
  • Aggravated allergies
  • Problems sleeping

Humidity is something you have to get right: not too much, not too little.

Other Factors That Affect Humidity Levels in Winter

No two families and their homes are the same, and there are a wide variety of factors that will impact your humidity level.

Besides ventilation and your humidifier setting, there’s also:

  • Your insulation: air leaking in and out of your house can change the climate inside.
  • Your daily routine: through activities like showering and cooking, we generate moisture. The more moisture you and your family generate, the higher your home’s humidity level will be.
  • Your climate: this one is pretty self-explanatory. Depending on the season the naturally occurring humidity levels will change. While most homes are well-sealed against outdoor elements, if you have any insulation problems or drafts, air entering your home will impact both the temperature and your humidity levels.

Different people have different comfort levels. While 30-40% is a good baseline for humidity levels in winter, you’ll have to go through a period of adjusting temperatures and your humidifier to find your perfect setting. But once you do, there’s no better feeling!

How Do I Know What My Humidity Level Is?

The best way to determine your home’s humidity level is to use a hygrometer.

A hygrometer (hy·grom·e·ter) is a tool specifically designed to measure the water vapour content of the air.

Hygrometers can be purchased at your local hardware store, and range from $10 and up.

Do You Need a Furnace Humidifier? Come to Us!

Does your home need some help to achieve the right indoor humidity levels?

At Dr. HVAC we carry a range of furnace humidifiers that will work with any make or model of furnace. Our home comfort specialists can take you through each one and find the perfect fit for your home and your budget.

Learn More About Humidifiers