Understanding Condensation on Windows

February 11th 2011
Understanding Condensation on Windows

Condensation on windows is the most noticeable sign that you have excessive humidity levels in your home. A little condensation, now and then is to be expected but high humidity often causes consistently foggy windows that should be addressed.

Water condensation is a natural occurrence on all surfaces in the home when moisture levels are too high. Inefficient windows (i.e. single pane with aluminum frames) or inadequate ventilation can result in condensation, frost, or pools of water on windows and sills. When water vapor comes in contact with a surface which has a cooler temperature such as windows, the vapor turns into visible droplets of moisture, which can be seen on the glass. This water vapor also adheres to the walls, which can be a more serious problem because it can penetrate walls and constant excess moisture can lead to mold, mildew, and deterioration of your drywall.

Humidity in your home comes from everyday living; steamy showers, boiling water, dishwashers, washing machines, dryers, wet and snowy boots and clothing, and many other sources. Poorly insulated crawl spaces can increase the humidity in your home often resulting in a musty odor.

It's important to remember that there is no such thing as a condensation free window and windows themselves do not cause condensation, they simply prevent moisture from escaping to the outside. Seeing condensation build-up on your window signals that steps need to be taken to reduce the moisture in the air inside your home:

- Regularly use ventilation fans in kitchens, bathrooms and laundry rooms to circulate the air.
- Ceiling fans can also help circulate the air.

- Squeegee your tub surround and shower enclosure, then use your towel to dry off the excess moisture and leave your bathroom ventilation fan on for at least 1 hour after every shower.
- Open interior doors and windows to circulate airflow.
- If you have a humidifier or dehumidistat set them to the correct outside temperature settings.
- Make sure you have adequate ventilation through your soffits, roof ridge, basement and crawl space.
- Install energy efficient windows.
- Your blinds and curtains can prevent air movement around your windows.  Keep your curtains and blinds open as much a possible to allow the air to move freely around your windows.

Your House as a System

New Energy Efficient Windows:

Sometimes homeowners will notice more condensation when they install new energy efficient windows. That's because their old windows were probably drafty and the moisture was escaping through small air gaps. Once the home is tightened up with more energy efficient windows the humidity is trapped in the house and doesn't escape through the cracks. However, the energy-efficient replacement windows are far better for energy efficiency and comfort than drafty windows. It just means that homeowners need to be more aware of properly ventilating their homes.

Installing a New Furnace

Condensation issues can also arise when upgrading to a higher efficiency heating system or a high effiiciency furnace. Changing one item can cause issues elsewhere if your home's ventilation is not adjusted, resulting in excess moisture and condensation problems as seen on your windows.

Upgrading to a high efficiency furnace is a wise choice that will save money on your energy bills. When installing a new furnace, Shell Busey recommends purchasing a high efficiency unit with a 2 stage burner and a variable speed DC motor installed by a reputable company who will determine the best high efficiency system for your home. Click here to find a Heating and Air Conditioning in your area.

Always think of your house as a system keeping in mind that one reason you're seeing these changes in your home after your upgrades is your new high efficient heating system operates differently than your old furnace. For example, your old furnace would draw air from inside the home for combustion, but the new high efficient units have their own supply line that go into the combustion chamber and is exhausted outside through their own vent pipe (plastic).

Exhaust ventilation has to be provided to accommodate increased relative humidity in the home otherwise high humidity may be the outcome.

Relative Humidity Settings

Moisture levels must be controlled within the home. The following settings are recommended:

Outside Air Temperature/Inside Humidity Setting

Summer Temperature = 50%

  0  to -12oC 40%
-12 to -18oC 35%
-19 to -24oC 25%
-25 to -30oC 20%
-31 or below 15%

Another great solution to humidity that also improves the air quality within your home is by installing a heat recovery ventilation system (HRV.) These units are designed to provide an energy efficient way to bring in fresh filtered air while removing stale air. For more information on HRV's, contact Lifebreath by going to their website at www.lifebreath.com or contact Shell Busey's HouseSmart Referral Network office directly at 604-542-2236 or toll-free 1-888-266-8806.