EFCO Special Purpose Windows General Maintenance Instructions - Manual (Page 15)

 Heat loss to the night air and sky cools outside of window.
 Less energy efficient windows allow heat from inside the
building to warm up exterior surface of window.
 Condensation does not appear because the temperature
of the exterior surface of window is above the dew point.
General Service and Maintenance Manual
SECTION 5
CONDENSATION
5.a. ABOUT CONDENSATION:
Exterior Condensation:
Exterior condensation generally occurs in the summer months. It is caused by three main conditions: high outdoor hu-
midity, little or no wind and a clear night sky. It forms in the same way as roomside condensation when the temperature
of the window is cooled below the dew point of the outside air (as opposed to inside air in roomside condensation).
To combat exterior condensation, open window coverings at night to warm up exterior glass and remove or trim shrub-
bery near windows or doors to promote air circulation. Increasing the air conditioner setting by a couple of degrees
warmer might also help.
Condensation Between Glass:
Condensation between two pieces of insulated glass is not controllable and is an indication of glass seal failure.
Contact your local EFCO sales representative or EFCO Corporation.
Effects of Condensation:
Higher interior humidity can lead to structural damage to the building and health hazards. Because these effects
frequently occur unseen in wall cavities, drops ceilings, and crawl spaces, the visible signs of condensation on the
window is a good clue that humidity levels are too high.
Problems such as window condensation and musty odor are nuisances, while others can be more serious such as water
stains on walls and ceilings or structural damage. The important thing to remember is that the windows are trying to tell
you to reduce indoor humidity before it causes unseen, costly problems elsewhere in the building.
EFCO CORPORATION 2013 PAGE 14
High Performance Insulated Glass
w/ Low-E coating and Argon infill Standard Clear Insulated Glass
Interior Interior Exterior
Exterior
Air Temp: 50 ̊ F
Dew Point: 48 ̊ F
Temp of
Ext. Surface
of Window: 47 ̊ F
Interior Air
Temp: 70 ̊ F
 Heat loss to the night air and sky cools outside glass.
 Energy efficient windows keep heat inside the building
so exterior surface of window stays cool.
 Condensation appears because exterior window tem-
perature is below the dew point.
Interior Air
Temp: 70 ̊ F
Air Temp: 50 ̊ F
Dew Point: 48 ̊ F
Temp of
Ext. Surface
of Window: 55 ̊ F