Frequently Asked Questions (FAQs)


I’ve noticed condensation (fog, moisture or sweating) on the inside of my windows during colder months. Is it true that’s because my vinyl windows are super-efficient?

Yes. Condensation is caused by household humidity. That fog or moisture you see occurs when humid air comes in contact with a surface that is cooler than the air. This happens most often in winter months when your doors and windows are kept closed, hence holding in the moisture-filled air. A thin film of dew or frost on your windows is normal and will not damage them. However, if you see excessive condensation such as beads of water flowing down your windows or walls – that’s a sign of too much household humidity.

How can I reduce the level of humidity in my home to combat condensation?

There are many sources of household humidity. The humidity that leads to condensation results from everyday life: taking showers, boiling water on the stove, etc. Humidifiers, water pans on radiators or wood stoves, kerosene heaters, drying laundry and house plants also contribute to household humidity.

The construction of your home – the kind and amount of ventilation, the presence or absence of a basement – even the soil type and drainage patterns of the land on which it is built can add humidity as well. In many cases, you can reduce humidity simply by being aware of the sources and reducing your daily use – for example, boil less and bake more when cooking and take shorter showers.

Here are more ideas for reducing humidity in your home:

  1. When using bathrooms, the kitchen or laundry room, turn on any built-in fans.
  2. Install an exhaust fan in your attic to draw moist air out of your home.
  3. Use a dehumidifier. And discontinue the use of any humidifiers or the placement of water pans on your radiators or wood stove.
  4. Open a door or window for a few minutes every day to air out your home. You can also open fireplace dampers and basement or attic louvers.
  5. During cold months, move your house plants to a sunroom or seldom-used room.
  6. Waterproof your basement floors and walls using a moisture-sealing paint available at most hardware stores.

If your home still has excessive humidity issues after you’ve tried the above steps, you may have a more serious problem. Talk to a professional such as your architect or heating contractor for assistance. 

What does condensation on the outside of my vinyl windows mean? Is there something wrong with my windows?

Nothing is wrong with your windows. The presence of moisture on the outside of your windows indicates that a specific set of atmospheric conditions exists and that the insulating glass is indeed doing its job – that of insulating your home from the environment. In this case, that insulation capability is what retards the flow of building heat through the glass and prevents warming of the exterior above the dew point.

Though there’s little to nothing you can do to prevent exterior condensation, you can try keeping draperies open to allow as much heat transfer through the glass as possible. Shrubs near windows can increase the humidity in that area and may need to be moved. 


What is design pressure? Performance grade?

Design Pressure (DP)
According to the American Architectural Manufacturers Association (AAMA), DP is a rating that identifies the load induced by wind or other dynamic pressures. The higher a DP rating, the more resistant it is to the effects of wind and other pressures.

Performance Grade (PG)
A numeric designation that defines the performance of a product in accordance with AAMA standards. PG is determined upon successful completion and verification of all applicable tests (air, water, structure).


Are there additional tests beside air, water and structure that hurricane window undergo?

Yes. To be a certified hurricane window, the window must pass an impact test. The test window is impacted by a “missile” (Viwinco uses a 9-lb. 2x4) and then subjected to 4,500 positive and 4,500 negative static pressure differentials. As part of the certification test, wind speeds 1.5 times the associated DP are cycled to ensure the window will meet greater wind loads.