www.bulit-glass.bg> FAQ


1. What is the price of your products?
The price is formed according to the following factors:
  • Glass type
  • Glass thickness
  • Unit quantity, square area and linear area
  • Glass pane cutting optimization (the amount of wastage)
  • Manual labor costs
  • Additional processing costs
Each order is strictly individual and the cost can be determined only after analyzing the above parameters. We are able to give our customers the exact price in written only after an official inquiry on their side, which also must be in a written form. Our standard offers are only an approximation. Any serial production inquiries undergo an individual price negotiation with the client in order to achieve best conditions for both sides.
2. How does one submit an inquiry?
In order to process your inquiries fast and effective please use our Inquiry Form. In case of a manual inquiry submission (scripted), the inquiry must be written clean and error free to prevent any free interpretation. The requestor must sign at the bottom as a proof of authenticity.
3. What is the warrany of your products?
Bulit Glass Ltd. gives a warranty for 5 years on all products. We offer a product replacement for all claims that are in accordance to our claim policy.
4. What is the claim policy?
(Under construction...)
5. What is Low-E (low emittance) glass?
Low-emittance (Low-E) coating are microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. The principal mechanism of heat transfer in multilayer glazing is thermal radiation from a warm pane of glass to a cooler pane. Coating a glass surface with a low-emittance material and facing that coating into the gap between the glass layers blocks a significant amount of this radiant heat transfer, thus lowering the total heat flow through the window. Low-E coatings are transparent to visible light. Different types of Low-E coatings have been designed to allow for high solar gain, moderate solar gain, or low solar gain.
6. What is the difference between Low-E glass with soft and hard coating?
There are two types of Low-E glass: hard coating and soft coating. As you might imagine, they have different properties. In fact, they actually look different.Hard coated Low-E glass is manufactured by pouring a thin layer of molten tin onto a sheet of glass while the glass is still slightly molten. The tin actually becomes "welded" to the glass. This process makes it difficult or "hard" to scratch or remove the tin. Often this glass has a blueish tint to it. Soft coated Low-E glass, on the other hand, involves the application of silver, zinc or tin to glass in a vacuum. The glass enters a vacuum chamber filled with an inert gas which is electrically charged. The electricity combined with the vacuum allows molecules of metal to sputter onto the glass. The coating is fairly delicate or "soft." Furthermore, if silver is used (and it often is) this coating can oxidize if exposed to normal air. For this reason, soft coated Low-E glass must be used in an insulated glass assembly. Sealing the soft coating in between two pieces of glass protects the soft coating from outside air and sources of abrasion. Also, the space between the two pieces of glass is often filled with argon gas. The argon gas inhibits oxidation of the metallic coating. It also acts as an additional insulator. The two types of Low-E glass have different performance characteristics. The soft coat process has the ability to reflect more heat back to the source. It typically has a higher R value. R values are a measure of resistance to heat loss. The higher the R value of a material, the better its insulating qualities.
7. What is the K-Glass (Ka Glass)?
The K-Glass is very popular on the Bulgarian market. It is in essense a Low-E glass with hard coating by a company named Pilkington. It is mistakenly compared to the Low-E glass with soft coating and offers worse qualities in general.
8. What is tempered (toughened) glass and how does one toughen the glass?
Tempered glass is one of two kinds of safety glass regularly used in applications in which standard glass could pose a potential danger. Tempered glass is four to five times stronger than standard glass and does not break into sharp shards when it fails. Tempered glass is manufactured through a process of extreme heating and rapid cooling, making it harder than normal glass.
9. How much does a tempered glass weigh?
The process of tempering the glass does not affect its weight. It is calculated by the formula M = 2,5 kg. * the glass thickness in milimeters. * m2 (square meters).E.g. 1 m2 float glass with thickness of 4mm. weighs: M = 2,5 * 4 * 1 = 10kg.(10 kilos ~ 22 pounds)
10. Why can the glass no longer be processed after it has been tempered?
The tension created inside the glass by the tempering process would lead to immediate breakage in case of any processing attempt. All processing must happen beforehand. Only suraface processing (e.g. making the glass matted) is possible after tempering the glass.
11. Why are there optical deviations when looking at a tempered glass under a certain angle?
The process of tempering the glass creates tension areas in it. These sometimes cause a dobule optical diffraction which under certain conditions become visible. This phenomenon is physically acceptable and normal for the tempered glass and could not be a subject of claim.
12. What is the coefficient of heat transmission (U-value)?
U-value (Europe) Heat-transfer coefficient The heat-transfer coefficient (or U-value) is the amount of heat in watts transmitted per hour through 1 m2 of wall (glass) with a difference of 1 Kelvin Degrees between the inside and the outside (W/m2.oK).
13. Why does the IGU sometimes inflate or deflate?

The insulating glass unit (IGU) is a solid closed unit in respect to the air and responds to the air conditions. Any change of air temperature or air pressure reflects on the IGU"s volume as well. This is a normal reaction of the IGU and cannot be avoided or a subject of claim. However, it can be minimized if the IGUs are put together vertically and manufactured on an altitude close the one of the place where they will be installed.

For example:

  • Inflation - if the IGU was manufactured in March under 18oC, in August under 30oC it will look slightly inflated. If the IGU was manufactured in Varna and installed some place in the mountains where the air pressure is lower it will again look slightly inflated.
  • Deflation - deflation works the opposite way. If the IGU was manufactured in June, in January under negative temperature, it will look slightly deflated. If it was manufactured in Sofia and installed in Varna, because of the air pressure difference, it will look slightly deflated.
14. Why does the IGU sometimes condensate?
(Under construction...)
15. What is the greenhouse effect?
Due to the high light and heat transmission factor of the regular transparent glass, sun light goes into the room easily and warms up the floor, walls, furniture, etc. On its way back the heat waves are reflected by the silver coating of the low-e glass and thus they remain inside. During the winter this occurance contributes to lower heating costs. In the summer however, the energy generated by the greenhouse effect brings discomfort which can be avoided with appropriate solar protection.
16. Is there an optimal glazing using insulating glass units?
(Under construction...)

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