Picture this all-too-familiar situation: you’re in your living room and see that it’s snowing outside. You walk over to the window to admire the wonder of winter, when you notice your windows are sweating like they’ve just finished running a marathon. Is it time to replace your windows? Not so fast! Window condensation isn’t always a problem, necessarily. It is important to know what causes window condensation, how to fix it, and when it becomes a problem.
What Causes Indoor Window Condensation?
In short, humid indoor air + cold outdoor temperature = window condensation. Humidity is the amount of water vapor in the air, and when that warm, humid air meets your cool windows, condensation occurs. And, because homes are better sealed and thus more energy efficient and airtight than ever before, the water vapor doesn’t have anywhere to go to escape, and moisture gets trapped inside. Where does the moisture in the air come from? Well, from what you’re doing right now; breathing! It can also be produced or increased by cooking, doing laundry, running dishwashers, pets, plants, exercising, aquariums, brewing coffee, or having multiple people in a room/space at one time. And, your windows are not the only surfaces that will “sweat”. Mirrors, walls, ceilings, and doors can have condensation too, especially after somebody has taken a hot shower.
Where to get condensation proof windows
Well, there is good news and bad news. The bad news? There is no such thing as condensation proof windows. That’s because windows are not the cause of the condensation, they are simply keeping the heat and moisture from escaping your home. The good news? There are things you can do to reduce the chances of condensation in your home.
How to reduce indoor condensation
The EPA recommends that you keep your indoor humidity between 30-50% relative humidity to avoid indoor condensation. Most modern thermostats will tell you your humidity level. If not, you can purchase a humidity meter (hygrometer) online or in hardware stores. (This humidity meter is only $15 and has a five-star review on Amazon.) And, the recommended indoor humidity percentage level depends on the outdoor temperature. This is because the colder it is outside, the cooler the surface temperatures are, and the lower your humidity levels need to be. Remember, humid indoor air + cold outdoor temperature = window condensation! For your convenience, we created this temperature guide below. You can also download our Recommended Indoor Relative Humidity Guide to print out and keep next to your thermostat.
To control the humidity/moisture in your home:
- Open your curtains and blinds for more circulation around your windows
- Use kitchen and bathroom exhaust fans
- Vent clothes dryers, stoves, gas appliances, etc.
- Run a dehumidifier
- Set your humidifier (if you have one) according to the outside temperatures (see chart above)
When It’s A problem
- Condensation on the inside and outside of your window does not always indicate a problem. Condensation between the glass panes, however, means the seal has failed. If this is the case, its time to call a professional to evaluate the health of your window. While there are de-fogging services out there, this does not fix the broken seal, it only clears up the fog temporarily. Windows cannot be resealed. The only true way to fix the issue is to replace the window.
- A little condensation here and there shouldn’t be an issue, especially if is temporary, like during a crowded holiday house party when there is bound to be excess humidity. However, if your windows sweat often, even after taking steps (like the ones we listed above) to reduce the likelihood of condensation, or if they sweat so much and require a dry towel wipe down, this is a problem. That much moisture will lead to mold and decay, and its time to get a professional opinion.
If you are concerned about your indoor window condensation, or if you have questions about window condensation in the winter (or any season!), give Renewal By Andersen of Eastern Iowa a call, we would be happy to give you honest advice.