by xjr328 »
Thu Aug 13, 2009 11:26 pm
Pressure equalisation of sealed units is a achieved by drilling into the units either through the glass or through the spacer bar, the holes are then screened using a micro screen that allows air to enter the unit and filter out water droplets and dust etc, to understabd why a sealed unit distorts is very simple, the air molocules trapped between the two panes of glass react to temperature changes (atmospheric pressure (AP)), the air molocules vibrate on a hot day and rise this causes the pressure inside the unit to rise and the glass unit will start to swell in the centre causing the visual distortion. the opposite happens in cold weather when the air molocules cool down and shrink causing the centre of the unit to pull inward.
Pressure equalising the unit stops this thermal pumping, thermal pumping is the main reason all sealed units fail, it is this constant expansion and contraction of the glass that causes the primary and secondary seals on IGU's (Insulated Glass Units) to fail, so you would have thought that is it then a simple solution to a massive problem, not so. what you have now done is allowed the unit to draw air in instead of going into negative deflection, the air that is entering the unit will contain moisture, the air passing through the unit will not condensate untill the AP changes and the Dew Point is achieved at this stage the moisture in the air passing through the unit (Vapour) will condense on the glass at the top of the unit and begin to run down the glass and build up in the bottom spacer bar, the following day when the temperature rises the water trapped in the bottom spacer bar turns to vapour and the cycles starts all over again. the only difference is that if the air passing through the unit and has a low moisture level (Low humidity) the unit appears to have been cured, unfortunatley this is only a temporary repair and will not prevent the unit condensating in high humidity areas and times of the year(Spring).
There is a solution to the problem Crystal Clear Window Works Uk and its network of dealers not only pressure equalise the units they also apply a Super-hydrophilic coating to the unit that prevents the moisture in the air passing through the unit showing up as fog or consensation on the glass, similar coating are used on mirrors in bathrooms to prevent them from steaming up whilst taking a shower etc.
The long term problem of sealed unit failure by the application of the patented coating is changing the double glazing industry.
However be aware of individuals and companies offering to remove the moisture by simply installing valves or sieves IT DOES NOT WORK and can not work, a very basic understanding of the physics inside the unit and understanding dew points, moisture vapour and atmospheric pressure
affecting the unit is all that is needed to discredit these individuals.
The savings made from having the units re-engineered is massive and the enviromental savings made are impressive reducing landfill waste and carbon footprints.
crystalclearwindow.co.uk is the website to check out.