Condensation occurs when the temperature of the air drops to the point where humidity becomes liquid, known as the dew point. Condensation forms on windows when the surface of the glass becomes cold, forcing the humidity to convert to liquid water. The actual temperature of the dew point depends on the amount of humidity in the air. The colder the temperature and greater the humidity, the more likely condensation will form.
Condensation Resistance (CR) is the term for measuring how well a window resists the formation of condensation on the inside surface. CR is expressed as a number between 1 and 100. The rating value is based on interior surface temperatures at 30%, 50%, and 70% indoor relative humidity for a given outside air temperature of 0° Fahrenheit under 15 mph wind conditions. The higher the number, the better the window is able to resist condensation.
Thermolite contracted an independent lab company to measure the CR of our RetroWAL Silver and RetroWAL Gold interior window systems. The prime test windows were fixed, 4-sided curtain wall lites with aluminum non-thermally broken frames. The test reports concluded that the existing curtain wall window performed at a CR 13 rating, which means condensation builds easily. Thermolite’s RetroWAL Silver Series improved the CR factor to 56, and the RetroWAL Gold Series improved the CR factor to 68.
We routinely see this type of CR improvement in our window systems – especially during cold snowy weather when condensation forms easily. For example, during the Polar Vortex in February when the temperature dropped to more than 20 degrees below zero, Thermolite windows installed at 625 N. Michigan St. in Chicago had significantly less condensation than those in the same building that were not retrofitted with Thermolite storm windows.
Condensation is an important concern to consider when upgrading the windows in your building. While Thermolite interior window systems do not eliminate condensation completely, our windows never cause condensation and, on the contrary, have been laboratory proven to significantly decrease condensation by improving the CR factor.
Thermolite takes condensation seriously and has numerous independent test reports to show how our windows systems perform in various applications. Contact us today to learn more about how Thermolite interior window retrofits can help reduce condensation in your building.