Condensation on your windows can be an annoying surprise—especially in a brand-new home. Many homeowners worry that foggy or "sweaty" windows signal a defect, but in most cases, the windows are doing their job. They’re acting as a messenger, letting you know it’s time to take a closer look at your home’s humidity levels.
In this article, we’ll walk through common questions about condensation, how to manage indoor humidity, and what to watch for to protect your home from moisture-related damage.
Energy-efficient homes are built more airtight than ever. But in addition to sealing in warmth and air conditioning, they also tend to hold in too much moisture filled air. If your home contains excessive moisture and it’s cold outside, the first place you’ll see it is on your windows.
You may think this means there’s a problem with your windows, but there’s not. In fact, the vast majority of window condensation problems are not the result of faulty windows. The windows are just indicating that your home needs added ventilation to lower the amount of moisture in the air.
An occasional bead of moisture on the glass of your windows usually isn’t a problem. For example, it’s likely your bathroom mirror and windows will steam up after a hot shower. Or your kitchen window may fog up when you’re boiling food on the stove. But in both these cases, the moisture clears in a matter of minutes. However, if your windows are “sweating” at other times – or stay that way for any length of time – you probably do have a problem.
Although the glass itself may not be affected, dripping condensation and excess moisture can not only damage your windows but potentially your entire home.d
That’s why it’s important to reduce excess indoor humidity before it becomes a bigger problem.
Moisture inside your home comes from a surprising number of everyday activities:
Fun Fact: A family of four can generate up to 18 gallons of water per week just from daily living.
The key to managing condensation is balancing moisture and ventilation. Here’s how you can reduce excess humidity:
You’ve probably heard that your home will feel warmer in the winter if the humidity is higher. That’s true, and why many people use humidifiers to counteract dry, static-filled air during the heating season. In older homes excess moisture usually isn’t a problem because the structure “breathes” through unsealed cracks and crannies in the construction, creating a regular exchange of outdoor and indoor air. That’s why it is often a struggle to keep enough moisture inside older homes.
But with today’s modern construction techniques, homes are much tighter and energy-efficient. As a result, newer homes don’t usually need a way to add moisture – they’re more likely to have trouble getting rid of it.
So how much humidity is enough to keep us comfortable without dampening our surroundings? Refer to the following guide for temperature and humidity levels that are generally considered comfortable. Below are general guidelines for indoor humidity based on the outdoor temperature:
Note: Sustainable 9 leaves a humidistat in every home we build to help monitor these levels. If you don’t have one, reach out to us or check Amazon—affordable options are available. We recommend placing one on each level of your home.
Relative humidity is a measure of the amount of water vapor in the air compared to the maximum amount possible at a given temperature.
Here are some additional actions that may help reduce excessive humidity levels:
If moisture problems still persist, talk to a HVAC professional or your gas or electric company. They may have additional suggestions for reducing humidity, including venting gas-burning heaters and appliances, adding ventilation fans or getting an air-makeup unit for your furnace which takes outside air and warms it up.
Sometimes, condensation is just temporary. Two common causes include:
In both cases, you’ll see less condensation over time.
As building experts often point out, windows should not be blamed for condensation. They merely are an indicator of too much moisture in the air. In the unlikely event you see condensation between the panes of glass in an insulating window, contact the manufacturer of your window. Moisture between the two panes of glass means that the seals in your glass have failed.
Condensation is often misunderstood, but managing it is all about keeping indoor humidity in check. A little awareness—and a few ventilation upgrades—can go a long way in keeping your home comfortable, efficient, and healthy.
Got questions about humidity in your home? We’re here to help.
