Winter Cold



Through a process called convection, warm air will always move toward colder air, meaning that during the winter the air inside your home is always trying to escape the house and move toward the cold air outside. Warm air also expands, and therefore has the capacity to hold more moisture than cold air — moisture that is picked up naturally from inside your house. As the air cools, it contracts and loses some of its capacity, so the moisture is given off to cooler surrounding surfaces… YOUR SLIDING PATIO DOOR.

Learn more with Understanding Condensation (PDF)


1. High Humidity

Reduce the setting on your humidistat to 20-30° instead of 40-50°. Increase setting slightly if static electricity becomes a problem.

2. High Temperatures

The warmer the air, the more moisture it holds. Keeping your home slightly cooler in winter will reduce condensation and frost.

3. Thermopane Seal Lost

If the atmosphere between your panes of glass has been compromised, clarity and resistance to temperature will be negatively affected. Glass replacement is necessary.

4. Air Circulation

Poor air circulation near interior glass surface.

5. Northern Exposure

Southern exposure enjoys warm solar gain in winter. An obstruction on your patio could block sunshine.

6. Aluminum Frame

Wood is a better insulator than aluminum.

7. Door Seal

Weatherstripping is worn or missing. Door may be out of alignment allowing a draft. Door does not lock tightly.

8. Nothing’s Wrong

Even when all is right the 50+ square feet of patio door glass is colder in the winter than your walls. And, since cold air is heavier than warm air, the temperature at the floor near the door will be colder as the air naturally cascades down the glass. This seems to be noticed more in kitchen areas where owners can often be found in bare feet or wearing slippers.

Call us for a complimentary DVD about “Controlling Indoor Condensation”