Author: Zsolt Tóth
2009-02-28
Probably a lot of people makes the question: „Did I really recieve the glazing with the U-value as I ordered it?
The sticker – telling you that the k-value is 1,4 W/m2K – can be put on every glazing, but it is not sure that it fits reality.
The current article presents the case of the window visible above. In a few words about the antedecent: we built in the wooden window in the Agust of 2008, with the k-value of 1,4 W/m2K. (Nowadays the k-value for theheat transfer coefficient is called the U-value, but not many people know it like that.) The house was finished at the end of Agust and the clients moved in right away. I met them again in December, when they showed their window which was – without any doubt – humid. The vapor content in the kitchen was way higher than the average (70-80%) tough. The habitants did not ventillate, in order to keep the warm in the house. The demister I gave them was subtracting 3-4 liters of water from the air daily. Despite the dehumidification, the case could not be considered as closed, so I went after the truth.
The 4-16-4 mark used in our case means that the 16 mm thick spacer layer is straddled with 4 mm thick glazing two times. We can see a perforated layer at the edge of the window, this is the place where vapor absorbing globules are fixed into the frame. This is the way how the condensation can be avoided between the two layers of glazing.
Whick k-value glazings are found the most often?
I asked for two pieces of 30x30cm large glass panes from the glazing manufacturer, one with a k-value of 1,4 W/m2K, the other with 2,8 W/m2K. I orderd two glasses with different heat transfer coefficients in order to avoid having one with 2,8 W/m2K k-value, marked with the 1,4 W/m2K sticker.
I used the 1,4 W/m2K glazing as a reference. For the experiment – in which I compared the reference glazing with the casement which I wanted to test – I used two pieces of 250 W bulbs. (This is the bulb which is often used to keep grilled chiken warm.)
The test can be done anywhere, if we have an infra lamp
I recieved a stunning result: the heat transfer capabilities of the built-in glazing was easy to sense by measuring the transferred heat. Putting my hand 10 cm close to the reference glazing, (k-value 1,4 W/m2K) I only felt tepid warm, while the examined glazing – transferring more heat – warmed up my hand way more. Even for me, the result was surprising, as I did not expect the two glazings to be different. Not only my sense organs proved it, even in the photo, the difference can be seen: as if there was a bulb with a higher performance below the 2,8 glazing, despite the fact that the surroundings during the experiment (distance, performance) were the same.
In the k= 1,4 W/m2K glazing (on the left) less heat can transfer than in the k=2,8 W/m2K glazing
An other interesting addition: I took a photo from the changed glazing from the outside. It can be seen quite clearly that one of the panes (on the left edge) reflects the light differently than the others. Turned out that only four of the five faulty panes were changed, and instead of changing the fifth faulty, a good one was also removed. In result, a faulty pane can be seen in the picture...
The weakness can be seen on the left part of the enlargened image of the window
Two days after the change, the glazings were tested and I was called to get to know that the controversial window is OK. It is quite probable that only one pane was tested and it was the one which was OK and taken … where is the red… our pragmatic report will continue as soon as we will have development.
Milyen üvegezések közül választhatunk?
Kiskertemben uborka... uborka még nincs, a terasz viszont kifejezetten jó lett!
Ajtóablak helyzet... bemegy vagy kihagyja?
Szarügy... avagy milyen WC-t válasszunk?
Bevásárlókörút a megrendelõinkkel
What a neat arlteic. I had no inkling.
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