Condensation is the result of water vapor in the air dropping in temperature and becoming liquid water, the phase that is known as the water’s dew point. This accumulation of liquid water can be problematic indoors, such as on window surfaces, and is the result of cold temperatures preventing the water from evaporating and instead building up. Windows are especially vulnerable to condensation because of the heat loss that often occurs within window frames and glass.
Variables that contribute to window condensation:
- Temperature – Exterior temperature (this variable can’t be controlled for obvious reasons) and interior temperature (warmer room temperatures cause liquid water to evaporate and revert back to its vapor state and eradicate condensation, while cold temperatures in the room allow the buildup of condensation and even possibly ice.)
- Interior humidity – humidity is the amount of water vapor in the air; therefore, the higher the humidity level, the more opportunity for condensation to form on colder window surfaces.
- Thermal performance of the windows – a higher insulating value of windows can maintain the temperature in the room to prevent water vapor from reaching the dew point and becoming condensation.
Causes of excess window condensation:
- Window glass with a low U value (measures insulation and heat transfer abilities)
- Window frames with air leakage
Problems with excess window condensation can be prevented by selecting windows best equipped for Condensation Resistance (CR), a rating by the National Fenestration Rating Council (NFRC). CR is calculated by the performance of factors, such as thermal conductivity and airflow resistance, which are determined through simulations in various temperature and humidity levels. The score ranges from 0 to 100, with anything above 50 being considered optimal by the NFRC.
Thermolite’s interior curtain wall retrofit systems are designed to prevent the buildup of condensation – a basic curtain wall piece of glass fitted with our RetroWAL™ Silver Series has a CR score of 56, while our RetroWAL™ Gold Series features a CR of 68. In comparison, a basic curtain wall alone has a CR score of just 15. (Request to view reports of findings in entirety.)
Interior windows and condensation reduction:
Thermolite’s interior curtain wall retrofit system is a window system that installs on the interior of existing windows. This allows for the improvement in performance of current exterior windows without the need for altering or replacement. By fitting existing windows with our window systems, condensation is reduced because of the improvement in the current window’s U-value due to our glass’s double or triple glazing. Interior windows also reduce the air infiltration that is counterproductive to insulating efforts.
Window condensation is not simply a nuisance. If it is not addressed, the accumulated moisture can cause significant damage to window frames. In worst case scenarios, extreme condensation can leak into the wall cavity and result in mold or structural decay. Contact Thermolite today to learn more about how our affordable interior window systems are a quick and non-disruptive way to prevent condensation problems.
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The Thermolite engineering staff is an innovative structural, energy modelling, and implementation team that works to create unique window systems alternatives to traditional replacement windows. Our systems protect against blasts, hurricanes, and sound, while being energy efficient and quick and easy to install. We serve a wide range of industry buildings including government, military, historical, schools and universities, financial, health care, hospitality, and offices. Contact us today to learn how we could update your building’s window systems.
Chicago Window Expert – http://chicagowindowexpert.com/2010/12/09/top-10-causes-of-window-condensation/
National Fenestration Rating Council – http://www.nfrc.org/WindowRatings/
Minnesota Sustainable Housing Initiative – http://www.mnshi.umn.edu/kb/scale/condensationresistance.html